Q - DPG-Verhandlungen
Q - DPG-Verhandlungen
Q - DPG-Verhandlungen
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Fachverband Quantenoptik und Photonik (Q) Übersicht<br />
Fachsitzungen<br />
Fachverband Quantenoptik und Photonik (Q)<br />
Matthias Weidemüller<br />
Physikalisches Institut der Universität Freiburg<br />
Hermann-Herder-Str. 3<br />
79104 Freiburg<br />
weidemueller@physik.uni-freiburg.de<br />
Übersicht der Fachsitzungen<br />
(Hörsäle 1A, 1B, 1C, 2B/C, 2D, 2F, 2G, 3C, 3D, 3G und 3H; Poster C1 und Poster C2)<br />
Q 1.1–1.4 Mo 14:00–16:00 1A Quantengase I [gemeinsam mit A]<br />
Q 2.1–2.7 Mo 14:00–16:00 1B Quanteninformation (Atome und Ionen I)<br />
Q 3.1–3.4 Mo 14:00–16:00 3D Präzisionsmessungen und Metrologie I<br />
Q 4.1–4.8 Mo 14:00–16:00 3H Laserentwicklung (Festkörperlaser I)<br />
Q 5.1–5.5 Mo 16:30–19:00 1A Quantengase II [gemeinsam mit A]<br />
Q 6.1–6.10 Mo 16:30–19:00 1B Quanteninformation (Atome und Ionen II)<br />
Q 7.1–7.6 Mo 16:30–18:15 3C Ultrakurze Pulse (Attosekundenphysik) [gemeinsam mit A und<br />
K]<br />
Q 8.1–8.6 Mo 16:30–18:00 3D Präzisionsmessungen und Metrologie II<br />
Q 9.1–9.10 Mo 16:30–19:00 3H Laserentwicklung (Halbleiterlaser)<br />
Q 10.1–10.7 Di 8:30–10:30 3G Kalte Moleküle I [gemeinsam mit MO]<br />
Q 11.1–11.8 Di 8:30–10:30 3H Laserentwicklung (Festkörperlaser II / Andere Laserquellen)<br />
Q 12.1–12.8 Di 11:00–13:00 3G Kalte Moleküle II [gemeinsam mit MO]<br />
Q 13.1–13.8 Di 11:00–13:00 3H Laserentwicklung (Nichtlineare Effekte und Anwendungen)<br />
Q 14.1–14.6 Di 14:00–15:45 1B Quanteninformation (Quantencomputer I)<br />
Q 15.1–15.8 Di 14:00–16:00 1C Quantengase (Gitter I)<br />
Q 16.1–16.8 Di 14:00–16:00 2B/C Photonik I<br />
Q 17.1–17.8 Di 14:00–16:00 2F Ultrakalte Atome I [gemeinsam mit A]<br />
Q 18.1–18.7 Di 14:00–15:45 3D Präzisionsmessungen und Metrologie III<br />
Q 19.1–19.8 Di 14:00–16:00 3G Kalte Moleküle III [gemeinsam mit MO]<br />
Q 20.1–20.7 Di 14:00–15:45 3H Laseranwendungen (Lebenswissenschaften und Umwelt)<br />
Q 21.1–21.4 Di 16:30–17:30 1B Quanteninformation (Quantencomputer II)<br />
Q 22.1–22.6 Di 16:30–18:00 1C Quantengase (Gitter II)<br />
Q 23.1–23.6 Di 16:30–18:00 2B/C Photonik II<br />
Q 24.1–24.6 Di 16:30–18:00 3G Ultrakalte Moleküle [gemeinsam mit MO]<br />
Q 25.1–25.9 Di 16:30–18:45 3H Laseranwendungen (Spektroskopie)<br />
Q 26.1–26.12 Di 16:30–19:00 Poster C1 Poster Ultrakurze Laserpulse<br />
Q 27.1–27.28 Di 16:30–19:00 Poster C2 Poster Quantengase<br />
Q 28.1–28.26 Di 16:30–19:00 Poster C2 Poster Quanteninformation<br />
Q 29.1–29.19 Di 16:30–19:00 Poster C2 Poster Quanteneffekte<br />
Q 30.1–30.7 Di 16:30–19:00 Poster C2 Poster Präzisionsmessungen und Metrologie<br />
Q 31.1–31.8 Do 8:30–10:30 1B Quanteninformation (Konzepte und Methoden I)<br />
Q 32.1–32.7 Do 8:30–10:15 1C Quantengase (Gitter III)<br />
Q 33.1–33.6 Do 8:30–10:00 2F Ultrakalte Atome II [gemeinsam mit A]<br />
Q 34.1–34.6 Do 8:30–10:00 2G Ultrakalte Rydberggase [gemeinsam mit A]<br />
Q 35.1–35.6 Do 8:30–10:00 3H Laseranwendungen (Optische Messtechnik)<br />
Q 36.1–36.8 Do 11:00–13:00 1B Quanteninformation (Konzepte und Methoden II)<br />
Q 37.1–37.9 Do 11:00–13:15 1C Quantengase (Wechselwirkungseffekte I)<br />
Q 38.1–38.8 Do 11:00–13:15 2D Quanteneffekte (Verschränkung und Dekohärenz)<br />
Q 39.1–39.8 Do 11:00–13:00 3H Ultrakurze Laserpulse (Erzeugung I)<br />
Q 40.1–40.8 Do 14:00–16:00 1A Quantengase (Bosonen I)<br />
Q 41.1–41.8 Do 14:00–16:00 1B Quanteninformation (Konzepte und Methoden III)<br />
Q 42.1–42.7 Do 14:00–16:00 1C Ultrakalte Atome (Manipulation und Detektion / Quantengase)<br />
Q 43.1–43.8 Do 14:00–16:00 2B/C Photonik III
Fachverband Quantenoptik und Photonik (Q) Übersicht<br />
Q 44.1–44.9 Do 14:00–16:15 2D Quanteneffekte (Interferenz / Sonstige)<br />
Q 45.1–45.7 Do 14:00–15:45 3G Materiewellenoptik<br />
Q 46.1–46.9 Do 14:00–16:15 3H Ultrakurze Laserpulse (Erzeugung II / Anwendungen I)<br />
Q 47.1–47.9 Do 16:30–18:45 1A Quantengase (Bosonen II / Fermionen)<br />
Q 48.1–48.10 Do 16:30–19:00 1B Quanteninformation (Quantenkommunikation)<br />
Q 49.1–49.11 Do 16:30–19:15 3H Ultrakurze Laserpulse (Anwendungen II)<br />
Q 50.1–50.26 Do 16:30–19:00 Poster C2 Poster Ultrakalte Atome<br />
Q 51.1–51.6 Do 16:30–19:00 Poster C2 Poster Ultrakalte Moleküle<br />
Q 52.1–52.1 Do 16:30–19:00 Poster C2 Poster Materiewellenoptik<br />
Q 53.1–53.11 Do 16:30–19:00 Poster C2 Poster Photonik<br />
Q 54.1–54.11 Do 16:30–19:00 Poster C2 Poster Laserentwicklung<br />
Q 55.1–55.9 Do 16:30–19:00 Poster C2 Poster Laseranwendungen<br />
Q 56.1–56.8 Fr 11:00–13:00 1A Quanteninformation (Photonen und nichtklassisches Licht I)<br />
Q 57.1–57.8 Fr 11:00–13:00 2D Quanteneffekte (QED / Lichtstreuung)<br />
Q 58.1–58.5 Fr 11:00–12:30 3B Ultrakalte Atome (Einzelne Atome)<br />
Q 59.1–59.5 Fr 11:00–12:30 3C Transport in ultrakalten Gasen und Plasmen [gemeinsam mit<br />
A]<br />
Q 60.1–60.8 Fr 11:00–13:00 3G/H Quantengase (Gemische / Tunneleffekte)<br />
Q 61.1–61.6 Fr 14:00–15:30 1A Quanteninformation (Photonen und nichtklassisches Licht II)<br />
Q 62.1–62.7 Fr 14:00–15:45 3B Ultrakalte Atome (Fallen und Kühlung)<br />
Q 63.1–63.8 Fr 14:00–16:00 3G/H Quantengase (Wechselwirkungseffekte II / Spinorgase)<br />
Mitgliederversammlung des Fachverbands Quantenoptik und Photonik<br />
Donnerstag 13:10–14:00 Raum 1C<br />
• Bericht des Vorsitzenden<br />
• Bericht der AG Photonik<br />
• Wahl eines neuen Vorsitzenden und Stellvertreters<br />
• Verschiedenes
Fachverband Quantenoptik und Photonik (Q) Montag<br />
Q 1: Quantengase I [gemeinsam mit A]<br />
Zeit: Montag 14:00–16:00 Raum: 1A<br />
Hauptvortrag Q 1.1 Mo 14:00 1A<br />
Cavity Optomechanics — •Tobias J. Kippenberg — Max Planck<br />
Institut fuer Quantenoptik<br />
Achieving the quantum regime with mechanical objects offers fascinating<br />
possibilities for applied and fundamental Physics alike but has yet<br />
has been unattained so far. Remarkably, research groups working on<br />
mechanical systems ranging in size from nanometer-scale oscillators to<br />
centimeter-scale optical cavities to kilometer-scale gravity wave detectors<br />
are now all independently approaching a regime in which either<br />
the mechanical system or its interaction with the environment must<br />
be described quantum mechanically. These experiments will mark the<br />
beginning of the new research field of cavity Quantum Optomechanics.<br />
In this talk I will review our own efforts at the MPQ in this emerging<br />
research field; specifically, we have developed a novel laser cooling<br />
method (1,2) with which mechanical oscillators can be cooled - analogous<br />
to atomic laser cooling - and achieved unprecedented readout of<br />
mechanical motion. This technique provides a route towards ground<br />
state cooling of a mechanical oscillator. The mechanical oscillators in<br />
our work are provided by monolithic micro-cavities, which inherently<br />
combine mechanical and optical degree of freedom. I will describe the<br />
various efforts my group made towards achieving this interesting, yet<br />
highly challenging regime including the mechanical analog of Resolved<br />
Sideband Cooling.<br />
References:<br />
(1) A. Schließer et al. Phys. Rev. Lett. 97, 243905 (2006)<br />
(2) I. Wilson-Rae et al. Phys. Rev. Lett. 99, 093901 (2007)<br />
Gruppenbericht Q 1.2 Mo 14:30 1A<br />
Bose-Einstein condensates coupled to solid state systems<br />
on an atom chip — •Philipp Treutlein 1,2 , David Hunger 1,2 ,<br />
Stephan Camerer 1,2 , Pascal Böhi 1,2 , Max Riedel 1,2 , Johannes<br />
Hoffrogge 1,2 , Theodor W. Hänsch 1,2 , Daniel König 2 , Jörg P.<br />
Kotthaus 2 , and Jakob Reichel 3 — 1 Max-Planck-Institut für Quantenoptik,<br />
Garching — 2 Fakultät für Physik, Ludwig-Maximilians-<br />
Universität München — 3 LKB, Ecole Normale Superieure, Paris<br />
We present the status of two experiments which explore the interaction<br />
of atoms with micro- and nanofabricated solid state systems on a chip.<br />
The first experiment aims at coupling a BEC to the mechanical<br />
oscillations of a nanoscale cantilever with a magnetic tip. Theoretical<br />
investigations of the magnetic coupling mechanism show that the<br />
atoms can be used as a sensitive probe for the cantilever dynamics.<br />
At low temperatures, the backaction of the atoms onto the cantilever<br />
is significant and the system represents a mechanical analog of cavity<br />
QED in the strong coupling regime [P. Treutlein et al., Phys. Rev.<br />
Lett. 99, 140403 (2007)].<br />
In the second experiment, the solid state system is a miniaturized<br />
microwave guiding structure, which can be used to manipulate BECs.<br />
Through microwave dressing of hyperfine states, state-selective double-<br />
Q 2: Quanteninformation (Atome und Ionen I)<br />
well potentials can be created. Such potentials have applications in<br />
quantum information processing, the study of Josephson effects, and<br />
could be used to entangle atoms via state-selective collisions [P. Treutlein<br />
et al., Phys. Rev. A 74, 022312 (2006)].<br />
Gruppenbericht Q 1.3 Mo 15:00 1A<br />
Dissipation Fermionizes a One-Dimensional Gas of Bosonic<br />
Molecules — •Dominik M. Bauer, Niels Syassen, Matthias Lettner,<br />
Thomas Volz, Daniel Dietze, Juan J. Garcia-Ripoll, Ignacio<br />
Cirac, Gerhard Rempe, and Stephan Dürr — Max-Planck-<br />
Institut für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching,<br />
Germany<br />
Many-body systems usually behave differently depending on whether<br />
the particles are bosons or fermions. However, bosons are forced to behave<br />
much like fermions if the system is one-dimensional (1D) and the<br />
interactions dominate the dynamics. This strongly correlated system<br />
is called a Tonks-Girardeau gas [1,2] and was observed with atoms in<br />
optical lattices [3,4]. All this work dealt with conservative interactions.<br />
Here we demonstrate a surprising generalisation, namely that inelastic<br />
collisions produce a dissipative analogue of the Tonks-Girardeau<br />
gas. We report on an experiment with molecules confined to 1D in an<br />
optical lattice. Inelastic collisions between the molecules create strong<br />
correlations that suppress the molecule loss rate by a factor of about 10.<br />
We dramatically increase this suppression by adding a lattice along the<br />
1D direction. We develop theory which agrees with our experimental<br />
observations. Our work offers perspectives to create other, and possible<br />
new, strongly correlated states using dissipation.<br />
[1] Tonks, L. Phys. Rev. 50, 955-963 (1936).<br />
[2] Girardeau, M. J. Math. Phys. 1, 516-523 (1960).<br />
[3] Paredes, B. et al. Nature 429, 277-281 (2004).<br />
[4] Kinoshita, T. et al. Science 305, 1125-1128 (2004).<br />
Gruppenbericht Q 1.4 Mo 15:30 1A<br />
Strong dipolar effects in Chromium Bose-Einstein condensates<br />
(Gruppenbericht) — •Jonas Metz, Bernd Fröhlich, Tobias<br />
Koch, Thierry Lahaye, Axel Griesmaier, and Tilman Pfau<br />
— 5. Physikalisches Institut, Universität Stuttgart<br />
The experimental observation of strong dipolar effects in a Bose-<br />
Einstein condensate of Chromium are presented. Starting with dipolar<br />
interactions which perturb the usual contact interactions, we use a<br />
Feshbach resonance to reduce and finally switch off the contact interaction.<br />
We investigate the stability diagram of a purely dipolar gas<br />
for various trap shapes and find a universal behaviour in the large N<br />
case for all dipolar gases. We then induce a dipolar collapse and study<br />
the dynamics. Quantitative comparison with theoretical calculations<br />
by the Ueda group of Tokyo University are presented. The symmetry<br />
of the dipolar interaction is observed in the collapse products.<br />
Zeit: Montag 14:00–16:00 Raum: 1B<br />
Gruppenbericht Q 2.1 Mo 14:00 1B<br />
Entanglement and Quantum Networking with Trapped<br />
Atoms — •David Moehring 1,2 , Jörg Bochmann 1 , Dzmitry<br />
Matsukevich 2,3 , Peter Maunz 2,3 , Martin Mücke 1 , Tobias<br />
Müller 1 , Steven Olmschenk 2,3 , Holger Specht 1 , Bernhard<br />
Weber 1 , Christopher Monroe 2,3 , and Gerhard Rempe 1 — 1 Max-<br />
Planck-Institut für Quantenoptik, D-85748 Garching, Germany —<br />
2 FOCUS Center and Department of Physics, University of Michigan,<br />
Ann Arbor, MI 48109-1040, USA — 3 JQI and Department of Physics,<br />
University of Maryland, College Park, Maryland 20742, USA<br />
Distant, entangled qubits represent a universal resource for distributed<br />
quantum computing. One method to entangle two distant particles<br />
involves detecting a single photon from each particle after the photons<br />
have interfered. When two atoms each become entangled with an<br />
emitted single photon, subsequent interference and detection of these<br />
photons can leave the trapped atom qubits in an entangled state. Although<br />
this entanglement is probabilistic, it is not post-selective and<br />
therefore can be utilized for long-distance quantum communication<br />
and large-scale quantum computation.<br />
I will discuss the experimental realization of remote-entanglement<br />
of two individually trapped ions separated by one meter [1] as well as<br />
current efforts toward deterministic entanglement via atoms trapped<br />
within high-finesse optical cavities [2,3].<br />
[1] Moehring et al., Nature 449, 68 (2007)<br />
[2] Wilk et al., Science 317, 488 (2007)<br />
[3] Hijlkema et al., Nature Physics 3, 253 (2007)<br />
Q 2.2 Mo 14:30 1B<br />
Ion trap quantum gates with amplitude-modulated laser<br />
beams — •Christian Roos — Institut für Quantenoptik und Quanteninformation,<br />
Österreichische Akademie der Wissenschaften, Otto-<br />
Hittmair-Platz 1, 6020 Innsbruck, Österreich<br />
In ion traps, entangling gate operations can be realized by a bichromatic<br />
pair of laser beams that collectively interact with the ions. A new
Fachverband Quantenoptik und Photonik (Q) Montag<br />
method of modelling the laser-ion interaction is introduced that turns<br />
out to be superior to standard techniques for the description of gate<br />
operations on optical qubits. The treatment allows for a comparison<br />
of the performance of gates based on σz ⊗ σz and σφ ⊗ σφ interactions<br />
on optical transitions where the bichromatic laser field can be realized<br />
by an amplitude-modulated laser resonant with the qubit transition<br />
[1]. Shaping the amplitude of the bichromatic laser pulse is shown to<br />
make the gates more robust against experimental imperfections. An<br />
experimental implementation of the gate using a pair of calcium ions<br />
have shown very promising results [2].<br />
[1] C. F. Roos, arXiv:0710.1204, accepted for publication in<br />
New. J. Phys.<br />
[2] J. Benhelm, G. Kirchmair, C. F. Roos, R. Blatt, manuscript in<br />
preparation.<br />
Q 2.3 Mo 14:45 1B<br />
Towards fault-tolerant quantum computing with trapped<br />
ions — •Jan Benhelm 1,2 , Gerhard Kirchmair 1,2 , Christian F.<br />
Roos 1,2 , and Rainer Blatt 1,2 — 1 Institut für Experimentalphysik,<br />
Innsbruck — 2 Institut für Quantenoptik und Quanteninformation,<br />
Österreichische Akademie der Wissenschaften, Innsbruck<br />
For fault-tolerant computation, it is commonly believed that error<br />
thresholds ranging between 10 −4 and 10 −2 will be required depending<br />
on the noise model and the computational overhead for realizing<br />
the quantum gates. Up to now, all experimental implementations have<br />
fallen short of these requirements.<br />
Here, we report on the experimental realization of a Mølmer-<br />
Sørensen type entangling gate operation with a fidelity of 99.3% which<br />
together with single-qubit operations forms a universal set of quantum<br />
gates. The gate operation is performed on a pair of qubits encoded<br />
in two trapped calcium ions using a single amplitude-modulated laser<br />
beam interacting with both ions at the same time. A robust gate operation,<br />
mapping separable states onto maximally entangled states, is<br />
achieved by adiabatically switching on and off the laser-ion coupling.<br />
We analyse the performance of a single gate and concatenations of up<br />
to 21 gate operations.<br />
Q 2.4 Mo 15:00 1B<br />
Deterministic Entanglement Swapping with Trapped Ions<br />
— •Mark Riebe 1 , Thomas Monz 1 , Kihwan Kim 1 , Alessandro<br />
Villar 2 , Philipp Schindler 1 , Markus Hennrich 1 , and Rainer<br />
Blatt 1,2 — 1 Institut für Experimentalphysik, Universität Innsbruck,<br />
Austria — 2 Institut für Quantenoptik und Quanteninformation,<br />
Österreichische Akademie der Wissenschaften, Austria<br />
Entanglement is a key feature in the field of quantum information processing,<br />
as it allows for quantum communication, secret key sharing<br />
and quantum computation. Many of these applications require entangled<br />
states distributed among distant locations. Distribution of entangled<br />
states can be aided by a scheme known as entanglement swapping<br />
[1]. We demonstrate this scheme with a string of four trapped 40 Caions,<br />
which carry quantum information in their internal states S 1/2<br />
and D 5/2 [2]. Initially, ion pairs 1,2 and 3,4 are each prepared in the<br />
Bell state Ψ − = (|DS〉−|SD〉)/ √ 2. Then, ion 1 and 4 are measured in<br />
the Bell basis. The result of this measurement is perfectly correlated<br />
with the Bell state into which the previously unentangled ions 2 and<br />
3 are projected. We make use of this fact and apply further rotations<br />
to ion 3 conditioned by the Bell measurement result, such that ions 2<br />
and 3 are deterministically mapped to the state Ψ − . This is confirmed<br />
by determining the final state of ions 2,3 by state tomography, which<br />
proves that we prepare the state Ψ − with a fidelity of 79%.<br />
[1] J. W. Pan et al., Phys. Rev. Lett. 80, 3891 (1998).<br />
[2] F. Schmidt-Kaler et al., Appl. Phys. B 77, 789 (2003).<br />
Q 2.5 Mo 15:15 1B<br />
Three-qubit Toffoli gate with trapped ions — •Thomas<br />
Monz 1 , Kihwan Kim 1 , Wolfgang Hänsel 1 , Alessandro Villar 2 ,<br />
Philipp Schindler 1 , Mark Riebe 1 , Markus Hennrich 1 , and Rainer<br />
Blatt 1,2 — 1 Institut für Experimentalphysik, Universität Innsbruck,<br />
Austria — 2 Institut für Quantenoptik und Quanteninformation,<br />
Österreichische Akademie der Wissenschaften, Austria<br />
Quantum algorithms are usually decomposed into a sequence of gate<br />
operations each acting only on a few qubits. A well-known set for<br />
this purpose is a two-qubit controlled NOT (CNOT) gate combined<br />
with single qubit rotations. However, gates that connect more than<br />
two qubits could facilitate quantum computations. One example is the<br />
three-qubit Toffoli gate, which is a valuable tool for quantum error<br />
correction. The Toffoli gate acts on a register of two control qubits<br />
|c1, c2〉 and one target qubit |t〉 as |c1, c2, t〉 → |c1, c2, (c1 ∧ c2) ⊕ t〉.<br />
We implement this gate with a string of trapped ions, where we use<br />
the ion’s internal states as qubits and manipulate these with suitable<br />
laser pulses. Our implementation relies on an extension of the Cirac-<br />
Zoller gate proposal [1]: First a carefully designed sequence of laser<br />
pulses encodes the information (c1 ∧ c2) in one of the ion string’s vibrational<br />
modes. Then a CNOT gate between the target qubit and the<br />
vibrational mode realizes the operation |t〉 → |(c1 ∧ c2) ⊕ t〉. Finally,<br />
the initial encoding procedure is reversed. We analyze the Toffoli gate<br />
operation by quantum process tomography, and obtain a mean gate<br />
fidelity of 79%.<br />
[1] J. I. Cirac and P. Zoller, Phys. Rev. Lett. 74, 4091 (1995).<br />
Q 2.6 Mo 15:30 1B<br />
Coupling trapped ions via transmission lines — Rob<br />
Clark 1,2 , Sankaranarayanan S 1 , •Nikos Daniidilis 1 , and Hartmut<br />
Häffner 1 — 1 Institut für Quantenoptik und Quanteninformation,<br />
Österreichische Akademie der Wissenschaften, Innsbruck,<br />
Österreich — 2 Center for Ultracold Atoms, Massachusetts Institute<br />
of Technology, START project Cambridge, MA, USA<br />
An oscillating trapped ion induces oscillating image charges in the trap<br />
electrodes. If this current is send to the electrodes of a second trap, it<br />
influences the motion of an ion in the second trap. The expected time<br />
for a complete exchange of the ion motions is 1 ms for a trap with a<br />
characteristic size of 50 µm. This inter–trap coupling may be used for<br />
scalable quantum computing, cooling ion species that are not directly<br />
accessible to laser cooling, for the non-invasive study of superconductors,<br />
and for coupling an ion–trap quantum computer to a solid–state<br />
quantum computer, e.g. a system of Josephson junctions.<br />
We will discuss the feasibility of experiments towards these goals<br />
with trapped Calcium ions. The most relevant source of decoherence<br />
is heating of the ion motion due to noise in the trap electrodes (e.g.<br />
Johnson–noise). By operating ion traps at cryogenic temperatures,<br />
heating will be greatly reduced, allowing the coherent coupling of two<br />
ions. In this context, we will present results from currently operating<br />
planar traps, as well as efforts in developing microfabricated planar<br />
traps. In particular, we will discuss the influence of an electrically<br />
floating coupling electrode on trap performance.<br />
Q 2.7 Mo 15:45 1B<br />
Long-distance atom-photon entanglement and its coherence<br />
properties — •Michael Krug 1 , Wenjamin Rosenfeld 1 , Fred<br />
Hocke 1 , Florian Henkel 1 , Andreas Deeg 1 , Christian Jakob 1 ,<br />
Markus Weber 1 , and Harald Weinfurter 1,2 — 1 Sektion Physik,<br />
Ludwig-Maximilians-Universität München, Schellingstrasse 4, D-80799<br />
München — 2 Max-Planck Institut für Quantenoptik, D-85748 Garching<br />
Long-distance Atom-Photon Entanglement: The distribution of entanglement<br />
between quantum memories at remote locations is one major<br />
challenge for the first demonstration of a quantum repeater. Entanglement<br />
between matter and light [1] is crucial for achieving this<br />
task. Here we report the observation of entanglement between a single<br />
trapped atom and a single photon, separated 300 m via an optical<br />
fiber. The entanglement is verified by appropriate correlation measurements<br />
of the atom-photon pair after communicating the photon<br />
through the fiber. In addition we analyzed the temporal evolution of<br />
the atomic density matrix after projecting the atom-photon pair via<br />
a state measurement of the photon onto a well defined atomic spin<br />
state. We find that the atomic Zeeman qubit decoheres after 100 µs.<br />
Our results represent important steps towards the realization of entanglement<br />
between single neutral atoms at distances of several 100<br />
m.<br />
[1] J. Volz, M. Weber, D. Schlenk et al., Phys. Rev. Lett. 96, 030404<br />
(2006).
Fachverband Quantenoptik und Photonik (Q) Montag<br />
Q 3: Präzisionsmessungen und Metrologie I<br />
Zeit: Montag 14:00–16:00 Raum: 3D<br />
Gruppenbericht Q 3.1 Mo 14:00 3D<br />
A Michelson-Morley Type Test of Lorentz Invariance<br />
using electromagnetic Resonators — •Alexander Senger 1 ,<br />
Katharina Möhle 1 , Moritz Nagel 1 , Sven Herrmann 2 , Evgeny<br />
Kovalchuk 1 , Holger Müller 2 , and Achim Peters 1 — 1 Institut<br />
für Physik, Humboldt-Universität zu Berlin — 2 Physics Department,<br />
Stanford University, USA<br />
The experiment of A. A. Michelson and E. W. Morley, has served as a<br />
sensitive test of special relativity and Lorentz invariance for more than<br />
a century now. Modern versions of this experiment rely on the comparison<br />
of electromagnetic eigenfrequencies of rotating high-finesse resonators.<br />
This approach allows to search for tiny violations of Lorentz<br />
Invariance in the optical sector of the underlying test theory (SME,<br />
Standard Model Extension), and also for deviations regarding the electronic<br />
properties of the material used to build the resonators.<br />
We report on the progress made in our improved version of the<br />
experiment, where the measurement is performed by monitoring an<br />
optical resonator continuously rotating on a precision turntable, which<br />
currently allows for a sensitivity at the 10 −17 level for a direction dependent<br />
variation of the speed of light. We discuss limiting effects in<br />
our setup and present steps towards a measurement spanning more<br />
than one year which should give an improvement of at least an order<br />
of magnitude in accuracy compared to previous tests. Furthermore,<br />
we present results from a collaboration employing two complementary<br />
experiments leading to limits on Lorentz Violation in the electronic<br />
sector of the SME.<br />
Gruppenbericht Q 3.2 Mo 14:30 3D<br />
A Picometer Resolution Heterodyne Interferometer for LISA<br />
and its Application to Technology Verification — •Dennis<br />
Weise 1 , Martin Gohlke 1,2 , Thilo Schuldt 2,3 , Thomas Heinrich 3 ,<br />
Ulrich Johann 1 , Achim Peters 2 , and Claus Braxmaier 3 — 1 EADS<br />
Astrium GmbH — 2 Humboldt-Universität zu Berlin — 3 HTWG Konstanz<br />
Within the LISA Mission Formulation study currently funded by ESA,<br />
EADS Astrium has developed and investigated various concepts for<br />
the LISA payload architecture, all of which utilize an Optical Readout<br />
(ORO) to detect relative motion between the inertial reference (i. e. the<br />
proof mass) and the spacecraft. In collaboration with the Humboldt<br />
University Berlin and the HTWG Konstanz, a prototype ORO has<br />
been realized over the past years, which meanwhile is close to achieving<br />
the required picometer-sensitivity in translation and nanoradsensitivity<br />
in attitude metrology. The polarizing heterodyne interferometer<br />
is characterized by a highly symmetric setup and employs differential<br />
wavefront sensing for determination of the proof mass tilt in 2<br />
degrees of freedom. We will discuss the experimental setup and its latest<br />
performance, as well as its application to first verification of critical<br />
LISA subsystems. For example, the interferometer has been applied to<br />
characterize the CTE of various CFRP samples with ultra-high sensitivity,<br />
including “near-zero-CTE” tubes. Our current activities further<br />
include novel developments for other critical parts of the optical<br />
Q 4: Laserentwicklung (Festkörperlaser I)<br />
metrology chain, namely the laser source and the phasemeter, where<br />
the respective approach and first results will be presented.<br />
Gruppenbericht Q 3.3 Mo 15:00 3D<br />
LISA Pathfinder: spaceborne testbed towards millihertz<br />
gravitational wave astronomy — •Felipe Guzman Cervantes 1 ,<br />
Frank Steier 1 , Antonio Francisco Garcia Marin 1 , Michael<br />
Troebs 1 , Anneke Monsky 1 , Martin Hewitson 1 , Gudrun<br />
Wanner 1 , Ingo Diepholz 1 , Oliver Jennrich 2 , Gerhard Heinzel 1 ,<br />
and Karsten Danzmann 1 — 1 Albert-Einstein-Institut Hannover —<br />
2 ESA-ESTEC<br />
LISA Pathfinder is a ESA technology demonstration mission planned<br />
to be launched in 2010 to test LISA core technologies that cannot<br />
be tested on ground. The LISA Pathfinder satellite carries two experiments:<br />
the LISA Technology Package (LTP) from ESA, and the<br />
Disturbance Reduction Noise (DRS) from NASA. The LISA Technology<br />
Package will primarly demonstrate test mass drag-free control and<br />
isolation to better than 3×10 −14 ms −2 / √ Hz, and spacecraft control<br />
with micronewton thrusters. A set of 4 heterodyne Mach-Zehnder interferometers<br />
is utilized for the read out of test mass displacement and<br />
rotation to better than 10 pm/ √ Hz and 10 nrad/ √ Hz in the frequency<br />
range from 3-30 mHz respectively. Currently we are testing engineering<br />
models of different subsystems and preparing a test bed for investigations<br />
on flight hardware. This talk presents the current status in the<br />
development and implementation of the LISA Technology Package and<br />
a series of tests conducted as software and hardware simulations for<br />
on-orbit operation.<br />
Gruppenbericht Q 3.4 Mo 15:30 3D<br />
LISA: Laser interferometry for the spaceborne gravitational<br />
wave detection — •Antonio Francisco Garcia Marin 1 , Felipe<br />
Guzman Cervantes 1 , Frank Steier 1 , Simon Barke 1 , Christian<br />
Diekmann 1 , Roland Fleddermann 1 , Benjamin Sheard 1 ,<br />
Michael Tröbs 1 , Juan Jose Esteban Delgado 1 , Iouri Bykov 1 ,<br />
Jens Reiche 1 , Oliver Jennrich 2 , Gerhard Heinzel 1 , and Karsten<br />
Danzmann 1 — 1 Albert-Einstein-Institut Hannover, Max-Planck-<br />
Institut für Gravitationsphysik and Universität Hannover, Germany<br />
— 2 ESA ESTEC, Noordwijk, The Netherlands<br />
The Laser Interferometer Space Antenna (LISA) is a joint ESA-NASA<br />
mission designed to observe gravitational waves in the frequency range<br />
between 0.1 to 100 mHz, where ground-based detectors are limited by<br />
terrestrial noise. Sources in this frequency range include supermassive<br />
black holes and galactic binary stars. LISA consists of three identical<br />
spacecraft separated by 5 million kilometers carrying a total of six free<br />
flying test masses in heliocentric drag-free orbit. The fluctuations in<br />
separation between two of these test masses located in different satellites<br />
will be measured by laser interferometry with picometre precision.<br />
I will present a brief overview of the LISA mission with special emphasis<br />
on the laser interferometry, the research field at the Albert Einstein<br />
Institute.<br />
Zeit: Montag 14:00–16:00 Raum: 3H<br />
Q 4.1 Mo 14:00 3H<br />
Yb-Faserverstärker bei Wellenlängen abseits des<br />
Verstärkungs-Maximums — •Mathias Sinther, Hanne Beck,<br />
Sergej Molleker und Thomas Walther — TU Darmstadt, Institut<br />
für Angewandte Physik, Schlossgartenstr. 7, D-64289 Darmstadt<br />
Neben Yb-Faserlasern erfreuen sich auch Yb-dotierte Faserverstärker<br />
in letzter Zeit immer größerer Beliebtheit. In diesem Beitrag werden<br />
schmalbandige Yb-Faserverstärker mit Leistungen im Watt-Bereich<br />
präsentiert, deren Betriebswellenlängen sowohl unterhalb als auch<br />
oberhalb des Verstärkungsmaximums liegen.<br />
Q 4.2 Mo 14:15 3H<br />
Ein ns-Titan:Saphir Laser als nahezu universelle Lichtquelle<br />
— •Daniel Depenheuer, Henning Gläßer und Thomas Walther<br />
— TU Darmstadt, Institut für angewandte Physik, Laser- und Quantenoptik,<br />
Schlossgartenstr. 7, 64297 Darmstadt<br />
Wir stellen ein gepulstes Titan:Saphir Lasersystem vor, das durch<br />
nichtlineare Frequenzkonversionsprozesse den Spektralbereich von<br />
190nm bis 6300nm nahezu lückenlos abdecken kann. Durch injectionseeding<br />
werden fourierlimitierte Pulse erreicht. Aufgrund seiner kompakten<br />
Bauweise bietet das System sehr stabile und kurze Buildup<br />
Zeiten. Dies ermöglicht nicht nur Summen- und Differenzfrequenzmischen<br />
des Titan:Saphir Pulses mit dem Pumppuls, sondern auch die<br />
Synchronisation mehrerer Lasersysteme. Die nichtlinearen Konversionsprozesse<br />
sind aufgrund der sehr hohen (spektralen) Energiedichte<br />
äußerst effizient.<br />
Q 4.3 Mo 14:30 3H
Fachverband Quantenoptik und Photonik (Q) Montag<br />
Theoretische und experimentelle Limits von modengekoppelten<br />
Scheibenlasern mit Cavity-Dumping — •Martin Siegel,<br />
Guido Palmer, Nils Pfullmann, Andy Steinmann und Uwe<br />
Morgner — Institut für Quantenoptik, Leibniz Universität Hannover,<br />
Deutschland<br />
Mittels modengekoppelter Scheibenlaser mit Cavity-Dumping können<br />
Pulsenergien von drei Mikrojoule bei Repetitionsraten von einem Megahertz<br />
erreicht werden [1]. Dies macht sie zu interessanten Strahlquellen<br />
für viele Anwendungen in der Mikromaterialbearbeitung, der<br />
nichtlinearen Spektroskopie sowie der Augenchirurgie.<br />
Numerische Simulationen erlauben die Modellierung der dynamischen<br />
Eigenschaften solcher Systeme und ermöglichen damit ein besseres<br />
Verständnis des Zusammenspiels der verschiedenen Designparameter.<br />
Im Vergleich mit jüngst veröffentlichten experimentellen Daten<br />
können so prinzipielle Limitierungen eines solchen Laserdesigns<br />
identifiziert und erklärt werden. Aufbauend hierauf werden Optimierungsmöglichkeiten<br />
sowie Abschätzungen über zukünftig erreichbare<br />
Pulsenergien vorgestellt [2].<br />
[1] G. Palmer, et al. Opt. Letters 32, 1593 (2007)<br />
[2] M. Siegel, et. al. Opt. Express accepted (2007)<br />
Q 4.4 Mo 14:45 3H<br />
Passiv modengekoppelter Yb:KYW-Oszillator mit Cavity-<br />
Dumping im positivem Dispersionsregime — Guido Palmer,<br />
Moritz Emons, Martin Siegel, Andy Steinmann und •Uwe Morgner<br />
— Institut für Quantenoptik, Leibniz Universität Hannover, Welfengarten<br />
1, 30167 Hannover<br />
Viele Anwendungen, wie z.B. die nichtlineare Spektroskopie oder die<br />
Laser-Mikromaterialbearbeitung profitieren von hochenergetischen Laserpulsen<br />
im Femtosekunden-Regime mit MHz-Repetitionsraten. Der<br />
Einsatz von passiv modengekoppelten Lasern mit Cavity-Dumping<br />
ermöglicht die Erschließung des Mikrojoule-Bereiches mit Oszillatoren<br />
ohne weitere Verstärkungseinheiten. Mit der Leistungsskalierung solitär<br />
modengekoppelter Systeme geht ein deutlicher Anstieg der Kerr-<br />
Nichtlinearitäten insbesondere in der Luft im Resonator einher. Mit<br />
Hilfe der Modenkopplung im positiven Dispersionsregime konnte bereits<br />
für Ti:Saphir-basierte Systeme eine deutliche Reduktion der resonatorinternen<br />
Spitzenleistung bei Mikrojoule-Energien erreicht werden.<br />
Wir präsentieren einen auf Yb:KY(WO4)2 basierenden, direkt<br />
diodengepumpten Oszillator mit Cavity-Dumping, der im positiven<br />
Dispersionsbereich betrieben wird. Der durch einen sättigbaren Absorber<br />
modengekoppelte Laser emittiert Pulsenergien über 2 Mikrojoule<br />
bei einer Repetitionsrate von 1 MHz und einer Zentralwellenlänge von<br />
1030 nm. Im Vergleich zum solitären Betrieb (1,3 Mikrojoule) konnte<br />
dadurch eine deutliche Steigerung der Pulsenergie demonstriert werden.<br />
Die positiv gechirpten Pulse aus dem Oszillator werden durch eine<br />
Transmissionsgitterkonfiguration extern auf etwa 400 fs komprimiert.<br />
Q 4.5 Mo 15:00 3H<br />
Faser-basierte Nachverstärkung eines Yb:KYW Lasers mit<br />
Cavity-Dumping — •Andy Steinmann, Moritz Emons, Guido<br />
Palmer und Uwe Morgner — Institut für Quantenoptik, Leibniz<br />
Universität Hannover<br />
Lasersysteme, die Femtosekundenpulse mit Energien im Mikrojoulebereich<br />
bei MHz-Repetitionsraten emittieren, sind ideale Lichtquellen<br />
für eine Vielzahl von Anwendungen wie z.B. dem Wellenleiterschreiben<br />
in transparenten Materialien, der Mikromaterialbearbeitung, der<br />
Multiphotonen-Mikroskopie oder der nichtlinearen Spektroskopie. Diodengepumpte<br />
Yb:KYW Laser mit elektrooptischem Cavity-Dumping<br />
ermöglichen Pulsenergien über einem Mikrojoule bei Wiederholraten<br />
von einem MHz.<br />
Wir präsentieren ein Faser-basiertes CPA-System, das durch externe<br />
Nachverstärkung eine weitere deutliche Steigerung der Pulsenergie<br />
ermöglicht. Zum Strecken der Pulse dient dabei ein Gitterstretcher,<br />
der aus einem einzelnen Gitter und zwei konzentrischen Spiegeln besteht,<br />
als Verstärkerfaser kommt eine 50 cm lange Yb-dotierte rodtype-Faser<br />
zum Einsatz, und als Kompressor wird ein Paar Quarz-<br />
Transmissionsgitter verwendet.<br />
Auf diese Weise können 420 fs Pulse mit einer Pulsenergie von 9 µJ<br />
realisiert werden. Das System ist eine ideale Pumpquelle für optisch<br />
parametrische Verstärker mit MHz-Repetitionsraten.<br />
Q 4.6 Mo 15:15 3H<br />
Photophysical Characterisation of Pyrromethene 597 Laser<br />
Dye in Cross-linked Silicon-containing Organic Copolymers<br />
— •Amit Tyagi 1 , David del Agua 2 , Alfons Penzkofer 1 , O.<br />
García 2 , Robert Sastre 2 , Angel Costela 3 , and Immaculata<br />
García-Moreno 3 — 1 Institut II - Physik, Universität Regensburg, D-<br />
93040 Regensburg — 2 Instituto de Ciencia y Tecnología de Polímeros,<br />
CSIC, Juan de la Cierva 3, 28006 Madrid, Spain — 3 Instituto de<br />
Química Física ”Rocasolano”, CSIC, Serrano 119, 28006 Madrid, Spain<br />
Dipyrromethene-BF2 PM597 dye-doped copolymers resembling<br />
inorganic-organic hybrids were characterized towards their application<br />
as solid-state laser rods. The inorganic function was entered by<br />
the silicon containing constituent 3-(trimethoxysilyl)propyl methacrylate<br />
(TMSPMA). The organic constituents are monomers with one<br />
[methyl methacrylate (MMA)], two [ethylene glycol dimethacrylate<br />
(EGDMA)], three [pentaerythriol triacrylate (PETA)], and four<br />
[pentaerythriol tetraacrylate (PETRA)] polymerizable groups. The<br />
thermo-mechanical stability of the samples increased with the number<br />
of cross-linking groups (studied by thermogravimetry and differential<br />
scanning calorimetry), while the optical and lasing parameters<br />
were found to be similarly good for all investigated silicon containing<br />
samples (fluorescence quantum yield around 60 %, excited-state<br />
absorption less than 10 % of ground-state absorption, more than 3<br />
million excitation cycles before degradation).<br />
Q 4.7 Mo 15:30 3H<br />
Frequency stabilized pulsed dual rod Nd:YAG ring-oscillator<br />
following a Pound-Drever-Hall method — •Martin Ostermeyer<br />
and Alexander Sträßer — Universität Potsdam, Am neuen<br />
Palais 10, 14469 Potsdam<br />
An injection seeded pulsed Nd:YAG ring laser oscillator has been setup<br />
for single frequency operation. A monolith ring-laser (NPRO) serves as<br />
seed laser. It has been frequency stabilized following a radio-frequencysideband<br />
scheme. This dual rod oscillator emits pulses with 23 ns<br />
duration and 20 mJ energy. The beam quality is almost diffraction<br />
limited (M2 = 1.2). The frequency stability was characterized with<br />
a heterodyne method to 1.0 MHz (rms) [1]. This oscillator will serve<br />
as front-end for a series of Lidar devices for spectrally sensitive measurements.<br />
The ring resonator comes up with a less critical isolation<br />
from the seed laser, a wider stability range, and a wider separation of<br />
the longitudinal modes compared to a linear standing wave resonator.<br />
The Pound-Drever-Hall-method (PDH) supplies an unambiguous error<br />
signal for the length control of the cavity. However there are time<br />
dependent length and phase changes in the resonator due to time dependent<br />
pumping and Q-switching. They pose a challenge for reaching<br />
a fast and accurate length control of the resonator.<br />
Q 4.8 Mo 15:45 3H<br />
Resonatorinterne Frequenzverdopplung von GaN-laserdiodengepumpten<br />
cw-Pr:LiLuF4-Lasern — •Nils-Owe Hansen,<br />
André Richter, Nicky Thilmann, Ernst Heumann und Günter<br />
Huber — Institut für Laser-Physik, Luruper Chaussee 149, 22761<br />
Hamburg<br />
Es wird erstmals über laserdiodengepumpte Praseodym(Pr)-Laser berichtet,<br />
die resonatorintern frequenzverdoppelt sind und UV-Licht bei<br />
320 nm emittieren. Die verwendeten LiLuF4(LLF)-Laserkristalle unterschiedlicher<br />
Länge sind unbeschichtet und besitzen eine Praseodymkonzentration<br />
von 0,45 at.%. Als Pumpquellen wurden zwei GaN-<br />
Laserdioden mit einer geeigneten Emissionswellenlänge von 444 nm<br />
und Ausgangsleistungen von je 500 mW eingesetzt. Auf der Grundwellenlänge<br />
des Pr-Lasers konnten bei einer absorbierten Pumpleistung<br />
von 650 mW und 3,6% Auskopplung maximal 208 mW Laserleistung<br />
erzielt werden. Die resonatorinterne Frequenzverdopplung erfolgt<br />
durch LiB3O5 (LBO) unter Typ I Phasenanpassung im einfach gefalteten<br />
Resonator. Die Länge des verwendeten LBO-Kristalls für die<br />
ersten Experimente bei reduzierter Pumpleistung betrug 8 mm. Damit<br />
konnte eine maximale UV-Leistung von 14,3 mW bei einer absorbierten<br />
Pumpleistung von 275 mW erreicht werden. Das entspricht einer Umwandlungseffizienz<br />
von 19% von der Fundamentalen in die frequenzverdoppelte<br />
Strahlung und einem optisch-optischen Wirkungsgrad von<br />
5%. Im Vortrag wird auch über Ergebnisse aus Experimenten zur Leistungsskalierung<br />
berichtet.
Fachverband Quantenoptik und Photonik (Q) Montag<br />
Q 5: Quantengase II [gemeinsam mit A]<br />
Zeit: Montag 16:30–19:00 Raum: 1A<br />
Hauptvortrag Q 5.1 Mo 16:30 1A<br />
Dynamical quantum phase transitions — •Ralf Schuetzhold<br />
— TU Dresden, Institut fuer Theoretische Physik<br />
A sweep through a quantum phase transition by means of a timedependent<br />
external parameter entails non-equlilibrium phenomena<br />
(break-down of adiabaticity): Since the energy gap vanishes at the<br />
critical point, the response time diverges and thus the external timedependence<br />
drives the system away from the ground state (assuming<br />
zero temperature initially). In this way, the initial quantum fluctuations<br />
are amplified and may become observable. By means of several<br />
examples based on ultra-cold atoms, possible effects of these amplified<br />
quantum fluctuations are studied and universal features (such as<br />
freezing) are discussed.<br />
Gruppenbericht Q 5.2 Mo 17:00 1A<br />
Bose-Einstein condensates in presence of defects and disorder.<br />
— •Tobias Paul, Mathias Albert, Nicolas Pavloff, and<br />
Patricio Leboeuf — Laboratoire de Physique Théorique et Modèles<br />
Statistiques, Universite Paris Sud, F-91405 Orsay<br />
Superfluidity and Anderson localization are genuine many-body manifestations<br />
of quantum coherence which are nowadays revisited in dilute<br />
Bose gases. Recent theoretical results obtained in our group in Orsay<br />
are reviewed: First, we study the coherent flow of interacting Bosecondensed<br />
atoms in presence of a single defect or an extended disorder<br />
potential. We discuss the different regimes of quantum transport induced<br />
by a variation of the condensate flow-velocity v: We point out<br />
that for v much smaller than the sound velocity c the flow is in general<br />
superfluid, whereas beyond a critical velocity the formation of solitons<br />
and shockwaves sets on. For v ≫ c, a regime of quasi-dissipationless<br />
transport is found. There, for long disorder samples, the system enters<br />
an Anderson localized phase.<br />
In a second step, we consider the experimental relevant case where<br />
a harmonic trap is superimposed to the defect potential. We obtain<br />
a global picture characterizing the dynamical properties of the dipole<br />
oscillations where we recover the different regimes of quantum transport<br />
introduced in the first part of the talk. We discuss our findings in<br />
the context of recent experiments [1,2] and address the question under<br />
which circumstances Anderson localization could be observed.<br />
[1] J. E. Lye et al., Phys. Rev. A 75, 061603 (2007)<br />
[2] P. Engels and C. Atherton, Phys. Rev. Lett. 99, 160405 (2007)<br />
Gruppenbericht Q 5.3 Mo 17:30 1A<br />
Tailoring quasi-particles in ultra-cold matter: soliton oscillations,<br />
longest lifetimes and fillings. — •Christoph Becker 1 ,<br />
Parvis Soltan-Panahi 1 , Simon Stellmer 1 , Sören Dörscher 1 , Eva-<br />
Maria Richter 1 , Mathis Baumert 1 , Jochen Kronjäger 1 , Kai<br />
Bongs 1,2 , and Klaus Sengstock 1 — 1 Institut für Laser-Physik,<br />
Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg —<br />
2 Midlands Centre for Ultracold Atoms, University of Birmingham,<br />
Edgbaston, Birmingham B15 2TT, UK<br />
Solitons are distinguishing features of many non-linear physical systems.<br />
Stabilized by a balance between spreading due to dispersion<br />
and focusing mediated by non-linearities, solitons emerge as nonspreading<br />
wavepackets. BEC’s provide fascinating possibilities concerning<br />
quantum-state engineering, necessary for the creation and observation<br />
of solitons. Dark solitons appear as dips in the density distribution<br />
and have so far been produced in few experiments limited by<br />
very short lifetimes.<br />
Here we report on the generation of dark solitons in an optically<br />
Q 6: Quanteninformation (Atome und Ionen II)<br />
trapped 87 Rb BEC with an extraordinary life-time of up to several<br />
seconds. For the first time, we observe oscillations of dark solitons<br />
with a characteristic frequency in excellent agreement with theoretical<br />
predictions. By filling the dark soliton with atoms in another hyperfine<br />
state we are able to create dark-bright solitons with a substantially<br />
greater oscillation period.<br />
The experimental results are combined with theoretical studies based<br />
on the Gross-Pitaevskii equation.<br />
Gruppenbericht Q 5.4 Mo 18:00 1A<br />
Strongly interacting Fermi gases in an optical lattice —<br />
•Henning Moritz 1 , Niels Strohmaier 1 , Robert Jördens 1 , Kenneth<br />
J. Günter 1,2 , Yosuke Takasu 1,3 , Michael Köhl 1,4 , and<br />
Tilman Esslinger 1 — 1 Institute of Quantum Electronics, ETH<br />
Zürich, Hönggerberg, CH-8093 Zürich, Switzerland — 2 Department<br />
for Electronic Science and Engineering, Kyoto University, Japan —<br />
3 Cavendish Laboratory, University of Cambridge, Cambridge CB3<br />
0HE, United Kingdom — 4 Laboratoire Kastler Brossel, 24, rue<br />
Lhomond, 75005 Paris<br />
When fermionic atoms are placed in the periodic potential of an optical<br />
lattice, they behave very much like electrons in a solid. However,<br />
the properties of this synthetic material can be changed at will. Here,<br />
we report on the experimental realization and investigation of strongly<br />
interacting Fermi gases with tunable interactions.<br />
By changing the attractive interaction strength we are able to control<br />
the transport properties: while dipole oscillations are observed for<br />
a non-interacting gas, the cloud relaxes very slowly to its equilibrium<br />
position for strong attractive interactions. We suggest an interpretation<br />
in the framework of the Hubbard model including external confinement.<br />
The strong attraction induces bound states, which can only<br />
tunnel very slowly via second order processes.<br />
Furthermore, experiments on the behavior of repulsive Fermi gases<br />
will be presented.<br />
Gruppenbericht Q 5.5 Mo 18:30 1A<br />
First Bose-Einstein Condensate in microgravity — •Tim van<br />
Zoest 1 , Wojtek Lewoczko-Adamczyk 2 , and Anika Vogel 3 for<br />
the QUANTUS-Collaboration — 1 Institut für Quantenoptik, Leibniz-<br />
Universität Hannover — 2 Institut für Physik, Humboldt Universität<br />
Berlin — 3 Institut für Laserphysik, Universität Hamburg<br />
Promising techniques for fundamental tests in the quantum domain<br />
are matter-wave sensors based on cold atoms, which use atoms as<br />
unperturbed microscopic test bodies for measuring inertial forces or<br />
as frequency references. Microgravity is of high relevance for matterwave<br />
interferometers and experiments with quantum matter, like Bose-<br />
Einstein-condensates , as it permits the extension of an unperturbed<br />
free fall in a low-noise environment.<br />
The project QUANTUS is a feasibility study of a compact, robust<br />
and mobile experiment for the creation of a BEC in a weightlessness<br />
environment at the droptower in Bremen (ZARM). The experiment<br />
has to be implemented in a dropcapsule with a length of 215 cm and<br />
60 cm diameter and has to withstand forces up to 50 g (1). The experimental<br />
setup as well as the latest results, the realization of the first<br />
weightlessness Bose-Einstein Condensate with longest time of flights<br />
and the adiabatic expansion to very shallow traps (less than 20 Hz),<br />
are described. In future, the apparatus will serve as an experimental<br />
platform to investigate various aspects of ultra-cold gases in microgravity<br />
like adiabatic release, extended coherent evolution and features of<br />
atom lasers.<br />
(1) A. Vogel et al., Appl. Phys. B, 84, 04 (2006)<br />
Zeit: Montag 16:30–19:00 Raum: 1B<br />
Q 6.1 Mo 16:30 1B<br />
A table-top experiment on the early universe — •Hector<br />
Schmitz, Axel Friedenauer, Jan Glückert, Lutz Petersen, Steffen<br />
Kahra, Günter Leschhorn, Christian Schneider, Robert<br />
Matjesch, and Tobias Schätz — MPQ Garching<br />
Having a look at the conditions of the early universe isn’t easy. Even<br />
state of the art accellerators are not able to create the extremely high<br />
energies gouverning the very first cosmological period in which quantum<br />
phenomena become crucial in the development of space and time.<br />
Some details might be accessible for investigations in an analog way,
Fachverband Quantenoptik und Photonik (Q) Montag<br />
namely the creation of new particle-antiparticle pairs within the violent<br />
days of the inflationary epoch of the universe. Following calculations<br />
[1,2] an analog vaccuum quantum processes that might have lead to<br />
the creation of new pairs of photons and other particles during a phase<br />
of rapid expansion should create pairs of phonons in an ion crystal if<br />
the confining potential is changed exponentially.<br />
Here we present and discuss the realisation of this simulation in a<br />
linear Paul trap. A single ion is cooled via sideband cooling down to the<br />
motional ground state – mimicing the ground state of the vaccuum.<br />
Then the confining potential is lowered slowly. While the potential<br />
raises nonadiabatically back to its initial strength, pairs of phonons<br />
will show up, whose signature is discriminated form heating processes.<br />
[1] R. Schützhold, T. Schätz et. al., Phys. Rev. Lett. 99, 201301 (2007)<br />
[2] ”Quantum quirk may reveal early universe”, New Scientist 2607,<br />
p. 11 (2007)<br />
Q 6.2 Mo 16:45 1B<br />
Experimental techniques for quantum information processing<br />
with trapped 43 Ca + ions — •Gerhard Kirchmair 1,2 , Jan<br />
Benhelm 1,2 , René Gerritsma 1,2 , Florian Zähringer 1,2 , Christian<br />
Roos 1,2 , and Rainer Blatt 1,2 — 1 Institut für Experimentalphysik,<br />
Universität Innsbruck, Österreich — 2 Institut für Quantenoptik und<br />
Quanteninformation, Österreichische Akademie der Wissenschaften,<br />
Innsbruck, Österreich<br />
We demonstrate the complete set of experimental techniques that are<br />
necessary to employ the isotope 43 Ca + for quantum information processing.<br />
Ground state cooling, robust state initialization and efficient<br />
read out are experimentally realized on a single 43 Ca + ion. With microwave<br />
transitions, we find the coherence time for storing quantum<br />
information in the hyperfine qubit (F = 4, mF = 0 ↔ F = 3, mF = 0)<br />
to be many seconds. Phase coherence during the interaction with a<br />
Raman laser is sustained for more than 200 ms. All techniques are<br />
also applicable to ion strings and the ability to move the ions makes<br />
individual addressing possible. We show that the motional coherence<br />
of a single ion is preserved during the shuttling process.<br />
Q 6.3 Mo 17:00 1B<br />
Realization of decoherence-free ion trap quantum computation<br />
— •Kihwan Kim 1 , Thomas Monz 1 , Alessandro Villar 2 ,<br />
Philipp Schindler 1 , Michael Chwalla 1 , Mark Riebe 1 , Markus<br />
Hennrich 1 , Wolfgang Hänsel 1 , and Rainer Blatt 1,2 — 1 Institut<br />
für Experimentalphysik, Universität Innsbruck, Austria — 2 Institut<br />
für Quantenoptik und Quanteninformation, Österreichische Akademie<br />
der Wissenschaften, Austria<br />
Quantum computation is limited by decoherence from technical noise<br />
and coupling of the qubits to the environment. However, certain states<br />
were shown to be protected from decoherence due to their symmetry<br />
[1]. These states form a decoherence-free subspace (DFS) of the<br />
Hilbert space. Using the DFS as a robust computational space will<br />
help to realize large scale quantum computing. In this talk we show<br />
the first realization of a universal set of gate operations in a DFS with<br />
ion strings. We use trapped 40 Ca ions and store quantum information<br />
in the ion’s electronic states S 1/2 and D 5/2. A DFS is formed by the<br />
two states |SD〉 and |DS〉 which are used as logical qubits |0L〉 and<br />
|1L〉. In this DFS, single-qubit rotations are realized using a Mølmer-<br />
Sørensen gate between the two ions of the logical qubit. For two-qubit<br />
operations between logical qubits a σz-type geometric phase gate is<br />
applied to neighbouring ions of two adjacent logical qubits [2]. We obtain<br />
fidelities of around 94% for a single qubit π/2-rotation and around<br />
75% for a CNOT gate in DFS.<br />
[1] D. Kielpinski et al., Nature 417, 709 (2002).<br />
[2] L. Aolita et al., Phys. Rev. A 75, 052337 (2007).<br />
Q 6.4 Mo 17:15 1B<br />
Optimised particle transport in a potential well — •Michael<br />
Murphy and Tommaso Calarco — Inst. f. Quanteninformationsverarbeitung,<br />
Ulm, D<br />
We analyse a quantum system with which we require non-adiabatic<br />
transport of a specified quantum state. We first consider analytically<br />
the situation of a 1-d harmonic potential confining a particle in a given<br />
quantum state, corresponding to the motional states of bound particles<br />
such as ions in a microtrap, or atoms in an optical lattice. We<br />
show analytic solutions exist for the transport function such that perfect<br />
transport is achieved in an arbitrary time, by which we mean that<br />
given an initial quantum state, the final state is the same as the initial<br />
state but displaced by our transport distance, and the state has<br />
evolved only as one would have found in a static harmonic potential.<br />
We also show that the system is robust against a class of distorting<br />
functions that describe homogeneous broadening. Furthermore, we apply<br />
Optimal Control Theory to optimise the transport function when<br />
the system is coupled to the environment.<br />
Q 6.5 Mo 17:30 1B<br />
Nichtadiabatischer Transport von Ionen in einer segmentierten,<br />
linearen Paulfalle in Leiterplattentechnologie —<br />
•Gerhard Huber, Thomas Deuschle, Wolfgang Schnitzler,<br />
Max Hettrich, Rainer Reichle, Kilian Singer und Ferdinand<br />
Schmidt-Kaler — Universität Ulm, Institut für Quanteninformationsverarbeitung,<br />
Albert-Einstein-Allee 11, 89069 Ulm<br />
Wir beschreiben die Konstruktion und den Betrieb einer segmentierten,<br />
linearen Paulfalle, gefertigt in Leiterplattentechnologie mit einer<br />
Segmentbreite von 500 µm [1]. Um die Eignung dieser Technologie<br />
zum Fangen und Manipulieren geladener Teilchen zu demonstrieren,<br />
speichern und laserkühlen wir Kristalle aus einzelnen 40 Ca + -Ionen.<br />
Die gemessenen radialen und axialen Fallenfrequenzen stimmen bis auf<br />
wenige Prozent mit den durch numerische Rechnungen vorhergesagten<br />
Werten überein.<br />
Um die Vielseitigkeit und Verlässligkeit dieser Fallentechonologie zu<br />
demonstrieren, untersuchen wir den Transport einzelner Ionen entlang<br />
der Fallenachse über eine Distanz von 2 mm hin und zurück. Die durchgeführten<br />
Experimente ergeben hohe Erfolgsraten auch im Bereich sehr<br />
schneller, nichtadiabatischer Transporte, die nur noch wenige axiale<br />
Oszillationsperioden des Ions dauern. Wir untersuchen in numerischen<br />
Simulationen und experimentell die durch solche schnellen Transporte<br />
erzeugte Vibrationsanregung des Ions.<br />
[1] G. Huber et al., arXiv:0711.2947v1<br />
Q 6.6 Mo 17:45 1B<br />
Efficient coupling of light to a single molecule and the observation<br />
of its fluorescence Mollow triplet — •Martin Pototschnig,<br />
Gert Wrigge, Ilja Gerhardt, Jaesuk Hwang, Lutz<br />
Petersen, and Vahid Sandoghdar — Laboratory for Physical Chemistry,<br />
ETH Zurich, CH-8093 Zurich, Switzerland<br />
Dye molecules in organic matrices are solid-state quantum emitters<br />
that can have lifetime limited linewidths at temperatures below 2K.<br />
Single molecules in such systems have been conventionally detected<br />
with fluorescence excitation spectroscopy, where the molecule is excited<br />
via its narrow zero-phonon line and its Stokes-shifted emission is<br />
detected. We report here on the coherent detection of a single molecule<br />
in transmission. Our experiments in the near- [1,2] and far-field [3] directly<br />
show between 5 and 12% dip on the transmission of a laser<br />
beam without using any noise suppression methods such as lock-in detection.<br />
Our efficient coupling of light to a single molecule has allowed<br />
us to study its resonance fluorescence over 9 orders of magnitude. We<br />
will show the power dependent coherent scattering and the first direct<br />
measurement of the Mollow fluorescence triplet in a solid-state system<br />
[3]. In the weak excitation regime we show that it is possible to detect<br />
a single molecule by using excitation powers below a femtoWatt.<br />
The efficient coupling combined with the coherent nature of extinction<br />
detection pave the way for further fundamental quantum optical<br />
experiments. [1]I.Gerhardt et. al., PRL 98,033601(2007). [2]I.Gerhardt<br />
et. al., OL 32,1420(2007). [3]G.Wrigge et. al., arXiv:0707.3398 to appear<br />
in Nature Physics.<br />
Q 6.7 Mo 18:00 1B<br />
Erzeugung zweidimensionaler Cluster-Zustände mit gespeicherten<br />
Ionen — •Harald Wunderlich und Christof Wunderlich<br />
— Fachbereich Physik, Universität Siegen, 57068<br />
Cluster-Zustände bilden die Grundlage für den sogenannten One-<br />
Way Quantum Computer [1]. Die zu Grunde liegenden Cluster<br />
können in unterschiedlichen Dimensionen existieren. Zur Realisierung<br />
eines universellen Satzes von effizienten Quanten-Gattern mit<br />
dem One-Way Quantum Computer werden mindestens zwei Dimensionen<br />
benötigt. Wir zeigen, dass die Erzeugung von zweidimensionalen<br />
Cluster-Zuständen mit Ionen, welche in einem linearen elektrodynamischen<br />
Käfig gespeichert werden, effizient möglich ist, wenn diese<br />
über eine, durch ein zusätzliches Magnetfeld induzierte Spin-Spin-<br />
Wechselwirkung gekoppelt sind [2] . Ein beliebiger zweidimensionaler<br />
n × m-Cluster kann durch einen n × 2-Cluster simuliert werden. Es<br />
wird ein Verfahren entwickelt, um solche n × 2-Cluster zu generieren,<br />
welches lediglich auf einem linearen Cluster-Zustand und Selective-<br />
Recoupling-Sequenzen mit vier Ionen beruht. Der experimentelle Aufwand<br />
zur Realisierung eines zweidimensionalen Clusters wächst nach<br />
diesem Schema lediglich linear mit der Anzahl der Ionen.
Fachverband Quantenoptik und Photonik (Q) Montag<br />
[1] R. Raussendorf, H. J. Briegel, Phys. Rev. Lett. 86, 5188-5191<br />
(2001).<br />
[2] Chr. Wunderlich, in Laser Physics at the Limit (Springer, Heidelberg,<br />
2002), p. 261; auch quant-ph/0111158.<br />
Q 6.8 Mo 18:15 1B<br />
A quantum memory of light in nuclear spins of a quantum<br />
dot — •Heike Schwager, Geza Giedke, and Ignacio Cirac — Max-<br />
Planck Institut für Quantenoptik, 85748 Garching<br />
A quantum memory is an essential building block for quantum information<br />
and communication. Nuclear spins have long decoherence times<br />
and are thus a good candidate for a quantum memory.<br />
We couple the field of an optical microcavity to the polarized nuclear<br />
spins of a charged quantum dot by a detuned Raman process. Eliminating<br />
the trion, we show that STIRAP allows to map the state of the<br />
cavity field to the nuclei. Similar techniques can be used to generate<br />
two-mode squeezed states of the nuclear spin-cavity system, enabling<br />
e.g. a light matter interface through teleportation.<br />
Q 6.9 Mo 18:30 1B<br />
Gauss sum factorization with cold atoms — •Michael<br />
Gilowski, Thijs Wendrich, Christian Schubert, Ernst M. Rasel,<br />
and Wolfgang Ertmer — Institut für Quantenoptik, Leibniz Universität<br />
Hannover<br />
A factorization scheme taking advantage of the periodicity properties<br />
of Gauss sums has been proposed [1] and recently verified by two<br />
NMR-experiments [2] and one experiment based on short laser pulses<br />
[3]. In the present contribution we report the first implementation of<br />
a Gauss sum factorization based on matter-wave interferometry with<br />
cold rubidium atoms [4].<br />
The implementation of the Gauss sums is performed by applying a<br />
sequence of light pulses which imprints on a two-level quantum system<br />
a sequence of well-defined phases. For appropriately chosen pulses<br />
the excitation probability takes the form of a Gauss sum. With this<br />
technique we factor the number N=263193. In contrast to the Shor<br />
algorithm our method in the present form is based on classical atomic<br />
ensembles and does not take benefit of the parallel computing of quantum<br />
information. The experimental realization as well as the results of<br />
the factorization experiment will be presented. This work is supported<br />
by SFB 407 and the FINAQS cooperation of the European Union.<br />
[1] Clauser, et al. Phys. Rev. A 53, 4587 (1996) and Harter, et al.<br />
Phys. Rev. A 64, 012312 (2001) [2] Mehring, et al. Phys. Rev. Lett.<br />
98, 120502 (2007) and Mahesh, et al. Phys. Rev. A 75, 062303 (2007).<br />
[3] Bigourd, et al. Phys. Rev. Lett. in press. [4] Gilowski, et al. Phys.<br />
Rev. Lett. in press.<br />
Q 6.10 Mo 18:45 1B<br />
Efficiency of entanglement of distant atoms by projective<br />
measurement — Georgina Olivares Renteria 1 , Stefano<br />
Zippilli 1 , Giovanna Morigi 1 , Felix Rohde 2 , •Carsten Schuck 2 ,<br />
and Jürgen Eschner 2 — 1 Departament de Fisica, Universitat Autonoma<br />
de Barcelona, 08193 Bellaterra, Spain — 2 ICFO - Institut de<br />
CIencies Fotoniques, 08860 Castelldefels (Barcelona), Spain<br />
We compare the efficiency of two schemes for the preparation of entangled<br />
states of distant atoms proposed in [1,2]. In these proposals<br />
the atoms do not interact and the entanglement is realized by means<br />
of the measurement of the scattered field which project the two atoms<br />
into the desired state. We quantify the efficiency of the schemes using<br />
the fidelity between the state of the system after the detection of a<br />
photon and an ideal entangled state of the two atoms. In [1] the atoms<br />
interact with two optical cavities and the enhanced probability of emission<br />
into the cavities allows for high detection efficiency. This scheme<br />
is limited by the finite probability of emission of two photons. Thus,<br />
even under the assumption of perfect detection efficiency, the fidelity<br />
of the scheme never reaches unity. In [2] emission of two photons is<br />
suppressed by low excitation strength, but the detection efficiency is<br />
low since the atoms scatter into free space and only a small fraction<br />
of the photons is measured. In this case the fidelity is conditioned on<br />
single-photon detection and results to be higher. The comparison is<br />
quantitatively evaluated for an ongoing experiment with two distant<br />
trapped single Ca+ ions. [1] S. Bose, et al, Phys. Rev. Lett. 83, 5158<br />
(1999). [2] C. Cabrillo, et al, Phys. Rev. A 59, 1025 (1999).<br />
Q 7: Ultrakurze Pulse (Attosekundenphysik) [gemeinsam mit A und K]<br />
Zeit: Montag 16:30–18:15 Raum: 3C<br />
Hauptvortrag Q 7.1 Mo 16:30 3C<br />
Coherent Control with Shaped Attosecond Soft-X-Rays:<br />
Techniques and Application — •Thomas Pfeifer — Departments<br />
of Chemistry and Physics, University of California & Lawrence Berkeley<br />
National Laboratory, Berkeley, CA 94720, USA<br />
Recent progress in ultrafast laser technology enables the generation<br />
of soft-x-ray pulses down to ∼ 100 attoseconds in duration, thus allowing<br />
access to the unexplored realm of electron dynamics. On the<br />
other hand, coherent control of matter with shaped laser fields has<br />
reached its maturity with regard to controlling the relative motion of<br />
atoms (vibrations/phonons, phase transitions, molecular reactions and<br />
rotation). However, due to the lack of laser pulse shaping techniques<br />
in the soft-x-ray spectral region, coherent control has so far had only<br />
limited capability of controlling the electronic wavefunction directly,<br />
which is of fundamental importance to physics (multi-electronic correlation)<br />
and chemistry (bonding dynamics). In this talk, it will be<br />
shown how Coherent Control can be transferred to, and combined<br />
with Attosecond Science towards the goal of gaining comprehensive<br />
mastery of matter on the quantum scale. Experimental results, theoretical<br />
concepts, and simulations demonstrate the feasibility of using<br />
a) multicolor laser fields, b) phase-shaped laser pulses, and c) medium<br />
control in high-harmonic generation to enable shaping of pulses and<br />
pulse trains in the attosecond soft-x-ray domain. Also, the first experimental<br />
application of shaped coherent soft-x-rays towards the optimal<br />
control of electronic quantum processes (dissociative photoionization<br />
of SF6) will be presented.<br />
Q 7.2 Mo 17:00 3C<br />
Molecular orbital tomography using short laser pulses —<br />
•Elmar van der Zwan, Ciprian Chirila, and Manfred Lein —<br />
Institute for Physics, University of Kassel, Germany<br />
Recently a method to perform tomographic imaging of molecular orbitals<br />
using high-harmonic generation has been proposed [1]. The<br />
method is based on the simplification that the returning electron in the<br />
three-step model can be modeled as a plane wave. Orbitals of arbitrary<br />
symmetry can be reconstructed if one uses extremely short laser pulses<br />
that ensure the continuum wave packet recombines from one side only.<br />
We compare two different forms for the reconstruction, and introduce<br />
an error-reduction algorithm that can be used to optimize the results.<br />
One of the challenges of the scheme lies in the accurate determination<br />
of the continuum wave packet. We determine the continuum wave<br />
packet in the Lewenstein model, assuming that the molecular orbital<br />
is known, and compare this with various methods to determine the<br />
continuum wave packet without knowledge of the orbital.<br />
[1] J. Itatani, J. Levesque, D. Zeidler, H. Niikura, H. Pépin, J.C.<br />
Kieffer, P.B. Corkum and D.M. Villeneuve. Tomographic imaging of<br />
molecular orbitals. Nature 432, 867-871 (2004)<br />
Q 7.3 Mo 17:15 3C<br />
Dressing and high-order harmonic generation in small<br />
molecules — •Ciprian Chirila and Manfred Lein — Universität<br />
Kassel, Institute of Physics, Heinrich-Plett-Str. 40, 34132 Kassel, Germany<br />
The strong-field approximation was recently extended to take into account<br />
the effect of vibrational motion and laser-induced coupling of the<br />
Born-Oppenheimer states on high-harmonic generation in molecules.<br />
We present detailed calculations of the harmonic spectra in H2 and<br />
D2 for long laser wavelengths (2000 nm), comparing the effects of the<br />
dressing to the case of 800 nm. The main effect of dressing is an overall<br />
reduction of the harmonic generation and, at long wavelengths, a<br />
non-negligible change in the ratio of harmonic signals from different<br />
isotopes.<br />
Q 7.4 Mo 17:30 3C<br />
Extended Strong-Field Approximation including Collectivity<br />
— •Michael Ruggenthaler and Dieter Bauer — Max-Planck-
Fachverband Quantenoptik und Photonik (Q) Montag<br />
Institut für Kernphysik, Heidelberg<br />
High-order harmonic generation may often be treated within a single<br />
active electron picture using the so-called strong-field approximation<br />
(SFA) [1] to propagate the initial wave-function. However, if collective<br />
phenomena are to be included the standard SFA treatment will<br />
not suffice. Although the SFA may be extended via an extra term in<br />
the Hamiltonian accounting for the collective behavior of the multielectron<br />
system, there is no straightforward definition of this term.<br />
The problem can be reformulated in time-dependent densityfunctional<br />
theory [2,3] where the so-called Kohn-Sham orbitals are<br />
propagated such that total single-particle density is the same as those<br />
of the interacting system. The linear response of the density to the<br />
external potential gives rise to a time-dependent Hartree-exchangecorrelation<br />
potential which then can be used within the framework of<br />
the extended SFA.<br />
[1] W. Becker et al, Phys. Rev. A 56, 645 (1996)<br />
[2] E. Runge and E. K. U. Gross, Phys. Rev. Lett. 52, 997 (1984)<br />
[3] M. A. L. Marques et al, Time Dependent Density Functional Theory,<br />
Lect. Notes Phys. 706 (Springer, Heidelberg, 2006)<br />
Q 7.5 Mo 17:45 3C<br />
Formation of Amplitude and Phase during High Harmonic<br />
Generation — •Markus Gühr, Brian K. McFarland, Joe P. Farrell,<br />
and Philip H. Bucksbaum — Stanford PULSE Center, Stanford<br />
University and SLAC, California, USA<br />
High Harmonics of a laser field are generated during the interaction of<br />
an intense laser pulse with an atomic or molecular gas. The amplitude<br />
and phase of the harmonics contain information about the generation<br />
process and the symmetry of the electronic wave functions of the involved<br />
atoms or molecules [1].<br />
We measure the amplitude of high harmonics generated in N2 and<br />
Ar. Furthermore, we obtain the relative phase between the harmon-<br />
Q 8: Präzisionsmessungen und Metrologie II<br />
ics from N2 and Ar by interferometric measurements on mixtures of<br />
the two gases. We observe phase jumps at the 33rd and the 25th harmonic.<br />
The first is accompanied by an amplitude minimum in Ar and<br />
attributed to a Cooper minimum. The second is accompanied by an<br />
amplitude minimum and a linewidth broadening in N2. It results from<br />
the symmetry of the N2 highest occupied molecular orbital.<br />
The discussed phenomena have important implications for the amplitude<br />
and phase of attosecond pulses generated via high harmonic<br />
generation.<br />
[1] M. Gühr, B. K. McFarland, J. P. Farrell and P. H. Bucksbaum,<br />
J. Phys. B: At. Mol. Opt. Phys., 40, 3745-3755 (2007)<br />
Q 7.6 Mo 18:00 3C<br />
Enhancement of high-order harmonic generation by rare gas<br />
mixtures — •Mirko Prijatelj, Tobias Vockerodt, Daniel Steingrube,<br />
Uwe Morgner, and Milutin Kovacev — Institut für Quantenoptik,<br />
Leibniz Universität Hannover<br />
We study the enhancement of high-order harmonic generation (HHG)<br />
by rare gas mixtures. Our experiment confirms recent results mixing<br />
He and Xe atoms. The harmonics from Xe atoms enhance the observed<br />
yield from He atoms by about two orders of magnitude. Moreover<br />
the cut-off position is extended compared to the spectrum of pure<br />
He atoms. We report on the experimental parameter sensitivity of the<br />
enhancement process and show first results which indicate that the<br />
atomic state structure is an important prerequisite. Our investigation<br />
extends as well towards experimental conditions suited for low-energy<br />
pump pulses as for example mode-locked Ti:sapphire femtosecond oscillator<br />
pulses with MHz repetition rates. These conditions are interesting<br />
for generating harmonics either intracavity or directly from a<br />
femtosecond oscillator. This experimental approach promises to lead<br />
to a joint frontier of precision spectroscopy and ultrafast science by<br />
extending frequency comb technology into the XUV spectral region.<br />
Zeit: Montag 16:30–18:00 Raum: 3D<br />
Q 8.1 Mo 16:30 3D<br />
The SYRTE’s fountain clocks: towards 10 −16 accuracy —<br />
•Peter Rosenbusch, Sébastien Bize, Frédéric Chapelet, Jocelyne<br />
Guéna, Philippe Laurent, Daniele Rovera, Giorgio<br />
Santarelli, and André Clairon — SYRTE, Observatoire de Paris,<br />
FRANCE<br />
Today’s best microwave clocks are atomic fountains. About 10 9 atoms<br />
are laser cooled to 1µK and launched up vertically, where they pass,<br />
rising and falling, through a microwave cavity. This Ramsey interrogation<br />
leads to a 10 10 quality factor of the central fringe [S. Bize et al.,<br />
J. Phys. B vol. 38, S449 (2005)]. The SYRTE disposes of three fountain<br />
clocks, one of which uses Cs and Rb, operating quasi-continuously<br />
thanks to an interference-filter stabilised laser system [X. Baillard et<br />
al., Opt. Comm., vol. 266, 609 (2006)]. The fountains exhibit a relative<br />
accuracy of 4×10 −16 , making the second the best realised SI unit.<br />
Here, we present efforts to further decrease the uncertainty to 10 −16 .<br />
Additionally, measurements of the 87 Rb hyperfine transition and their<br />
relevance to possible variations of the fine structure constant α are<br />
presented.<br />
Q 8.2 Mo 16:45 3D<br />
Absolute frequency measurement of the 4s 2 S 1/2 ↔ 3d 2 D 5/2<br />
clock transition of a single 40 Ca + in a Paul trap — •Michael<br />
Chwalla 1 , Kihwan Kim 1 , Gerhard Kirchmair 2 , Mark Riebe 1 ,<br />
Thomas Monz 1 , Mark Riebe 1 , Philipp Schindler 1 , Alessandro<br />
Villar 2 , Christian F. Roos 2 , Wolfgang Hänsel 1 , Rainer<br />
Blatt 1,2 , Michel Abgrall 3 , Daniele Rovera 3 , and Philippe<br />
Laurent 3 — 1 Institut für Experimentalphysik, Universität Innsbruck,<br />
Techikerstr. 25, A-6020 Innsbruck — 2 Institut für Quantenoptik und<br />
Quanteninformation, Österreichische Akademie der Wissenschaften,<br />
Otto Hittmair-Platz 1, A-6020 Innsbruck — 3 SYRTE, Observatoire<br />
de Paris, 61 Av. de l’Observatoire, 75014 Paris, France<br />
We present an absolute frequency measurement of a single, trapped<br />
40 Ca + ion at the 10 −15 level, where a Cs referenced frequency comb is<br />
used to measure the frequency of the 4s 2 S 1/2 ↔ 3d 2 D 5/2 quadrupole<br />
transition at 411 042 129 776 396.2 ± 1.2 Hz. This is the most accurate<br />
measurement of Ca + at present. A careful analysis of the estimated<br />
systematic shifts is given as well as an outlook on future improvements,<br />
which are required to possibly exceed the current precision of Cs-based<br />
frequency standards.<br />
Q 8.3 Mo 17:00 3D<br />
Frequenzkamm-Spektroskopie des 1S-3S Übergangs in atomarem<br />
Wasserstoff – Statusreport — •Elisabeth Peters 1 , Sascha<br />
Reinhardt 1 , Scott Diddams 2 , Thomas Udem 1 und Theodor<br />
Hänsch 1 — 1 Max-Planck-Institut für Quantenoptik, Garching<br />
— 2 NIST, Boulder<br />
Das Wasserstoffatom ist ein einfaches Modellsystem, was uns erlaubt,<br />
fundamentale Theorien wie die QED gebundener Zustände, zu<br />
überprüfen. Für einen Test der QED werden die Rydbergkonstante<br />
und die Lambverschiebung aus experimentell gewonnenen Daten bestimmt.<br />
Dazu müssen mindestens zwei Übergangsfrequenzen mit einer<br />
hohen Genauigkeit gemessen werden.<br />
Einer der Frequenzen ist die bereits mit der relativen Genauigkeit von<br />
1.4 ∗ 10 −14 bekannte Frequenz des 1S-2S Übergangs in Wasserstoff.<br />
Als zweite Frequenz wollen wir die Übergangsfrequenz des 1S-3S zwei<br />
Photonenübergangs bei 205nm messen.<br />
Die für die Spektroskopie erforderliche Wellenlänge wird durch zweifache<br />
Frequenzverdopplung (SHG) des modengekoppelten Ti:Saphir Lasers<br />
erzeugt. Unter Verwendung eines modengekoppelten Lasers lassen<br />
sich höhere Ausgangsleistungen bei nichtlinearen Prozessen erzielen, in<br />
unserem Fall bis zu 50mW bei 205nm. Bei der Zweiphotonenspektroskopie<br />
tragen alle Moden des Frequenzkamms bei, der AC-Starkeffekt<br />
resultiert aus der mittleren Leistung und die Auflösung ist durch die<br />
Linienbreite einer Frequenzmode und nicht durch die Bandbreite des<br />
Lasers gegeben.<br />
Q 8.4 Mo 17:15 3D<br />
A mobile atom interferometer for high precision measurements<br />
of local gravity — •Malte Schmidt, Alexander Senger,<br />
Tais Gorkhover, Ulrich Eismann, Evgeny Kovalchuk, and<br />
Achim Peters — Humboldt Universität zu Berlin, Institut für Physik,<br />
Hausvogteiplatz 5-7, 10117 Berlin, Germany<br />
In recent years, matter wave interferometry has developed into a pow-
Fachverband Quantenoptik und Photonik (Q) Montag<br />
erful tool for the ultra precise measurement of accelerations and rotations.<br />
It is used in various laboratories for experiments in the fields of<br />
fundamental physics and metrology.<br />
We present a new design for a gravimeter based on atom interferometry<br />
which is optimized for mobility and mechanical stability. This<br />
setup will open up the possibility to perform on-site high precision<br />
measurements of local gravity. We report on the status of the project<br />
and its subsystems including a rack-mounted cooling and raman laser<br />
system.<br />
This gravimeter is developed within the FINAQS project, a collaboration<br />
of five European research groups that aims at developing new<br />
atomic quantum sensors.<br />
Q 8.5 Mo 17:30 3D<br />
Frequenzverdoppeltes Hochleistungs-Faserlasersystem zur<br />
Laserkühlung von Rubidium Atomen bei 780 nm — •Evgeny<br />
Kovalchuk und Achim Peters — Humboldt-Universität zu Berlin,<br />
Institut für Physik, Hausvogteiplatz 5-7, 10117 Berlin<br />
Wir stellen ein Dauerstrich Hochleistungs-Lasersystem vor, das speziell<br />
für die Laserkühlung von Rubidium Atomen im Rahmen des europäischen<br />
Kooperationsprojekts FINAQS für Anwendungen in der<br />
Atominterferometrie entwickelt wurde. Es basiert auf einem schmalbandigen<br />
durchstimmbaren External-Cavity Diodenlaser (ECDL) bei<br />
1560 nm, der in einem polarisationserhaltenen Erbium-Faserverstärker<br />
(Spektralbereich von 1545 nm bis 1565 nm) verstärkt wird. Die Ausgangsstrahlung<br />
mit einer Leistung von bis zu 15 W wird danach in<br />
einem periodisch gepolten Lithiumniobat Kristall (PPLN) frequenzverdoppelt.<br />
Die erreichte Laserleistung von mehr als 6 W bei 780 nm<br />
entspricht einer Konversionseffizienz von ca. 50 %. Durch optimierte<br />
Verdopplungskristalle mit besserer Qualität der Kristallpolung, in<br />
Kombination mit einer höheren Verstärkerleistung, sollten in Zukunft<br />
Q 9: Laserentwicklung (Halbleiterlaser)<br />
auch Ausgangsleistungen deutlich über 10 W realisierbar sein.<br />
Weiterhin diskutieren wir Möglichkeiten zur simultanen Erzeugung<br />
von zwei phasengelockten Ausgangsfrequenzen, zum Beispiel für Anwendungen<br />
als Raman-Beamsplitter in der Atominterferometrie.<br />
Q 8.6 Mo 17:45 3D<br />
Laserinterferometer für eine GRACE-Nachfolgemission —<br />
•Marina Dehne, Ben Sheard, Gerhard Heinzel und Kartsen<br />
Danzmann — Albert-Einstein-Institut Hannover, Max-Planck-Institut<br />
für Gravitationsphysik und Universität Hannover, Callinstr. 38, D-<br />
30167 Hannover<br />
Das Ziel einer zukünftigen GRACE Nachfolgemission wird es sein,<br />
das Erdgravitationsfeld mit einer höheren Auflösung aufzunehmen.<br />
Die beiden im Low-Earth Orbit (LEO) mit einem Abstand von 10 km<br />
hintereinander fliegenden identischen Satelliten reagieren empfindlich<br />
auf kleinste Änderungen in der Gravitationsbeschleunigung. Diese<br />
Längenänderungen im Frequenzbereich 1...100 mHz sollen von einem<br />
Laser-Interferometer mit nm-Präzision beobachtet werden.<br />
Für die Bereitstellung einer konstanten thermischen Umgebung, sowie<br />
um Einstrahlungen auf der optischen Achse zu vermeiden, stellt ein<br />
kreisförmiger sonnensynchroner Orbit (i = 96.78 ◦ ) die geeignete Wahl<br />
dar. Der Luftwiderstand in einem solchen Orbit ist signifikant und<br />
muss kompensiert werden. Für diesen Zweck ist die bereits für LISA<br />
Pathfinder entwickelte ”drag-free”Technologie geeignet.<br />
Das vorgeschlagene Interferometer benutzt weiterhin einige für LISA<br />
und LISA Pathfinder entwickelten Phasenauslesungs- und Regelungstechnologien.<br />
Im Vortrag wird ein mögliches Interferometer vorgestellt,<br />
welches die Anforderungen (2.5 nm/ √ Hz von 10 bis 100 mHz mit einem<br />
1/f-Anstieg zwischen 10 und 1 mHz) unter den gegebenen Randbedingungen<br />
erfüllen könnte.<br />
Zeit: Montag 16:30–19:00 Raum: 3H<br />
Q 9.1 Mo 16:30 3H<br />
Spektral breitbandige Diodenlaser zur Erzeugung energiereicher,<br />
ultrakurzer Pulse — •Thorsten Ulm, Florian Harth, Johannes<br />
L’huillier und Richard Wallenstein — Technische Universität<br />
Kaiserslautern, Fachbereich Physik, Erwin-Schrödinger-Straße 46,<br />
67663 Kaiserslautern<br />
Die Entwicklung neuartiger Hochleistungsverstärker mit über 1 W<br />
Ausgangsleistung im Pulsbetrieb und guter räumlicher Strahlqualität<br />
macht modengekoppelte Diodenlaser heute zu einer interessanten Alternative<br />
zu Festkörper-Strahlquellen wie z.B. Titan-Saphir-Lasern.<br />
Elektrisch gepumpte Diodenlaser eignen sich außerdem zum Aufbau<br />
miniaturisierter Strahlquellen.<br />
Das von uns realisierte passiv modengekoppelte Diodenlaser-MOPA-<br />
System erzeugt Pulse mit mehr als 4 nm spektraler Breite. Allein<br />
durch Kompensation des linearen Chirps können so 480 fs kurze Pulse<br />
erzeugt werden. Dabei wurden mittlere Leistungen von 740 mW<br />
und Pulsspitzenleistungen von 340 W erreicht. Zur Modenkopplung<br />
wurde ein in den Wellenleiter integrierter sättigbarer Absorber verwendet.<br />
Die sättigbaren Verluste lassen sich durch Anlegen einer DC-<br />
Gegenspannung einstellen und wurden im Hinblick auf die anschließende<br />
Verstärkung und Pulskompression optimiert. Die verwendeten<br />
Halbleiter-Bauelemente werden hinsichtlich ihrer Bandbreite, Ausgangsleistung,<br />
der zeitlichen und spektralen Pulsform sowie ihres Sättigungsverhaltens<br />
charakterisiert. Durch Modellierung der Gewinnsättigung<br />
im Wellenleiter konnte gezeigt werden, dass im Oszillator bereits<br />
bei einer geringen Rückkopplung von 20% Gewinnsättigung auftritt.<br />
Q 9.2 Mo 16:45 3H<br />
Kompaktes Diodenlasersystem mit variabler Repetitionsrate<br />
im MHz-Bereich — •Florian Harth, Thorsten Ulm, Johannes<br />
L’huillier und Richard Wallenstein — Technische Universität Kaiserslautern,<br />
Fachbereich Physik, Erwin-Schrödinger-Straße 46, 67663<br />
Kaiserslautern<br />
Kompakte, effiziente Strahlquellen auf Diodenlaserbasis mit einstellbarer<br />
Repetitionsrate und Pulsenergie sind für eine Vielzahl von Anwendungen<br />
wie z.B. der Mikromaterialbearbeitung von Interesse.<br />
Es wird ein System vorgestellt, das aus einem modengekoppelten Diodenlaser<br />
mit externem Resonator, einem nachgeschaltetem LiNbO3-<br />
Mach-Zehnder-Modulator und einem Yb-Faserverstärker besteht. Der<br />
Oszillator emittiert Impulse mit einer Impulslänge von 6 ps und einer<br />
Repetitionsrate von 500 MHz bei einer Wellenlänge von 1066 nm.<br />
Mit Hilfe des Modulators können einzelne Impulse oder auch Impuls-<br />
Bursts aus dem Pulszug des Oszillators ausgeschnitten werden. Die<br />
Impulsenergien der verstärkten Impulse betrugen 380 pJ, bei nur geringen<br />
Änderungen in der zeitlichen und spektralen Impulsform. Diese<br />
Impulsenergie ist ausreichend für die Verstärkung in nachfolgenden<br />
Hochleistungsverstärkern.<br />
Bei der gewählten Impulswiederholrate von 10 MHz bildete sich im<br />
Yb-Faserverstärker verstärkte Spontanemission (ASE) aus. Es werden<br />
Konzepte zur Unterdrückung der ASE vorgestellt.<br />
Q 9.3 Mo 17:00 3H<br />
Optimierung und Automatisierung eines ECDLs basierend<br />
auf einem Modell zur Modensprungdynamik — •Thorsten<br />
Führer und Thomas Walther — TU Darmstadt, Institut für Angewandte<br />
Physik, AG Laser und Quantenoptik, Schlossgartenstr. 7,<br />
D-64289 Darmstadt<br />
ECDLs finden in vielen Bereichen Anwendung, beispielsweise für<br />
Sensor-Applikationen oder in der Präzisionsspektroskopie. Dabei ist<br />
ein großer modensprungfreier Durchstimmbereich von Vorteil. Um diesen<br />
zu erreichen werden bei einem ECDL in Littrow-Konfiguration<br />
typischerweise sowohl die Position und der Winkel des Reflexionsgitters<br />
als auch der Strom durch die Laserdiode aufeinander abgestimmt<br />
variiert. Die manuelle Justage aller Parameter ist zeitaufwändig und<br />
schwierig. Darüberhinaus müssen diese Parameter aufgrund äußerer<br />
Störungen oft angepasst werden, um den modensprungfreien Betrieb<br />
aufrecht zu erhalten.<br />
Es wird ein Modell präsentiert, mit dem sich die Dynamik der Modensprünge<br />
als Funktion der freien Parameter beschreiben lässt. Basierend<br />
auf diesem Modell und der Detektion der Modensprünge während<br />
des Durchstimmens des ECDLs wird ein Fehlersignal erzeugt und damit<br />
eine Regelung implementiert. Zusätzlich werden etwaige Nichtlinearitäten<br />
beispielsweise der Piezoaktoren durch eine selbstoptimierende<br />
nichtlineare Nachführung des Laserdiodenstroms ausgeglichen. Mit<br />
der Automatisierung wird der modensprungfreie Betrieb eines ECDLs<br />
schnell erreicht und aufrechterhalten.
Fachverband Quantenoptik und Photonik (Q) Montag<br />
Q 9.4 Mo 17:15 3H<br />
Erzeugung von sub-300-fs-Pulsen mit einem Halbleiterscheibenlaser<br />
— •Peter Klopp 1 , Florian Saas 1 , Uwe Griebner 1 ,<br />
Martin Zorn 2 und Markus Weyers 2 — 1 Max-Born-Institut, Max-<br />
Born-Straße 2a, D-12489 Berlin — 2 Ferdinand-Braun-Institut, Gustav-<br />
Kirchhoff-Straße 4, D-12489 Berlin<br />
Die Erzeugung von ultrakurzen Pulsen mit einem optisch gepumpten,<br />
oberflächenemittierenden Halbleiterlaser wird vorgestellt. Die<br />
Verstärkungsstruktur besteht aus mehreren Quantentrögen (QWs) in<br />
spezieller, unregelmäßiger Anordnung. Die Absorption der 840 nm–<br />
Diodenlaser–Pumpstrahlung erfolgt in gradierten Barrieren zwischen<br />
den QWs [1]. Ein sättigbarer single–QW–Halbleiter–Absorberspiegel<br />
mit Relaxationszeiten < 5 ps dient zur passiven Modenkopplung des<br />
Lasers. Mit diesem rein halbleiterbasierten Laser konnten optische<br />
Pulse mit einer Dauer von 290 fs erzeugt werden. Bei einer Pulsfolgefrequenz<br />
von 3 GHz wird eine mittlere Leistung von 10 mW im<br />
Wellenlängenbereich um 1030 nm erzielt. Unter Ausnutzung des AC–<br />
Stark–Effekts und ohne weitere Elemente zur Dispersionskontrolle im<br />
Resonator gelang die Erzeugung nahezu Fourier–limitierter, solitonenartiger<br />
Pulse.<br />
[1] F. Saas et al., Appl. Phys. Lett. 89, 151120 (2006).<br />
Q 9.5 Mo 17:30 3H<br />
Active frequency stabilization of an infrared diode laser at<br />
1115 nm for the generation of UV light — •Steffen Oppel 1 ,<br />
Günter Guthöhrlein 2 , Wilhelm Kaenders 3 , and Joachim von<br />
Zanthier 1 — 1 Institut für Optik, Information und Photonik, Max-<br />
Planck-Forschungsgruppe, Universität Erlangen-Nürnberg, Germany<br />
— 2 Fachbereich Elektrotechnik, Lasertechnik und Werkstofftechnik,<br />
Helmut Schmidt Universität der Bundeswehr Hamburg, Germany —<br />
3 Toptica Photonics AG, Gräfelfing (München), Germany<br />
We present a novel method of active frequency stabilization of a<br />
commercial high power external-cavity diode laser near 1115 nm to<br />
atomic transitions in praseodymium (Pr I). The spectrum of neutral<br />
Pr is recorded in a hollow cathode lamp via laser-induced fluorescence<br />
(LIF). Laser irradiation between 1105 and 1123 nm leads to a<br />
wide variety of excitation lines with Doppler linewidths of typically<br />
500 MHz, identified via fluorescence light in the visible. The excitation<br />
signals are strong enough to enable the lock of the laser onto<br />
most of the lines of the spectrum by means of a lock-in detection<br />
technique. In this way the frequency drifts of the unlocked laser (of<br />
more than 30 MHz/h) can be reduced to below 2 MHz/h. Frequency<br />
quadrupling of the referenced infrared diode laser can produce in the<br />
future frequency-stable UV-light in the range 276 - 281 nm. In particular,<br />
using a strong hyperfine component of the excitation line<br />
E = 16502, 616 J=7/2 cm −1 → E ′ = 25442, 742 o J=9/2 cm−1 of Pr at<br />
1118,54 nm allows - after frequency quadruplification - to excite the<br />
D2-transition of trapped Mg + ions at 279,64 nm.<br />
Q 9.6 Mo 17:45 3H<br />
Kohärente Addition von twei TA verstärkten Laserstrahlen<br />
für eine kontinuierliche Hochleistungslaserquelle — •Daniel<br />
Kolbe, Martin Scheid, Frank Markert und Jochen Walz — Johannes<br />
Gutenberg Universität Mainz, Institut für Physik<br />
Kohärente kontinuierliche Strahlung bei 121,56 nm, dem 1S – 2P<br />
Übergang in Anti-Wasserstoff, kann durch Vierwellenmischen in<br />
Quecksilber erzeugt werden. Zur effizienten Produktion werden drei<br />
Laser mit Wellenlängen in der Nähe von atomaren Resonanzen im<br />
Quecksilber benötigt. Eine dieser Resonanzen, die 6 3 P – 7 1 S Resonanz,<br />
liegt bei einer Wellenlänge von 407,9 nm und kann durch einen<br />
frequenzverdoppelten Titan:Saphir-Laser erzeugt werden.<br />
Alternativ können auch gitterstabilisierte Laserdioden bei 815,8 nm<br />
frequenzverdoppelt werden. Jedoch ist deren Fundamentalleistung auf<br />
wenige 100 mW beschränkt. Durch die Weiterentwicklung von Halbleiterverstärkerchips<br />
(tapered amplifier; kurz: TA) lassen sich Laserdioden<br />
im nahinfraroten Spektrum auf Leistungen bis zu 1 Watt<br />
verstärken. Um eine weitere Leistungssteigerung zu ermöglichen, wird<br />
ein System vorgestellt, das zwei durch TAs verstärkte Laserstrahlen<br />
kohärent addiert und damit Ausgangsleistungen von bis zu 1,6 Watt<br />
ermöglicht. Die Effizienz dieser Überlagerung ist dabei hauptsächlich<br />
durch die Strahlprofile der beiden TA-Strahlen begrenzt.<br />
Q 9.7 Mo 18:00 3H<br />
Entwicklung eines Diodenlasersystems mit Frequenzverdopplung<br />
zur zweistufigen Anregung von Cäsium-Atomen in Ryd-<br />
bergzustände — •Andreas Müllers, Frank Markert, Daniel<br />
Kolbe, Martin Scheid und Jochen Walz — Johannes Gutenberg<br />
Universität Mainz, Institut für Physik<br />
Für die Anregung von Cäsium-Atomen in Rydbergzustände wird ein<br />
zweistufiges Diodenlasersystem entwickelt. Der erste Übergang des<br />
Anregungsschemas von 6S1/2 nach 6P3/2 benötigt Laserlicht einer<br />
Wellenlänge von 852 nm. Hierfür verwenden wir eine gitterstabilisierte<br />
Laserdiode. Die zweite Anregungsstufe von 6P3/2 → 38D5/2 ist bei 511 nm Wellenlänge. Für diesen Schritt wird eine antireflexbeschichtete<br />
Laserdiode ebenfalls per Gitterstabilisierung auf 1022 nm<br />
abgestimmt, mit einem Tapered Amplifier (TA) verstärkt und anschließend<br />
in einem externen Resonator frequenzverdoppelt. Gewöhnlich<br />
verwendet man für die Verdopplung einen Aufbau bestehend aus Einund<br />
Auskoppelspiegel sowie zwei Umlenkspiegeln (Doppel-Z-Aufbau).<br />
Wir ersetzen die beiden Umlenkspiegel durch ein Prisma und erhalten<br />
so einen dreieckigen Resonator. Die Strahllänge reduziert sich für diese<br />
Geometrie von ca. 80 cm auf 15 cm.<br />
Anwendung findet das System bei der Erzeugung von kaltem Antiwasserstoff<br />
über einen zweifachen Ladungstransfer: Positronen bilden<br />
mit den Rydberg-Elektronen der Cäsium-Atome Positronium<br />
(Cs∗ + e + → P s∗ + Cs + ), welches wiederum mit Anti-Protonen zu<br />
Anti-Wasserstoff reagiert (P s∗ + ¯p → ¯ H∗ + e− ).<br />
Der Stand des Systems wird vorgestellt und diskutiert.<br />
Q 9.8 Mo 18:15 3H<br />
Hocheffiziente Frequenzverdopplung von Diodenlasern mit<br />
periodisch gepolten Wellenleiterkristallen bei 488 nm —<br />
•Andreas Jechow und Ralf Menzel — Universität Potsdam, Institut<br />
für Physik, Photonik, Am Neuen Palais 10, 14469 Potsdam<br />
Die Entwicklung von periodisch gepolten Wellenleiterkristallen auf der<br />
Basis von Lithiumniobat (PPLN) ermöglicht hocheffiziente Frequenzverdopplung<br />
(SHG) im Einfachdurchgang für Pumplaser mit moderaten<br />
cw-Ausgangsleistungen [1].<br />
Sowohl DFB-Diodenlaser als auch Breitstreifenlaserdioden im externen<br />
Resonator [2] liefern Ausgangsleistungen von mehreren Hundert<br />
Miliwatt bei sehr guter Strahlqualität und schmalbandiger spektraler<br />
Emission. Aufgrund der sehr guten Strahleigenschaften war es möglich<br />
mehr als 60% des infraroten Lichtes in einen Wellenleiter mit einer<br />
Apertur von 3,5µm × 5µm und 10 mm Länge einzukoppeln.<br />
Bei einer Zentralwellenlänge von 488 nm konnten Leistungen von<br />
mehr als 150 mW und Konversionseffizienzen von über 50% realisiert<br />
werden. Die Gesamteffizienz (wall-plug efficiency) konnte dabei auf<br />
Werte von über 5% gesteigert werden.<br />
[1] A. Jechow, D. Skoczowsky, and R. Menzel, Opt. Express 15,<br />
6976–6981 (2007)<br />
[2] A. Jechow, V. Raab, and R. Menzel, M. Cenkier, S. Stry, and J.<br />
Sacher, Opt. Commun. 277, 161–165 (2007)<br />
Q 9.9 Mo 18:30 3H<br />
Passive Modenkopplung eines Breitstreifen-Diodenlasers im<br />
externen Resonator mit Hilfe eines sättigbaren Absorbers —<br />
•Danilo Skoczowsky, Axel Heuer, Andreas Jechow und Ralf<br />
Menzel — Universität Potsdam, Lehrstuhl Photonik, Am Neuen Palais<br />
10, 14469 Potsdam<br />
Breitstreifen-Diodenlaser mit einem externem Resonator zeigen unter<br />
bestimmten Bedingungen eine Selbst-Modenkopplung und emittieren<br />
ps-Pulse mit einer Wiederholrate, die der reziproken Resonatorumlaufzeit<br />
entspricht. Bei einem streifig kontaktierten Laserchip in einem<br />
V-förmigen Resonator konnten so Pulse von 25 ps Dauer mit einer<br />
Pulsspitzenleistung von 4,7 W bei einer Repetitionsrate von 3 GHz<br />
beobachtet werden [1].<br />
Möchte man unabhängig vom Aufbau der Diode und der Resonatorgeometrie<br />
einen ps-Laser realisieren, so bietet sich eine passive<br />
Modenkopplung mit einem sättigbaren Absorber an. Auf Basis einer<br />
Breitstreifen-Laserdiode wird ein Resonator vorgestellt, der eine Modenkopplung<br />
und damit eine gepulste Emission bei einer Emissionswellenlänge<br />
von 976 nm ermöglicht. Entsprechend der Länge des externen<br />
Resonators von 15 cm ergibt sich eine Pulsfolgefrequenz von 1 GHz.<br />
Zusätzlich kann der Laser über eine Strommodulation aktiv modengekoppelt<br />
werden.<br />
[1] D. Skoczowsky, A. Heuer, A. Jechow and R. Menzel. Opt. Com.<br />
279, 341–345, 2007.<br />
Q 9.10 Mo 18:45 3H<br />
Waveguide mode dynamics of (Al,In)GaN Laser Diode —<br />
•Ulrich Schwarz and Harald Braun — Institute for Experimental<br />
and Applied Physics, University of Regensburg, D-93040 Regensburg,
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
Germany<br />
We measure the waveguide mode dynamics of (Al,In)GaN laser diodes<br />
emitting in the near UV to blue wavelength range. The combination<br />
of a scanning near–field microscope (SNOM) with a high spectral resolution<br />
monochromator and/or temporal resolution allows collecting<br />
multi–dimensional data sets (space, time, and wavelength) of the laser<br />
diode during pulsed operation. For highest temporal resolution — to<br />
measure relaxation oscillations and delay of lasing onset — we use a<br />
Q 10: Kalte Moleküle I [gemeinsam mit MO]<br />
streak camera in combination with the SNOM. The measurements are<br />
then compared with basic simulations within the framework of rate<br />
equations. The central question is whether the physical effects which<br />
are particular for the group III-nitrides (i.e. carrier localization caused<br />
by indium fluctuations and quantum confined Stark effect) result in<br />
a fundamentally different behavior when compared to standard laser<br />
diodes operating in the red and infrared spectral region. We demonstrate<br />
how optical gain measurements already indicate the impact of<br />
indium fluctuations on (Al,In)GaN laser diode properties.<br />
Zeit: Dienstag 8:30–10:30 Raum: 3G<br />
Hauptvortrag Q 10.1 Di 8:30 3G<br />
Cold Polar Molecules: From Production to State-Selective<br />
Detection — •Pepijn W.H. Pinkse, Laurens D. van Buuren,<br />
Michael Motsch, Markus Schenk, Christian Sommer, Martin<br />
Zeppenfeld, and Gerhard Rempe — Max-Planck-Institut für Quantenoptik,<br />
Hans-Kopfermann-Str. 1, 85748 Garching<br />
Cold polar molecules promise opportunities in various research fields<br />
such as chemistry, metrology, molecular physics and quantum information<br />
processing. To this end, advanced production, trapping and<br />
cooling techniques are required.<br />
An overview will be given of the methods developed in our laboratory:<br />
we filter slow molecules out of a thermal ensemble by exploiting<br />
the Stark effect in polar molecules such as formaldehyde, ammonia<br />
and water. The thermal ensemble in the source can be at room temperature<br />
or at cryogenic temperature, in which case helium is used<br />
as a cold buffer gas. Using suitably shaped electric fields, slow polar<br />
molecules are guided into ultrahigh vacuum, where we can store them<br />
in an electric trap.<br />
While the motional energy of the filtered molecules is in the 1K<br />
range, the rotational temperature is higher. Depending on the temperature<br />
of the source and the molecular constants, many rotational states<br />
can be occupied. As a preparation for optical measurements, we performed<br />
high-resolution molecular UV spectroscopy on formaldehyde.<br />
With the gained information, we can now measure the distribution<br />
over the internal states of guided formaldehyde by state-selectively depleting<br />
the beam by optical pumping. Precise knowledge over the state<br />
distribution will be vital for further cooling down the molecules, for<br />
instance by means of an optical cavity.<br />
Q 10.2 Di 9:00 3G<br />
Cryogenic buffer-gas cooling and magnetic trapping of CrH<br />
and MnH molecules — •Michael Stoll 1 , Joost Bakker 2 , Gerard<br />
Meijer 1 , and Achim Peters 3 — 1 Fritz-Haber-Institut der Max-<br />
Planck-Gesellschaft , Berlin — 2 FOM Institute for Plasma Physics,<br />
Rijnhuizen, the Netherlands — 3 Humboldt Universität zu Berlin, Institut<br />
für Physik<br />
Buffer gas loading of molecules into a cryogenic He-filled cell and<br />
magnetic trapping of the thermalized molecules has been proven to<br />
be a powerful method for the production of samples of trapped cold<br />
molecules.<br />
We report on the successful cooling of MnH and CrH molecules to<br />
sub-Kelvin temperatures using a He dilution refrigerator. Subsequently<br />
the molecules were loaded into a trapping field generated by a superconducting<br />
quadrupole magnet. Storage times of ˜120 ms could be<br />
demonstrated for both molecules.<br />
We modeled the dynamics of our system using a Monte Carlo approach<br />
in order to investigate different possible inelastic scattering processes<br />
responsible for limitations to the trapping time. Collision cross<br />
sections were obtained by fitting this model to the measured diffusion<br />
times of both molecules. Combining our system with the already<br />
demonstrated methods for rapid extraction of the buffer gas should in<br />
principle allow for the preparation of thermally isolated samples with<br />
then much longer lifetimes.<br />
Q 10.3 Di 9:15 3G<br />
The electrostatic analogue of a Ioffe-Pritchard trap — •Moritz<br />
Kirste, Melanie Schnell, and Gerard Meijer — Fritz-Haber-<br />
Institut der MPG, Abt. Molekülphysik, Faradayweg 4-6, D-14195<br />
Berlin<br />
By exploiting the Stark effect one can trap polar molecules. In an<br />
electric field the molecules separate, due to the Stark effect, in lowfield<br />
seeking and high-field seeking states, where molecules in lowfield<br />
seeking states can be confined in the minimum of an electrostatic<br />
quadrupole trap. Trapped molecules are useful in the study of<br />
dipole-dipole interaction, the alignment of molecules in external fields<br />
and for high-resolution spectroscopy. These techniques are limited by<br />
the density of trapped molecules, the trap depth, trap frequency and<br />
trapping-time. Trap losses arise from inelastic collisions and from Majorana<br />
transitions. In electrostatic traps, the Majorana losses can be<br />
compensated by the use of an electric analogue to a magnetic Ioffe-<br />
Pritchard trap, which generates a trapping field that is non-zero at<br />
the center. In this talk we will introduce the first Ioffe-Pritchard like<br />
electrostatic trap. We will present our experimental results, characterizing<br />
the trap and will sketch its possible applications.<br />
Q 10.4 Di 9:30 3G<br />
Lifetime measurements with electrostatically trapped cold<br />
molecules — •Joop J. Gilijamse, Steven Hoekstra, Markus<br />
Metsälä, Sebastiaan Y.T. van de Meerakker, and Gerard Meijer<br />
— Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany<br />
With a Stark decelerator, bunches of state-selected molecules with<br />
a controlled velocity and with longitudinal temperatures as low as a<br />
few mK can be produced. These slow bunches of molecules can subsequently<br />
be trapped in an electrostatic trap. We will report on the<br />
deceleration and trapping of ground state OH, and metastable CO<br />
and NH molecules. The OH radicals are trapped at a density of 10 7<br />
- 10 8 cm −3 and at a temperature of around 50 mK, and their trap<br />
lifetime is measured to be 2.8 s. The long interaction time afforded by<br />
the trap can be exploited to measure lifetimes of vibrationally excited<br />
states or electronically excited metastable states. Such lifetimes can<br />
be used as an accurate test of theoretical models. We will present<br />
experiments on the lifetime of OH (X 2 Π 3/2, v = 1) and of metastable<br />
CO (a 3 Π, v = 0). The different loss processes that play a role in the<br />
trap, like optical pumping by blackbody radiation, were studied in<br />
detail.<br />
[1] S. Hoekstra et al., Optical pumping of trapped neutral molecules<br />
by blackbody radiation, PRL 98: 133001 (2007)<br />
[2] J.J. Gilijamse et al., The radiative lifetime of metastable CO<br />
(a 3 Π, v = 0), J.Chem.Phys, [in press], Arxiv:0710:2240 (2007)<br />
Q 10.5 Di 9:45 3G<br />
Guiding and decelerating polar molecules above a microstructured<br />
electrode array — •Samuel A. Meek, Hendrick L. Bethlem,<br />
Horst Conrad, and Gerard Meijer — Fritz-Haber-Institut der<br />
MPG, Faradayweg 4-6, 14195 Berlin<br />
The feasibility of manipulating polar molecules by means of inhomogeneous<br />
electric fields has been successfully demonstrated by various devices,<br />
such as Stark decelerators, electrostatic traps and storage rings.<br />
While previous electrode configurations at the mm scale require potential<br />
differences of tens of kV at the electrodes, similar fields can be<br />
produced between 10µm-sized electrodes using potentials of hundreds<br />
of volts. Here, we present an electrostatic decelerating and trapping<br />
device consisting of a periodic array of 1254 microstructured linear<br />
electrodes deposited on a planar glass substrate. Application of harmonic<br />
waveforms to periodic groups of six electrodes forms a series of<br />
periodic minima which move along the array in a continuous manner<br />
without changing their distances above the electrodes. Deceleration is<br />
achieved by linearly reducing the frequency of the applied waveforms.
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
First experiments have been performed using a supersonic beam of<br />
a 3 Π1 CO, which has a lifetime of 2.6 milliseconds. Molecules are excited<br />
with a laser directly after the nozzle and later detected using Auger<br />
deexcitation at a gold surface. TOF spectra clearly demonstrate the<br />
velocity-selective guiding of CO*, with guided velocities proportional<br />
to the frequency of the applied waveforms. First results of decelerating<br />
the CO* molecules by linearly decreasing the frequency of the<br />
waveforms, i.e. velocity of the minima, are also presented.<br />
Q 10.6 Di 10:00 3G<br />
Spatially separating individual conformers of neutral<br />
molecules — •Frank Filsinger, Undine Erlekam, Henrik Haak,<br />
Gert von Helden, Jochen Küpper, and Gerard Meijer — Fritz-<br />
Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, Berlin,<br />
Germany<br />
Large (bio)molecules exhibit multiple conformers (structural isomers),<br />
even under the cold conditions present in a supersonic jet. For various<br />
applications, i. e., scattering experiments, it would be highly desirable<br />
to prepare molecular packets of individual conformers.<br />
It is well-known that polar molecules can be manipulated using<br />
strong electric fields. Many techniques have been developed for the manipulation<br />
of small molecules in low-field-seeking quantum states. However,<br />
application of these techniques to large molecules is not straightforward,<br />
because, for larger molecules, all states are high-field seeking<br />
at the relevant electric field strengths. To manipulate the motion of<br />
large molecules one has to use Alternate Gradient (dynamic) focusing.<br />
This method has been successfully demonstrated in the Alternate Gradient<br />
deceleration of CO and YbF. Using the same Alternate Gradi-<br />
ent focusing principle, applying switched electric fields in a quadrupole<br />
guide, we have set up a new experiment to spatially separate individual<br />
conformers of large molecules. This experiment exploits the different<br />
mass-to-dipole (m/µ) ratios, similar to a quadrupole mass-to-charge<br />
(m/q) filter for ions.<br />
In a proof-of-principle experiment, we have demonstrated the conformer<br />
selection of cis- and trans-3-aminophenol.<br />
Q 10.7 Di 10:15 3G<br />
Formation of ultracold heteronuclear dimers in electric<br />
fields — •Michael Mayle 1 , Rosario Gonzalez-Ferez 2 , and Peter<br />
Schmelcher 1,3 — 1 Theoretische Chemie, Universität Heidelberg, Im<br />
Neuenheimer Feld 229, 69120 Heidelberg — 2 Instituto ’Carlos I’ de<br />
Física Teórica y Computacional and Departamento de Física Atómica<br />
Molecular y Nuclear, Universidad de Granada, E-18071 Granada,<br />
Spain — 3 Physikalisches Institut, Universität Heidelberg, Philosophenweg<br />
12, 69120 Heidelberg<br />
The effects of a strong electric field on the radiative and steric properties<br />
of heteronuclear alkali dimers are investigated. In particular, we<br />
study the formation of ultracold LiCs molecules via stimulated emission<br />
followed by a radiative deexcitation cascade in the presence of a<br />
static electric field. By analyzing the corresponding cross sections, we<br />
demonstrate the possibility to populate the lowest rotational excitations<br />
via photoassociation. The modification of the radiative cascade<br />
due to the electric field leads to narrow rotational state distributions in<br />
the vibrational ground state. External fields might therefore represent<br />
an additional valuable tool towards the ultimate goal of quantum state<br />
preparation of molecules.<br />
Q 11: Laserentwicklung (Festkörperlaser II / Andere Laserquellen)<br />
Zeit: Dienstag 8:30–10:30 Raum: 3H<br />
Q 11.1 Di 8:30 3H<br />
Eine verstimmbare Dauerstrich-Laserlichtquelle geringer Linienbreite<br />
bei 546 nm mit einer Ausgangsleistung von<br />
4 W realisiert durch externe Frequenzverdoppelung eines<br />
Ytterbium-dotierten einmodigen Faserlasersystems — •Frank<br />
Markert, Martin Scheid, Daniel Kolbe und Jochen Walz — Institut<br />
für Physik, Johannes Gutenberg-Universität, Staudingerweg 7,<br />
D-55128 Mainz, Germany<br />
In diesem Vortrag wird eine kohärente kontinuierliche Hochleistungs-<br />
Lichtquelle bei 545,5 nm vorgestellt [1]. Wir verwenden<br />
8,3 W Laserlicht eines Ytterbium-dotierten einmodigen Faser-<br />
Oszillator/Verstärker-Systems als Eingangsleistung in einen externen<br />
Frequenzverdoppelungsresonator. Dieser Aufbau liefert bis zu 4,1 W<br />
stabile grüne einfrequente Laserstrahlung, die über einen Bereich von<br />
±95 GHz um die Zentralwellenlänge durchgestimmt werden kann. Eine<br />
Jod-Absorptionsspektroskopie über den vollen verstimmbaren Bereich<br />
des Faserlasers und Sättigungsspektroskopie an einer starken Jodlinie<br />
des dopplerverbreiterten Spektrums dienen zur Charakterisierung des<br />
Lasersystems.<br />
[1] F. Markert, M. Scheid, D. Kolbe, and J. Walz, Optics Express 15,<br />
14476-14481 (2007).<br />
Q 11.2 Di 8:45 3H<br />
Towards a compact high-average-power femtosecond supercontinuum<br />
source — Felix Hoos 1 , •Bernd Braun 2 , and Harald<br />
Giessen 1 — 1 4. Physikalisches Institut, Universität Stuttgart — 2 FH<br />
Nürnberg<br />
In this talk we will present a way towards a cost effective, compact,<br />
and highly efficient pump source for high-average-power femtosecond<br />
supercontinuum lasers.<br />
Supercontinuum sources have become an important tool for measurements<br />
and experiments in various fields of science. There are many<br />
experiments for which it is desirable to have a controllable spectral<br />
power over a wide wavelength range, e.g., for white light interferometry<br />
with low reflective samples, spectroscopy over a wide wavelength<br />
range or pump-probe experiments with pump and probe light being<br />
extracted from the supercontinuum. Especially for the latter case it<br />
might also be important to provide femtosecond pulses for improved<br />
temporal resolution. Currently, commercial supercontinuum systems<br />
are available with average powers in the order of several watts based<br />
on nonlinear fibers pumped by pico- or nanosecond sources. However,<br />
until now there exist to our knowledge no high average power femtosecond<br />
supercontinuum sources.<br />
We will present our approach for a suitable pump laser for supercontinuum<br />
generation based on Yb:KGW in a slab geometry which is<br />
pumped by a single laser diode resulting in an average power of several<br />
watts. We will discuss the heat removal in the case of a slab geometry<br />
of the laser crystal as well as the influence of thermal effects.<br />
Q 11.3 Di 9:00 3H<br />
Photoleitungsmessungen zur Identifizierung nicht-linearer<br />
Verluste in hoch-dotiertem Yb:YAG — •Christian Hirt, Susanne<br />
Teruko Fredrich-Thornton, Friedjof Tellkamp, Klaus<br />
Petermann und Günter Huber — Insitut für Laser-Physik, Universität<br />
Hamburg, Luruper Chaussee 149, 22761 Hamburg<br />
Yb-dotierte Oxide werden häufig in Hochleistungslasern verwendet,<br />
da aufgrund ihres einfachen Energieniveauschemas interne Verlustprozesse<br />
wie Kreuzrelaxation, Up-conversion und ESA nicht zu erwarten<br />
sind.<br />
Scheibenlaserexperimente an hochdotiertem Yb:YAG zeigten jedoch,<br />
dass nicht-lineare Verlustprozesse auftreten, die abhängig von<br />
der Dotierungskonzentration und Anregungsdichte die Lasertätigkeit<br />
stark einschränken und bei Konzentrationen über 15% einen Scheibenlaserbetrieb<br />
sogar unmöglich machen.<br />
Photoleitungsmessungen zeigen, dass ein Up-conversion Mechanismus<br />
von angeregten Yb-Ionen existiert, über den Elektronen in das<br />
Charge Transfer Band gelangen. Ein Model für diesen Up-conversion<br />
Prozess wird vorgestellt, und der Zusammenhang mit den im Scheibenlaser<br />
beobachteten Verlusten wird diskutiert.<br />
Q 11.4 Di 9:15 3H<br />
Hocheffizienter Yb:Lu2O3-Scheibenlaser — •Rigo Peters,<br />
Christian Kränkel, Klaus Petermann und Günter Huber — Institut<br />
für Laser-Physik, Universität Hamburg<br />
Aufgrund der herausragenden thermomechanischen Eigenschaften des<br />
Wirtskristalls und des bekannt geringen Quantendefektes von Yb 3+<br />
ist Yb:Lu2O3 ein hervorragend geeignetes Material für Hochleistungs-<br />
Festkörperlaser im Bereich um 1 µm. Durch die Verwendung dünner<br />
Kristallscheiben im Scheibenlaserkonzept lassen sich prinzipiell Ausgangsleistungen<br />
von mehreren kW pro Scheibe erzielen.<br />
In Laserexperimenten wurden hochreine Kristalle mit einer Dotierung<br />
zwischen 1 at.% und 10 at.%, sowie Scheibendicken zwischen
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
0,08 mm und 0,45 mm untersucht. Für einen 0,15 mm dicken, 5 at.%dotierten<br />
Kristall konnte für die maximale Pumpleistung von 49,8 W<br />
bei 976 nm eine Laserausgangsleistung von 36,3 W bei 1034 nm und<br />
einem differentiellen Wirkungsgrad von 80% erzielt werden. Der dabei<br />
erreichte optisch-zu-optische Wirkungsgrad von 73% übertrifft damit<br />
den des am häufigsten in Hochleistungsscheibenlasern verwendeten<br />
Materials Yb:YAG deutlich [1].<br />
Bis zu einer Yb-Konzentration von 5 at.% konnte keine Beeinflussung<br />
der Lasereffizienz durch die Scheibendicke oder Dotierhöhe beobachtet<br />
werden. Dies verdeutlicht die gleich bleibend sehr hohe optische Qualität<br />
der Kristalle in den unterschiedlichen Zuchten und zeigt das große<br />
Potential von Yb:Lu2O3 für zukünftige Hochleistungsanwendungen.<br />
[1] A. Giesen et al., Photonics Spectra 41, 52-58 (2007)<br />
Q 11.5 Di 9:30 3H<br />
Efficient cw Thin Disk Laser Operation of Yb:Ca4YO(BO3)3<br />
with 20W Output Power — •Christian Kränkel, Rigo Peters,<br />
Klaus Petermann, and Günter Huber — Institut für Laser-Physik,<br />
Universität Hamburg<br />
We report on continuous-wave (cw) laser operation with<br />
Yb(15 at.%):Ca4YO(BO3)3 (Yb:YCOB) exceeding 20 W of outputpower<br />
in the thin disk laser setup.<br />
50% of optical-to-optical efficiency at a slope efficiency of more than<br />
60% were realized in E X-polarization. A tuning range of 95 nm with<br />
high output powers could be obtained.<br />
Furthermore, applying the pinhole method the fluorescence lifetime<br />
was determined to be 2.2 µs.<br />
The obtained results revealed that Yb:YCOB is a promising candidate<br />
for the generation of very short pulses at high pulse energies in<br />
the thin disk laser setup.<br />
Q 11.6 Di 9:45 3H<br />
Novel approach for mode-selective polarization measurement<br />
and its application in few-mode fiber amplifier systems —<br />
•Niklas Andermahr 1 , Thomas Theeg 1 , and Carsten Fallnich 2<br />
— 1 Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116<br />
Braunschweig, Germany — 2 Institut für Angewandte Physik - WWU<br />
Münster, Corrensstraße 2, 48149 Münster, Germany<br />
In the field of high-power fiber amplifiers large core diameters are of<br />
advantage to reduce the power density. However, these fibers often<br />
loose pure single transverse mode behavior. A better understanding of<br />
the propagation and interaction of higher order modes (HOMs) can<br />
help either to suppress or to use them.<br />
We present a polarization-sensitive measurement of HOMs from a<br />
few-mode optical fiber using a three-mirror ring resonator. Measuring<br />
the power fraction as well as the polarization state we analyze a fewmode<br />
fiber amplifier system and show that the HOMs prefer orthogonal<br />
polarization states. This is explained, as the fiber modes thereby<br />
maximize the overlap of the intensity profile with the gain region.<br />
Q 12: Kalte Moleküle II [gemeinsam mit MO]<br />
Q 11.7 Di 10:00 3H<br />
Erhöhung der Effizienz eines Er:ZBLAN Faserlasers bei 546<br />
nm — •Florian Engel, Ortwin Hellmig, Klaus Sengstock und<br />
Valeri Baev — Institut für Laserphysik, Universität Hamburg<br />
Ein Er:ZBLAN upconversion Faserlaser bei 546 nm wird durch eine<br />
zweistufige Anregung mit einer Laserdiode bei 975 nm optisch gepumpt.<br />
Bei dieser Anregung wird zusätzlich ein Zwischenniveau 4 I 13/2<br />
mit einer Lebensdauer von ca. 10 ms bevölkert, was die Effizienz des<br />
Lasers bei 546 nm senkt. Dieses Problem lässt sich durch die Abregung<br />
dieses Niveaus mit einem zusätzlichen IR-Laserbetrieb bei ca. 1,6 µm<br />
beseitigen. Es wurde gezeigt, dass die zusätzliche Laseremission bei<br />
1,556 µm eine bessere Unterstützung für die grüne Emission liefert<br />
als die Laseremission bei 1,536 µm. Dabei konnte die Reduzierung der<br />
Laserschwelle bei 546 nm um 60% und die Erhöhung der Leistung<br />
um 35% demonstriert werden. Mit einer 1000 ppm Er-dotierten 50 cm<br />
ZBLAN-Faser wurde bei einer absorbierten Pumpleistung von ca 20<br />
mW eine Leistung von 1,15 mW bei 546 nm erreicht.<br />
Die entwickelte Methode ist nicht nur auf Faserlaser beschränkt<br />
und bietet deshalb auch für andere Er-dotierten Festkörperlaser eine<br />
Möglichkeit, die Effizienz zu steigern.<br />
Q 11.8 Di 10:15 3H<br />
Fourier Domain Mode Locked (FDML) Laser mit hochgradig<br />
linearer Frequenz-Zeit Abstimmcharakteristik — •Christoph<br />
Eigenwillig, Benjamin Biedermann, Gesa Palte und Robert Huber<br />
— Lehrstuhl für biomolekulare Optik, Fakultät für Physik, LMU<br />
München<br />
Die optische Kohärenztomographie (OCT) [1] stellt ein optisches<br />
Bildgebungsverfahren mit zahlreichen biomedizinischen Anwendungen<br />
dar. Mit dem Ziel höherer Abtastraten werden zunehmend<br />
schmalbandige, wellenlängenabstimmbare Laser-Quellen eingesetzt.<br />
Dabei konnte durch den Einsatz von FDML-Lasern die OCT-<br />
Abbildungsgeschwindigkeit um das 100 bis 1000-fache gesteigert werden<br />
[2]. FDML Laser erreichen Abstimmraten von 370kHz, instantane<br />
Linienbreiten von 50pm und optische Abstimmbereiche von<br />
über 150nm bei 1300nm. Da in OCT Anwendungen zur Extraktion<br />
der tiefenabhängigen Streuintensität die Messwerte in einem<br />
äquidistanten Frequenzraster vorliegen müssen, wäre eine Lichtquelle<br />
mit einer nahezu perfekt linearen Frequenz-Zeit Abstimmcharakteristik<br />
wünschenswert, jedoch konnten bisherige abstimmbare Laser- und<br />
Spektrometer-Anordnungen für OCT keine ausreichende Linearität erreichen.<br />
Es wird ein FDML-Laser mit hochgradig linearem Abstimmverhalten<br />
vorgestellt, verschiedene Strategien zur hochgenauen Linearisierung<br />
diskutiert und die Anwendung dieses Lasers für die OCT-<br />
Bildgebung demonstriert.<br />
1. Huang D. et al. Science 254:1178-1181 (1991).<br />
2. Huber R. et al. Optics Express 14:3225-3237 (2006).<br />
Zeit: Dienstag 11:00–13:00 Raum: 3G<br />
Q 12.1 Di 11:00 3G<br />
Deceleration, trapping and accumulation of NH molecules —<br />
•Steven Hoekstra, Markus Metsälä, Peter C. Zieger, Ludwig<br />
Scharfenberg, Joop J. Gilijamse, Sebastiaan Y.T. van de Meerakker,<br />
and Gerard Meijer — Fritz-Haber-Institut der Max-Planck-<br />
Gesellschaft, Berlin, Germany<br />
We report on the Stark-deceleration and electrostatic trapping of<br />
metastable NH molecules. Furthermore, the progress towards higher<br />
densities of cold neutral molecules by accumulation of multiple Starkdecelerated<br />
packets of NH molecules in a magnetic trap will be presented.<br />
NH molecules in the long-lived metastable a 1 ∆(v = 0, J = 2) state<br />
are ideally suited for Stark deceleration experiments because of their<br />
relatively large Stark shift and low mass. The metastable molecules<br />
(τ > 2.7s) are produced in a supersonic expansion with a velocity of<br />
∼ 450 m/s, and are decelerated to a standstill by a 108-stage decelerator.<br />
Subsequently the metastable molecules are trapped electrostatically,<br />
with a temperature of about 50 − 100 mK, a density of ∼ 10 6<br />
cm −3 and a 1/e trapping lifetime of 1.4 s.<br />
Following the deceleration and trapping, the metastable NH<br />
molecules are detected by the excitation of a spin-forbidden transition,<br />
resulting in spontaneous decay to the electronic ground state (X 3 Σ − ).<br />
The electronic ground state has a negligible Stark shift, but can be<br />
trapped magnetically. The first experiments on the accumulation of<br />
ground state NH molecules in a magnetic trap will be presented.<br />
Q 12.2 Di 11:15 3G<br />
Alternating gradient focusing and deceleration of large<br />
molecules — Kirstin Wohlfart, •Fabian Grätz, Frank<br />
Filsinger, Gerard Meijer, and Jochen Küpper — Fritz-Haber-<br />
Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin,<br />
Germany<br />
During the last decade, fascinating progress has been made in the<br />
spectroscopy of the “molecular building blocks of life”. Meanwhile,<br />
our group has been developing methods to decelerate neutral, polar<br />
molecules using time varying inhomogeneous electric fields. Extending<br />
these techniques to bio-molecules would allow, for instance, to<br />
increase observation times for precision spectroscopy or to separate<br />
different conformers. However, for such large molecules all states are<br />
practically high-field seeking. Therefore, alternating gradient focusing
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
has to be applied. Here, we demonstrate the focusing and deceleration<br />
of benzonitrile (C7H5N) from a molecular beam. Benzonitrile is<br />
prototypical for large asymmetric top molecules that exhibit rich rotational<br />
structure and a high density of states. It is decelerated in its<br />
absolute ground state from 320 m/s to 289 m/s, and similar velocity<br />
changes are obtained for excited rotational states. We are setting up<br />
a longer alternating gradient decelerator, which will enable us to decelerate<br />
benzonitrile or larger molecules to much lower velocities and<br />
to thereby completely separate the decelerated packet from the rest of<br />
the beam pulse.<br />
Q 12.3 Di 11:30 3G<br />
On the Stark effect of NaK — •Andreas Gerdes, Horst<br />
Knöckel, and Eberhard Tiemann — Institut für Quantenoptik, Gottfried<br />
Wilhelm Leibniz Universität Hannover, Welfengarten 1, 30167<br />
Hannover<br />
After preliminary measurements in a heatpipe setup [1] and characterization<br />
of our new molecular beam aparatus we show the next step<br />
of investigation concerning the heteronuclear molecule NaK. A homogeneous<br />
electric field in the detection zone will modify the rotational<br />
structure of the spectral lines under consideration. For a model description<br />
of the line shapes, not only the molecular Stark effect of the<br />
absolute ground state X 1 Σ + of the molecule, but also the splitting<br />
of the excited state B 1 Π has to be taken into account. Results of<br />
our investigation into this direction will be shown. A comparison with<br />
theoretical predictions is possible [2]. Prospects heading to the target<br />
molecule KRb will be discussed.<br />
[1] A. Gerdes et al., To be published<br />
[2] M. Aymar and O. Dulieu, J. Chem. Phys 122 204302 (2005)<br />
Q 12.4 Di 11:45 3G<br />
Simulations of LiCs spectra — •Anna Grochola, Johannes<br />
Deiglmayr, Jörg Lange, Karin Mörtlbauer, Christian Glück,<br />
Roland Wester, and Matthias Weidemüller — Albert-Ludwigs<br />
Universität, Physikalisches Institut, Hermann-Herder-Str. 3, 79104<br />
Freiburg i.Brsg., Germany<br />
Recently the formation of ultracold LiCs molecules was achieved in<br />
our group [1] and spectra of resonant enhanced one-color two photon<br />
ionization were recorded.<br />
Here we present predictions for photoassociation and REMPI spectra<br />
of the LiCs molecule based on theoretical potential energy curves [2-4]<br />
and experimental data [5,6]. Hund’s cases (a) and (c) are taken into account.<br />
The Franck-Condon factors are calculated for the B 1 Π←X 1 Σ +<br />
system for the free-bound and bound-bound transitions. The results<br />
of spectra simulations are compared with the experimental results.<br />
[1] S. D. Kraft et al., J. Phys. B 39, S993 (2006)<br />
[2] M. Aymar and O. Dulieu, J. Chem. Phys. 122, 204302 (2005)<br />
[3] M. Korek et al., Can. J. Phys. 78, 977 (2000)<br />
[4] Dunia Houalla, Master Thesis, Beirut Arab University (2005)<br />
[5] P. Staanum et al., Phys. Rev. A 75, 042513 (2007)<br />
[6] A. Pashov, private communication<br />
Q 12.5 Di 12:00 3G<br />
Triplet spectroscopy on ultracold 87Rb2 molecules —<br />
•Florian Lang 1 , Gregor Thalhammer 1,2 , Klaus Winkler 1 ,<br />
Christoph Strauss 1 , Rudolf Grimm 1,3 , and Johannes Hecker<br />
Denschlag 1 — 1 Institut für Experimentalphysik und Forschungszentrum<br />
für Quantenphysik, Universität Innsbruck — 2 LENS European<br />
Laboratory for Nonlinear Spectroscopy and Dipartimento di Fisica,<br />
Università di Firenze — 3 Institut für Quantenoptik und Quanteninformation,Österreichische<br />
Akademie der Wissenschaften<br />
Starting from a pure sample of ultracold 87Rb2 Feshbach molecules<br />
held in a 3D optical lattice we have performed spectroscopic measurements<br />
on electronically excited triplet molecules. We investigate the<br />
vibrational ladder down to the vibrational ground state with high resolution<br />
in the order of 1 MHz and find good coupling strength to the<br />
electronic ground state. In combination of our previous results[1],[2]<br />
this offers a promising route towards the production of molecules in<br />
the triplet ground state. In my talk I will report on the latest progress<br />
in our work.<br />
[1] Coherent optical transfer of Feshbach molecules to a lower vibrational<br />
state, K. Winkler, F. Lang, G. Thalhammer, P. v.d. Straten, R.<br />
Grimm, J. Hecker Denschlag Phys. Rev. Lett. 98, 043201 (2007)<br />
[2] Cruising through molecular bound state manifolds with radio frequency,<br />
F. Lang, P.v.d. Straten, B. Brandstätter, G. Thalhammer, K.<br />
Winkler, P.S. Julienne, R. Grimm, J. Hecker Denschlag, submitted for<br />
publication, arXiv:0708.3958<br />
Q 12.6 Di 12:15 3G<br />
Photoexcitation and photodissociation of H +<br />
— •Dennis<br />
3<br />
Bing1 , Max H. Berg1 , Holger Kreckel2 , Annemieke Petrignani1 ,<br />
Sascha Reinhardt1,3 , Xavier Urbain4 , and Andreas Wolf1 —<br />
1Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg,<br />
Germany — 2Columbia University, 550 West 120th Street,<br />
New York, NY 10027, USA — 3Max-Planck-Institut für Quantenoptik,<br />
Hans-Kopfermann-Str. 1, 85748 Garching, Germany — 4Département de Physique, Université Catholique de Louvain, B-1348, Louvain-la-<br />
Neuve, Belgium<br />
We present ro-vibrational laser spectroscopy of cold H +<br />
3 towards the<br />
dissociation limit and photodissociation of vibrationally excited H +<br />
3<br />
ions, using two distinct experimental setups. The photoexcitation of<br />
H +<br />
3 was performed in a 22-pole radiofrequency ion trap, where the<br />
ions were cooled down to their lowest rotational states and then<br />
ro-vibrationally excited by ∼1 eV (∼5 vibrational quanta), i.e., above<br />
the molecule’s barrier to linearity. Transitions of about 11230 - 13330<br />
cm−1 were scanned with a Titanium-Sapphire laser, finding lines with<br />
predicted Einstein A-coefficients down to
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
Q 13: Laserentwicklung (Nichtlineare Effekte und Anwendungen)<br />
Zeit: Dienstag 11:00–13:00 Raum: 3H<br />
Q 13.1 Di 11:00 3H<br />
Resonatorinterne Frequenzkonversion von fs-Lichtimpulsen<br />
in den sichtbaren Spektralbereich mit sektioniert periodisch<br />
gepoltem MgO:LiNbO3 — •Felix Rübel, Peter Haag, Richard<br />
Wallenstein und Johannes L’huillier — Technische Universität<br />
Kaiserslautern, Fachbereich Physik, Erwin-Schrödinger-Str. 46, 67663<br />
Kaiserslautern<br />
Ultrakurze Lichtimpulse im sichtbaren Spektralbereich sind für viele<br />
wissenschaftliche und technische Anwendungen, wie z.B. der zeitaufgelösten<br />
Spektroskopie, der Medizin oder der Display-Technologie, von<br />
besonderem Interesse. Der Wellenlängenbereich zwischen 500 nm und<br />
700 nm kann jedoch nicht von kerrlinsen-modengekoppelten Ti:Saphir-<br />
Lasern oder deren Harmonischen abgedeckt werden. Eine Möglichkeit<br />
zur Erzeugung von fs-Impulsen in diesem Bereich bietet die Frequenzkonversion<br />
der IR-Strahlung synchron gepumpter OPOs. Durch resonatorinterne,<br />
kaskadierte Frequenzverdopplung der Signalstrahlung<br />
konnten fs-Impulse im gelben Spektralbereich bei 593 nm erzeugt werden.<br />
Hierzu wurden periodisch gepolte MgO:LiNbO3-Kristalle mit unterschiedlichen,<br />
kaskadierten Polungsperioden verwendet, so dass sowohl<br />
der OPO- als auch der SHG-Prozess im gleichen Kristall realisiert<br />
werden konnte. Gepumpt mit 1,3 W und 100 fs bei einer Repetitionsrate<br />
von 82 MHz, wurde in dem kaskadierten OPO-SHG-Prozess eine<br />
maximale Ausgangsleistung von 220 mW erzeugt. Für die Konversion<br />
von Pumpstrahlung zu sichtbarer Strahlung entspricht dies einer Effizienz<br />
von 17 %. Die minimale Impulsdauer betrug 280 fs. Es ergab sich<br />
ein Zeit-Bandbreiten-Produkt von 1,09.<br />
Q 13.2 Di 11:15 3H<br />
Temperaturabhängigkeit des Koerzitivfeldes in VTE-LiTaO3<br />
— •Alexander Quosig 1 , Volker Wesemann 2 , Daniel Rytz 2 und<br />
Johannes L’Huillier 1 — 1 Technische Universität Kaiserslautern,<br />
Fachbereich Physik, Erwin-Schrödinger-Strasse 46, 67663 Kaiserslautern<br />
— 2 FEE GmbH, Struthstrasse 2, 55743 Idar-Oberstein<br />
Kongruentes LiTaO3 (CLT) ist aufgrund des hohen nichtlinearen Koeffizienten<br />
d33=14,6pm/V und der hohen Transparenz im mittleren infraroten,<br />
sichtbaren und ultravioletten Spektralbereich ein geeignetes<br />
Material zur Frequenzkonversion von Laserstrahlung durch Quasiphasenanpassung<br />
(QPM) mittels periodisch angeordneter ferroelektrischer<br />
Domänen. Die mit dem Czochralski-Verfahren gezüchteten Kristalle<br />
weisen ein Lithium-Defizit auf. Daraus resultierende nachteilige Eigenschaften<br />
wie grün-induzierte Infrarotabsorption (GRIIRA) und Photorefraktivität<br />
lassen sich durch eine Nachbehandlung des Materials<br />
mittels Vapour-Transport-Equilibration (VTE) stark reduzieren. Die<br />
Verringerung des Koerzitivfeldes durch VTE von 21kV/mm bei CLT<br />
auf bis zu 0,1kV/mm ermöglicht darüber hinaus die Herstellung dicker<br />
QPM-Kristalle (>1mm). In Ferroelektrika mit niedrigem Koerzitivfeld<br />
sind die thermische Stabilität der Domänenwände und die Polungsdynamik<br />
von besonderem Interesse. Temperaturerhöhung von 13 ◦ C auf<br />
80 ◦ C bewirkt in VTE-LT mit einem Li2O-Anteil von 49,95mol% eine<br />
Abnahme des Koerzitivfeldes um 23% von 256V/mm auf 198V/mm.<br />
Die Polungsdynamik und die Temperaturabhängigkeit des Koerzitivfeldes<br />
konnte durch ein quantitatives zweidimensionales Modell des<br />
Domänenwachstums theoretisch beschrieben werden.<br />
Q 13.3 Di 11:30 3H<br />
Diodengepumpter einfachresonanter dauerstrich-optischparametrischer<br />
Oszillator — •Jens Kießling, Rosita Sowade,<br />
Ingo Breunig, Bastian Knabe und Karsten Buse — Physikalisches<br />
Institut, Universität Bonn, Wegelerstr. 8, 53115 Bonn<br />
Dauerstrich-optisch-parametrische Oszillatoren (OPOs) zeichnen sich<br />
durch ihren weiten Durchstimmbereich bei schmaler Linienbreite aus<br />
und sind deshalb beliebte Lichtquellen für spektroskopische Anwendungen.<br />
Longitudinal und transversal einmodige Laserdioden sind für<br />
solche Systeme kompakte und preisgünstige Pumpquellen, jedoch ist<br />
ihre Ausgangsleistung begrenzt. Um sie dennoch hierfür einsetzen zu<br />
können, muss die Pumpschwelle des OPOs deutlich unter 1 W gesenkt<br />
werden. Dafür bieten sich doppelt- und dreifachresonante Oszillatoren<br />
an, deren Aufbau und Stabilisierung im Vergleich zu einfachresonanten<br />
Systemen allerdings aufwändiger ist. Wir demonstrieren einen alternativen<br />
Ansatz, der es ermöglicht, eine transversal und longitudinal<br />
einmodige Laserdiode mit weniger als 100 mW Ausgangsleistung als<br />
Pumpquelle für einen einfachresonanten OPO zu verwenden.<br />
*Gefördert von der Deutsche Telekom AG.<br />
Q 13.4 Di 11:45 3H<br />
Ramanstreuung in einem einfachresonanten dauerstrichoptisch-parametrischen<br />
Oszillator — •Ingo Breunig, Jens<br />
Kießling, Rosita Sowade, Bastian Knabe und Karsten Buse —<br />
Physikalisches Institut, Universität Bonn, Wegelerstr. 8, 53115 Bonn<br />
In einem einfachresonanten optisch-parametrischen Oszillator (OPO)<br />
entstehen aus einem Pumpfeld ein Idler- und ein Signalfeld, wobei<br />
letzteres resonant überhöht wird. Die Bandbreite der parametrischen<br />
Verstärkung liefert eine obere Grenze für die spektrale Breite des Signalfelds.<br />
In unserem Aufbau beobachten wir Linien außerhalb dieses<br />
Verstärkungsprofils, deren Anzahl sich mit steigender Pumpleistung<br />
erhöht. Die ermittelten Frequenzabstände von 1.4 THz bzw. 7.5 THz<br />
stimmen mit bekannten Ramanverschiebungen des verwendeten nichtlinearen<br />
Materials (Lithiumniobat) überein. Weiterhin lässt sich ein<br />
Zusammenhang zwischen spektraler Reinheit des Signalfelds und Idlerleistung<br />
feststellen.<br />
*Gefördert von der Deutsche Telekom AG.<br />
Q 13.5 Di 12:00 3H<br />
Messung von Emissionsspektren der Brillouin Streuung in<br />
Ytterbium dotierten einfrequenten Faserverstärkern mit 130<br />
W Ausgangsleistung — •Sebastian Büsche, Matthias Hildebrandt,<br />
Maik Frede und Dietmar Kracht — Laser Zentrum Hannover<br />
e.V., Hollerithallee 8, 30419 Hannover<br />
Es werden Heterodyn-Messungen von Emissionsspektren der spontanen<br />
und stimulierten Brillouinstreuung eines einfrequenten Faserverstärkers<br />
vorgestellt. Dazu wurde ein schmalbandig emittierender<br />
Ringlaser (NPRO) mit einer diodengepumpten Ytterbium<br />
dotierten Doppelkernfaser auf bis zu 130 W verstärkt. Durch<br />
Überlagerung der gestreuten Brillouinstrahlung mit einem zweiten<br />
schmalbandigen Ringlaser wurden Brillouinspektren über den gesamten<br />
Verstärkerleistungsbereich detektiert. Mit steigender Ausgangsleistung<br />
zeigen die Spektren einen Übergang von Lorentz- zu Gaußprofilen<br />
bei einer exponentiellen Abnahme der Halbwertsbreiten. Ein zweites<br />
Experiment mit ungepumpter Faser, bei der ein zweiter Ringlaser<br />
gegenläufig zur Seedquelle in die Faser gekoppelt und mit seiner<br />
Kristalltemperatur diskret über den Frequenzbereich des Brillouin<br />
Verstärkungsprofils gestimmt wurde, verifizierte die Heterodyn-<br />
Messung. Die gemessenen Verstärkungsprofile stimmen gut mit den<br />
Profilen bei niedriger Verstärkerleistung überein. Die experimentellen<br />
Ergebnisse sollen zum Verständnis der Entwicklung stimulierter<br />
Brillouinstreuung in Hochleistungsverstärkerfasern beitragen und<br />
zukünftig eine weitreichende Unterdrückung dieses leistungslimitierenden<br />
Effekts ermöglichen.<br />
Q 13.6 Di 12:15 3H<br />
Fourier Domain Mode Locking (FDML): Ein neuer Operationsmodus<br />
von Lasern und dessen Anwendungen — Christoph<br />
Eigenwillig 1 , Benjamin Biedermann 1 , Desmond Adler 2 , James<br />
Fujimoto 2 und •Robert Huber 1 — 1 Lehrstuhl für BioMolekulare<br />
Optik, Fakultät für Physik, LMU München — 2 Department of Electrical<br />
Engineering and Computer Science, and Research Laboratory of<br />
Electronics, Massachusetts Institute of Technology<br />
Fourier Domain Mode Locking (FDML) stellt einen neuartigen,<br />
stationären Betriebszustand von Lasern dar [1]. Im Gegensatz<br />
zur herkömmlichen Modenkopplung basiert FDML nicht auf einem<br />
Amplituden- oder Phasen-Modulationsmechanismus, sondern es<br />
kommt ein schnell abstimmbarer, schmalbandiger spektraler Filter zum<br />
Einsatz. FDML-Laser emittieren sehr schnelle, schmalbandige Wellenlängendurchläufe<br />
mit Bandbreiten von mehr als 150nm und instantanen<br />
Linienbreiten von etwa 50pm bei Repetitionsraten von mehreren<br />
100 kHz. Die Emissionscharakteristik ist äquivalent zu einer Serie<br />
extrem dispersiver (gechirpter) Lichtimpulse. Neben der Hauptanwendung<br />
von FDML Lasern für die optische Kohärenztomographie<br />
(engl.: optical coherence tomography - OCT) in der biomedizinische<br />
Bildgebung, wird der Einsatz von FDML Lasern für Profilometrie-<br />
Anwendungen mit pm-Auflösung, für die Echtzeitspektroskopie an chemischen<br />
Reaktionsprozessen in Verbrennungsmotoren und für die Zustandsanalyse<br />
von Gemälden vorgestellt.<br />
1. Huber R. et al. Optics Express 14:3225-3237 (2006).
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
2. Huang D. et al. Science 254:1178-1181 (1991).<br />
Q 13.7 Di 12:30 3H<br />
PLD-hergestellte, kristalline Antireflexbeschichtungen und<br />
dichroitische Spiegel — •Friedjof Tellkamp, Teoman Gün, Bilge<br />
Ileri, Klaus Petermann und Günter Huber — Institut für<br />
Laser-Physik, Universität Hamburg, Luruper Chaussee 149, 22761<br />
Hamburg<br />
Mittels Pulsed Laser Deposition (PLD) hergestellte kristalline Vielschichtsysteme<br />
wurden bezüglich ihrer strukturellen und optischen<br />
Qualität analysiert. Die Schichtsysteme werden in situ mittels Reflection<br />
High Energy Electron Diffraction (RHEED) und Reflektometrie<br />
sowie ex situ mittels Röntgenstrukturanalyse (XRD) und Spektroskopie<br />
auf Transmissivität und Struktur untersucht.<br />
Es konnte anhand der Antireflexsysteme Sc2O3/Al2O3 auf (0001)-<br />
Saphir und LuAG/YAG auf {100}-YAG gezeigt werden, dass sich die<br />
Reflexion um das theoretisch zu erwartende Maß reduzieren lässt. Die<br />
XRD-Messungen lassen auf ein texturiertes Wachstum der Schichten<br />
schließen. Die RHEED-Analyse an dem System LuAG/YAG auf YAG<br />
zeigt einkristallines Schichtwachstum.<br />
Ferner wurden gitterangepasste LuGdAG-Schichten untersucht. Die<br />
mittels XRD gemessene Gitterfehlanpassung lag bei < 0,5 %; mit<br />
RHEED konnte epitaktisches Wachstum auch nach Deposition von<br />
Q 14: Quanteninformation (Quantencomputer I)<br />
29 Schichten bei einer Gesamtdicke von 1850 nm gezeigt werden. Allerdings<br />
wurde eine sich kontinuierlich vermindernde Depositionsrate<br />
festgestellt, sodass die Reflexionseigenschaften dieser dichroitischen<br />
Spiegel noch nicht zu beobachten waren. Eine in situ Schichtdickenregelung<br />
wird dieses Problem in Zukunft beheben.<br />
Q 13.8 Di 12:45 3H<br />
Neue Entwicklungen bei ps-Laserstrahlquellen für die Mikromaterialbearbeitung<br />
— •Achim Nebel — Lumera Laser GmbH,<br />
Opelstr. 10, 67661 Kaiserslautern<br />
Ultrakurzpulslaser haben für die Mikromaterialbearbeitung eine Vielzahl<br />
von Vorteilen. Sie bearbeiten alle Materialien und das mit höchster<br />
Qualität. Für den industriellen Einsatz besonders ausgezeichnet haben<br />
sich ps-Laser. Sie sind diodengepumpt, ermöglichen höchste Wiederholraten<br />
und hohe Leistungen. Ihre beugungsbegrenzte polarisierte<br />
Strahlung ermöglicht zudem eine effiziente Frequenzkonversion bis in<br />
den UV-Bereich, so dass Prozessoptimierungen auch mit hohen Leistungen<br />
bei 532nm- und 355nm möglich sind. Vorgestellt werden u.a.<br />
verstärkte Nd:YVO4 ps-Laser. Die neueste Generation dieser Laser hat<br />
mittlere Leistungen größer 50 W bei Wiederholraten von 1MHz (50 µJ<br />
Pulsenergie). Anhand von Bearbeitungsbeispielen wird der große Nutzen<br />
der Pikosekundenlaser für die Präzisionsmikromaterialbearbeitung<br />
dargestellt.<br />
Zeit: Dienstag 14:00–15:45 Raum: 1B<br />
Gruppenbericht Q 14.1 Di 14:00 1B<br />
Simulation of a Quantum Magnet — •Axel Friedenauer 1 ,<br />
Hektor Schmitz 1 , Jan Glueckert 1 , Lutz Petersen 2 , and Tobias<br />
Schaetz 1 — 1 Max Planck Institut für Quantenoptik, Garching,<br />
Deutschland — 2 ETH Zuerich<br />
Simulating quantum mechanical systems is a hard task since the<br />
amount of degrees of freedom scale exponentially with the number<br />
of constituents. We are aiming to circumvent this difficulty by introducing<br />
a quantum simulator based on the idea that systems governed<br />
by the same Hamiltonian evolve alike.<br />
Our system for a feasibility study is a linear chain of magnesium<br />
ions. External fields and interactions between the ions are simulated/controled<br />
via rf- and laser-fields respectively. To initialize our<br />
system, we cool up to three ions close to the axial-motional ground<br />
state ¯n < 0.05.To calibrate our operational fidelities, we implemented<br />
a geometric phase gate 1 and prepared an entangled Bell state of two<br />
ions with a fidelity exceeding 95%. Subsequently, we were able to simulate<br />
an adiabatic evolution of two spins described by the Quantum-<br />
Ising-Hamiltonian from paramagentic into ferromagnetic order 2,3 with<br />
an fidelity of 95%. We proof that this transition is driven by quantum<br />
(not thermal) fluctuations providing us even an entangled state with<br />
a lower bound for the fidelity of 70%. We discuss these results and<br />
comment on the possibilities to increase the size of our system.<br />
[1] D. Leibfried et al., Nature 422, 412 (2003)<br />
[2] D. Porras and J.I. Cirac, Phys. Rev. Lett. 92, 207901 (2004)<br />
[3] to be published<br />
Q 14.2 Di 14:30 1B<br />
Effects of imperfections for Shor’s factorization algorithm —<br />
•Ignacio Garcia-Mata, Klaus M. Frahm, and Dima L. Shepelyansky<br />
— Laboratoire de Physique Theorique, UMR 5152 du CNRS, Universite<br />
Toulouse III<br />
We study effects of imperfections induced by residual couplings between<br />
qubits on the accuracy of Shor’s algorithm using numerical simulations<br />
of realistic quantum computations with up to 30 qubits. The<br />
factoring of numbers up to N = 943 show that the width of peaks,<br />
which frequencies allow to determine the factors, grow exponentially<br />
with the number of qubits. However, the algorithm remains operational<br />
up to a critical coupling strength ɛc which drops only polynomially<br />
with log 2 N. The numerical dependence of ɛc on log 2 N is explained<br />
by analytical estimates that allows to obtain the scaling for functionality<br />
of Shor’s algorithm on realistic quantum computers with a large<br />
number of qubits.<br />
Q 14.3 Di 14:45 1B<br />
Quantum Simulator for the Ising model with electrons float-<br />
ing on helium film — •Sarah Mostame and Ralf Schützhold<br />
— Institut für Theoretische Physik, Technische Universität Dresden,<br />
01062 Dresden, Germany<br />
We propose a physical setup that can be used to simulate the quantum<br />
dynamics of the Ising model. Our scheme consists of electrons floating<br />
on liquid helium which interact via Coulomb forces. In the limit<br />
of low temperatures (0.1 kelvin) the system will stay near the ground<br />
state where its Hamiltonian is equivalent to the Ising model. Furthermore,<br />
the proposed design is relevant to study the adiabatic quantum<br />
computers.<br />
Q 14.4 Di 15:00 1B<br />
Quantum Computation with Gaussian Continuous-Variable<br />
Cluster States — •Peter van Loock — Optical Quantum Information<br />
Theory Group, Max Planck Research Group, Institute of Optics,<br />
Information and Photonics, Staudtstr. 7/B2, 91058 Erlangen, Germany<br />
We describe an extension of the cluster-state model for universal quantum<br />
computation from qubits to quantized harmonic oscillators, i.e.,<br />
a translation from discrete to continuous quantum variables [1]. Compared<br />
to the discrete case, many features of the continuous-variable<br />
model have their direct analogues: cluster-state preparation via Gaussian<br />
(Clifford) operations, realization of any Gaussian transformation<br />
via Gaussian measurements in arbitrary order (Clifford computation<br />
and parallelism), and universal quantum computation via at least one<br />
non-Gaussian (non-Clifford) measurement including feedforward. For<br />
the optical creation of approximate cluster states in form of multimode<br />
squeezed Gaussian states [2] and the optical implementation<br />
of small-scale cluster computations [3], we discuss various protocols<br />
including linear-optics generation schemes and protocols for finitesqueezing-induced<br />
error filtration.<br />
[1] N. C. Menicucci, P. van Loock, M. Gu, C. Weedbrook, T. C. Ralph,<br />
and M. A. Nielsen, Phys. Rev. Lett. 97, 110501 (2006).<br />
[2] P. van Loock, C. Weedbrook, and M. Gu, Phys. Rev. A 76, 032321<br />
(2007).<br />
[3] P. van Loock, J. Opt. Soc. Am. B 24, 340 (2007).<br />
Q 14.5 Di 15:15 1B<br />
Pseudo bound entanglement in NMR quantum computing —<br />
•Hermann Kampermann 1 , Xinhua Peng 2 , Dagmar Bruß 1 , and Dieter<br />
Suter 2 — 1 Theoretische Physik III, Universität Düsseldorf —<br />
2 Experimentelle Physik IIIa, Universität Dortmund<br />
In NMR we have precise coherent control of small qubit systems (up<br />
to roughly 12 qubits), but NMR systems used today consist of large<br />
ensembles of nuclear spin quantum processors in a higly mixed (separable)<br />
state. So-called pseudo pure states are used to circumvent this
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
problem. We use liquid state Nuclear Magnetic Resonance (NMR) to<br />
generate a 3-qubit ”pseudo bound entangled state”and characterize it<br />
via state tomography and by detection of a witness operator for this<br />
class of states.<br />
Q 14.6 Di 15:30 1B<br />
A Quantum CISC Compiler and Scalable Assembler for<br />
Quantum Computing on Large Systems — •Thomas Schulte-<br />
Herbrüggen, Andreas Spörl, and Steffen Glaser — Dept. Chemistry,<br />
Technical University of Munich (TUM), 85747 Garching<br />
Using the cutting edge high-speed parallel cluster HLRB-II (with a<br />
total LINPACK performance of 63.3 TFlops/s) we present a quantum<br />
CISC compiler into time-optimised or decoherence-protected complex<br />
Q 15: Quantengase (Gitter I)<br />
instruction sets. They comprise effective multi-qubit interactions with<br />
up to 10 qubits. We show how to assemble these medium-sized CISCmodules<br />
in a scalable way for quantum computation on large systems.<br />
Extending the toolbox of universal gates by optimised complex multiqubit<br />
instruction sets paves the way to fight decoherence in realistic<br />
Markovian and non-Markovian settings.<br />
The advantage of quantum CISC compilation over standard RISC<br />
compilations into one- and two-qubit universal gates is demonstrated<br />
inter alia for the quantum Fourier transform (QFT) and for multiplycontrolled<br />
NOT gates. The speed-up is up to factor of six thus giving<br />
significantly better performance under decoherence. – Implications for<br />
upper limits to time complexities are also derived.<br />
Zeit: Dienstag 14:00–16:00 Raum: 1C<br />
Q 15.1 Di 14:00 1C<br />
Bogoliubov vs. chaotic energy spectrum for Bose atoms in<br />
optical lattices — •Andrey Kolovsky — Kirensky Institute of<br />
Physics, 660036 Krasnoyarsk, Russia<br />
Recent experiments with cold bosonic atoms in optical lattices has renewed<br />
the theoretical studies of the Bose-Hubbard model, which constitutes<br />
one of the fundamental Hamiltonians in the condensed matter<br />
theory. The number of phenomena, discussed in the frame of this<br />
model, is so diverse that sometimes it is difficult to see any link between<br />
them. In particular, this concerns the phenomena of superfluidity and<br />
Quantum Chaos. Indeed, the former phenomenon assumes the regular<br />
phononlike excitation spectrum, described by the Bogoliubov theory,<br />
while the latter phenomenon implies a highly irregular excitation spectrum,<br />
described by the random matrix theory. This seeming contradiction<br />
is resolved by noting that these two spectra refer to different<br />
characteristic energies of the system. In the talk I shall explain of how<br />
the regular Bogoliubov spectrum of the Bose-Hubbard system evolves<br />
into an irregular one as the system energy is increased. A manifestation<br />
of this transition for the excitation dynamics of the superfluid state of<br />
cold atoms in optical lattices is discussed as well [1].<br />
[1] A. R. Kolovsky, Phys. Rev. Lett. 99, 020401 (2007); Phys. Rev.<br />
E 76, 026207 (2007).<br />
Q 15.2 Di 14:15 1C<br />
Many-body Wannier-Stark dynamics — •Patrick Plötz 1,2 and<br />
Sandro Wimberger 1,2 — 1 Institut für Theoretische Physik, Universität<br />
Heidelberg, Philsophenweg 19, 69120 Heidelberg — 2 Heidelberg<br />
Graduate School of Fundamental Physics, Albert-Ueberle-Str. 3-5,<br />
69120 Heidelberg<br />
Interacting bosons in a one-dimensional optical lattice are studied in<br />
the presence of an additional and tunable tilting force in the stronglycorrelated<br />
many-particle regime. We use a multi-band Bose-Hubbard<br />
model to describe this many-body Wannier-Stark problem. Tomadin<br />
et al. [Phys. Rev. Lett. 98, 130402 (2007)] perturbatively included the<br />
first excited energy band on top of the widely used single band approximation,<br />
and found clear signatures of complex quantum dynamics in<br />
the interband tunneling rates. We investigate, in turn, the dynamics<br />
of a complete two-band model non-perturbatively. The dominant<br />
coupling channels between the bands are found for a realization with<br />
ultracold atoms. Our model allows us to study the vertical transport<br />
in energy space as well as the horizontal quantum transport along the<br />
lattice and their interdependence.<br />
Q 15.3 Di 14:30 1C<br />
Bloch oscillations and Landau-Zener tunneling of interacting<br />
ultracold atoms — •Ghazal Tayebirad and Sandro Wimberger<br />
— Institut für Theoretische Physik, Universität Heidelberg, D-69120<br />
Heidelberg<br />
A series of recent experiments measured the impact of atom-atom<br />
interactions on Bloch oscillations [1,2] and on Landau-Zener interband<br />
tunneling [3] of ultracold atoms in a tilted periodic (washboard)<br />
potential. We investigate the effect of interactions in the mean-field<br />
regime on these dynamical processes. Moreover, we discuss possibilities<br />
of controlling quantum transport in the interacting Wannier-Stark<br />
system by time-dependent and spatially inhomogeneous potentials.<br />
[1] M. Fattori et al., arXiv:0710.5031.<br />
[2] M. Gustavsson et al., arXiv:0710.5083.<br />
[3] C. Sias et al., Phys. Rev. Lett. 98, 120403 (2007).<br />
Q 15.4 Di 14:45 1C<br />
Phase Diagram of Spin-1 Bosons in Optical Lattice at Non-<br />
Zero Temperature — •Matthias Ohliger 1 and Axel Pelster 2<br />
— 1 Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195<br />
Berlin, Germany — 2 Fachbereich Physik, Universität Duisburg-Essen,<br />
Lotharstraße 1, 47048 Duisburg, Germany<br />
We extend previous zero-temperature mean-field studies [1,2] for the<br />
location of the superfluid-Mott insulator transition of spin-1 bosons<br />
in an optical lattice to finite temperatures. We find that the phase<br />
boundary changes continuously with the magnetization of the system<br />
and that a complete magnetization reproduces the phase diagram of<br />
spin-0 bosons [3,4]. For an antiferromagnetic interaction, however, the<br />
zero-temperature limit of our phase diagram deviates significantly from<br />
the zero-temperature mean-field studies [1,2], where a degenerate perturbation<br />
theory is applied for an odd number of bosons per site.<br />
[1] S. Tsuchiya, S. Kurihara, and T. Kimura, Phys. Rev. A 70,<br />
043628 (2004)<br />
[2] T. Kimura, S. Tsuchiya, M. Yamashita, and S. Kurihara, J. Phys.<br />
Soc. Japan 75, 074601 (2006)<br />
[3] P. Buonsante and A. Vezzani, Phys. Rev. A 70, 033608 (2004).<br />
[4] K.V. Krutitsky, A. Pelster, and R. Graham, New J. Phys. 8, 187<br />
(2006).<br />
Q 15.5 Di 15:00 1C<br />
Diagrammatic Calculation of Finite-Temperature Properties<br />
of the Bose-Hubbard Model — Henrik Enoksen 1 , Alexander<br />
Hoffmann 2 , •Matthias Ohliger 3 , and Axel Pelster 4 —<br />
1 Department of Physics, Norwegian University of Science and Technology,<br />
N-7491 Trondheim, Norway — 2 Arnold Sommerfeld Center<br />
for Theoretical Physics, Theresienstr. 37, Department Physik, Universität<br />
München, 80333 München, Germany — 3 Fachbereich Physik,<br />
Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany —<br />
4 Fachbereich Physik, Universität Duisburg-Essen, Lotharstraße 1,<br />
47048 Duisburg, Germany<br />
Following an approach first worked out by Metzner in the context of<br />
electrons in conductors [1], we use a diagrammatic hopping expansion<br />
to calculate finite-temperature Green’s functions for the Bose-Hubbard<br />
model which describes bosons in an optical lattice. This allows us to<br />
reconstruct in a qualitative way the time-of-flight absorption pictures,<br />
which are taken after the optical lattice is switched off. Furthermore,<br />
the technique makes summations of subsets of diagrams possible, leading<br />
to non-perturbative results for locating the boundary between the<br />
superfluid and the Mott phase for finite temperatures. Whereas the<br />
first-order calculation reproduces the seminal mean-field result, the<br />
second order goes beyond and shifts the phase boundary in the immediate<br />
vicinity of the critical parameters determined by Monte-Carlo<br />
simulations of the Bose-Hubbard model.<br />
[1] W. Metzner, Phys. Rev. B 43, 8549 (1993)<br />
Q 15.6 Di 15:15 1C<br />
Quantum Corrections of Mean-Field Phase Diagram for<br />
Bosons in Lattices — •Francisco Ednilson Alves dos Santos 1
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
and Axel Pelster 2 — 1 Fachbereich Physik, Freie Universität Berlin,<br />
Arnimallee 14, 14195 Berlin, Germany — 2 Fachbereich Physik, Universität<br />
Duisburg-Essen, Lotharstraße 1, 47048 Duisburg, Germany<br />
We improve the zero-temperature mean-field calculations for bosons<br />
in optical lattices by systematically working out the effect of quantum<br />
corrections. To this end we decompose the underlying nonlocal<br />
Bose-Hubbard Hamiltonian into the local mean-field Hamiltonian and<br />
treat the difference between them perturbatively. Using a diagrammatic<br />
technique, we calculate the ground-state energy up to second<br />
order in the quantum corrections. Therein, we interpret the order parameter<br />
ψ as a variational parameter, which is determined from optimizing<br />
the ground-state energy. With this analytical approach we<br />
obtain for arbitrary spatial dimension an improved boundary between<br />
Mott insulator and superfluid phase in accordance with previous highprecision<br />
results from quantum Monte-Carlo simulations.<br />
Q 15.7 Di 15:30 1C<br />
AC-induced superfluidity — •André Eckardt and Martin<br />
Holthaus — Institut für Physik, Carl von Ossietzky Universität,<br />
26111 Oldenburg<br />
In previous work we have shown that it should be possible to coherently<br />
control the transition from a superfluid to a Mott insulator in the<br />
Bose-Hubbard model by an oscillating force through an effective modification<br />
of the tunneling matrix element [Eckardt et al., PRL 95, 260404<br />
(2005)]. The effective tunnel modification has recently been observed<br />
experimentally by the Arimondo group in Pisa, without notable loss<br />
of coherence caused by the drive [Lignier et al., cond-mat/0707.0403<br />
(2007)]. In this talk we will consider a Bose-Hubbard system that is<br />
subjected to a static potential tilt such that tunneling is strongly suppressed<br />
due to the localization of the Wannier-Stark states. We show<br />
Q 16: Photonik I<br />
that tunneling can be restored partially in a coherent way by resonantly<br />
driving the system at high frequencies (a few kHz for a typical<br />
experiment with Alkali atoms in an optical lattice). For integer<br />
filling, the interplay between interparticle repulsion and this kind of<br />
“photon”-assisted tunneling should give rise to a Mott-like transition,<br />
with (quasi) long-range order (i.e. superfluidity) being established by<br />
switching on the AC-drive [Eckardt & Holthaus, EPL 80, 50004 (2007)].<br />
It is also possible to control the sign of the effective tunneling matrix<br />
element by varying the amplitude of the drive. We argue that an adiabatic<br />
passage of the system’s ground state through such a sign change<br />
is a many-body effect that relies on the existence of a Mott-insulator<br />
phase.<br />
Q 15.8 Di 15:45 1C<br />
Ultracold bosons in optical superlattices with and without<br />
disorder: A numerical approach — •Dominik Muth, Alexander<br />
Mering, and Michael Fleischhauer — Fachbereich Physik, Technische<br />
Universität Kaiserslautern, D-67663 Kaiserslautern<br />
The time-evolving block decimation algorithm (TEBD) for onedimensional<br />
systems and its modification for infinite size systems<br />
(iTEBD) can be used to determine the ground state for various Hamiltonians.<br />
We apply this method to determine the superfluid to Mottinsulator<br />
phase transition for a Bose-Hubbard model with a superlattice.<br />
While for small hopping parameter J the loophole-shaped insulator<br />
domains, derived by a mean-field approach [1], fit quite well to<br />
our numerical results, the results differ for large hopping as expected.<br />
Adding disorder to the system, we show that the loophole domains<br />
detach from the J=0 axis, creating insulating islands surrounded by a<br />
Bose-glass phase.<br />
[1] P. Buonsante, A. Vezzani - Phys. Rev. A 72, 013614 (2005)<br />
Zeit: Dienstag 14:00–16:00 Raum: 2B/C<br />
Q 16.1 Di 14:00 2B/C<br />
Nonlinear optical response of metal nanoantennas —<br />
•Barbara Wild, Jörg Merlein, Tobias Hanke, Alfred Leitenstorfer,<br />
and Rudolf Bratschitsch — Departement of Physics and<br />
Center for Applied Photonics, University of Konstanz, D-78464 Konstanz,<br />
Germany<br />
We have investigated the nonlinear optical response of bowtie-shaped<br />
gold nanoantennas fabricated with the colloidal mask technique. The<br />
structures were excited by picosecond light pulses with a center wavelength<br />
of 790 nm. The excitation frequency is equal to the plasmon<br />
resonance of the nanoantennas, which has been determined via darkfield<br />
scattering spectroscopy. The spectrum emitted by the nanoantennas<br />
consists of a broadband continuum overlapped with a narrowband<br />
second harmonic signal at λ = 395 nm. We will discuss the influence<br />
of the exciting laser spectrum on the nonlinear response of the metal<br />
nanoantennas and possible applications of this effect.<br />
Q 16.2 Di 14:15 2B/C<br />
Volumenholographie durch Löcher mit Sub-Wellenlängen<br />
Durchmesser* — •Felix Kalkum, Sebastian Broch und Karsten<br />
Buse — Physikalisches Institut, Universität Bonn, Wegelerstraße<br />
8, 53115 Bonn<br />
Licht trifft auf einen Metallfilm mit einem Loch, das einen Durchmesser<br />
kleiner als die Wellenlänge hat. Hinter dem Metallfilm befindet sich ein<br />
photosensitiver Kristall. In diesem kann das Beugungsmuster, die sogenannte<br />
Signalwelle, durch Überlagerung mit einer kohärenten Referenzwelle<br />
holographisch gespeichert werden. Phasenkonjugiertes Lesen<br />
erzeugt das phasenkonjugierte Signallicht, welches fokussiert wird und<br />
wieder durch das Loch nach außen tritt. Das Ziel ist, eine besonders<br />
gute Fokussierung zu erreichen, da sich Strahlen aus allen Richtungen<br />
im Fokus überlagern können. Dies entspricht einer sehr hohen Numerischen<br />
Apertur. Außerdem sollen kompliziertere Muster auf der Oberfläche,<br />
zum Beispiel für die Nanolithographie, effizient ausgeleuchtet<br />
werden können. Wir haben hierfür einen aktiv stabilisierten Aufbau<br />
hergestellt. Die Hologramme werden in eisendotierten Lithiumniobatkristallen<br />
gespeichert. Zum Schreiben und Lesen verwenden wir Licht<br />
der Wellenlänge 532 nm. Die Leistung des rekonstruierten Lichts erreicht<br />
zum Beispiel bei einem Loch mit Durchmesser 500 nm bis zu<br />
10 −4 des einfallenden phasenkonjugierten Referenzlichts. Dieser An-<br />
teil kann unter anderem maximiert werden, indem die Kristallgröße<br />
geeignet gewählt wird.<br />
*Gefördert von der DFG (FOR 557) und der Deutschen Telekom<br />
Stiftung.<br />
Q 16.3 Di 14:30 2B/C<br />
Bindungsmechanismus von Solitonenmolekülen in dispersionsalternierenden<br />
Glasfasern — •Alexander Hause, Haldor<br />
Hartwig und Fedor Mitschke — Universität Rostock, Fachbereich<br />
Physik, Universitätsplatz 3, 18051 Rostock<br />
Kürzlich konnte von uns gezeigt werden[1], dass in Glasfaserstrecken<br />
mit periodisch wechselnder Dispersion stabile Verbundzustände aus<br />
Solitonen, so genannte Solitonenmoleküle, existieren. Die phasensensitive<br />
Charakterisierung dieser Koppelzustände mit Hilfe des neuartigen<br />
und eindeutigen Vampire-Messverfahrens [2] (very advanced method of<br />
phase and intensity retrieval of E-fields) sowie numerische Simulationen<br />
lieferten Hinweise auf die Phasendynamik als Ursache der Bindung<br />
des Moleküls.<br />
Abhängig vom Abstand und Chirp der Einzelimpulse ergibt sich ein<br />
anziehendes oder abstoßendes Verhalten des Doppelimpulses. Bei einem<br />
bestimmten Abstand ist die resultierende Kraft null, bei kleineren<br />
Abständen zeigt sich eine Abstoßung und bei größeren Abständen eine<br />
Anziehung. Dies definiert einen stabilen Gleichgewichtsabstand.<br />
Störungstheoretische Betrachtungen der Phasendynamik liefern ein<br />
Modell, das dieses typische Verhalten zeigt und die Bindung der Solitonen<br />
erklären kann.<br />
[1] M. Stratmann et. al., Phys. Rev. Lett. 95, 143902 (2005)<br />
[2] A. Hause et. al., Phys. Rev. A 75, 063836 (2007)<br />
Q 16.4 Di 14:45 2B/C<br />
Eine Unschärferelation für optische Solitonen — •Michael<br />
Böhm und Fedor Mitschke — Universität Rostock, Institut für Physik,<br />
Universitätsplatz 3, 18055 Rostock<br />
Numerische Simulationen der Ausbreitung optischer Lichtimpulse in<br />
Glasfasern, welche man beispielsweise bei der Datenübertragung verwendet,<br />
können erfolgreich die Veränderung der Impulsform, Dauer,<br />
etc. beschreiben. Wegen der Nichtlinearität der Faser enthalten die<br />
Lichtimpulse im allgemeinen Solitonen. Der Solitonengehalt geht allerdings<br />
nicht aus der Simulation hervor. Er kann mit der Inversen
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
Streutheorie [1] bestimmt werden. Diese ist allerdings auf integrable<br />
Systeme beschränkt und daher streng genommen nicht auf reale Fälle<br />
anwendbar. Mit einem kürzlich eingeführten Verfahren, dem ” solitonradiation<br />
beat analysis“ [2], kann man nun den Solitonengehalt auch<br />
für nichtintegrable Systeme ermitteln, insbesondere auch für Systeme<br />
in denen sich die Energie ändert. Mithilfe dieses Verfahrens konnten<br />
wir eine Unschärferelation zwischen der Energie und der Position in<br />
der Glasfaser für Solitonen formulieren.<br />
[1] V. E. Zakharov and A. B. Shabat, Exact theory of two-dimensional<br />
self-focusing and one-dimensional self-modulation of waves in nonlinear<br />
media, Soviet Phy. JETP, 34 1, (1972) 62-69<br />
[2] M. Böhm und F. Mitschke, Soliton-radiation beat analysis, Phys.<br />
Rev. E 73 066615, (2006)<br />
Q 16.5 Di 15:00 2B/C<br />
Selbstorganisierte Erzeugung von Superkontinuum in einem<br />
passiven, nichtlinearen Faser-Ring-Resonator — •Toralf<br />
Ziems, K. V. Adarsh, Michael Böhm und Fedor Mitschke — Universität<br />
Rostock, Institut für Physik, Universitätsplatz 3, 18055 Rostock<br />
Optisches Superkontinuum ist für eine Fülle photonischer Anwendungen<br />
nutzbar. Meistens wird dieses Superkontinuum erzeugt, indem intensive<br />
ultrakurze (ps, fs) Laserpulse durch hoch-nichtlineare Glasfasern<br />
geleitet werden. Wir verfolgen einen modifizierten Ansatz, bei<br />
dem die Glasfaser zu einem nichtlinearen Ringresonator geschlossen<br />
wird. Ein modengekoppelter Nd:YAG-Laser (1064 nm) liefert Pikosekundenpulse.<br />
In dem nichtlinearen Rückkoppelsystem bilden sich spontan<br />
komplexe, sehr kurze zeitliche Strukturen, die ein extrem breites<br />
Spektrum bedingen. Mit einer ” holey fiber“ geeigneter Dispersion erreichen<br />
wir derzeit mit einer eingekoppelten Spitzenleistung von lediglich<br />
500 W experimentell ein etwa 150 THz breites Spektrum. Dies ist<br />
das selbstorganisierte Ergebnis eines Wechselspiels der verschiedenen<br />
physikalischen Prozesse, wie Selbstphasenmodulation, Modulationsinstabilität,<br />
Ramaneffekt etc. sowie Dispersion (auch höherer Ordnung)<br />
in Verbindung mit der Interferenz bei der Rückkopplung. Zusätzlich<br />
durchgeführte numerische Simulationen sollen dazu dienen, diese komplexe<br />
Interaktion aufzuschlüsseln.<br />
Q 16.6 Di 15:15 2B/C<br />
Charakterisierung eines integriert-optischen Nahfeldsensors<br />
mit erhöhter evaneszenter Feldintensität — •Julia Hahn,<br />
Frank Fecher, Jürgen Petter und Theo Tschudi — Institut für<br />
Angewandte Physik, Technische Universität Darmstadt<br />
Zur Verbesserung der Empfindlichkeit eines Evaneszentfeldsensors soll<br />
bei gleich bleibender Eindringtiefe der Anteil der im zu untersuchenden<br />
Medium vorliegenden Intensität erhöht werden.<br />
Die evaneszenten Felder über den zu diesem Zweck mit hochbrechendem<br />
Titandioxid beschichteten Wellenleiterstrukturen in Lithiumniobat<br />
charakterisieren wir im sichtbaren Spektralbereich mit einem<br />
SNOM (Scanning Near-Field Optical Microscope) im Vergleich zu unbeschichteten<br />
Wellenleitern. Die angespitzte Glasfaser des im Kollektionsmodus<br />
betriebenen SNOMs nimmt hierbei in präszise positionierten<br />
Scans punktgenau die Intensität des evaneszenten Feldes auf.<br />
Es wurden sowohl Scans entlang der Wellenleiteroberfläche als auch<br />
senkrecht zur Oberfläche als Funktion des Abstandes aufgenommen.<br />
Hierbei konnte gezeigt werden, dass die Titandioxid-Beschichtung auf<br />
dem Wellenleiter zu einer fünfzehnfachen Erhöhung der evaneszen-<br />
Q 17: Ultrakalte Atome I [gemeinsam mit A]<br />
ten Feldintensität an der Oberfläche zum Deckmedium führt. Hierbei<br />
bleibt die Eindringtiefe unverändert in der Größenordnung von wenigen<br />
zehn Nanometern.<br />
Q 16.7 Di 15:30 2B/C<br />
Monolithische dielektrische mikrostrukturierte Oberfläche<br />
mit 100% Reflektivität — •Frank Brückner, Tina Clausnitzer,<br />
Ernst-Bernhard Kley und Andreas Tünnermann — Institut für<br />
Angewandte Physik, Friedrich-Schiller-Universität Jena, Deutschland<br />
In der Optik werden hochreflektierende Oberflächen meist durch<br />
den Einsatz dielektrischer Vielschichtsysteme realisiert. Aufgrund der<br />
Kombination von Materialien unterschiedlicher Festkörperstruktur<br />
wird die ursprünglich hohe mechanische Güte des Substrats erheblich<br />
reduziert. An diese werden jedoch für spezielle Anwendungen sehr<br />
hohe Anforderungen gestellt. Alternative Spiegelarchitekturen sind als<br />
Wellenleitergitter bekannt, welche mit Hilfe einer mikrostrukturierten<br />
hochbrechenden Schicht auf einem niedrigbrechenden Substrat hohe<br />
Reflektivitäten erreichen. Somit ist mindestens noch eine Schicht aus<br />
einem substratfremden Material erforderlich. Wir schlagen deshalb eine<br />
rein monolithische Spiegelgeometrie vor, die auf der Mikrostrukturierung<br />
einer dielektrischen Oberfläche basiert. Dadurch wird der Einsatz<br />
eines zusätzlichen Materials überflüssig und die mechanische Güte<br />
des Substrats nur minimal gestört. Die Strukturierung der Oberfläche<br />
resultiert dabei in T-förmigen Stegen eines Subwellenlängengitters, wodurch<br />
ein resonantes Koppelverhalten des einfallenden Lichts zum Erhalt<br />
höchster Reflektivität aus Luft ausgenutzt werden kann. Dies wird<br />
basierend auf der Funktion herkömmlicher Wellenleitergitter und der<br />
Einführung eines effektiven niedrigbrechenden Mediums theoretisch erklärt.<br />
Neben systematischen Designbetrachtungen werden auch potenzielle<br />
Herstellungsmöglichkeiten präsentiert.<br />
Q 16.8 Di 15:45 2B/C<br />
Fabrication and Characterization of Silicon Inverse Spiral<br />
and Slanted Pore Structures — Martin Hermatschweiler 1,2 ,<br />
•Isabelle Staude 1 , Michael Thiel 1 , Martin Wegener 1,2 , and<br />
Georg von Freymann 2 — 1 Center for Functional Nanostructures and<br />
Institut für Angewandte Physik, Universität Karlsruhe (TH), 76128<br />
Karlsruhe — 2 Institut für Nanotechnologie, Forschungszentrum Karlsruhe<br />
GmbH, 76021 Karlsruhe<br />
We here realize a variety of silicon inverse (SI) photonic crystal (PC)<br />
structures for the first time. Direct laser writing of polymeric templates<br />
and a silicon single-inversion procedure [1] allow for the fabrication of<br />
3D photonic band gap (PBG) structures. This leads to broad and<br />
prominent stop bands in the near infrared.<br />
Several different types of structures that theoretically exhibit large<br />
PBGs are demonstrated: (i) SI spiral PCs consisting of circular/square<br />
spirals arranged on a bcc/tetragonal lattice, respectively. [2,3] (ii) SI<br />
slanted pore structures arranged on a tetragonal lattice. [4] To our<br />
knowledge, none of the structures (i) can be accessed by any different<br />
method. Optical reflectance and transmittance measurements suggest<br />
the existence of PBGs for all proposed geometries. The experimental<br />
formation of PBGs shall be verified by comparison of the measurements<br />
to scattering-matrix as well as band structure calculations.<br />
[1] M. Hermatschweiler et al., Adv. Funct. Mater. 18, 2273 (2007)<br />
[2] A. Chutinan et al., Phys. Rev. B 57, R2006 (1998)<br />
[3] O. Toader et al., Science 292, 1133 (2001)<br />
[4] O. Toader et al., Phys. Rev. Lett. 90, 233901-1 (2003)<br />
Zeit: Dienstag 14:00–16:00 Raum: 2F<br />
Q 17.1 Di 14:00 2F<br />
Cold bosonic atoms in a π – flux lattice — •Stephan Rachel and<br />
Martin Greiter — Institut für Theorie der Kondensierten Materie,<br />
Universität Karlsruhe, 76128 Karlsruhe<br />
We present a model where the rare phenomenon of fragmented Bose–<br />
Einstein condensation occurs: we consider a system of neutral, bosonic<br />
atoms on a square lattice subject to an effective magnetic field. We<br />
focus on a magnetic flux of half a Dirac flux quantum through every<br />
lattice cell. The effective flux yields two minima in the lower single particle<br />
band. We show that in the many particle ground state, the particles<br />
are evenly distributed over both minima. The two macroscopically<br />
occupied minima correspond to two distinct Bose condensates.<br />
Regarding the low-energy excitations of the system, we show that<br />
Josephson tunneling is only possible for pairs of bosons, while single<br />
particle tunneling between both condensates is absent. We further find<br />
a massive mode describing fluctuations in the relative density of the<br />
two condensates.<br />
Q 17.2 Di 14:15 2F<br />
Bose-Einstein condensation in a periodic potential: A perturbation<br />
approach — •Ming-Chiang Chung 1 , Victor Lopez-<br />
Richard 2 , Carlos Trallero-Giner 3 , and Andreas Buchleitner 4<br />
— 1 Max-Planck-Institut für Physik Komplexer Systeme* Noethnitzer<br />
Str. 38, D-01187 Dresden, Germany — 2 Departamento de Fisica,<br />
Universidade Federal de S\˜{a}o Carlos, 13.565-905, S\˜{a}o Carlos,
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
S\˜{a}o Paulo, Brazil — 3 Faculty of Physics, Havana University, 10400<br />
Havana, Cuba — 4 Quantum Optics and Statistics Institute of Physics<br />
Albert-Ludwigs-Universitaet Freiburg Hermann-Herder-Str. 3 D-79104<br />
Freiburg, Germany<br />
Considering the Gross-Pitaevskii equation for Bose-Einstein condensate<br />
in a stationary one dimensional optical lattice with period $d$ in<br />
reduced coordinates, we are able to formally obtain closed analytical<br />
solutions for the order parameter and for the chemical potential. We<br />
report solutions for different range of values for the repulsive and the<br />
attractive non-linear interactions in the condensate and laser parameters<br />
creating the lattice. We have preformed a quantitative analysis<br />
with numerical solutions and theoretical estimation of the reported<br />
analytical equations allowing the determination of validity ranges of<br />
the perturbation approach. This study gives a very useful result establishing<br />
the universal range of the non-linear coupling term and lattice<br />
parameter values where each solution can be easily implemented.<br />
Q 17.3 Di 14:30 2F<br />
Improving the analytical determination of bound state energies<br />
and scattering lengths in molecular potentials – especially<br />
near threshold — •Patrick Raab and Harald Friedrich —<br />
Physik Department T30a, Technische Universität München, D-85747<br />
Garching<br />
Conventional WKB quantization can be improved substantially by including<br />
the appropriate reflection phases at the classical turning points.<br />
By application of the Effective-Range-theory we are able to calculate<br />
the reflection phase at the outer turning point in an attractive potential<br />
up to linear order in energy. For arbitrary energy we estimate the<br />
reflection phase by matching the low energy expansion with known<br />
formulas for high energies. This model, which includes only one free<br />
parameter is a significant improvement over the approximate eigenenergies<br />
obtained by other methods. The scattering length is completely<br />
determined by the knowledge of one of the highest bound energy levels<br />
(not necessarily by the highest one) and the asymptotic behavior of<br />
the potential.<br />
Q 17.4 Di 14:45 2F<br />
Jost-Functions & Attractive Singular Potentials — •Florian<br />
Arnecke, Javier Madronero, and Harald Friedrich — Physik Department<br />
T30a, Technische Universität München, D-85747 Garching<br />
We use Jost-functions to determine the leading and next-to-leading<br />
terms of the phase shifts δl(k) in the case of homogeneous attractive<br />
singular potentials −1/r α , α > 2, for arbitrary angular momentum<br />
l with incoming boundary conditions at small distances. The Jostsolutions<br />
are obtained by solving a Volterra-equation and a more general<br />
ansatz is used to fit the Jost-solutions to the WKB-waves in the<br />
inner region, where the WKB-approximation is accurate. A connection<br />
between the phase shifts of attractive and repulsive homogeneous<br />
singular potentials is presented.<br />
Q 17.5 Di 15:00 2F<br />
Stable dark solitons in three-dimensional dipolar Bose-<br />
Einstein condensates — •Rejish Nath 1 , Paolo Pedri 2 , and Luis<br />
Santos 1 — 1 Institute of Theoretical Physics, Leibniz university of<br />
Hannover, Appelstrasse 2, 30167, Hannover, Germany — 2 Laboratoire<br />
de Physique Théorique de la Matière Condensée, Université Pierre at<br />
Marie Curie, case courier 121 , 4 place Jussieu, 75252 Paris Cedex,<br />
France<br />
We study the dynamical stability of dark solitons in dipolar Bose-<br />
Q 18: Präzisionsmessungen und Metrologie III<br />
Einstein condensates. In the absence of non-locality due to the dipolar<br />
interaction, stationary dark solitons (nodal planes) are unstable<br />
against transversal excitations (snake instability) in 2D and 3D. On<br />
the contrary, due to its non local character, the dipolar interaction<br />
allows for stable 3D stationary dark solitons. We discuss in detail the<br />
conditions to achieve this stability, which demand the use of an additional<br />
optical lattice.<br />
Q 17.6 Di 15:15 2F<br />
Correlation dynamics of strongly-correlated lattice bosons<br />
out of equilibrium — •Karen Rodriguez and Luis Santos —<br />
Institut für Theoretische Physik, Leibniz Universität Hannover, Appelstraße<br />
2, 30167 Hannover<br />
We analyze by means of matrix product states techniques the dynamics<br />
of strongly-correlated Bose gases in a finite one-dimensional optical<br />
lattice after a change of the lattice parameters within the superfluid<br />
region. We analyze different regimes of perturbation, which range from<br />
adiabatic to non-adiabatic. In particular, we are interested in the evolution<br />
of different correlations in the system in time, showing that the<br />
different correlations present different time scales in their reaction to<br />
the change of parameters. As a consequence, when local quantities are<br />
converged correlation to distant neighbours or the quasi-condensate<br />
fraction may still present a significant dynamics. In addition, the different<br />
time scales for different correlations open the possibility to have<br />
different criteria for adiabaticity in the system.<br />
Q 17.7 Di 15:30 2F<br />
Laser Cooling and Trapping of a Leaky System: Barium —<br />
•Subhadeep De, Joost van den Berg, Aran Mol, Klaus Jungmann,<br />
and Lorenz Willmann — KVI, University of Groningen,<br />
Groningen, The Netherlands<br />
Heavy alkaline earth elements like radium are excellent candidates to<br />
test fundamental symmetries by searches for permanent electric dipole<br />
moments and atomic parity violation. Sensitive experiments require<br />
the trapping of these isotopes. Nevertheless, the two electron atoms<br />
have no simple two-level system for laser cooling due to the strong<br />
transitions between the singulet and the triplet system. The strongest<br />
transition from the ground state 1 S0- 1 P1 show a leak of 1:500 to<br />
metastable D-states. We have studied such a system with barium,<br />
where the branching into the D-states is 1:330(30). Repumping from<br />
these states uses the same excited state as the cooling transition, which<br />
leeds to coherent Raman transitions. Trapping and cooling of barium<br />
requires a set of seven lasers running at the same time. We report on<br />
the first successful trapping of barium in a magneto optical trap. The<br />
performance of the cooling and trapping will be discussed.<br />
Q 17.8 Di 15:45 2F<br />
Non-Abelian Statistics in a Quantum Antiferromagnet —<br />
•Martin Greiter and Ronny Thomale — Institut für Theorie der<br />
Kondensierten Materie, Universität Karlsruhe, D 76128 Karlsruhe<br />
We propose a novel spin liquid state for a S=1 antiferromagnet in two<br />
dimensions. The ground state is a spin-singlet, fully invariant under<br />
the symmetries of the underlying lattice, and possess a threefold topological<br />
degeneracy. The spinon and holon excitations obey non-abelian<br />
statistics, with the braiding of half-quantum vortices governed by zero<br />
energy modes in the vortex cores. We present numerical evidence that<br />
the universality class of this topological liquid can be stabilized by a<br />
model Hamiltonian involving three-spin interactions. We discuss possible<br />
realizations with polar molecules in optical lattices as well as<br />
potential applications in quantum computing.<br />
Zeit: Dienstag 14:00–15:45 Raum: 3D<br />
Q 18.1 Di 14:00 3D<br />
Gequetschtes Licht für den Gravitationswellendetektor<br />
GEO 600 — Henning Vahlbruch, •Alexander Khalaidovski, Simon<br />
Chelkowski, Moritz Mehmet, Boris Hage, Hartmut Grote,<br />
Benno Willke, Harald Lück, Karsten Danzmann und Roman<br />
Schnabel — Max-Planck-Institut für Gravitationsphysik (Albert Einstein<br />
Institut), Hannover, Deutschland<br />
Eine der großen Herausforderungen der modernen Experimentalphysik<br />
ist der direkte Nachweis der im Jahre 1916 von Albert Einstein vorher-<br />
gesagten Gravitationswellen. Im Laufe der letzten Jahre hat daher ein<br />
weltweites Netzwerk interferometrischer Detektoren den Betrieb aufgenommen,<br />
um eine direkte Messung der durch Gravitationswellen bedingten<br />
winzigen Längenänderungen zu erbringen. Zukünftige Detektoren<br />
werden in ihrer Empfindlichkeit im wesentlichen durch Quantenrauschen<br />
limitiert sein. Einen Ansatz, dieses zu verringern und somit<br />
die Sensitivität der Interferometer weiter zu erhöhen, bietet der Einsatz<br />
gequetschter Zustände des elektromagnetischen Feldes mit nichtklassischer<br />
Rauschdistribution. Der Beitrag diskutiert den Aufbau eines
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
“table-top“ Interferometers mit nichtklassisch verbesserter Sensitivität<br />
sowie die geplante Implementierung der vorgestellten Konzepte in den<br />
britisch/deutschen Gravitationswellendetektor GEO 600.<br />
Q 18.2 Di 14:15 3D<br />
Charakterisierung einer Siliziumnitrid-Membran — •Tobias<br />
Westphal, Yanbei Chen, Stefan Danilishin, Daniel Friedrich,<br />
Stefan Goßler, Kentaro Somiya, Kazuhiro Yamamoto, Karsten<br />
Danzmann und Roman Schnabel — Max-Planck-Institut für Gravitationsphysik<br />
(AEI), Institut für Gravitationsphysik der Leibniz Universität<br />
Hannover, Callinstraße 38, 30167 Hannover<br />
Quantenmechanisches Strahlungsdruckrauschen gewinnt in den Gravitationswellendetektoren<br />
der nächsten Generation zunehmend an Bedeutung.<br />
Zur Bestätigung der bisherigen theoretischen Modelle bauen<br />
wir ein strahlungsdruckdominiertes Interferometer auf. Die optomechanische<br />
Kopplung dieses Quanteneffekts wird durch einen beidseitig<br />
genutzten Endspiegel realisiert, welcher durch eine Siliziumnitrid-<br />
Membran ausgeführt wird.<br />
Die ersten Ergebnisse der Charakterisierung dieser Membran hinsichtlich<br />
mechanischer Güte und optischer Eigenschaften sowie das<br />
Layout des darauf basierenden Interferometers werden hier vorgestellt.<br />
Q 18.3 Di 14:30 3D<br />
Phasengenauigkeit von elektro-optischen Modulatoren für<br />
die wissenschaftliche Weltraummission LISA — •Simon Barke,<br />
Michael Tröbs, Benjamin Sheard, Gerhard Heinzel und Karsten<br />
Danzmann — Max-Planck-Institut für Gravitationsphysik, Hannover,<br />
Germany<br />
Die Laser Interferometer Space Antanna (LISA) besteht aus drei jeweils<br />
5 Millionen Kilometer entfernten Satelliten, die ein Interferometer<br />
aufspannen und über Phasenverschiebungen der Schwebungssignale<br />
Gravitationswellen detektieren.<br />
Da die Größe der erwarteten Phasenverschiebungen im Bereich von<br />
wenigen pm/ √ Hz liegt, stellt dies enorme Anforderungen an die Phasenmessung:<br />
Phasenänderungen aufgrund von Schwankungen in der<br />
Referenzfrequenz können nicht von Gravitationswellen-Signalen unterschieden<br />
werden. Die für LISA zur Verfügung stehenden Taktgeber<br />
erfüllen jedoch nicht die nötigen Anforderungen an die Frequenzgenauigkeit.<br />
Um die Missionsziele zu erreichen, soll das Frequenzrauschen<br />
der Taktgeber miteinander vergleichen werden, um es nachträglich<br />
vom Messsignal zu subtrahieren. Dazu wird das Signal der Taktgeber<br />
mittels elektro-optischer Modulatoren (EOMs) als Seitenbänder<br />
auf die Laserstrahlen aufgeprägt, so dass das Rauschen der Taktgeber<br />
zu den entfernten Satelliten übertragen werden kann. Das durch die<br />
EOMs zusätzlich eingefügte Phasenrauschen darf hierbei nicht mehr<br />
als 1 pm/ √ Hz betragen. Der Vortrag beschreibt mögliche Rauschquellen<br />
der untersuchten EOMs und stellt neben dem Messaubau für die<br />
Bestimmung der Phasengenauigkeit auch erste Ergebnisse vor.<br />
Q 18.4 Di 14:45 3D<br />
LTPDA - Datenanalyse für LISA Pathfinder — •Anneke Monsky,<br />
Ingo Diepholz, Felipe Guzman, Frank Steier, Martin Hewitson,<br />
Gerhard Heinzel und Karsten Danzmann — Albert-Einstein-<br />
Institut, Callinstr. 38, Hannover<br />
LISA (Laser Interferometer Space Antenna) ist eine gemeinsame Satellitenmission<br />
von ESA und NASA und soll den direkten Nachweis von<br />
Gravitationswellen im Bereich 0,1 mHz - 1 Hz liefern. Um kritische<br />
Technologien vorab zu testen, wird zuvor die Mission LISA Pathfinder<br />
durchgeführt. LISA Pathfinder wird vorraussichtlich 2010 gestartet.<br />
Zur Datenanalyse von LISA Pathfinder wurde in MATLAB ein Softwaretool<br />
zusammengestellt, das aus einer Vielzahl für die Auswertung<br />
nötiger Algorithmen aufgebaut ist, die von jedem Benutzer individuell<br />
zusammengestellt werden können. Die Idee ist, dass die Ergebnisse<br />
einer jeden Auswertung zu jeder Zeit vollständig reproduzierbar und<br />
genau nachvollziehbar bleiben. Relevante Ergebnisse werden in Form<br />
spezieller Konstrukte auf einem gemeinsamen Server gespeichert und<br />
für weitere Analysen zur Verfügung gestellt. Jede Analyse kann so<br />
exakt wiederholt oder auch modifiziert werden, wobei wiederum alle<br />
durchgeführten Prozesse gespeichert werden.<br />
Weiter wurden, basierend auf einem einfachen Model des Experiments<br />
Daten generiert und ausgewertet. Erste Ergebnisse dieser Datenanalyse<br />
für das LISA Technology Package werden vorgestellt.<br />
Q 18.5 Di 15:00 3D<br />
Novel LISA Payload Architectures with In-Field Pointing<br />
— •Dennis Weise 1 , Pierangelo Marenaci 1 , Peter Weimer 1 ,<br />
Hans Reiner Schulte 1 , Peter Gath 1 , Claus Braxmaier 2 , Ulrich<br />
Johann 1 , and Marcello Sallusti 3 — 1 EADS Astrium GmbH,<br />
Claude-Dornier-Str., 88039 Friedrichshafen — 2 HTWG Konstanz,<br />
Brauneggerstr. 55, 78462 Konstanz — 3 European Space Agency, P.O.<br />
Box 299, 2200 AG Noordwijk ZH, The Netherlands<br />
As ESA’s prime contractor within the on-going LISA Mission Formulation<br />
Study, EADS Astrium has recently suggested and investigated<br />
payload architectures utilizing so-called “In-Field Pointing” for accommodation<br />
of seasonal constellation dynamics. Here, the annual variation<br />
in the angle between the interferometer arms of roughly ±1 ◦ is<br />
compensated by steering the lines of sight of the individual telescopes<br />
with a comparatively small actuated mirror located in an intermediate<br />
pupil plane inside the telescopes. This introduces a high flexibility<br />
for the overall payload configuration and allows for the realization of<br />
very compact designs. We will show that despite the presence of an<br />
active mirror in the measurement chain it should be feasible to achieve<br />
the required pciometer pathlength stability over relevant timescales by<br />
employing a specifically designed telescope and a special Gimbal-type<br />
pointing mechanism. In combination, these minimize pathlength disturbances<br />
to design-values below 1 pm/ √ Hz by passive means in the<br />
measurement band. According payload architectures with both a single<br />
active proof mass and two active proof masses per spacecraft will<br />
be presented.<br />
Q 18.6 Di 15:15 3D<br />
Messung des nichtreziproken Phasenrauschens einer polarisationserhaltenden<br />
Glasfaser für LISA — •Roland Fleddermann,<br />
Frank Steier, Michael Tröbs, Gerhard Heinzel und Karsten<br />
Danzmann — Albert-Einstein-Institut Hannover, Max-Planck-<br />
Institut für Gravitationsphysik und Universität Hannover, Callinstr.<br />
38, D-30167 Hannover<br />
Laser Interferometer Space Antenna (LISA) ist eine gemeinschaftliche<br />
Mission der ESA und der NASA mit dem Ziel, Gravitationswellen im<br />
Frequenzbereich zwischen 0,1 mHz und 0,1 Hz zu messen.<br />
Drei Satelliten befinden sich hierzu in speziellen heliozentrischen<br />
Umlaufbahnen die ein gleichseitiges Dreieck bilden. Die Richtung<br />
der zur interferometrischen Distanzmesung ausgesandten Laserstrahlen<br />
muss dabei variabel sein, da sich der Winkel zwischen den Satelliten<br />
um bis zu ± 1,5 ◦ ändert. Da es wünschenswert ist, das relativ schwache<br />
ankommende Licht mit einem Teil des Lichts zu Überlagern, das<br />
zum anderen Satelliten ausgesandt wird, ist eine flexible Verbindung<br />
zwischen beiden an Bord befindlichen optischen Bänken notwendig.<br />
Glasfasern sind hierfür die vielversprechendsten Kandidaten.<br />
Wir messen das nichtreziproke Phasenrauschen einer polarisationserhaltenden<br />
Glasfaser, um zu verifizieren, dass diese Rauschquelle die<br />
Phasenmessungen bei LISA mit einer Genauigkeit von 10 µrad/ √ Hz<br />
∧<br />
≈ 2 pm/ √ Hz @ 1064 nm nicht zerstört.<br />
Wir geben eine Übersicht über mögliche Messaufbauten, erste Ergebnisse<br />
und über Untersuchungen der externen Einflüsse auf das beobachtete<br />
nichtreziproke Phasenrauschen.<br />
Q 18.7 Di 15:30 3D<br />
Interspacecraft laser ranging for LISA — •Juan Jose Esteban<br />
Delgado, Antonio Francisco Garcia Marin, Iouri Bykov, Gerhard<br />
Heinzel, and Karsten Danzmann — Albert-Einstein-Institut<br />
Hannover, Max-Planck-Institut für Gravitationsphysik*und Universität<br />
Hannover<br />
The Laser Interferometer Space Antenna (LISA) is an international<br />
space project to detect and observe Gravitational waves in the frequency<br />
regime from 0.1 mHz to 100 mHz. LISA is a cluster of three<br />
spacecraft separated by five millions kilometers communicating with<br />
each other via three bidirectional laser links and forming an equilateral<br />
triangle.<br />
The LISA data processing requires ranging between the spacecraft<br />
to monitor continuously their huge separation with an absolute precision<br />
of ten meters. The laser links are not only used to measure this<br />
distance but also to transmit information and clock synchronization<br />
between the satellites.<br />
We present a possible implementation of the onboard processing system<br />
dedicated to extract the required information from the incoming<br />
laser phase using a binary phase shift keying demodulation scheme.
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
Q 19: Kalte Moleküle III [gemeinsam mit MO]<br />
Zeit: Dienstag 14:00–16:00 Raum: 3G<br />
Q 19.1 Di 14:00 3G<br />
Cumulenic carbon chains: giant absorbers — •Dmitry Strelnikov<br />
and Wolfgang Krätschmer — Max-Planck-Institut für Kernphysik,<br />
69117 Heidelberg.<br />
Cumulenic carbon chains have extremely strong IR and UV-Vis absorptions,<br />
a feature which facilitates their detection even in minute<br />
quantities. We present our results obtained by IR and UV-Vis spectroscopy<br />
on bare carbon chains and their oxides trapped in cryogenic<br />
matrices. IR spectra of a novel hybrid molecule consisting of a C3<br />
carbon chain attached to a C60 fullerene will also be presented and<br />
discussed.<br />
Q 19.2 Di 14:15 3G<br />
Internal-state thermometry by depletion spectroscopy in<br />
a cold guided beam of formaldehyde — •Michael Motsch,<br />
Markus Schenk, Laurens D. van Buuren, Martin Zeppenfeld,<br />
Pepijn W.H. Pinkse, and Gerhard Rempe — Max-Planck-Institut<br />
für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching, Germany<br />
Velocity filtering by means of an electrostatic quadrupole guide is an<br />
efficient technique to produce slow beams of polar molecules from a<br />
thermal reservoir. For formaldehyde, fluxes of 10 10 s −1 with velocities<br />
down to ∼10 m/s have been demonstrated [1]. However, so far the<br />
internal-state distribution of the velocity filtered molecules was not<br />
accessible in the experiment.<br />
We present measurements of the internal-state distribution of electrostatically<br />
guided formaldehyde [2]. Upon excitation with continuously<br />
tunable ultraviolet laser light, molecules can be excited to a<br />
dissociating state, leading to a decrease in the molecular flux. The<br />
population of individual guided states is measured by addressing transitions<br />
originating from them. The measured populations of selected<br />
states show good agreement with theoretical calculations for different<br />
temperatures of the molecule reservoir. The purity of the guided beam<br />
as deduced from the entropy of the guided sample using a reservoir<br />
temperature of 150 K corresponds to that of a thermal ensemble with<br />
a temperature of about 30 K.<br />
[1] S.A. Rangwala et al., Phys. Rev. A 67, 043406 (2003)<br />
[2] M. Motsch et al., arXiv:chem-phys 0710.3316v1 (2007), accepted<br />
for publication in Phys. Rev. A<br />
Q 19.3 Di 14:30 3G<br />
Cooling and Slowing in High Pressure Jet Expansions —<br />
•Wolfgang Christen and Klaus Rademann — Institut für Chemie,<br />
Humboldt-Universität zu Berlin, Brook-Taylor-Strasse 2, 12489 Berlin<br />
The expression for the mean flow velocity in supersonic beams of ideal<br />
gases is extended to include real gas properties. This procedure yields<br />
an explicit dependence of the flow velocity on pressure, as observed in<br />
recent experiments of free jet expansions [1,2]. Applied to stagnation<br />
conditions slightly above the critical point, the model suggests that<br />
seeded high pressure jets might be suitable for slowing down virtually<br />
any molecule with high efficiency. Moreover, we discuss the consequence<br />
of a pressure-dependent flow velocity v0 for the speed ratio<br />
S = v0/∆v with respect to collisional cooling and suggest to use the<br />
velocity spread ∆v as a more non-ambiguous measure of translational<br />
temperature in high pressure jet expansions.<br />
[1] L. W. Bruch, W. Schöllkopf, J. P. Toennies, J. Chem. Phys. 117,<br />
1544 (2002).<br />
[2] W. Christen, T. Krause, K. Rademann, Rev. Sci. Instrum. 78,<br />
073106 (2007).<br />
Q 19.4 Di 14:45 3G<br />
Überschallexpansion von überkritischen Fluiden - Ethen und<br />
Propan — •Oliver Korup, Klaus Rademann und Wolfgang<br />
Christen — Institut für Chemie, Humboldt-Universität zu Berlin,<br />
Brook-Taylor-Strasse 2, 12489 Berlin<br />
Mit hochaufgelösten Flugzeitmessungen gepulster Überschallmolekularstrahlen<br />
wird die Geschwindigkeitsverteilung von reinem<br />
Ethen und Propan als Funktion des Stagnationsdrucks und der Stagnationstemperatur<br />
bestimmt. Beide Spezies werden hierzu unter präzise<br />
definierten Stagnationsbedingungen [1] ins Vakuum expandiert. Der<br />
untersuchte Druck- und Temperaturbereich umfasst den gasförmigen,<br />
flüssigen und überkritischen Aggregatzustand. Die Messungen werden<br />
durch Untersuchungen zur Clustergrößenverteilung, unter Verwen-<br />
dung der Gegenfeldmethode [2], ergänzt. Ausgangspunkt zu den hier<br />
präsentierten Ergebnissen sind vorangegangene Untersuchungen [3]<br />
zur überraschend effizienten Kühlung bei der Überschallexpansion<br />
von CO und CO2, die in dieser Arbeit eine Erweiterung auf größere<br />
Moleküle finden.<br />
[1] W. Christen, T. Krause, K. Rademann, Rev. Sci. Instr. 78, 073106<br />
(2007).<br />
[2] J. Bauchert, O.-F. Hagena, Z. Naturforschg. 20a, 1135-1142 (1965).<br />
[3] W. Christen, K. Rademann, U. Even, J. Chem. Phys. 125, 174307<br />
(2006).<br />
Q 19.5 Di 15:00 3G<br />
Competing chemical dynamics in F − + CH3Cl — •Rico<br />
Otto, Jochen Mikosch, Sebastian Trippel, Christoph Eichhorn,<br />
Matthias Weidemüller, and Roland Wester — Physikalisches Institut,<br />
Universität Freiburg, Hermann-Herder-Str. 3, 79104 Freiburg<br />
Chemical reactions often show a variety of competing reaction mechanisms<br />
depending on the energy available. We have studied this for<br />
anion molecule nucleophilic substitution (SN2) reactions [1], which are<br />
described by a complex potential energy surface with a submerged barrier<br />
and by weak coupling of the relevant rotational-vibrational quantum<br />
states.<br />
Here we present results for the anion molecule reaction F − + CH3I<br />
which we studied in a crossed beam imaging experiment at low energies<br />
between 0.3 - 12.5 eV. We have observed three distinct reaction<br />
channels which we identified by time of flight analysis of the formed<br />
product ions. By mapping the transfer from translational energy into<br />
internal vibrational modes we could identify different reaction mechanisms<br />
for each of these channels.<br />
[1] J. Mikosch, S. Trippel, C. Eichhorn, R. Otto, U. Lourderaj, J. X.<br />
Zhang, W. L. Hase, M. Weidemüller, R. Wester, Science (in press)<br />
Q 19.6 Di 15:15 3G<br />
Nonequilibrium magnesium complexes formed in helium<br />
nanodroplets — •Andreas Przystawik, Sebastian Göde, Josef<br />
Tiggesbäumker, and Karl-Heinz Meiwes-Broer — Institut für<br />
Physik, Universität Rostock, Universitätsplatz 3, 18051 Rostock<br />
Doping helium droplets with alkaline earth atoms is an interesting tool<br />
to investigate the interaction with the superfluid helium. Magnesium<br />
is a corner case regarding the degree of solvation in helium [1,2] which<br />
may enable the detection of quantized vortices in helium droplets.<br />
In this contribution we add another facet to the discussion. The<br />
absorption of helium droplets doped with magnesium atoms is measured<br />
with resonant two-photon ionization at different combinations<br />
of droplet size and the number of doped Mg atoms. This enables the<br />
unambiguous identification of the absorption of an isolated atom inside<br />
the droplet centered around 279 nm. When increasing the Mg content<br />
of the droplet we find evidence for the formation of metastable, weakly<br />
bound Mg complexes. After excitation of such a complex it collapses<br />
to a Mg cluster on a timescale of 20 ps.<br />
[1] J. Reho et al., J. Chem. Phys. 112, 8409 (2000)<br />
[2] Y. Ren and V.V. Kresin, Phys. Rev. A 76, 043204 (2007)<br />
Q 19.7 Di 15:30 3G<br />
High Resolution Spectroscopy of Acetylene-Furan in Ultracold<br />
Helium — •Anja Metzelthin, Özgür Birer, and Martina<br />
Havenith — Physikalische Chemie II, Ruhr Universität Bochum, Universitätsstr.<br />
150, D-44780 Bochum<br />
The acetylene-furan system is an interesting benchmark system for<br />
the evaluation of hydrogen bonds. Since acetylene is the smallest<br />
molecule containing two hydrogens and a π-system it is interesting<br />
to study the influence of a C-H ”lone-pair”hydrogen-bond and a CH-π<br />
or even a π-π interaction.<br />
The global and local minimum structures have been predicted in a<br />
recent study [1]. For the experiment the molecules have been embedded<br />
in superfluid helium nanodroplets. The radiation source was a singleresonant<br />
OPO with an output power of up to 2.7 W and a resolution<br />
of up to 4 × 10 −5 cm −1 . Helium clusters, which have a temperature of<br />
0.37 K are doped with acetylene (pick-up pressure 1.3 × 10 −5 mbar)<br />
and furan (pick-up pressure 0.9×10 −5 mbar) and are then excited with<br />
the OPO-radiation. A mass-spectrometer is used to detect the depletion<br />
of the cluster beam. With this setup measurements were carried
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
out in the region of the asymmetric stretch vibration of the acetylene.<br />
Between 3256 cm −1 and 3280 cm −1 five acetylene-furan cluster peaks<br />
could be detected. Two of these could be assigned to the acetylen-furan<br />
dimer. We will present a detailed analysis of the data.<br />
[1] E. Sánchez-García, A. Mardyukov, A. Tekin, R. Crespo-Otero, L.A.<br />
Montero, W. Sander, G. Jansen, submitted<br />
Q 19.8 Di 15:45 3G<br />
Molecular Spectroscopy in Superfluid Helium Nanodroplets<br />
Created in a Pulsed Even-Lavie Nozzle — •Dominik<br />
Pentlehner and Alkwin Slenczka — Universität Regensburg, Institut<br />
für Physikalische und Theoretische Chemie, 93053 Regensburg,<br />
Germany<br />
Pulsed molecular beam sources provide enhanced particle density while<br />
the average flux of gas is reduced. Therefore, molecular spectroscopy<br />
with pulsed lasers provides a better signal to noise ratio in a pulsed<br />
molecular beam than obtained in a continuous beam. One of the most<br />
reliable pulsed molecular beam sources developed by U. Even and N.<br />
Lavie [1] was tested at low temperatures to produce a pulsed beam of<br />
superfluid helium droplets. By the observation of Rayleigh scattering<br />
and laser induced fluorescence the pulsed droplet source was characterized.<br />
The reliability of the Even-Lavie nozzle as helium droplet source<br />
appears to be excellent for repetition rates below 30 Hz. The fluorescence<br />
excitation spectra of organic molecules doped into the droplets<br />
generated in the pulsed nozzle expansion will be presented.<br />
[1] U. Even, J. Jortner, D. Noy, and N. Lavie, C. Cossart-Magos, J.<br />
Chem. Phys. 112 (2000), 8068.<br />
Q 20: Laseranwendungen (Lebenswissenschaften und Umwelt)<br />
Zeit: Dienstag 14:00–15:45 Raum: 3H<br />
Q 20.1 Di 14:00 3H<br />
Quantitative Analyse von 14 NO und 15 NO aus menschlichem<br />
Blut — •Thomas Fritsch 1 , Paris Brouzos 2 , Kathrin Heinrich 1 ,<br />
Petra Kleinbongard 2 , Malte Kelm 2 , Peter Hering 1 und Manfred<br />
Mürtz 1 — 1 Institut für Lasermedizin, Universitätsklinikum<br />
Düsseldorf, Universitätsstr. 1 , 40225 Düsseldorf — 2 Molekulare Kardiologie/Medizinische<br />
Klinik I, Universitätsklinikum Aachen, Pauwelstr.<br />
30, 52074 Aachen<br />
In den vergangenen Jahrzehnten hat sich die Chemilumineszenzdetektion<br />
(CLD) aufgrund ihrer hohen Empfindlichkeit und Zeitauflösung<br />
zum Goldstandard des Nachweises von Stickstoffmonoxid (NO) entwickelt.<br />
Um Isotopen-markierte Substanzen im Körper verfolgen zu<br />
können, müssen andere Methoden genutzt werden, da die CLD prinzipiell<br />
nicht zwischen unterschiedlichen Isotopologen unterscheiden kann.<br />
Wir präsentieren hier die Evaluation eines Cavity Leak-Out Spektrometers<br />
(CALOS) bei 5,2 µm. Zum Vergleich der Methoden wurden<br />
Prüfgasmischungen, Nitritlösungen und menschliche Blutproben<br />
genutzt. Neben einer hohen Übereinstimmung der Messergebnisse erreichen<br />
beide Methoden vergleichbare Nachweisgrenzen im ppt-Bereich<br />
(parts per trillion, 10 −12 ) bei Zeitauflösungen im Bereich weniger Sekunden.<br />
CALOS ergänzt diese Eigenschaften mit der Möglichkeit eines<br />
höchstempfindlichen isotopologenselektiven Nachweises.<br />
Diese Evaluation öffnet den Weg in ein weites Gebiet von Anwendungen<br />
im biologischen und medizinischen Bereich.<br />
Q 20.2 Di 14:15 3H<br />
Laser-spectroscopic online analysis of hydrocarbons in exhaled<br />
human breath — •Sven Thelen, Daniel Halmer, Peter<br />
Hering, and Manfred Mürtz — Heinrich-Heine-Universität<br />
Düsseldorf, Institut für Lasermedizin, 40225 Düsseldorf, www.ilm.uniduesseldorf.de/tracegas<br />
The quantitative and single breath-resolved analysis of trace gases contained<br />
in human breath has constantly gained importance for medical<br />
diagnostics. A prominent example is the ethane molecule which is released<br />
as a by-product of free radical induced lipid peroxidation in the<br />
human body. Thus a rapid and non-invasive detection of ethane as<br />
a volatile marker for the oxidative stress status is very attractive for<br />
medical diagnostics.<br />
We use Cavity Leak-Out Spectroscopy (CALOS) implementing a<br />
50 cm long absorption cell enclosed with two high reflectivity mirrors<br />
resulting in an effective absorption path length of 3.6 km. Our<br />
Difference-Frequency Generation (DFG) laser source provides a continuous<br />
tuning range between 3.30 µm and 3.67 µm and a laser power<br />
of 280 µW.<br />
With this technique we have analyzed the washout dynamics of<br />
ethane in the human body. We have also investigated single breath<br />
exhalations of methane regarding reproducibilty of concentration and<br />
slope of the alveolar phase. Furthermore we present the results of an<br />
intercomparison study with Gas Chromatography/Flame Ionization<br />
(GC-FID).<br />
Q 20.3 Di 14:30 3H<br />
Echtzeitanalyse von 13 CO mittels Cavity Leak-Out Spektroskopie<br />
im mittleren Infrarot — •Marcus Sowa, Thomas Fritsch,<br />
Peter Hering und Manfred Mürtz — Institut für Lasermedizin,<br />
Universitätsklinikum Düsseldorf, Universitätsstr. 1, 40225 Düsseldorf<br />
Kohlenmonoxid (CO) entsteht im Körper beim Abbau des Häm-<br />
Moleküls, einem Bestandteil der roten Blutkörperchen. Das abgeschiedene<br />
CO wird auf Grund seiner hohen Affinität zum Hämoglobin,<br />
von diesem als Carboxyhämoglobin (HbCO) gebunden. In der Lunge<br />
wird das CO zwischen der Atemluft und dem Blut ausgetauscht.<br />
Die zu bestimmenden Konzentrationen von 13 CO liegen im Normalfall<br />
im Bereich weniger ppb. Die Messung beruht auf dem Prinzip<br />
der Cavity Leak-Out Spektroskopie (CALOS) im mittleren Infrarot<br />
bei ca. 5µm. Die Nachweisgrenze des verwendeten Systems liegt bei<br />
0,7ppb·Hz −1/2 für das 13 CO. Der verwendete Aufbau ermöglicht die<br />
isotopologenselektive und atemzugsaufgelöste Detektion des 13 CO aus<br />
der Atemluft, sowie die Analyse anderer biologischer Proben. Mögliche<br />
Anwendungen sind z.B. die Durchführung von CO-Atemtests mit so<br />
geringen Konzentrationen und Mengen an CO, dass die zulässigen<br />
Höchstwerte, auch bei längeren Tests, nicht überschritten werden. Des<br />
Weiteren kann unter Hinzunahme von spirometrischen Daten die Carboxyhämoglobinkonzentration<br />
der Testperson isotopologenselektiv bestimmt<br />
werden. Im Rahmen des Vortrags sollen das Messsystem und<br />
erste Ergebnisse präsentiert werden.<br />
Q 20.4 Di 14:45 3H<br />
Isotopologenselektive Echtzeitmessung von 14 NO und 15 NO<br />
im menschlichen Atem mittels höchstsensitiver Cavity-Leak-<br />
Out Spektroskopie — •Kathrin Heinrich, Thomas Fritsch, Peter<br />
Hering und Manfred Mürtz — Institut für Lasermedizin, Universitätsklinikum<br />
Düsseldorf, Universitätsstr.1, 40225 Düsseldorf<br />
Mit zunehmender Erkenntnis über die Bedeutung von Spurengasen<br />
im menschlichen Atem steigt die Relevanz einer höchstempfindlichen<br />
Nachweismethode zur Detektion kleinster Molekülkonzentrationen in<br />
gasförmigen Proben. Viele für die medizinische Diagnostik interessanten<br />
Moleküle besitzen im mittleren Infrarotbereich ein charakteristisches<br />
Absorptionsspektrum. Die Cavity-Leak-Out Spektroskopie<br />
ermöglicht einen Nachweis dieser Spurengase im sub-ppb Bereich bei<br />
einer Zeitauflösung von unter 1 s. Auf der Basis eines durchstimmbaren<br />
CO-Lasers (λ=5 µm) wird die Abschwächung der Laserintensität nach<br />
dem Durchgang durch die gasförmige Probe, welche sich in einem optischen<br />
Resonator befindet, gemessen. Die kontinuierliche Durchstimmbarkeit<br />
des Lasersystems bietet zudem die Möglichkeit eines isotopologenselektiven<br />
Nachweises. Als ein mögliches Anwendungsbeispiel wird<br />
der isotopologenselektive, atemzugsaufgelöste Nachweis von 14 NO und<br />
15 NO im menschlichen Atem vorgestellt. Die rauschäquivalente Absorption<br />
beträgt 180 ppt/Hz 1/2 für 14 NO und 150 ppt/Hz 1/2 für 15 NO.<br />
Durch die simultane 14 NO/ 15 NO-Messung sind Veränderungen im Isotopenverhältnis<br />
detektierbar, so dass z.B. verschiedene Stoffwechselpfade<br />
nach Gabe von 15 N-markierten Substanzen verfolgt und differenziert<br />
werden können.<br />
Q 20.5 Di 15:00 3H<br />
Bohrungen in biologischem Hartgewebe mit gepulsten<br />
CO2- Lasern — •Romina Krieg 1 , Martin Werner 1,2 , Manfred<br />
Klasing 2 , Ulrike Endesfelder 2,3 und Peter Hering 1 —<br />
1 Institut für Lasermedizin, Heinrich Heine Universität Düsseldorf —<br />
2 Forschungszentrum caesar, Bonn — 3 Helmholtz Institut für Strahlenund<br />
Kernphysik, Rheinische Friedrich Wilhelms Universität, Bonn
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
Mit gepulster Laserstrahlung lässt sich Knochenmaterial gut in beliebiger<br />
Geometrie abtragen. Es wird gepulste CO2 - Laserstrahlung<br />
verwendet, die gut im Knochen absorbiert wird, und bei geeigneten Laserparametern<br />
keine thermischen Schäden im Gewebe verursacht. Das<br />
Ziel sind zylindrische Bohrungen mit beliebigem Durchmesser und Tiefe,<br />
um Implantate in den Kieferknochen ein zu bringen. Deshalb sollten<br />
die Bohrungen möglichst formtreu sein. Der Knochenabtrag wird<br />
dabei durch ein Füllmuster innerhalb der Geometrie erzeugt. Zur Verbesserung<br />
des Ergebnisses lässt sich zusätzlich der Rand der Bohrung<br />
abfahren. Bei dieser Art der Materialbearbeitung mit Lasern ist die abnehmende<br />
Effizienz mit zunehmender Tiefe problematisch, da konische<br />
Bohrungen entstehen können. Außerdem sind die Bohrungen im Profil<br />
nicht symmetrisch, was sich in unterschiedlichen Bohrwinkeln und<br />
schrägen Böden bemerkbar macht. Um diese Probleme zu beheben,<br />
wurden die effektivsten Bohrreihenfolgen bestimmt. Durch Variation<br />
der Reihenfolge von Füllmuster und Rand wurde die Konizität bereits<br />
erheblich verringert.<br />
Q 20.6 Di 15:15 3H<br />
Analyse der optischen und akustischen Feedback-Signale<br />
bei Ablation von biologischem Gewebe mit einem gepulsten<br />
CO2 Laser — •Ulrike Endesfelder 1,2 , Martin Werner 1,3 ,<br />
Manfred Klasing 1 , Peter Hering 1,3 und Romina Krieg 1,3 —<br />
1 Forschungszentrum caesar, Bonn — 2 HISKP, Universität Bonn —<br />
3 Institut für Lasermedizin, Universität Düsseldorf<br />
Die anwendbaren Laserapplikationen in der Medizin wurden in den<br />
letzten Jahren auch auf den Bereich der Laserosteotomie, d.h. die<br />
berührungslose Abtragung von Knochengewebe, erweitert.<br />
Die Laserosteotomie bietet einige Vorteile im Vergleich zu den<br />
üblichen Verfahren in der Chirurgie, vor allem durch eine sehr hohe<br />
Präzision und die freie Wahl der Abtragungsgeometrie.<br />
Die benutzten kurzgepulsten CO2-Laser stellen in Kombination mit<br />
einem Wasserspray und einer speziellen Multi-Pass-Scan-Technik eine<br />
effiziente und thermisch minimal belastende Möglichkeit dar, Knochengewebe<br />
für medizinische Anwendungen zu bearbeiten.<br />
Q 21: Quanteninformation (Quantencomputer II)<br />
Diese Arbeit stellt ein Kontrollverfahren des Bearbeitungsfortschritts<br />
vor. Entscheidend hierbei ist die Erkennung der Grenze zwischen<br />
dem Knochengewebe und dem unterliegendem Weichgewebe,<br />
welches geschont werden soll. Da die Laserablation von einem Leuchten<br />
in einem breiten Spektralbereich und von akustischen Signalen begleitet<br />
ist, liegt es nahe, beides für die Diagnostik zu nutzen.<br />
Im Rahmen dieser Arbeit wurden die gewebespezifischen Unterschiede<br />
in den laserinduzierten Ablationssignalen untersucht. Hierbei wurden<br />
insbesondere die Grenzen des Kontrollverfahrens ausgelotet.<br />
Q 20.7 Di 15:30 3H<br />
Weiterentwicklung eines optischen Messverfahrens zur<br />
Untersuchung der Gemischbildung von Kraftstoff-Luft-<br />
Gemischen — •Jens Müller, Jochen Scholz und Volker Beushausen<br />
— Laser-Laboratorium Göttingen e.V., Hans-Adolf-Krebs-<br />
Weg 1, 37077 Göttingen, www.llg-ev.de<br />
Die Emission von Schadstoffen und der Kraftstoffverbrauch von neuen<br />
Motorkonzepten hängen stark von der Präparierung des Luft-<br />
Kraftstoffgemisches und der räumlichen und zeitlichen Verteilung des<br />
Gemisches im Zylinder ab. Das Ziel unserer Arbeit ist die Entwicklung<br />
eines 2-D Messverfahrens zur ortsaufgelösten Erfassung des<br />
Luft/Kraftstoff-Verhältnisses (Lambda-Wert) im Motorbrennraum bei<br />
Einsatz von Realkraftstoffen ohne Zusatz von Kraftstofftracern. Zur<br />
Erfassung des Lambda-Wertes wird eine Variante der Laser-induzierten<br />
Fluoreszenz (LIF), das sogenannte ”Fuel-Air-Ratio-LIF” (FARLIF)<br />
eingesetzt. Hierbei werden fluoreszenzlöschende Eigenschaften von<br />
Sauerstoff ausgenutzt, die unter bestimmten Randbedingungen eine<br />
direkte Proportionalität der gemessenen Fluoreszenzlichtintensität<br />
zum Lambda-Wert generieren. Bisher konnte die Einsatzfähigkeit der<br />
FARLIF-Messtechnik nur unter Verwendung von nicht fluoreszierenden<br />
Modellkraftstoffen mit dem Fluoreszenztracer Toluol und nur moderaten<br />
Temperaturen nachgewiesen werden. Die hier präsentierten Arbeiten<br />
beschäftigen sich insb. mit der Validierung des FARLIF-Verfahrens<br />
für den Einsatz in Realkraftstoffen und bei hohen Temperaturen bis<br />
zu 700K.<br />
Zeit: Dienstag 16:30–17:30 Raum: 1B<br />
Q 21.1 Di 16:30 1B<br />
Towards two-dimensional quantum simulations with trapped<br />
ions — •Christian Schneider, Robert Matjeschk, and Tobias<br />
Schätz — Max-Planck-Institut für Quantenoptik<br />
An ion crystal in a Paul trap is a promising candidate for a quantum<br />
simulator or analogue quantum computer. Thereby a quantum system<br />
shall be implemented and studied which is described by the same<br />
Hamiltonian as the system to be simulated. The crucial parameters<br />
of the implemented system are accessible which is often not the case<br />
for the “real” sytem. First experimental results in building a quantum<br />
simulator for a quantum spin Ising Hamiltonian with two ions have<br />
recently been shown [1].<br />
To gain deeper insight into quantum dynamics, we plan to extend<br />
these fundamental experiments to more ions and into two dimensions<br />
[2]. As successful studies of one-dimensional planar Paul traps have<br />
been shown [3,4], a promising approach is to realize a two-dimensional<br />
array of trapped ions in a planar two-dimensional surface trap. We<br />
want to show our visions of two-dimensional quantum simulations and<br />
first steps towards their realization by a two-dimensional Paul trap of<br />
2 × 2 ions.<br />
[1] Phys. Rev. Lett., to be submitted<br />
[2] T. Schätz et. al., J. Mod. Opt., accepted<br />
[3] J. Chiaverini et. al., Quant. Inf. Comp. 5, 419–439<br />
[4] S. Seidelin et. al., Phys. Rev. Lett. 96, 253003–4<br />
Q 21.2 Di 16:45 1B<br />
Coherent Transport of Atoms in Arrays of Dipole Traps<br />
— •Jens Kruse, Andre Lengwenus, Malte Schlosser, Christian<br />
Gierl, Joost Sattler, and Gerhard Birkl — Institut für Angewandte<br />
Physik, TU Darmstadt, Schlossgartenstr. 7, 64289 Darmstadt<br />
For the experimental realization of quantum information processing it<br />
is essential to perform one- and two-qubit operations in a controlled<br />
fashion. In our approach, qubits are inscribed in the hyperfine states<br />
of rubidium atoms. The atoms are trapped in a two-dimensional array<br />
of well separated optical micro-potentials created by micro-fabricated<br />
lens arrays. We already demonstrated single-qubit operations by the<br />
coherent coupling of the hyperfine ground states of 85 Rb by stimulated<br />
Raman transitions.<br />
We plan the realization of two-qubit gates by the use of ultracold<br />
collisions. For this, atoms have to be transported from one trap position<br />
to another. We demonstrate the transfer of atoms in microtraps<br />
using steering methods which are based on the variation of the incident<br />
angle of the laser beam illuminating the array of microlenses. By using<br />
Ramsey and spin-echo methods we study the effects of transport on<br />
the coherence of the system. We observed that the transfer of atoms<br />
over a distance of up to the full trap separation does not cause any<br />
additional loss of coherence.<br />
Q 21.3 Di 17:00 1B<br />
Grundzustandskühlung und Qubit-Manipulation in einer segmentierten<br />
Mikroionenfalle — •Stephan Schulz, Ulrich Poschinger,<br />
Frank Ziesel und Ferdinand Schmidt-Kaler — Universität<br />
Ulm, Institut für Quanteninformationsverarbeitung, Albert-<br />
Einstein-Allee 11, 89069 Ulm<br />
Mikrostrukturierte segmentierte lineare Paulfallen zur Speicherung<br />
und Manipulation von Qubit-Systemen mittels Ionenkristallen sind ein<br />
aussichtsreicher Ansatz auf dem Weg zum skalierbaren Quantencomputer.<br />
Wir zeigen experimentelle Ergebnisse für eine lineare segmentierte<br />
Mikroionenfalle mit 40 Ca + -Ionen. Die insgesamt 31 Segmentpaare<br />
sind mit 62 verschiedenen elektrischen Spannungen ansteuerbar und<br />
in einen Speicher- (9 Segmentpaare), Transfer- (3) und Prozessorbereich<br />
(19) unterteilt. Die Breite der Segmentpaare beträgt 250µm bzw.<br />
100µm. Es werden radiale und axiale Fallenfrequenzen im MHz-Bereich<br />
gemessen.<br />
Die gefangenen Ionen werden nach Dopplerkühlen auf dem S 1/2 ↔<br />
P 1/2-Übergang durch Fluoreszenz auf diesem Übergang nachgewiesen.<br />
Mittels Seitenbandspektroskopie auf dem S 1/2 ↔ D 5/2-Übergang
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
wird die Mikroionenfalle charakterisiert und die Mikrobewegung<br />
kompensiert. Der Quadrupolübergang erlaubt die kohärente Qubit-<br />
Manipulation. Wir berichten von Grundzustandskühlen und Rabioszillationen<br />
in der Mikrofalle.<br />
Q 21.4 Di 17:15 1B<br />
New universal resource states — •David Gross and Jens Eisert<br />
— Institute for Mathematical Sciences, Imperial College London, 53<br />
Prince’s Gate, London SW7 2PG, UK<br />
Based on a previously established framework [1], we present new examples<br />
of universal resource states for measurement-based quantum computation.<br />
In particular, we discuss the concept of “quantum wires”.<br />
Q 22: Quantengase (Gitter II)<br />
These are quantum states on a one-dimensional string, which can be<br />
used to transport and process quantum information solely by means<br />
of local measurements. In a certain parameter regime, quantum wires<br />
can be completely parameterized and their properties explicitly computed.<br />
States of these kind may be thought of as primitives for the<br />
construction of two-dimensional resources states, universal for quantum<br />
computing. We discuss means of coupling such one-dimensional<br />
wires to form universal resources.<br />
[1] D. Gross and J. Eisert, Phys. Rev. Lett. 98, 220503 (2007); D.<br />
Gross, J. Eisert, N. Schuch, and D. Perez-Garcia, Phys. Rev. A 76,<br />
052315 (2007).<br />
Zeit: Dienstag 16:30–18:00 Raum: 1C<br />
Q 22.1 Di 16:30 1C<br />
Resonant Feshbach scattering of fermions in one-dimensional<br />
optical lattices — •Michael Grupp 1 , Reinhold Walser 1 , Wolfgang<br />
Schleich 1 , Alejandro Muramatsu 2 , and Martin Weitz 3 —<br />
1 Institut für Quantenphysik, Universität Ulm, Germany — 2 Institut<br />
für Theoretische Physik III, Universität Stuttgart, Germany —<br />
3 Institut für Angewandte Physik der Universität Bonn, Germany<br />
We consider Feshbach scattering of fermions in an one-dimensional<br />
optical lattice. By formulating the scattering theory in the crystal momentum<br />
basis, one can exploit the lattice symmetry and factorize the<br />
scattering problem in terms of center-of-mass and relative momentum<br />
in the reduced Brillouin zone scheme. Within a single-band approximation,<br />
we can tune the position of a Feshbach resonance with the<br />
center-of-mass momentum due to the non-parabolic form of the energy<br />
band. We present numerical results for the resonant scattering in an<br />
one-dimensional lattice. In order to understand this results we discuss<br />
an analytic model for the coherent tunneling of atoms and dimers in<br />
half spaces.<br />
[1] M. Grupp et al., J. Phys. B 40 (2007) 2703-2718<br />
Q 22.2 Di 16:45 1C<br />
Quantum Transport Experiments in Fourier-Synthesized Optical<br />
Lattices — •Tobias Salger, Carsten Geckeler, Sebastian<br />
Kling, and Martin Weitz — Institut für Angewandte Physik der<br />
Universität Bonn, Wegelerstr. 8, 53115 Bonn, Germany<br />
We report on experiments studying quantum transport of Bose-<br />
Einstein condensates in variable periodic optical potentials. We have<br />
studied the band structure of both ratchet-type asymmetric and symmetric<br />
optical potentials by the Landau-Zener effect and Bloch oscillations.<br />
The variable atom potential is realized by superimposing a<br />
conventional standing wave with λ/2 spatial periodicity with a fourthorder<br />
multiphoton potential of λ/4 periodicity. The multiphoton lattice<br />
is realized using the dispersive properties of multiphoton Raman transitions<br />
[1]. We find that the strength of interband transitions depends<br />
critically on the shape of the synthesized lattice potential [2]. Furthermore<br />
we report on studies of Bloch-oscillations in the variable lattice<br />
potential.<br />
[1] R. Ritt et al., Phys. Rev. A 74, 063622 (2006)<br />
[2] T. Salger et al., Phys. Rev. Lett. 99, 190405 (2007)<br />
Q 22.3 Di 17:00 1C<br />
Fermion induced long-range interaction in the Bose-Fermi-<br />
Hubbard model — •Alexander Mering and Michael Fleischhauer<br />
— Technische Universität Kaiserslautern<br />
We present recent results on the Bose-Fermi-Hubbard model in the<br />
limit of fast (ultralight) fermions. In this case, the fermions act as<br />
virtual quanta giving rise to an effective long-range density-density interaction<br />
for the bosons. Starting from the full BFH Hamiltonian we<br />
adiabatically eliminate the fast fermions. It is important to include<br />
the mean field backaction of the bosons into the free dynamics of the<br />
fermions. This yields a renormalized long-range boson-boson interaction.<br />
The resulting bosonic Hamiltonian is studied analytically using a<br />
bosonization approach as well as numerically using the density-matrixrenormalization-group<br />
(DMRG). In particular the transition between<br />
a CDW-phase and a compressible phase with exponentially decaying<br />
bosonic correlations is studied analytically compared to DMRG results.<br />
Q 22.4 Di 17:15 1C<br />
Counting atoms using interaction blockade in optical superlattices<br />
— •Ute Schnorrberger 1 , Patrick Cheinet 1 , Stefan<br />
Trotzky 1 , Michael Feld 1,2 , Simon Fölling 3 , and Immanuel<br />
Bloch 1 — 1 Institut für Physik der Universität Mainz — 2 Fachbereich<br />
Physik der Technischen Universität Kaiserslautern — 3 Harvard University,<br />
USA<br />
We demonstrate the ability to accurately measure the occupation number<br />
statistics of ultra cold atoms loaded in a 3D optical lattice by means<br />
of an interaction blockade effect analogue to the Coulomb blockade observed<br />
in mesoscopic solid state systems.<br />
We present results where a 87 Rb BEC was loaded in a 3D optical<br />
lattice either in the superfluid regime or in the Mott-Insulator regime.<br />
When ramping up an additional lattice on one axis with half the periodicity<br />
of the initial one we create an array of double wells. The bias,<br />
which means the tilt of the double wells, can be controlled by the relative<br />
phase between the two lattices forming this superlattice. Whenever<br />
the applied bias potential is high enough to compensate the interaction<br />
blockade, tunneling resonances occur. We observe these resonances by<br />
measuring the resulting atom numbers of each side of the double wells<br />
for the whole ensemble with different bias. The number distribution<br />
in the underlying long lattice is extracted from the resonance amplitudes<br />
measured for the ensemble of the double wells. This allows us to<br />
fully characterize the markedly different number distributions in the<br />
superfluid and Mott-Insulator regime.<br />
Q 22.5 Di 17:30 1C<br />
A new experiment towards single site addressability in optical<br />
lattices — •Christof Weitenberg, Jacob Sherson, Oliver<br />
Loesdau, Manuel Endres, Jan Petersen, Immanuel Bloch, and<br />
Stefan Kuhr — Institut für Physik,Universität Mainz, Staudingerweg<br />
7, 55128Mainz<br />
We build a new experiment with 87 Rb atoms in an optical lattice<br />
which will allow for atom detection and manipulation with single site<br />
resolution. The central part of the new experiment is an ultra-high resolution<br />
imaging system with a spatial resolution of 300 nm. Single site<br />
manipulation will be achieved by focussing an addressing laser onto<br />
individual lattice sites.<br />
Ultracold atoms will be loaded into the lattice from a Bose-Einstein<br />
condensate (BEC). It is generated in a crossed optical dipole trap<br />
formed by a 50 W YAG laser. The trap can be dynamically compressed<br />
by moving the foci of the laser beams. The BEC will be transported<br />
by a single beam dipole trap in front of the imaging system and transferred<br />
into the optical lattice.<br />
The aim of our project is to prepare and to study single one- and<br />
two dimensional quantum systems. Single site addressability will allow<br />
us to modify or perturb the system on a local scale and to observe<br />
the ensuing dynamics of the many-body system in real time. Quantum<br />
gates and entanglement between neighbouring atoms can, for example,<br />
be obtained by collisions in a spin-dependent lattice.<br />
Q 22.6 Di 17:45 1C<br />
Controlled Loading of an Ultracold Bose-Fermi-Mixture into<br />
an Optical Lattice Potential — •Sebastian Will, Thorsten<br />
Best, Ulrich Schneider, Lucia Hackermüller, Dries van Oosten,<br />
and Immanuel Bloch — Johannes Gutenberg-Universität Mainz<br />
The formation of heteronuclear molecules is a major goal of multi-
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
species experiments with ultracold atoms. In this context optical lattices<br />
are expected to enhance the lifetime of weakly bound Feshbach<br />
molecules considerably by protective enclosure of single molecules on<br />
single lattice sites. However, the achievement of this configuration necessitates<br />
appropriate loading of the atomic clouds into the lattice<br />
before association.<br />
In our setup we cool fermionic 40 K with bosonic 87 Rb sympathet-<br />
Q 23: Photonik II<br />
ically, reaching simultaneous quantum degeneracy with about 2 · 10 5<br />
atoms per species. We load this mixture into a blue-detuned optical<br />
lattice and adjust the external confinement independently with additional<br />
red-detuned laser beams. This allows for the creation of an<br />
almost homogeneous lattice potential. Together with tuneable interspecies<br />
interactions our setup permits controlled loading - suitable for<br />
the creation of molecules in the lattice.<br />
Zeit: Dienstag 16:30–18:00 Raum: 2B/C<br />
Q 23.1 Di 16:30 2B/C<br />
Limits for kinematical diffraction of visible light from three<br />
dimensional photonic crystals — •Marcel Roth 1 , Ullrich<br />
Pietsch 1 , Georg von Freymann 2 , and Martin Wegener 2 —<br />
1 Institute of solid state physics, University of Siegen, 57072 Siegen,<br />
Germany — 2 Institute of applied physics, University of Karlsruhe,<br />
76131 Karlsruhe, Germany<br />
For the majority of research studies with photonic crystal the existence<br />
and spectral width of a photonic band gap are of main interest.<br />
Light diffraction experiments with wavelengths in the visible and near<br />
infrared spectrum are predominantly used to verify the structural quality<br />
of the crystals.<br />
The usage of photonic crystals as purely diffractive elements in optical<br />
detectors is a relatively new idea. Due to the three dimensional periodic<br />
structuring an incoming white beam is spatially seperated into<br />
symmetry equivalent coloured spots that can be used for object recognition.<br />
All geometrical aspects can be understood in the framework of the von<br />
Laue equations. On the other side an analytical description for diffraction<br />
efficiencies is restricted to the case of kinematical scattering well<br />
known from the x-ray diffraction. This approximation is typically not<br />
valid for most photonic crystals because of large dielectric contrasts.<br />
In this talk we present experimental investigation and results of numerical<br />
calculations based on Maxwell equations which show that the<br />
limit for kinematical diffraction at photonic crystals is estimated for a<br />
relative dielectric mismatch of about 5%.<br />
Q 23.2 Di 16:45 2B/C<br />
Optical properties of three-dimensional photonic quasicrystals<br />
and their periodic approximants — •Alexandra<br />
Ledermann 1 , Costanza Toninelli 2 , Diederik S. Wiersma 2 , Martin<br />
Wegener 1 , and Georg von Freymann 1 — 1 Institut für<br />
Nanotechnologie, Forschungszentrum Karlsruhe in der Helmholtz-<br />
Gemeinschaft, DFG-Center for Functional Nanostructures (CFN)<br />
and Institut für Angewandte Physik, Universität Karlsruhe (TH) —<br />
2 European Laboratory for Nonlinear Spectroscopy (LENS) and INFM,<br />
Firence<br />
Quasicrystals (QC) represent a class of solids which lack translational<br />
symmetry, but exhibit perfect long-range order and reveal well-defined<br />
rotational symmetries, not necessarily consistent with periodicity.<br />
Using direct laser writing [1] we fabricate three-dimensional icosahedral<br />
SU-8 photonic QCs of high quality [2] and their so-called periodic<br />
approximants [3]. The optical properties of both QC and approximants<br />
are studied experimentally and show good agreement with corresponding<br />
simulations for the approximants. Time-resolved pulse propagation<br />
studies reveal the strongly diffracting character of QC which causes a<br />
strong delay and pulse reshaping during the propagation.<br />
This work is an important step towards a better understanding of<br />
the effects of quasiperiodicity.<br />
[1] M. Deubel et al., Nature Materials, 3, 444 (2004).<br />
[2] A. Ledermann et al., Nature Materials, 5, 942 (2006).<br />
[3] C. Janot, Quasicrystals- A Primer, Clarendon, Oxford (1992).<br />
Q 23.3 Di 17:00 2B/C<br />
Photonic Metamaterials by Direct Laser Writing and Silver<br />
Chemical Vapor Deposition — •Christine Plet 1 , Michael<br />
Rill 1 , Michael Thiel 1 , Stefan Linden 2 , Georg von Freymann 2 ,<br />
and Martin Wegener 1,2 — 1 Institut für Angewandte Physik, Universität<br />
Karlsruhe (TH), 76128 Karlsruhe, Germany — 2 Institut<br />
für Nanotechnologie, Forschungszentrum Karlsruhe in der Helmholtz-<br />
Gemeinschaft, 76021 Karlsruhe, Germany<br />
Metamaterials are man-made composite structures composed of metal-<br />
lic sub-wavelength scale functional building blocks that are densely<br />
packed into an effective material [1,2]. This approach especially allows<br />
for artificial magnetism at elevated frequencies.<br />
We fabricate planar magnetic photonic metamaterials via direct laser<br />
writing [3] and silver chemical vapor deposition, an approach, which is<br />
also suitable for three-dimensional structures.<br />
When retrieving effective metamaterial parameters for normal incidence<br />
of light, one has to be cautious because the fabricated structures<br />
are non-centrosymmetric. Thus, a description in terms of just electric<br />
permittivity ε and magnetic permeability µ is fundamentally not possible.<br />
Here, we follow the bi-anisotropic retrieval described in Ref. [4].<br />
[1] V.M. Shalaev, Nature Phot. 1, 41 (2006)<br />
[2] C.M. Soukoulis, S. Linden, and M. Wegener, Science 315, 47 (2007)<br />
[3] see, e.g., http://www.nanoscribe.de<br />
[4] X. Chen, B. Wu, J. Kong, and T. Grzegorczyk, Phys. Rev. E 71,<br />
046610 (2005)<br />
Q 23.4 Di 17:15 2B/C<br />
3D analysis of polarization singularities in Laser speckle —<br />
•Florian Flossmann 1 , Kevin OHolleran 1 , Miles J. Padgett 1 ,<br />
and Mark R. Dennis 2 — 1 University of Glasgow, United Kingdom,<br />
Department of Physics and Astronomy — 2 University of Bristol,<br />
United Kingdom, H.H. Wills Physics Laboratory<br />
Singularities of the polarization of light are the vectorial analogies to<br />
optical vortices (phase singularities) in scalar optics. Two types are<br />
known: L lines of linear polarization and C points of circular polarization,<br />
the latter can be further devided into lemon, star and monstar<br />
type C points. In 3D, they occur as L surfaces and C lines. Laser speckle<br />
fields, as a random superposition of coherent plane waves, form the<br />
most natural interference pattern and are therefore an obvious place<br />
to look for generic optical singularities ”in the wild”. Following our earlier<br />
work on the 3D topology of phase singularity lines in laser speckle<br />
(O‘Holleran, submitted PRL) and on the natural unfolding of optical<br />
vortices into generic polarization singularities (Flossmann,PRL 2005),<br />
we investigate both experimentally and numerically the singularities of<br />
polarization (C lines and L surfaces) in a random vector field as found<br />
in polarized laser speckle. With that we present the (to our knowledge)<br />
very first truely 3 dimensional visualization of polarization singularities<br />
in optics from experimentally obtained data. We show for example,<br />
how C loops always consist of lemon, star and monstar type C points<br />
and perform a statistical analysis of the ratios of those types per line<br />
length.<br />
Q 23.5 Di 17:30 2B/C<br />
Controlled coupling of emitters to SiN photonic crystal cavities<br />
— •Johannes Stingl 1 , Michael Barth 1 , Josef Kouba 2 , Bernd<br />
Löchel 2 , and Oliver Benson 1 — 1 Nano-Optik, Institut für Physik,<br />
Humboldt-Universität zu Berlin, Hausvogteiplatz 5-7, 10117 Berlin —<br />
2 Anwenderzentrum für Mikrotechnik, BESSY GmbH, Albert-Einstein-<br />
Str. 15, 12489 Berlin<br />
The controlled coupling of emitters to photonic crystal (PC) cavities<br />
is a crucial issue for future applications of integrated PC structures.<br />
Here we present a versatile approach to this problem based on the<br />
manipulation of nanoscopic particles on the PC surface by scanning<br />
probe techniques. This method allows a deterministic and reversible<br />
coupling of one or more light emitting particles to the cavities after<br />
the fabrication of the samples. We apply this approach to couple diamond<br />
nanocrystals containing NV color centers to SiN PC cavities.<br />
These cavities operate in the visible wavelength range between 550 nm<br />
and 800 nm and are therefore ideally suited to manipulate the emission<br />
properties of a broad variety of emitters in the visible. Despite the relatively<br />
small refractive index of SiN (n = 2.0) the cavity quality factors
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
have been optimized to values of up to 1500 by carefully designing the<br />
cavity geometry. Our experimental studies are accompanied by numerical<br />
simulations investigating the influence of nanoscopic particles on<br />
the optical properties of PC cavities. For the system studied here, the<br />
impact on the resonance frequency and quality factor turns out to be<br />
negligible for particle diameters well below 100 nm.<br />
Q 23.6 Di 17:45 2B/C<br />
A model for the photon — •Karl Otto Greulich — Fritz Lipmann<br />
Institute Jena Beutenbergstr. 11 07745 Jena<br />
Hundred years of research into the photon have not resulted in a model<br />
beyond the photon being the result of field quantisation. Quantum<br />
mechanics has no suitable operator to describe space details, quantum<br />
electrodynamics is inherently non relativistic. Here, a semi classical<br />
model is presented, which correctly predicts that E = h * v, that the<br />
Q 24: Ultrakalte Moleküle [gemeinsam mit MO]<br />
space requirements are governed by the wavelength and that the spin<br />
is h / 2pi. Also, the cross section of electron / positron pair production<br />
is predicted. The model is based on an LC oscillator and therefore<br />
requires formal / virtual charged matter as oscillating entity. The<br />
amomunt of charge required is, in a wavelength independent manner,<br />
the 1 / square root of alpha times the elementary charge. This at a<br />
first glance surprising result is supported by quantum electrodynamics,<br />
since 1 / square root of alpha is the inverse coupling constant, which<br />
can be interpreted as the probability of an electron to emit a photon.<br />
The fine structure constant alpha itself can then be interpreted as the<br />
inverse square of the formal number of elementary charges required to<br />
quantitatively describe a photon. Ref: K.O. Greulich in: The nature<br />
of light : what are photons R.Roychoudhuri et al eds. 2007 SPIE Vol<br />
66640B, 1<br />
Zeit: Dienstag 16:30–18:00 Raum: 3G<br />
Q 24.1 Di 16:30 3G<br />
Photoassociation of ultracold molecules by shaped femtosecond<br />
laser pulses — •Wenzel Salzmann 1 , Terry Mullins 1 , Simone<br />
Götz 1 , Roland Wester 1 , Magnus Albert 1 , Judith Eng 1 ,<br />
Matthias Weidemüller 1 , Fabian Weise 2 , Andrea Merli 2 , Stefan<br />
Weber 2 , Franziska Sauer 2 , Mateusz Plewicki 2 , Ludger Wöste 2 ,<br />
and Albrecht Lindinger 2 — 1 Physikalisches Institut, Universität<br />
Freiburg, Herrmann-Herder-Str.3, 79104 Freiburg — 2 Institut für<br />
Physik, Freie Universität Berlin, Arnimallee 14<br />
We present first experiments on the formation on photoassociation of<br />
ultracold molecules with shaped femtosecond laser pulses. In a pumpprobe<br />
sequence of laser pulses, molecules are produced in their excited<br />
state from an ultracold gas of rubidium atoms and subsequently ionized.<br />
Molecular ions are mass selectively detected with single ion effciency.<br />
Pulse shaping techniques are used to restrict the pump pulse<br />
spectral intensity to address only bound molecular potentials of the<br />
first electronically excited state and to suppress atomic losses from the<br />
trap due to ionization [1]. The pump-probe detected molecular ion signal<br />
shows rich oscillatory dynamics, caused by coherent interactions<br />
of molecular electronic dipole with the electric field of the pump pulse<br />
[2]. Analysis of the data is accompanied by quantum dynamical simulations<br />
which give detailed insight into the pulsed photoassociation<br />
process. We further find indications for the formation of molecules in<br />
their electronic ground state by spontaneous decay.<br />
[1] W. Salzmann et al., PRA 73, 023414 (2006)<br />
[2] A. Monmayrant et al., PRL 96, 103002 (2006)<br />
Q 24.2 Di 16:45 3G<br />
Engineering an all-optical route to ultracold molecules in<br />
their vibronic ground state — •Christiane P. Koch 1 and Robert<br />
Moszynski 2 — 1 Freie Universität Berlin, Institut für Theoretische<br />
Physik, Arnimallee 14, 14195 Berlin, Germany — 2 Dept. of Chemistry,<br />
University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland<br />
We propose an improved photoassociation scheme to produce ultracold<br />
molecules in their vibronic ground state. Formation of molecules<br />
is achieved by short laser pulses in a Raman-like pump-dump process<br />
where an additional (near-)infrared laser field couples the excited state<br />
to an auxiliary state. The efficiency of population transfer is determined<br />
by the shape of the excited state potential; it is dauntingly low<br />
for typical potentials. In our proposal, the coupling due to the additional<br />
field effectively changes the shape of the excited state potential,<br />
allowing for efficient population transfer to v=0. Such a field-induced<br />
coupling can significantly enhance any short pulse Raman-like process.<br />
Q 24.3 Di 17:00 3G<br />
Photoassociation of ultracold LiCs — •Christian Glück, Jörg<br />
Lange, Johannes Deiglmayr, Stephan Kraft, Karin Mörtlbauer,<br />
Anna Grochola, Roland Wester, and Matthias Weidemüller —<br />
Albert-Ludwigs Universität, Physikalisches Institut, Hermann-Herder-<br />
Str. 3, 79104 Freiburg i.Brsg., Germany<br />
We recently demonstrated the formation of ultracold LiCs molecules<br />
by the trapping light of a double species magneto optical trap [1]. After<br />
spontaneous decay into the electronic ground state and one-color twophoton<br />
ionization, the molecular ions are detected by a high-resolution<br />
time-of-flight mass spectrometer [2].<br />
Here we present the active photoassociation of ultracold LiCs<br />
molecules, leading to a significantly increased production rate. Photoassociation<br />
resonances in the B 1 Π potential correlated to the 2S 1/2-<br />
6P 3/2 asymptote are identified and the ro-vibrational state distribution<br />
of the produced ground state molecules is discussed. The perspectives<br />
for the production of LiCs molecules in the absolute ground state are<br />
evaluated and future experiments with an ultracold gas of polar LiCs<br />
molecules are outlined.<br />
[1] S. D. Kraft et al., J. Phys. B 39, S993<br />
[2] S. D. Kraft et al., to appear in Applied Physics B<br />
Q 24.4 Di 17:15 3G<br />
Towards a BEC of Ground State Molecules — •Johann Georg<br />
Danzl, Mattias Gustavsson, Elmar Haller, Manfred Mark, and<br />
Hanns-Christoph Nägerl — Institut für Experimentalphysik und<br />
Forschungszentrum für Quantenphysik, Universität Innsbruck, Innsbruck,<br />
Austria<br />
We report on recent progress on optical spectroscopy of ultracold Cs2<br />
Feshbach molecules. Our ultimate goal is the production of ultracold<br />
molecules in the rovibrational ground state of the singlet molecular<br />
potential [1] and the production of a BEC of ground state molecules.<br />
Coherent state transfer with an efficiency approaching unity should be<br />
possible by means of stimulated Raman adiabatic passage (STIRAP)<br />
[2]. We plan to apply two consecutive two-photon STIRAP steps where<br />
the first step will transfer the molecules from the initial Feshbach state<br />
to an intermediate vibrational level near ν=70 of the singlet potential.<br />
As part of the first step, we have found several strong bound-bound<br />
transitions in the wavelength region 1120 nm to 1130 nm, far off resonance<br />
from the atomic D1 and D2 lines.<br />
[1] D. Jaksch, V. Venturi, J. I. Cirac, C. J. Williams, and P. Zoller,<br />
Creation of a Molecular Condensate by Dynamically Melting a Mott<br />
Insulator, Phys.Rev. Lett. 89, 040402 (2002).<br />
[2] K. Winkler, F. Lang, G. Thalhammer, P. v.d. Straten, R. Grimm,<br />
J. Hecker Denschlag, Coherent optical transfer of Feshbach molecules<br />
to a lower vibrational state, Phys. Rev. Lett. 98, 043201 (2007)<br />
Q 24.5 Di 17:30 3G<br />
Few-body physics with ultracold Cs atoms and molecules<br />
— •Steven Knoop 1 , Francesca Ferlaino 1 , Martin Berninger 1 ,<br />
Harald Schöbel 1 , Michael Mark 1 , Hanns-Christoph Nägerl 1 ,<br />
and Rudolf Grimm 1,2 — 1 Institut für Experimentalphysik, Universität<br />
Innsbruck, Austria — 2 Institut für Quantenoptik und Quanteninformation,<br />
Innsbruck, Austria<br />
Ultracold atomic gases are versatile systems to study few-body physics<br />
because of full control over the external and internal degrees of freedom<br />
and the magnetic tunability of the scattering properties using Feshbach<br />
resonances. Here we experimentally study three- and four-body physics<br />
by investigating ultracold atom-dimer and dimer-dimer collisions with<br />
Cs Feshbach molecules in various molecular states and Cs atoms in different<br />
hyperfine states. Resonant enhancement of the atom-dimer relaxation<br />
rate is observed and interpreted as being induced by a trimer<br />
state [1]. For dimer-dimer collisions we have observed an unexpected
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
temperature dependence and a suppression of the collisional loss rate<br />
[2].<br />
[1] S. Knoop et al., in preparation [2] F. Ferlaino et al., in preparation<br />
Q 24.6 Di 17:45 3G<br />
Photoassociation spectroscopy in a mixture of ultracold<br />
Rb and Yb atoms — Nils Nemitz, •Florian Baumer, Frank<br />
Münchow, and Axel Görlitz — Institut für Experimentalphysik,<br />
HHU Düsseldorf, Germany<br />
Currently, many groups are pursuing the production of ultracold heteronuclear<br />
molecules in the electronic ground state. Among the most<br />
fascinating features that such a system would offer are the study of<br />
strongly dipolar quantum gases and potentially fundamental precision<br />
measurements for suitably chosen molecules.<br />
The goal of our experiment is the formation of molecules through<br />
Q 25: Laseranwendungen (Spektroskopie)<br />
photoassociation of ultracold paramagnetic Rb atoms and diamagnetic<br />
Yb atoms. The first step towards this goal is the investigation of onephoton<br />
spectroscopy from the atomic ground state of the two atomic<br />
species to an electronically excited state of the heteronuclear RbYb<br />
molecule.<br />
Here, we report on recent results of photoassociation spectroscopy<br />
close to the Rb D1-transition at 795 nm in a combined magneto-optical<br />
trap. By detecting the Yb trap loss as a function of the frequency of<br />
the photoassociation laser, we are able to observe spectral lines corresponding<br />
to several vibrational states and resolve the rotational substructure<br />
of the excited RbYb molecule.<br />
The next steps will be photoassociation spectroscopy of conservatively<br />
trapped RbYb mixtures and the extension to two-photon photoassociation<br />
in order to produce ultracold ground state molecules.<br />
Zeit: Dienstag 16:30–18:45 Raum: 3H<br />
Q 25.1 Di 16:30 3H<br />
Laserinduzierter, polarisationsabhängiger Übergang von Absorption<br />
zu Transparenz im Cäsiumatomstrahl — •Katrin<br />
Dahl, Luca Spani Molella, Rolf-Hermann Rinkleff und Karsten<br />
Danzmann — Max-Planck-Institut für Gravitationsphysik (Albert-<br />
Einstein-Institut), Institut für Gravitationsphysik, Leibniz Universität<br />
Hannover, Callinstr. 38, D-30167 Hannover<br />
Ein geschlossenes N-System zeigt üblicherweise elektromagnetisch induzierte<br />
Absorption, wenn es mit einem resonanten Koppel- und einem<br />
Probelaser wechselwirkt. Die Absorptionsprofile für verschiedene Polarisationskombinationen<br />
beider Laser (linear und senkrecht zueinander,<br />
entgegengesetzt zirkular zueinander, linear-zirkular sowie zirkularlinear)<br />
wurden in Abhängigkeit der Laserleistungen detektiert. Dabei<br />
ist beim Koppellaser für alle Polarisationskombinationen, außer der<br />
rein zirkularen, Absorption in Transparenz [1] beobachtet worden. Anders<br />
ausgedrückt war im Bereich um die 2-Photonen-Resonanz die Absorption<br />
kleiner als die der 1-Photonen-Resonanz. Zusätzlich befand<br />
sich ein Peak auf der 2-Photonen-Resonanz. Bei entgegengesetzt zirkular<br />
polarisiertem Licht wurde in Abhängigkeit der Laserleistungen<br />
ein Umklappen dieses Peaks beobachtet. Das Medium wurde für den<br />
Koppellaser transparenter. Es lag Transparenz in Transparenz vor.<br />
Dieses Projekt wurde im Rahmen des SFB407 der DFG gefördert.<br />
[1] L. Spani Molella, R.-H. Rinkleff, K. Danzmann, Phys. Rev. A 72,<br />
041802(R) (2005)<br />
Q 25.2 Di 16:45 3H<br />
Photo-induced electron and energy transfer in pyrene-flavinphenothiazine<br />
dyad and triad complexes — •Javid Shirdel 1 ,<br />
Alfons Penzkofer 1 , Roman Procházka 2 , Zhen Shen 2 , and Jörg<br />
Daub 2 — 1 Institut II - Physik, Universität Regensburg, D-93040 Regensburg<br />
— 2 Institut für Organische Chemie, Universität Regensburg,<br />
D-93040 Regensburg<br />
A pyrene-isoalloxazine dyad, a phenothiazine-phenylene-isoalloxazine<br />
dyad, and a pyrene-isoalloxazine-phenothiazine triad, dissolved in<br />
dichloromethane are characterized by absorption and emission spectroscopy.<br />
The dyads studied are model compounds for the flavin based<br />
blue-light photoreceptors phototropin (interaction between FMN and<br />
Cys) and BLUF (interaction between FAD and Tyr). The triad was<br />
designed to mimic the dye-based functions of blue-light cryptochrome<br />
photoreceptors (interaction between MTHF, FAD, and likely Trp).<br />
Absorption cross-section spectra, fluorescence quantum distributions,<br />
quantum yields, and decay times are determined. The absorption spectra<br />
of the dyads and the triad resemble the superposition of the absorption<br />
spectra of the constituents (1-methylpyrene, isoalloxazine, and<br />
phenylphenothiazine). Photo-excitation of the flavin moiety causes fluorescence<br />
quenching by reductive electron transfer in thermodynamic<br />
equilibrium with the exited flavin subunit. The charge-separated states<br />
recover by charge recombination. Photo-excitation of the pyrene or<br />
phenylphenothiazine moiety causes oxidative electron transfer with<br />
successive recombination, and additionally Förster-type and Dextertype<br />
energy transfer.<br />
Q 25.3 Di 17:00 3H<br />
Photo Dynamics of BLUF domain mutant H44R of AppA<br />
from Rhodobacter sphaeroides — •Peyman Zirak 1 , Alfons<br />
Penzkofer 1 , Peter Hegemann 2 , and Thilo Mathes 2 — 1 Institut<br />
II - Experimentelle und Angewandte Physik, Universität Regensburg,<br />
Universitätsstrasse 31, D-93053 Regensburg, Germany — 2 Institut für<br />
Biologie, Experimentelle Biophysik, Humboldt-Universität zu Berlin,<br />
Invalidenstr.42, D-10115 Berlin<br />
The photo-cycle dynamics of the H44R mutant of the BLUF domain<br />
of the protein AppA (AppA-H44R) from the purple bacterium<br />
Rhodobacter sphaeroides is studied. The amino acid residue histidine<br />
at position 44 is replaced by arginine. A 12 nm red-shifted signalling<br />
state is formed upon blue-light excitation, while in wild-type AppA<br />
(AppA-wt) the red-shift is 16 nm. The recovery time to the receptor<br />
dark state is 6.5 min. It is approximately a factor of 2.5 faster than the<br />
recovery of the wild-type counterpart. Extended light exposure of the<br />
mutant causes photo-degradation of flavin (mainly flavin conversion to<br />
lumichrome). No photo-degradation was observed for AppA-wt. The<br />
quantum efficiency of signalling state formation determined by intensity<br />
dependent absorption measurements is found to be 0.3 (for AppAwt:<br />
0.24). A two-component single-exponential fluorescence relaxation<br />
was observed with lifetimes of 80 ps and 900 ps (for AppA-wt: 1.3<br />
ps and 270 ps), which is interpreted as fast fluorescence quenching to<br />
an equilibrium by photo-induced electron transfer followed by slower<br />
fluorescence decay due to charge recombination. Based on the experimental<br />
findings, a photo-cycle model for BLUF domains is proposed.<br />
Q 25.4 Di 17:15 3H<br />
Spectroscopy of the two-photon resonance in atomic mercury<br />
vapour — •Thomas Beyer, Martin Scheid, Daniel Kolbe, Frank<br />
Markert, and Jochen Walz — University of Mainz, Germany<br />
We investigated the 6 1 S – 7 1 S two-photon resonance in mercury vapour<br />
driven by two different tuneable laser fields, one of them near the 6 1 S –<br />
6 3 P transition. This laser field is provided by a frequency-quadrupled<br />
solid-state Yb:YAG disk laser system generating up to 750mW output<br />
power at 253.7nm. The second laser field is provided by a gratingstabilized<br />
GaAs diode laser, boosted by tapered amplifiers and then<br />
frequency-doubled to 408.7nm, yielding output powers up to 30mW.<br />
Spectra for different detunings and mercury vapour pressures are<br />
presented and compared to theory involving solutions to the Optical<br />
Bloch Equations in a three-level quantum system. The results are of<br />
interest for the generation of continuous-wave coherent radiation at<br />
121.56nm, which is needed for cooling of anti-hydrogen, because the<br />
conversion efficiency for this process is strongly enhanced by selecting<br />
fundamental wavelengths near these mercury resonances.<br />
Q 25.5 Di 17:30 3H<br />
Doppler-free Spectroscopy of Rubidium Rydberg Transitions<br />
in a Room-temperature Gas Cell — Thomas Becker 1,2 ,<br />
•Pierre Thoumany 1,2 , Thomas Germann 1 , Gernot Stania 1 , Linas<br />
Urbonas 1 , and Theodor Hänsch 1 — 1 Max-Planck-Institut für<br />
Quantenoptik, Garching, Germany — 2 Physik Departement, Ludwig-<br />
Maximilians-Universität, Munich, Germany<br />
Until recently, Doppler-free detection of Rydberg transitions was limited<br />
to techniques, where the subsequent ionization of Rydberg atoms<br />
allows for an electronic detection. This requires the use of an atomic
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
beam apparatus or thermionic diodes. In our setup, we use a two stage<br />
cascaded laser setup (780 nm, 480nm) or a two stage V -scheme (297<br />
nm, 780 nm) to excite and detect Rydberg transitions in a room temperature<br />
gas cell. In both cases, the population of the Rydberg levels<br />
is monitored optically via the decreased absorbtion of the 780 nm radiation<br />
(rubidium D2 line). We discuss the general setup, the observed<br />
lineshapes and present results on laser frequency stabilization to Rydberg<br />
transitions using this technique. In addition, we discuss similarities<br />
to the well known electron shelving technique used to detect weak<br />
transitions in trapped ions.<br />
Q 25.6 Di 17:45 3H<br />
Stimmgabelverstärkte photoakustische Spektroskopie zur<br />
Sauerstoffdetektion — •Andreas Pohlkötter 1 , Stefan<br />
Böttger 2 , Christoph Bauer 2 , Ulrike Willer 1,2 und Wolfgang<br />
Schade 1,2 — 1 Institut für Physik und Physikalische Technologien,<br />
TU Clausthal — 2 Laser AnwendungsCentrum, TU Clausthal<br />
Das Verfahren der stimmgabelverstärkten photoakustischen Spektroskopie<br />
(engl.: quartz enhanced photoacoustic spectroscopy - QEPAS)<br />
ist eine Weiterentwicklung der klassischen photoakustischen Spektroskopie<br />
[1]. Hierbei wird ein modulierter Laserstrahl zwischen die Zinken<br />
einer Quarz-Stimmgabel fokussiert. Die durch die modulierte Lichtintensität<br />
erzeugte Schallwelle fungiert als treibende Kraft der erzwungenen<br />
Schwingung der Stimmgabel, welche durch den piezoelektrischen<br />
Effekt eine messbare Wechselspannung erzeugt. Die Vorteile der<br />
QEPAS Technik sind ein sehr kompakter Aufbau und bedingt durch<br />
die Stimmgabelgeometrie eine weitestgehende Unempfindlichkeit gegenüber<br />
Störgeräuschen. Mit dieser Technik wurde ein Sensorsystem<br />
aufgebaut, welches in der Lage ist, Sauerstoff in geringen Konzentrationen<br />
nachzuweisen. Ein weiterer Vorteil der photoakustischen Spektroskopie<br />
ist, dass kein optischer Detektor nötig ist, der eine Abhängigkeit<br />
von der Wellenlänge des Lichtes zeigt. Die Sensoren eignen sich daher<br />
in Kombination mit Quantenkaskaden-Lasern dazu, Spektroskopie<br />
im mittleren Infrarotbereich ohne gekühlte Detektoren durchzuführen.<br />
Erste Ergebnisse werden präsentiert.<br />
[1] A. A. Kosterev et. al., Opt. Lett. 27, 21 (2002) 1902-1904<br />
Q 25.7 Di 18:00 3H<br />
Evanescent-field-sensor for detection of CO2 dissolved in water<br />
— •Rozalia Orghici, Ulrike Willer, and Wolfgang Schade<br />
— TU Clausthal, Institute of Physics and Physical Technologies, Leibnizstraße<br />
4, 38678 Clausthal Zellerfeld<br />
The increase of the carbon dioxide (CO2) concentration in the earth<br />
atmosphere is considered to be one of the main factors responsible for<br />
global warming. Experts agree that one promising approach for the reduction<br />
of the CO2 amount entering the atmosphere is the storage of<br />
CO2 deep underground. A test site is available at Ketzin, Germany, for<br />
the study of the sequestration process, its dynamics and the temporal<br />
and spatial distribution of CO2. Carbon dioxide is injected into a saline<br />
aquifer at a depth of 800 m, whereas two observation boreholes allow<br />
the monitoring of the storage process. Therefore, sensors are needed<br />
which are able to monitor the concentration of the dissolved CO2 in<br />
water on-line and in situ. Evanescent-field-spectroscopy is an advantageous<br />
spectroscopic technique for detection and analysis of species in<br />
places difficult to access and in corrosive, absorbing or highly scattering<br />
media. Compared to other spectroscopic methods, which require<br />
Q 26: Poster Ultrakurze Laserpulse<br />
open optical paths, this sensing method can be attained in an all fiber<br />
coupled sensor by using optical fibers as sensing elements as well as<br />
for guiding the light to and from the sensor. The sensing region can be<br />
inserted into fluids, therefore enabling the real-time determination of<br />
the CO2 content in water. The experimental setup and the sensitivity<br />
of the evanescent-field-sensor will be presented.<br />
Q 25.8 Di 18:15 3H<br />
Untersuchung der Hyperfeinstruktur von Praseodym mittels<br />
laserinduzierter Fluoreszenzspektroskopie — •Bettina<br />
Gamper 1 , Imran Siddiqui 1 , Günter Guthöhrlein 2 und Laurentius<br />
Windholz 1 — 1 Institut für Experimentalphysik, Techn. Univ.<br />
Graz — 2 Fachbereich Elektrotechnik, Helmut Schmidt-Univ. der BW<br />
Hamburg, Holstenhofweg 85, 22043 Hamburg<br />
Das komplexe Praseodym-Spektrums ist bislang noch nicht vollständig<br />
analysiert. Die Liniendichte von Praseodym ist, vor allem im sichtbaren<br />
Wellenlängenbereich, sehr hoch, weshalb eine Identifizierung<br />
der zugehörigen Energieniveaus allein aus der Wellenzahl der Linien<br />
meistens nicht möglich ist. Auch unter Einbeziehung der in<br />
den Fouriertransformations-Spektren aufgelösten Hyperfeinstruktur<br />
gelingt eine Klassifizierung nicht immer. Sehr viele Strukturen, die<br />
im Fourier-Spektrum als einzelne Linie oder als Blend von 2 bis 3<br />
Linien erscheinen, stellten sich als Überlagerung von bis zu acht verschiedenen<br />
Übergängen dar. Mit Hilfe von laserspektroskopischen Untersuchungen<br />
können einzelne Linien einer Blend-Situation durch ihre<br />
Fluoreszenzlinien getrennt aufgezeichnet und somit klassifiziert werden.<br />
Bisher wurden sehr viele Linien, die meisten zwischen 570 und<br />
600 nm, klassifiziert und mehr als 50 neue Energieniveaus entdeckt.<br />
Q 25.9 Di 18:30 3H<br />
Anomale Intensität der Hyperfeinkomponenten von<br />
Praseodym-I - Linien — •Imran Siddiqui 1 , Bettina Gamper 1 ,<br />
Günter Guthöhrlein 2 und Laurentius Windholz 1 — 1 Institut<br />
für Experimentalphysik, Techn. Univ. Graz, Petersgasse 16, A-8010<br />
Graz — 2 Fachbereich Elektrotechnik, Helmut Schmidt-Univ. der BW<br />
Hamburg, Holstenhofweg 85, 22043 Hamburg<br />
Bei der laserspektroskopischen Anregung der Linie 578,051 nm wurde<br />
mittels laserinduzierter Fluoreszenz eine ungewöhnliche Hyperfeinstruktur<br />
beobachtet. Der niederfrequente Teil der Struktur ließ von<br />
den Komponentenabständen her auf einen Übergang Delta J=0, mit<br />
J=15/2, von den Komponentenintensitäten her aber auf einen kleinen<br />
Drehimpuls schließen. Aus den beobachteten Fluoreszenzwellenlängen<br />
wurde diese Linie als Übergang zwischen zwei neuen Energieniveaus<br />
(32486.80 cm-1, 15/2 even - 15192,08 cm-1, 15/2 odd) interpretiert.<br />
Weiters wurde bei Anregung von 578,027 nm eine weitere Linie mit<br />
ungewöhnlicher Hyperfeinstruktur auf denselben Fluoreszenzkanälen<br />
beobachtet. Damit ergab sich das Bild eines Niveautripletts, wobei die<br />
zwei weiteren unteren Niveaus J=13/2 besitzen und 0,18 bzw. 0,86 cm-<br />
1 unterhalb des Niveaus 15192,28 liegen. Diese drei eng benachbarten<br />
Energieniveaus stören sich gegenseitig, d.h., durch Wechselwirkungen<br />
wird die Lage der Hyperfeinniveaus geändert, wodurch die Formeln<br />
von Casimir nicht mehr streng gültig sind. Hier liegen nur sehr geringe<br />
Verschiebungen der Hyperfeinniveaus vor, trotzdem wird aber die<br />
Übergangswahrscheinlichkeit zwischen den Komponenten des oberen<br />
und unteren Niveaus sehr stark beeinflußt.<br />
Zeit: Dienstag 16:30–19:00 Raum: Poster C1<br />
Q 26.1 Di 16:30 Poster C1<br />
Femtosekunden OPO basierend auf MgO:PPLN mit aktiver<br />
Wellenlängenkontrolle — •Felix Rübel, Peter Haag, Richard<br />
Wallenstein und Johannes L’huillier — Technische Universität<br />
Kaiserslautern, Fachbereich Physik, Erwin-Schrödinger-Str. 46, 67663<br />
Kaiserslautern<br />
Durchstimmbare Femtosekunden Impulse im nahen und mittleren Infrarotbereich<br />
werden für Untersuchungen extrem schneller Prozesse<br />
benötigt. Da in diesem Wellenlängenbereich keine direkt emittierenden<br />
Strahlquellen existieren sind alternative Konzepte erforderlich. Eine<br />
Möglichkeit bieten synchron gepumpte optisch parametrische Oszillatoren<br />
(OPO). Basierend auf periodisch gepoltem MgO:LiNbO3 wurde<br />
ein signalresonanter fs-OPO bei Raumtemperatur realisiert. Durch Va-<br />
riation der Pumpwellenlänge kann die Signalwellenlänge von 1050 nm<br />
bis 1280 nm durchgestimmt werden. Gepumpt mit 1,3 W und 100 fs bei<br />
einer Repetitionsrate von 82 MHz wurde eine maximale Ausgangsleistung<br />
von 450 mW und eine minimale Impulsdauer von 215 fs erreicht.<br />
Durch aktive Kontrolle der Resonatorlänge konnte die Wellenlänge der<br />
Signalstrahlung über einen Zeitraum von mehr als 14 Stunden mit einer<br />
Abweichung von kleiner 0,5 nm stabil gehalten werden. Die relative<br />
Abweichung von der spektralen Breite des Signalimpulses liegt unter<br />
3 %.<br />
Q 26.2 Di 16:30 Poster C1<br />
Messung und Stabilisierung der Träger-Einhüllenden-Phase<br />
von Laseroszillatoren und Verstärkersystemen — •Anne<br />
Harth, Niels Meiser, Emilia Schulz, Thomas Binhammer, Ste-
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
fan Rausch, Milutin Kovacev und Uwe Morgner — Institut für<br />
Quantenoptik, Leibniz Universität Hannover<br />
Ein bezüglich der Träger-Einhüllenden-Phase (CEO-Phase) stabilisierter<br />
Laseroszillator ist für aktuelle Gebiete der Physik von<br />
großer Bedeutung. Die genaue Position der Trägerwelle unter seiner<br />
Einhüllenden ist z.B. für die Erzeugung von einzelnen Attosekunden-<br />
Pulsen notwendig. Für diese stark nichtlinearen Prozesse sind Pulsintensitäten<br />
von über 10 15 W/cm 2 notwendig, die problemlos durch<br />
Nachverstärkung erreicht werden. Daher müssen sowohl der Oszillator<br />
als auch der Verstärker bezüglich der CEO-Phase stabilisiert<br />
werden. Darüber hinaus bietet ein phasenstabiler Laser einen hochpräzisen<br />
Frequenzkamm mit entsprechenden Anwendungen in der<br />
Präzisionsmetrologie, aber auch einzelne phasenstabile Laserpulse direkt<br />
aus einem Oszillator, dessen Pulsdauern unter 10 fs liegen, eröffnen<br />
neue Anwendungsgebiete, wie z.B. die Untersuchung der Photoionisation<br />
von Metalloberflächen. In Hinblick auf solche Anwendungen werden<br />
die experimentellen Methoden zur Messung und Stabilisierung der<br />
Träger-Einhüllenden-Phase von verschiedenen Titan:Saphir Lasersystemen<br />
dargestellt.<br />
Q 26.3 Di 16:30 Poster C1<br />
Specially parameterized evolutionary algorithm for spatial<br />
optimization — •Jan Lohbreier, Stefan Eyring, Christian Kern,<br />
Robert Spitzenpfeil, Dominik Walter, and Christian Spielmann<br />
— Universität Würzburg, Physikalisches Institut, Am Hubland, 97074<br />
Würzburg<br />
We present a method to achieve an optimal spatial phase shape for a<br />
femtosecond laser pulse via an evolutionary algorithm. ’Optimal’ here<br />
is meant to be specifically designed for one signal (e.g. overall intensity<br />
as fitness) that is fed back to the computer. The 768x768 pixels of our<br />
pulse shaper allow high-resolution phase shaping but also need a lot of<br />
computing power for a real-time optimization. Our new approach is to<br />
minimize the required informational size of a generation and thus to<br />
reduce the computing time per generation. Furthermore the technique<br />
to use planes instead of meta-pixels generates a smoother phase mask<br />
which is generally preferred to a rough surface. To test this scheme a<br />
picture was set to be the ideal phase mask and the time for the algorithm<br />
to match the intended picture was measured. Thus it was possible<br />
to downsize the controlling environment to make the optimization<br />
as good and fast as possible for its current challenges.<br />
Q 26.4 Di 16:30 Poster C1<br />
The impact of the dipole phase on the population dynamics<br />
of bound-bound transitions — •Xiao-Tao Xie, Mihai Macovei,<br />
Martin Kiffner, and Christoph H. Keitel — Max-Planck-Institute<br />
for Nuclear Physics, Saupfercheckweg 1, 69117 Heidelberg, Germany<br />
The dipole phase plays an important role in strong-field processes and<br />
determines, e.g., the coherence properties of high-order harmonic radiation<br />
[1]. Here we consider the weak-field regime such that tunneling<br />
processes and multiphoton ionization are negligible, and investigate<br />
the impact of the permanent dipole phase on the population dynamics<br />
of bound-bound transitions that are illuminated by a few-cycle pulse.<br />
It is shown that the population of the excited states depends on the<br />
carrier-envelope phase as well as on the dipole phase. A scheme that<br />
allows to determine the dipole phase via the controlled adjustment of<br />
the carrier-envelope phase is discussed.<br />
[1] P. Salières, A. L’Huillier, and M. Lewenstein, Phys. Rev. Lett.<br />
74, 3776 (1995).<br />
Q 26.5 Di 16:30 Poster C1<br />
Analytical theory for the propagation of laser beams in nonlinear<br />
media — •Larisa Tatarinova and Marin Garcia — University<br />
of Kassel, Kassel, Germany<br />
The propagation of a laser beam of intensity I in a nonlinear media<br />
with a refraction index n(I) of arbitrary form is studied. In particular,<br />
the influence of the functional form n=n(I) on self-focusing and<br />
self-trapping is investigated. We also explicitly analyze the case of nonlinear<br />
self-focusing accompanied by multiphoton ionization. Influence<br />
of the spatial beam shape on the self-focusing is investigated. Case of<br />
propagation of two pulses with different intensities is studied analytically.<br />
For particular, already studied cases we considerably improve the<br />
accuracy of the results with respect to previous semi-analytical studies<br />
and obtain very good agreement with recent numerical simulations.<br />
Q 26.6 Di 16:30 Poster C1<br />
Compensation of undesired amplitude and phase effects<br />
in polarization pulse shaping — •Jens Köhler, Marc Krug,<br />
Cristian Sarpe-Tudoran, Matthias Wollenhaupt, and Thomas<br />
Baumert — Universität Kassel, Institut für Physik und Center for<br />
Interdisciplinary Nanostructure Science and Technology (CINSaT),<br />
Heinrich-Plett-Str. 40, D-34132 Kassel, Germany<br />
Undesired polarization dependent amplitude modulations and phase<br />
shifts are of great importance in femtosecond polarization pulse shaping.<br />
These effects are introduced by components of the pulse shaper<br />
itself as well as additional optical elements. For accurate generation<br />
of pulses with a desired time-dependent polarization profile on an ultrashort<br />
timescale it is important to understand and to control these<br />
effects. Here we present two approaches allowing for the compensation<br />
of these disturbing factors. Using VPHGs (Volume Phase Holographic<br />
Gratings) the polarization dependent losses normally present in polarization<br />
pulse shapers could be minimized. The phase shifts can be handled<br />
by the use of an appropriate retardation plate. Femtosecond laser<br />
pulses with different polarization states were generated with our highresolution<br />
polarization pulse shaper based on a 2x640 pixel LC-SLM<br />
(Liquid Crystal-Spatial Light Modulator). The shaped pulses were analyzed<br />
using a simple optical scheme and employing PEIS (Photoelectron<br />
Imaging Spectroscopy). First results demonstrating the successful<br />
compensation of the above mentioned amplitude and phase effects are<br />
presented.<br />
Q 26.7 Di 16:30 Poster C1<br />
Supercontinuum generation in a photonic crystal fiber,<br />
characterization and transient absorption spectroscopy —<br />
•Jutta Mildner, Johannes Schneider, Matthias Wollenhaupt,<br />
and Thomas Baumert — Universität Kassel, Institut für Physik und<br />
Center for Interdisciplinary Nanostructure Science and Technology<br />
(CINSaT), Heinrich-Plett-Str. 40, D-34132 Kassel, Germany<br />
Broadband ultrashort laserpulses are an important tool in ultrafast<br />
spectroscopy. Since Alfano and Shapiro generated the first supercontinua<br />
(SC) in diverse glass plates in 1970 [1], great interest and development<br />
has evolved on that subject. In this work, we present the setup<br />
of such a SC light source, its characterization and finally a first application.<br />
The SC are generated in a photonic crystal fiber being pumped by<br />
a common Ti:Sapphire femtosecond laser system in a setup analogous<br />
to [2]. The advantages of photonic crystal fibers lie in their high flexibility<br />
and low pump energies needed. The results of SC generation i.e.<br />
spectral properties and stability are discussed. Furthermore we present<br />
different approaches of SC pulse characterization containing autocorrelation,<br />
spectral interference and crosscorrelation techniques. Finally<br />
as an example of a first application of this light source, a transient absorption<br />
experiment of the laser dye DCM as a standard is conducted<br />
in a pump-SC probe setup. First results are shown.<br />
[1] R.R. Alfano and S.L. Shapiro: PRL 24, 592 (1970)<br />
[2] B.v. Vacano, W. Wohlleben and M. Motzkus: Opt. Lett. 31, 413<br />
(2006)<br />
Q 26.8 Di 16:30 Poster C1<br />
Construction of an Ultrafast Electron Diffraction Apparatus<br />
— •Christian Gerbig, Marc Winter, Matthias Wollenhaupt,<br />
and Thomas Baumert — Universität Kassel, Institut für Physik und<br />
Center for Interdisciplinary Nanostructure Science and Technology<br />
(CINSaT), Heinrich-Plett-Str. 40, D-34132, Germany<br />
In order to directly observe structural changes on a femtosecond or<br />
picosecond timescale with atomic resolution, a combination of an optical<br />
technique offering high temporal resolution (fs pump-probe) and a<br />
structural characterization technique (for example electron diffraction)<br />
is needed [1-3]. We show the setup and construction of an apparatus<br />
for time-resolved electron diffraction measurements based on an amplified<br />
30 fs Ti:Sapphire laser system and present first characterization<br />
data and current modifications.<br />
[1] B.J. Siwick, J. R. Dwyer, R.E. Jordan, R.J.D. Miller, Science<br />
302 (2003) 1382<br />
[2] W.E. King, G.H. Campbell, A. Frank, B. Reed, J.F. Schmerge,<br />
B.J. Siwick, B.C. Stuart, P.M. Weber, J. Appl. Phys. 97 (2005) 11101<br />
[3] A.H. Zewail, Annu. Rev. Phys. Chem. 57 (2006) 65<br />
Q 26.9 Di 16:30 Poster C1<br />
Erzeugung und Detektion von gepulster Terahertz Strahlung<br />
mit GaP-Kristallen — •Mathias Hoffmann 1 , Matthias<br />
Pospiech 1 , Andy Steinmann 1 , Guido Palmer 1 und Uwe<br />
Morgner 1,2 — 1 Institut für Quantenoptik, Leibniz Universität Hannover,<br />
Deutschland — 2 Laserzentrum Hannover e.V.
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
Wir verwenden einen modengekoppelten Yb:Glass Laser [1] mit<br />
Cavity-Dumping (375 fs, 100 nJ, 1 MHz), um in GaP-Kristallen<br />
durch Optische Gleichrichtung intensive gepulste Strahlung im THz-<br />
Spektralbereich zu erzeugen. GaP bietet sich hierfür an, da es im Bereich<br />
von 1030 nm Phasenanpassung bietet [2]. Die THz Strahlung wird<br />
im Time-Domain Verfahren über einen elektrooptischen Detektor –<br />
ebenfalls auf GaP Basis – aufgezeichet, und mittels Fouriertransformation<br />
wird aus diesen Daten das zugehörige Frequenzspektrum berechnet<br />
[3]. Wir berichten über Erzeugung und Detektion mit diesen<br />
Verfahren und zeigen die Skalierung der Parameter bei verschiedenen<br />
Kristalldicken.<br />
[1] A. Killi et. al., Opt. Lett. 29, 1288-1290 (2004)<br />
[2] Chang et. al., Optics Express (2006), Bd. 14(17):S. 7909–7913<br />
[3] Wu et. al. Applied Physics Letters (1997), Bd. 70(14):S. 1784 – 1786<br />
Q 26.10 Di 16:30 Poster C1<br />
Spatial characterization and wavefront measurements of<br />
high-order harmonics — •Stefan Eyring 1 , Christian Kern 1 , Jan<br />
Lohbreier 1 , Robert Spitzenpfeil 1 , Matthias Weger 2 , and Christian<br />
Spielmann 1 — 1 Universität Würzburg, Physikalisches Institut,<br />
Am Hubland, Würzburg, Deutschland — 2 ETH Zürich, Institut für<br />
Quantenelektronik, Zürich, Schweiz<br />
High-order harmonic radiation provides coherent light up to the soft<br />
x-ray regime. Because of the fundamentally low photon yield one needs<br />
to focus the generated radiation. The focussing of the beam of harmonics<br />
depends strongly on its wavefront. Therefore detailed information<br />
on the beam profile and wavefront are necessary.<br />
We present experimental measurements with a Hartmann-type<br />
wavefront sensor suited for use in the EUV region. For analysing the<br />
data Zernicke polynomials are used and quantitative physical interpretation<br />
is therefore possible. In addition we present measurements with<br />
a knife-edge scan to determine the beam parameter M 2 which is a<br />
wavelength-independent measure of beam quality. This scheme allows<br />
us to calculate different beam parameters of the beam of high-order<br />
harmonics.<br />
Using the information gained through this setup we utilise an adaptive<br />
spatial pulse shaping technique. Changing the wavefront of the<br />
incident driving laser beam of the generating process makes it possible<br />
to increase the high-order harmonic yield at the detector.<br />
Q 26.11 Di 16:30 Poster C1<br />
Resonant strong-field control of potassium atoms by spectral<br />
θ-step phase modulation — •Tim Bayer, Matthias Wollenhaupt,<br />
and Thomas Baumert — Universität Kassel, Institut für<br />
Physik und CINSaT, Heinrich-Plett-Str. 40, D-34132 Kassel, Germany<br />
Q 27: Poster Quantengase<br />
Selective Population of Dressed States (SPODS) is the key to coherent<br />
control of resonant quantum phenomena in strong laser fields. Recently<br />
two SPODS control schemes have been devised which make use<br />
of shaped femtosecond laser pulses [1,2]. It was shown that chirped<br />
pulses as well as pulse sequences can be used to steer potassium atoms<br />
into single dressed states, achieving high efficiency and selectivity. The<br />
underlying control mechanisms are based on continuously varying temporal<br />
phases (adiabatic SPODS) and discrete temporal phase jumps<br />
(non-adiabatic SPODS) respectively. Here, we employ a spectral phase<br />
modulation function of the form ϕ(ω) = θ/2 · σ(ω − δω), where σ denotes<br />
the signum function, which produces a double pulse structure<br />
in time with a linearly varying phase and a phase jump in between<br />
the two pulses. Hence, this pulse shape combines adiabatic with nonadiabatic<br />
aspects. We present measured photoelectron spectra from<br />
resonant multi-photon ionization of potassium atoms as a function of<br />
the spectral step size θ and the detuning δω. Our results show, that<br />
both parameters provide an efficient means to exert control on the<br />
dressed state populations.<br />
[1] M. Wollenhaupt et al.: PRA 73, 2006<br />
[2] M. Wollenhaupt et al.: APB 82, 2006<br />
Q 26.12 Di 16:30 Poster C1<br />
Kohärente Kontrolle nanoplasmonischer Ausbreitung mit ultrakurzen<br />
polarisationsgeformten Laserimpulsen — •Philip<br />
Tuchscherer1 , Dmitri V. Voronine1 , F. Javier García de Abajo2 ,<br />
Walter Pfeiffer3 und Tobias Brixner1 — 1Institut für Physikalische<br />
Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg,<br />
Germany — 2Instituto de Óptica, CSIC, Serrano 121, 28006 Madrid,<br />
Spain — 3Fakultät für Physik, Universität Bielefeld, Universitätsstr.<br />
25, 33516 Bielefeld, Germany<br />
Elektromagnetische Nahfelder zeigen Variationen auf Längenskalen unterhalb<br />
des optischen Beugungslimits und können partiell durch Methoden<br />
der kohärenten Kontrolle manipuliert werden. Von besonderem<br />
Interesse für verschiedene Anwendungen ist die räumliche Ausbreitung<br />
kohärenter Anregungen in Nanostrukturen.<br />
Wir untersuchen in Simulationsrechnungen, wie solche Anregungen<br />
mittels phasen- und polarisationsgeformter ultrakurzer Lichtimpulse<br />
gesteuert werden können.<br />
Die Größe der verwendeten metallischen Nanostrukturen wird entsprechend<br />
der Plasmonenresonanz gewählt, und durch Fokussieren der<br />
Lichtimpulse wird eine partielle Anregung der Nanostruktur bewirkt.<br />
Die Ausbreitung der Plasmonen soll dann durch geeignet geformte Laserpulse<br />
gesteuert werden, wobei die Pulsform durch einen Lernalgorithmus<br />
optimiert wird.<br />
Zeit: Dienstag 16:30–19:00 Raum: Poster C2<br />
Q 27.1 Di 16:30 Poster C2<br />
Transport properties of Bogoliubov excitations in correlated<br />
disorder — •Christopher Gaul, Christian J. Harrer, and Cord<br />
A. Müller — Universität Bayreuth<br />
We study 2D quantum transport in a many-body system by considering<br />
a Bose-Einstein condensate in a correlated disordered optical potential.<br />
The correlation length of the disorder potential together with<br />
the healing length are the two relevant length scales of the problem.<br />
The effective transport characteristics of Bogoliubov excitations are<br />
investigated by calculating suitable configuration averages. We obtain<br />
the disorder-broadened Bogoliubov dispersion relation, the scattering<br />
length, and the transport mean free path. In particular we examine<br />
the regime where the disorder correlation length is not the shortest of<br />
all length scales.<br />
Q 27.2 Di 16:30 Poster C2<br />
Bloch dynamics of a BEC: mean-field vs. microscopic descriptions<br />
— •Eva-Maria Graefe 1 , Andrey R. Kolovsky 2 , and Hans<br />
Jürgen Korsch 1 — 1 TU Kaiserslautern, Germany — 2 Kirensky Institute<br />
of Physics, Krasnoyarsk, Russia<br />
Recently much attention is paid to the Bloch dynamics of a BEC loaded<br />
into an optical lattice, subject to a static, for example, gravitational<br />
field. We compare two theoretical approaches to this problem, the<br />
mean-field description, based on the discrete nonlinear Schrödinger<br />
equation (DNLSE), and the microscopic description, based on the<br />
Bose-Hubbard model. Within the mean-field approach the main phenomena<br />
related to the Bloch dynamics are the dynamical instability<br />
(also known as modulation instability) and self-thermalization due to<br />
the onset of classical chaos in the DNLSE. We argue that the quantum<br />
manifestations of these phenomena are the depletion of the Floquet-<br />
Bogoliubov states, defined as the ”low-energy” eigenstates of the evolution<br />
operator over one Bloch period, and the decoherence of the BEC.<br />
The correspondence between mean-field and microscopic description is<br />
analysed in dependence on the number of particles as well as on the<br />
magnitude and direction (for 2D or 3D lattices) of the static field.<br />
Q 27.3 Di 16:30 Poster C2<br />
Atom Laser by all-optical means for Atom Interferometry —<br />
•Maic Zaiser, Temmo Wübbena, Stefan Jöllenbeck, Wolfgang<br />
Ertmer, and Ernst Maria Rasel — Leibniz Universität Hannover<br />
We present the current status of our all-optical ATom LASer (AT-<br />
LAS), an experiment aiming at Bose-Einstein-Condensation (BEC) in<br />
a dilute atomic gas of 87 Rb by all-optical means. The project is motivated<br />
by the possible improvements of the accuracy of matter-wave<br />
interferometers based on quantum degenerated atoms. Optical dipole<br />
traps allow a high repetition rate in an interferometer and are also<br />
able to trapp all mF -substates, especially mF = 0, which is in the<br />
first order insensitive to magnetic fields. We investigate the potential
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
of such an atomic source for precision atom interferometers, such as<br />
the Cold Atom Sagnac Interferometer (CASI) [1] currently being set<br />
up in Hanover.<br />
The atomic source consists of a three dimensional magneto-optical<br />
trap (3D-MOT) loaded by a 2D-MOT. We present the very compact<br />
vacuum chamber and a compact laser system for atom cooling employing<br />
modular integrated and fiber-based optics ensuring a high stability<br />
of the system. We will discuss the suitability of a high power Thulium<br />
fiber laser at 2 µm wavelength for trapping and evaporatively cooling<br />
atoms to quantum degeneracy. This work is part of the project FI-<br />
NAQS funded by the European Union. (www.finaqs.uni-hannover.de)<br />
[1] Versatile compact atomic sources for high resolution dual atom<br />
interferometry; T. Müller, T. Wendrich, M. Gilowski, C. Jentsch, E.M.<br />
Rasel, W. Ertmer Phys. Rev. A, in press.<br />
Q 27.4 Di 16:30 Poster C2<br />
Bose-Einstein condensation and atom optical experiments<br />
— •Thomas Lauber 1 , Susanne Hertsch 1 , Markus Krutzik 1 , Johanna<br />
Nes 1 , Oliver Wille 1 , Anna Sanpera 2 , and Gerhard Birkl 1<br />
— 1 Institut für Angewandte Physik; Technische Universität Darmstadt,<br />
Schlossgartenstr. 7, D-64289 Darmstadt — 2 Department of<br />
Physics, Theoretical Physics Group, Universitat Autónoma Barcelona,<br />
E-08193 Bellaterra<br />
Optical trapping and guiding configurations have evolved as a powerful<br />
tool for the manipulation of ultracold atoms. In our experiment,<br />
rubidium atoms are loaded in a crossed optical dipole trap of 1030nm<br />
laser beams directly from a MOT. We create ultracold atom samples<br />
in the sub-microKelvin temperature range by evaporative cooling.<br />
The advantage of a pure optical setup is its flexibility and independence<br />
of the magnetic properties of the trapped atoms. It is also<br />
possible to superimpose arbitrary magnetic fields on the trapping configuration.<br />
Our work aims at studying the coherence properties of ultracold<br />
thermal atoms and degenerate quantum gases in traps created<br />
by miniaturized optical lens structures. With these elements we can<br />
realize various trap geometries including a storage ring for atom interferometry<br />
experiments, and optical waveguides, in which the ultracold<br />
gas can be transferred.<br />
Recent calculations promise an interesting velocity selective behaviour<br />
in one-dimensional periodic structures superimposed on a<br />
waveguide. We can implement these structures either with standing<br />
waves or microlens arrays.<br />
Q 27.5 Di 16:30 Poster C2<br />
Mesoscopic physics in quantum gases — •Bruno Zimmermann,<br />
Torben Müller, Henning Moritz, and Tilman Esslinger — Institute<br />
of Quantum Electronics, ETH Zürich, Hönggerberg, CH-8093<br />
Zürich, Switzerland<br />
We present an experimental setup which allows us to study an ultracold<br />
fermionic quantum gas in a potential that can be arbitrarily<br />
controlled down to the smallest relevant length scale, i.e. that of the<br />
atomic wavefunction. The basic idea is to prepare an ultracold gas of<br />
fermionic lithium in a region of high optical access by using standard<br />
laser cooling and trapping technics, followed by a transport and direct<br />
evaporation in an optical dipole trap. In the final position the gas will<br />
be sandwiched between two microscopes. The shape of the laser beams<br />
focused by these microscopes, i.e. the shape of the optical potential, will<br />
be controlled by spatial light modulators. The interaction strength of<br />
colliding atoms can be tuned by accessing a Feshbach resonance. This<br />
setup will allow us to study Josephson oscillations in the BEC-BCS<br />
crossover regime and to manipulate strongly correlated atomic samples<br />
on a local scale. First results on the cooling and trapping will be<br />
shown.<br />
Q 27.6 Di 16:30 Poster C2<br />
Far-From-Equilibrium Dynamics of an Ultracold Fermi Gas<br />
— •Matthias Kronenwett and Thomas Gasenzer — Institut<br />
für Theoretische Physik, Universität Heidelberg, Philosophenweg 16,<br />
69120 Heidelberg<br />
The dynamics of ultracold Fermi gases far from thermal equilibrium<br />
is studied. A functional-integral approach based on the Schwinger-<br />
Keldysh closed time path integral is employed to derive the two-particle<br />
irreducible (2PI) effective action. From this, the two-point correlation<br />
functions are determined self-consistently. The action is expanded in<br />
inverse powers of the number of field components N , and the dynamic<br />
equations are derived in next-to-leading order of this expansion. This<br />
approach reaches far beyond mean-field theory and includes quantum<br />
statistical aspects of equilibration dynamics. It enables to describe,<br />
e. g., the dynamical evolution of trapped Fermi gases in optical lattices,<br />
as well as the BEC-BCS crossover dynamics.<br />
Q 27.7 Di 16:30 Poster C2<br />
Towards a degenerate mixture of 6 Li and 40 K — •Antje<br />
Ludewig, Tobias Tiecke, Sebastian Kraft, Steve Gensemer, and<br />
Jook Walraven — Van der Waals-Zeeman-Instituut, Universiteit van<br />
Amsterdam, The Netherlands<br />
We have constructed an apparatus for the simultaneous cooling of the<br />
fermionic isotopes 6 Li and 40 K. Our goal is to get a degenerate mixture<br />
to search for novel pairing mechanisms involving fermions of different<br />
masses.<br />
Instead of using a Zeeman slower as a source for cold lithium atoms<br />
we have developed a lithium 2D-MOT which is loaded directly from<br />
thermal vapor emitted by an hot oven at 400C. A second 2D-MOT,<br />
loaded from 40 K enriched vapor, serves as a potassium source.<br />
Using these bright sources we load via differential pumping sections<br />
10 9 atoms of both 6 Li and 40 K into a dual MOT in the main vacuum<br />
chamber. We then transfer both species into a magnetic trap and cool<br />
them by forced evaporation.<br />
The current status of the experiment is summarized on the poster.<br />
Q 27.8 Di 16:30 Poster C2<br />
Interacting Rubidium and Caesium Atoms — •Shincy John,<br />
Michael Haas, Nicolas Spethmann, Lars Steffens, Claudia Weber,<br />
Artur Widera, and Dieter Meschede — Institut für Angewandte<br />
Physik, Universität Bonn, Wegelerstr. 8, 53115 Bonn<br />
In our experimental set up we magnetically trap a mixture of Rubidium<br />
and a few Caesium atoms simultaneously. We selectively cool only<br />
Rubidium atoms by a microwave field tuned to the Rubidium ground<br />
state hyperfine transition. Caesium is sympathetically cooled via elastic<br />
collisions with Rubidium. We are able to cool down the mixture to<br />
temperatures below 1µK. Analysing the dynamics of sympathetic cooling<br />
we have estimated a lower limit for the Rubidium-Caesium s-wave<br />
scattering length to 150 a0. Our next step is to load the mixture in an<br />
optical dipole trap. Using an external homogeneous magnetic field we<br />
intend to tune the inter-species interaction. We will present our latest<br />
results.<br />
Q 27.9 Di 16:30 Poster C2<br />
Lattice physics in ultracold Bose-Fermi mixture gases —<br />
•Philipp Ernst 1 , Sören Götze 1 , Karsten Pyka 1 , Kai Bongs 2 , and<br />
Klaus Sengstock 1 — 1 Institut für Laserphysik, Universität Hamburg,<br />
Luruper Chaussee 149, 22761 Hamburg — 2 Midlands Centre<br />
for Ultracold Atoms, School of Physics and Astronomy, University of<br />
Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom<br />
Ultracold gas experiments have the huge advantage of being pure and<br />
tunable systems. In our experiment we use a KRb mixture giving access<br />
to different statistics which can be loaded into a far red-detuned optical<br />
lattice at 1030nm. The system furthermore offers several options<br />
to manipulate the gases from excellent magnetic field control to access<br />
Feshbach resonances over microwave and rf tools for spectroscopic as<br />
well as state preparation purposes. We present recent developments<br />
in the preparation, manipulation and detection of quantum states in<br />
optical lattices.<br />
Q 27.10 Di 16:30 Poster C2<br />
Transport of a quantum degenerate heteronuclear Bose-<br />
Fermi mixture in a harmonic trap — Carsten Klempt,<br />
Thorsten Henninger, •Oliver Topic, Johannes Will, Stephan<br />
Falke, Wolfgang Ertmer, and Jan Arlt — Institut für Quantenoptik,<br />
Leibniz Universität Hannover, Welfengarten 1, D-30167 Hannover,<br />
Germany<br />
We report on the simultaneous transport of mixed quantum degenerate<br />
gases of bosonic 87 Rb and fermionic 40 K in a harmonic potential.<br />
The samples are transported over a distance of up to 6 mm to the<br />
geometric center of the anti-Helmholtz coils of the QUIC trap.<br />
This magnetic transport scheme is an important tool for the manipulation<br />
of quantum degenerate gases, since it enables transport experiments<br />
with large quantum degenerate samples in macroscopic trap<br />
configurations without disturbances added by close by surfaces. Since<br />
the mechanism may be cascaded to cover even larger distances, it is<br />
of particular relevance for interference experiments which can particularly<br />
profit from the signal-to-noise ratio available with large samples.<br />
In addition, this novel method allows all experiments using QUIC<br />
traps to significantly improve the experimental conditions. We demon-
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
strate two particular experiments which profit from the transport<br />
scheme. By transporting the atoms to the centre of the trap, the highly<br />
homogeneous magnetic field that can be created there is available to<br />
experiments which exploit Feshbach resonances to tune the atomic interaction.<br />
The mechanism may also be used to accelerate and launch<br />
atomic clouds for further experiments.<br />
Q 27.11 Di 16:30 Poster C2<br />
From BEC to fermionization in 1-D double-well traps<br />
— •Sascha Zöllner 1 , Hans-Dieter Meyer 1 , and Peter<br />
Schmelcher 1,2 — 1 Universitaet Heidelberg, Theoretische Chemie,<br />
Im Neuenheimer Feld 229, 69120 Heidelberg — 2 Universitaet Heidelberg,<br />
Physikalisches Institut, Philosophenweg 12, 69120 Heidelberg<br />
We investigate the transition of a quasi-one-dimensional few-boson system<br />
from weak correlations to the fermionization limit of infinitely<br />
repulsive forces. Based on a numerically exact multi-configurational<br />
method (MCTDH), we show that the ground state reveals ‘localization’<br />
of the particles, which can be interpreted as mimicking Pauli’s<br />
exclusion principle. We provide a deeper understanding of that transition<br />
by relating it to the loss of coherence in the one-body density<br />
matrix and to the emerging long-range tail in the momentum distribution.<br />
This crossover has striking effects on the tunnel dynamics of few<br />
atoms in a double well. Starting from Rabi oscillations in the noninteracting<br />
limit, correlated pair tunneling evolves as the interaction is<br />
slightly increased, reminiscent of self-trapping for BECs. Toward the<br />
fermionization limit, however, we observe modulated Rabi oscillations<br />
of a strongly correlated atom pair.<br />
Q 27.12 Di 16:30 Poster C2<br />
Transport of Bose-Einstein condensates through twodimensional<br />
mesoscopic structures — •Timo Hartmann,<br />
Michael Hartung, Klaus Richter, and Peter Schlagheck — Institut<br />
für theoretische Physik, Universität Regensburg<br />
The tremendous progress over the last decade in the experimental techniques<br />
for Bose-Einstein condensates permits the creation of almost arbitrarily<br />
shaped confinement geometries for interacting matter waves<br />
on the basis of atom chips or atom-optical billiards [1]. This opens<br />
new experimental possibilities for probing the transport properties of<br />
Bose-Einstein condensates through mesoscopic scattering geometries.<br />
We numerically investigate the quasi-stationary propagation of a<br />
condensate through two dimensional cavities within the mean-field approximation<br />
of the condensate. This is accomplished using a generalisation<br />
of the approach used in Ref. [2] to two dimensions. Special<br />
attention is paid to the resonance structures in the transmission spectrum<br />
which are strongly modified through the non-linear term in the<br />
Gross-Pitaevskii equation.<br />
[1] V. Milner et al. Phys. Rev. Lett. 86, 1519 (2001), N. Friedman et<br />
al. Phys. Rev. Lett. 86, 1518 (2001)<br />
[2] T. Paul et al., Phys. Rev. Lett. 94 (2005)<br />
Q 27.13 Di 16:30 Poster C2<br />
How Dissipation Fermionizes a One-Dimensional Gas of<br />
Bosonic Molecules and Atom-Molecule Oscillations in a Mott<br />
Insulator — •Dominik Bauer, Matthias Lettner, Niels Syassen,<br />
Thomas Volz, Daniel Dietze, Stephan Dürr, and Gerhard Rempe<br />
— Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1,<br />
85748 Garching, Germany<br />
Here we report on our latest results about ultracold molecules in optical<br />
lattices.<br />
First, we show how dissipation creates a Tonks gas of molecules. If a<br />
gas of bosons is confined to 1D, the interaction between particles can<br />
become so important that the strongly correlated regime is reached.<br />
This is called a Tonks-Girardeau gas. In the limit of infinite interaction<br />
strength, one cannot find two bosons at the same position. Previous<br />
studies of the Tonks Gas relied on elastic interactions.<br />
Second, we observe large-amplitude Rabi oscillations between an<br />
atomic and a molecular state near a Feshbach resonance. The frequency<br />
and amplitude of the oscillations are well described by a two-level<br />
model. The observed density dependence of the oscillation frequency<br />
agrees well with the theoretical prediction. We confirm that the state<br />
produced after a half-cycle contains exactly one molecule at each lattice<br />
site. In addition, we show that for energies in a gap of the lattice<br />
band structure, the molecules cannot dissociate.<br />
Q 27.14 Di 16:30 Poster C2<br />
Bosonic and fermionic metastable neon atoms in optical and<br />
magnetic traps — •Jan Schütz, Eva-Maria Kriener, Wouter<br />
van Drunen, Norbert Herschbach, and Gerhard Birkl — Institut<br />
für Angewandte Physik, Technische Universität Darmstadt, Schlossgartenstr.<br />
7, 64289 Darmstadt<br />
We experimentally investigate the interactions of laser cooled<br />
metastable neon atoms in a magneto-optical trap (MOT), in magnetic<br />
traps, and optical dipole traps. For the bosonic isotopes 20 Ne<br />
and 22 Ne we determined the rate coefficients for inelastic collisions<br />
and the scattering lengths for atoms in the metastable 3 P2 state.<br />
As the next step, we succeeded in optically trapping both bosonic<br />
isotopes in the metastable 3 P0 state and are currently determining the<br />
two-body loss coefficients.<br />
Recent extensions of our laser configuration allow us to trap the<br />
fermionic isotope 21 Ne and mixtures of bosonic and fermionic isotopes.<br />
We report on the status of these experiments.<br />
Q 27.15 Di 16:30 Poster C2<br />
Ultracold Atomic Gases in 1D Optical Lattices: Qualitative<br />
behaviour of the DMRG method in inhomogenous topologies<br />
— •Felix Schmitt, Markus Hild, Sven Binder, and Robert Roth<br />
— Institut fuer Kernphysik, Technische Universitaet Darmstadt<br />
The Density Matrix Renormalisation Group (DMRG) has become the<br />
state of the art method to treat ultracold atomic gases in optical lattices.<br />
While the infinite-size algorithm is usually sufficient to describe<br />
cold atoms in homogenous lattices with high precision even with moderate<br />
numbers of many-particle states, it becomes unreliable once inhomogenities<br />
occur. In most cases this can be cured by the finite-size<br />
DMRG algorithm. We focus on the problem of the Bose-Glass transition<br />
in order to study the behaviour of DMRG when unequal degrees<br />
of freedom are appended. This may shed light on the behaviour of<br />
DMRG applied to other quantum mechanical many-body problems,<br />
e.g. for nuclei or nuclear matter.<br />
Q 27.16 Di 16:30 Poster C2<br />
Exact theoretical description of two ultracold atoms in a<br />
3D optical lattice — •Sergej Grishkevich and Alejandro Saenz<br />
— AG Moderne Optik, Institut für Physik, Humboldt-Universität zu<br />
Berlin, Hausvogteiplatz 5-7,10117 Berlin, Germany<br />
The physics of ultracold atoms has attracted a lot of interest since the<br />
experimental realization of Bose-Einstein condensation in dilute alkali<br />
atom gases. Besides the exciting physics at ultracold energies by itself,<br />
a further important progress was the positioning of the ultracold gas in<br />
an optical lattice formed with the aid of standing light waves. Atoms<br />
in lattice are important systems to study solid state physics since the<br />
optical lattice resembles in a certain sense the periodicity of a crystal<br />
potential. These systems are furthermore supposed to be of great<br />
interest for quantum information purposes.<br />
A theoretical approach was developed that allows for a full numerical<br />
description of a pair of ultracold atoms trapped in a three-dimensional<br />
optical lattice. This approach includes the possible coupling between<br />
center-of-mass and relative motion coordinates in a configurationinteraction<br />
type of calculations. The atoms are allowed to interact by<br />
their full interaction potential that is, presently, only limited to be<br />
central. With the aid of the newly developed method deviations from<br />
the harmonic approximation are discussed. The developed method is<br />
also used to model experimental data [1].<br />
[1] C. Ospelkaus, S. Ospelkaus, L. Humbert, P. Ernst, K. Sengstock,<br />
and K. Bongs, Phys.Rev.Lett. 97, 120402 (2006).<br />
Q 27.17 Di 16:30 Poster C2<br />
All-optical BEC for an optical lattice experiment with single<br />
site addressability — •Jacob Sherson, Oliver Loesdau,<br />
Manuel Endres, Jan Petersen, Christof Weitenberg, Immanuel<br />
Bloch, and Stefan Kuhr — Institut für Physik,Universität Mainz,<br />
Staudingerweg 7, 55128Mainz<br />
In optical lattice experiments, ultracold atoms have to be loaded from<br />
a Bose-Einstein condensate (BEC), in order to populate the lowest energy<br />
band of the lattice. We report on the generation of a BEC in a<br />
crossed optical dipole trap. Laser cooled atoms are transferred from a<br />
double MOT system directly into the dipole trap. The dipole trap is<br />
formed by a 50 W Yb:YAG fiber laser (1070 nm). The shape of the trap<br />
can be dynamically changed by moving the foci of the laser beams. This<br />
increases the collision rate and allows for rapid evaporative cooling to<br />
the BEC transition within typically 5 s.<br />
The BEC will then be transported by a single beam dipole trap to
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
the experimental region. There, the atoms are transferred into an optical<br />
lattice which is placed in front of an ultrahigh resolution optical<br />
imaging system. The imaging system is designed to operate at a wavelength<br />
of 420.3 nm, corresponding to the 5S 1/2 → 6P 3/2 transition of<br />
87 Rb. It has a numerical aperture of NA = 0.75 yielding a diffractionlimited<br />
resolution of about 300 nm, which will allow for the detection<br />
of individual sites of the optical lattice.<br />
Q 27.18 Di 16:30 Poster C2<br />
Preparing and Detecting Quantum States with Ultracold<br />
Atoms in an Optical Superlattice — •Stefan Trotzky 1 ,<br />
Ute Schnorrberger 1 , Patrick Cheinet 1 , Michael Feld 1,2 , Jeff<br />
Thompson 1 , Simon Fölling 1,3 , and Immanuel Bloch 1 — 1 Johannes<br />
Gutenberg Universität Mainz — 2 Technische Universität Kaiserslautern<br />
— 3 Harvard University, USA<br />
Ultracold atoms in optical lattices have shown to be versatile systems<br />
to mimick condensed matter physics. The concept of superlattices for<br />
ultracold atoms has recently been realized in experiments and extends<br />
the toolbox for the manipulation of the system on the many-body scale.<br />
Furthermore, it allows to control effective interactions and dynamics<br />
emerging in Hubbard-type models. In our experiments, we combine<br />
monochromatic optical lattices on two perpendicular axes with a superlattice<br />
on the third axis which is formed by the superposition of<br />
two standing light fields with periodicity d and 2d to yield an array of<br />
double well potentials. We demonstrate how this bichromatic superlattice<br />
can be used to realize effective spin Hamiltonians with controllable<br />
spin-spin interactions as well as how to measure the atomnumber distribution<br />
within the array by means of interaction blockade. Moreover,<br />
we are able to create entangled spin-triplet pairs in the double wells<br />
and detect these via the coherent transformation into spin-singlet pairs<br />
and back.<br />
Q 27.19 Di 16:30 Poster C2<br />
Optical lattice with a staggered magnetic field — •G. Wirth 1 ,<br />
A. Hemmerich 1 , L.-K. Lim 2 , and C. Morais Smith 2 — 1 Universitaet<br />
Hamburg, Institut fuer Laser-Physik, Luruper Chaussee 149, 22761<br />
Hamburg, Germany — 2 Institute for Theoretical Physics, Utrecht University,<br />
3508 TD Utrecht, The Netherlands<br />
We show how an effective staggered magnetic field can be implemented<br />
in a two-dimensional bosonic square optical lattice via stimulated Raman<br />
scattering and discuss the phase diagram of this quantum system.<br />
Apart from the homogeneous superfluid and the Mott insulator, known<br />
to exist in the conventional Bose-Hubbard model, a novel kind of superfluid<br />
phase arises characterized by finite momentum and a staggered<br />
vortex lattice. Its characteristic momentum spectrum permits straight<br />
forward experimental detection of this phase.<br />
Q 27.20 Di 16:30 Poster C2<br />
Interaction-induced dephasing of Bloch oscillations - experiments<br />
and simulations — •Manfred Mark, Matthias Gustavsson,<br />
Elmar Haller, Johann Danzl, and Hanns-Christoph Nägerl<br />
— Institut für Experimentalphysik und Forschungszentrum für Quantenphysik,<br />
Universität Innsbruck, 6020 Innsbruck, Austria<br />
A BEC in an optical lattice undergoes Bloch oscillations when subject<br />
to an external force. However, interactions lead to dephasing, limiting<br />
the number of oscillations one can observe.<br />
We quantitatively characterize this dephasing by tuning the interaction<br />
strength using a Feshbach resonance. For non-zero interaction<br />
strength, structure on a scale much smaller than the Bloch momentum<br />
can be observed in the momentum distribution of a dephased condensate.<br />
For vanishing interaction strength, we are able to follow more than<br />
20000 oscillations over 12 s. Also a measurement of the Ramsauer-<br />
Townsend minimum with a precision of 10 −5 was performed. In this<br />
regime breakdown and revival phenomena in the presence of an additional<br />
harmonic potential can be observed.<br />
The performed measurements are compared to numerical simulations<br />
of discrete and non-discrete 1D Gross-Pitaevskii equations.<br />
Q 27.21 Di 16:30 Poster C2<br />
Interaction-controlled transport of an ultracold Fermi gas —<br />
•Robert Jördens 1 , Niels Strohmaier 1 , Yosuke Takasu 2 , Kenneth<br />
Günter 3 , Michael Köhl 4 , Henning Moritz 1 , and Tilman<br />
Esslinger 1 — 1 Institute for Quantum Electronics, ETH Zurich, 8093<br />
Zurich, Switzerland — 2 Department for Electronic Science and Engineering,<br />
Kyoto University, Kyoto 615-8510, Japan — 3 Laboratoire<br />
Kastler Brossel, 75005 Paris, France — 4 Cavendish Laboratory, Uni-<br />
versity of Cambridge, Cambridge CB3 0HE, United Kingdom<br />
We explore the transport properties of an interacting Fermi gas in a<br />
three-dimensional optical lattice. In analogy to the characterization of<br />
transport behavior in condensed matter systems through conductivity<br />
measurements, we study the atom cloud’s center of mass motion after<br />
a sudden displacement of the trap minimum.<br />
Different interaction strengths and lattice fillings are shown to have<br />
a characteristic influence on the dynamics. With increasingly strong<br />
attractive interactions the weakly damped oscillation, observed for the<br />
non-interacting case, turns into a slow drift: local pairs with a reduced<br />
tunneling rate are formed for strong inter-atomic attraction. This interpretation<br />
is supported by a measurement of the number of doubly<br />
occupied lattices sites. Application of this technique in other interaction<br />
regimes, lattice depths and fillings in the Fermi-Hubbard model<br />
may provide a tool for the identification of quantum phases such as<br />
the fermionic Mott-insulator. Experimental results on repulsively interacting<br />
Fermi gases will be presented.<br />
Q 27.22 Di 16:30 Poster C2<br />
Dynamics of localization phenomena for hard-core bosons in<br />
optical lattices — •Birger Horstmann, Ignacio Cirac, and Tommaso<br />
Roscilde — Max-Planck-Institut für Quantenoptik, Garching,<br />
Deutschland<br />
We investigate the behavior of ultracold bosons in optical lattices with<br />
a disorder potential generated via a secondary species frozen in random<br />
configurations. The statistics of disorder is associated with the physical<br />
state in which the secondary species is prepared. The resulting<br />
random potential, albeit displaying algebraic correlations, is found to<br />
lead to localization of all single-particle states. We then investigate the<br />
real-time dynamics of localization for a hardcore gas of mobile bosons<br />
which are brought into sudden interaction with the random potential.<br />
Regardless of their initial state and for any disorder strength, the<br />
mobile particles are found to reach a steady state characterized by<br />
exponentially decaying off-diagonal correlations and by the absence of<br />
quasicondensation; when the mobile particles are initially confined in a<br />
tight trap and then released in the disorder potential, their expansion<br />
is stopped and the steady state is exponentially localized in real space,<br />
clearly revealing Anderson localization.<br />
Q 27.23 Di 16:30 Poster C2<br />
Degenerate ground states in a 0-π-junction of an atomic gas<br />
— •Matthias Mutschler, Oliver Crasser, Reinhold Walser, and<br />
Wolfgang P. Schleich — Institut für Quantenphysik, Universität<br />
Ulm, D-89081 Ulm<br />
0-π-Josephson-junctions are an important tool and research subject<br />
in superconductivity [1]. In the present contribution we examine an<br />
analogous model realised with a two-componend bosonic atomic gas<br />
which is trapped in a quasi one-dimensional double well potential.<br />
Within a simple four-mode approximation we obtain an system analogous<br />
to a 0-π-junction. We present an analysis of the ground states<br />
and tunneling effects between the degenerated ground state manifold.<br />
[1] W. Buckel and R. Kleiner, Superconductivity: Fundamentals and<br />
applications, Wiley-VCH, Berlin (2004)<br />
[2] E. Goldobin et al., Phys. Rev. B 72, 054527 (2005)<br />
[3] V.M. Kaurov and A.B. Kuklov, Phys. Rev. A 73, 013627 (2006)<br />
[4] E. Goldobin et al., New J. Phys., in preparation<br />
Q 27.24 Di 16:30 Poster C2<br />
Barrier transmission for the one–dimensional nonlinear<br />
Schrödinger equation: resonances and transmission profiles<br />
— •Kevin Rapedius and Hans Jürgen Korsch — Technische Universität<br />
Kaiserslautern, FB Physik, D-67653 Kaiserslautern, Germany<br />
The stationary nonlinear Schrödinger equation (or Gross-Pitaevskii<br />
equation) for one-dimensional potential scattering is studied. The nonlinear<br />
transmission function shows a distorted profile, which differs<br />
from the Lorentzian one found in the linear case. This nonlinear profile<br />
function is analyzed and related to Siegert type complex resonances.<br />
It is shown, that the characteristic nonlinear profile function can be<br />
conveniently described in terms of skeleton functions depending on a<br />
few instructive parameters. These skeleton functions also determine<br />
the decay behavior of the underlying resonance state. Furthermore we<br />
extend the Siegert method for calculating resonances, which provides<br />
a convenient recipe for calculating nonlinear resonances. Applications<br />
to a double Gaussian barrier and a square well potential illustrate our<br />
analysis.
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
Q 27.25 Di 16:30 Poster C2<br />
Kicked Bose-Hubbard systems and kicked tops – destruction<br />
and stimulation of tunneling — •Martin P. Strzys, Eva-Maria<br />
Graefe, and Hans Jürgen Korsch — TU Kaiserslautern, Germany<br />
In a two-mode approximation, Bose-Einstein condensates (BEC) in a<br />
double-well potential can be described by a many particle Hamiltonian<br />
of Bose-Hubbard type. We focus on such a BEC whose interatomic<br />
interaction strength is modulated periodically by δ-kicks which<br />
represents a realization of a kicked top. In the (classical) mean-field<br />
approximation it provides a rich mixed phase space dynamics with<br />
regular and chaotic regions. By increasing the kick-strength a bifurcation<br />
leads to the appearance of self-trapping states localized on regular<br />
islands. This self-trapping is also found for the many particle system,<br />
however in general suppressed by coherent many particle tunneling oscillations.<br />
By varying the kick-strength and the coupling between the<br />
two wells the quasi-energy levels undergo both avoided and even actual<br />
crossings. Therefore stimulation or complete destruction of tunneling<br />
can be observed for this many particle system. Thus real self-trapping<br />
is possible for the full quantum system and the system can be tuned<br />
from enforced tunneling to this regime. This yields the possibility of a<br />
systematic and accurate population transfer between the two potential<br />
wells.<br />
Q 27.26 Di 16:30 Poster C2<br />
Dynamics of a low-dimension ultracold Bose gas — •Cédric<br />
Bodet and Thomas Gasenzer — Institüt für Theoretishe Physik,<br />
Universität Heidelberg, Philosophenweg 16, 69120 Heidelberg<br />
The dynamical evolution of a Bose-Einstein condensate trapped in a<br />
one-dimensional lattice potential is investigated theoretically in the<br />
framework of the Bose-Hubbard model. The emphasis is set on the<br />
far-from-equilibrium evolution in a case where the gas is strongly interacting.<br />
This is realized by an appropriate choice of the parameters<br />
in the Hamiltonian, and by starting with an initial state, where one<br />
lattice well contains a Bose-Einstein condensate while all other wells<br />
are empty. Oscillations of the condensate as well as non-condensate<br />
fractions of the gas between the different sites of the lattice are found<br />
to be damped as a consequence of the collisional interactions between<br />
the atoms. We approach this problem by numerically solving the<br />
Schrödinger equation for this model. We study in detail the particle<br />
number fluctuations on-site and between sites in order to investigate<br />
Q 28: Poster Quanteninformation<br />
the conditions for producing squeezed states in experimentally realistic<br />
configurations.<br />
Q 27.27 Di 16:30 Poster C2<br />
Bose-Einstein condensates coupled to solid state systems<br />
— •Stephan Camerer 1,2 , David Hunger 1,2 , Daniel König 2 ,<br />
J.P. Kotthaus 2 , T.W. Hänsch 1,2 , Jakob Reichel 3 , and Philipp<br />
Treutlein 1,2 — 1 Max-Planck-Institut für Quantenoptik, Garching<br />
— 2 Fakultät für Physik, Ludwig-Maximilians-Universität München —<br />
3 LKB, Ecole Normale Superieure, Paris<br />
The experimental fusion of quantum optics and solid-state physics is<br />
an emerging and auspicious field of fundamental research. Due to their<br />
capability to control atom clouds near surfaces, atomchip experiments<br />
seem to be particularly well suited to provide an experimental interface<br />
between a quantum optics and a condensed matter system.<br />
Our experiment aims at studying the interaction between small atom<br />
clouds, particularly Bose-Einstein condensates (BECs), and nanomechanical<br />
resonators. We consider two different coupling schemes: the<br />
coupling of a nanoresonator to the magnetic spin of the atoms [P.<br />
Treutlein et al., Phys. Rev. Lett. 99, 140403 (2007)] and the coupling<br />
of a resonator to the motion of the atoms. In both cases, the BEC<br />
serves as a quantum probe for the mechanical motion of the resonator.<br />
The current status of the experiment is reported.<br />
Q 27.28 Di 16:30 Poster C2<br />
Functional renormalisation group approach to far-fromequilibrium<br />
quantum field dynamics — •Stefan Keßler, Jan<br />
M. Pawlowski, and Thomas Gasenzer — Institut für Theoretische<br />
Physik, Universität Heidelberg, Philosophenweg 16, 69120 Heidelberg<br />
We present a derivation of dynamic equations for quantum fields far<br />
from equilibrium by use of functional renormalisation group techniques.<br />
The obtained equations are non-perturbative and lead substantially<br />
beyond mean-field and quantum Boltzmann type approximations.<br />
The approach is based on a regularised version of the generating<br />
functional for correlation functions, where times greater than a<br />
chosen cutoff time are suppressed. As a central result a time evolution<br />
equation for the non-equilibrium effective action is derived. The time<br />
evolution of Green functions is computed within a vertex expansion.<br />
In a truncation of the flow equations the dynamic equations as known<br />
from the 1/N-expansion of the 2PI effective interaction are recovered.<br />
Zeit: Dienstag 16:30–19:00 Raum: Poster C2<br />
Q 28.1 Di 16:30 Poster C2<br />
Adaptive Estimation of Qubits by Linear Optical Measurements<br />
— •Christof Happ and Matthias Freyberger — Institut<br />
für Quantenphysik, Universität Ulm, 89069 Ulm<br />
Optical measurement methods for the estimation of an unknown qubit,<br />
of which only a limited number N of copies is available, are discussed.<br />
The studied methods compare a single copy of the unknown state |ψ〉<br />
to an arbitrary ruler state |rν〉 by beam splitter measurements. Using<br />
Monte Carlo simulations, schemes for estimating |ψ〉 as well as for<br />
adapting a reference state |rν〉 for further measurements on remaining<br />
copies of |ψ〉 were investigated. We present simulation results assessing<br />
the quality of estimation by the average fidelity ˛ ˛〈ψ|ψest N 〉˛˛ 2 between<br />
unknown and finally estimated state ˛ ¸<br />
˛ψest N .<br />
Q 28.2 Di 16:30 Poster C2<br />
Dephasing of two Qubits — •Julius Helm and Walter T. Strunz<br />
— Theoretical Quantum Dynamics, Institute of Physics, University of<br />
Freiburg, Hermann-Herder-Strasse 3, 79104 Freiburg, Germany<br />
We study quantum channels applied to systems of two qubits that may<br />
be described in terms of stochastically fluctuating classical fields (socalled<br />
random external fields or REF). For arbitrary pure initial states<br />
we examine the sensitivity of purity and entanglement of the composite<br />
quantum system when subject to dephasing channels, i.e., dissipationless<br />
quantum channels. With concurrence as entanglement measure we<br />
are able to identify certain accessible regions in the purity-concurrence<br />
diagram, generalizing results obtained for local unital channels [1]. Furthermore,<br />
we identify a class of initial states that are robust against<br />
disentanglement when only dephasing channels acting on both qubits<br />
simultaneously are involved.<br />
[1] Ziman, M and Buˇzek, V, ”Concurrence vs. purity: Influence of<br />
local channels on Bell states of two qubits”, Phys. Rev. A 72, 052325<br />
(2005)<br />
Q 28.3 Di 16:30 Poster C2<br />
Effect of local operations on entanglement-induced state ordering<br />
of two qubits — •Lars Erik Würflinger and Walter T.<br />
Strunz — Theoretical Quantum Dynamics, Institute of Physics, University<br />
of Freiburg, Hermann-Herder-Straße 3, 79104 Freiburg<br />
Any measure of entanglement E induces an ordering of states. Local<br />
operations on a bi-partite quantum system cannot create entanglement;<br />
but in what way do they affect the ordering of states? Focussing<br />
on the two qubit case we find that there are no unital local channels<br />
that preserve the ordering for all states, with unitary and entanglement<br />
breaking channels being the only (trivial) exceptions, as has been<br />
conjectured by Ziman and Buzek [1]. However, when restricted to certain<br />
one-parameter families of states such as Werner states, or pure<br />
states, ordering based on concurrence is preserved under all local unital<br />
channels. We therefore investigate in more detail to what extend<br />
entanglement-induced state ordering is preserved for a restricted class<br />
of states (or channels).<br />
[1] M. Ziman and V. Buˇzek: Entanglement-induced state ordering<br />
under local operations, Phys. Rev. A 61, 012312 (2006).<br />
Q 28.4 Di 16:30 Poster C2<br />
A planar Paul trap — •Robert Matjeschk, Christian Schneider,<br />
Hector Schmitz, Axel Friedenauer, Jan Glückert und Tobias<br />
Schätz — MPI für Quantenoptik, Hans-Kopfermann Str. 1, 85748<br />
Garching
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
In recent years, along with the idea of quantum-computing, the concept<br />
of quantum-simulations arose. This is considered to be a new approach<br />
to investigate the dynamics of quantum many-body systems in nature.<br />
A promising realization is the simulation based on trapped ions, in<br />
particular in Paul traps. Besides the principle study of feasibility, an<br />
important issue is scalability - the possibility to confine and control<br />
many ions. A magnitude of 100 to 1000 ions is supposed to lead to<br />
new insight into quantum many-body dynamics.<br />
In linear traps this scalability is hindered by the fact that all ions<br />
are trapped in one effective oscillator potential. This leads for example<br />
to a non-homogeneous distance distribution and thus to a nonhomogeneous<br />
interaction strength distribution between the ions. Also<br />
in such assemblies only one dimensional systems could be simulated.<br />
We are developing a 2D-surface-trap where each ion is confined in<br />
its own effective oscillator potential, while the (homogeneous) distance<br />
between the ions is still small enough (30-50 µm) to maintain a<br />
non-negligible ion-ion interaction (mediated by coulomb forces). The<br />
ions will be aranged in a two-dimensional plane, adressing yet unsolved<br />
two-dimensional problems like spin frustration in 2D lattices.<br />
Q 28.5 Di 16:30 Poster C2<br />
Techniques minimizing noise in a quantum simulation using<br />
trapped Mg ions — •Jan Tibor Glückert — Max-Planck-Institut<br />
für Quantenoptik, Garching, Deutschland<br />
Creating a robust experimental setup is a essential task for experiments<br />
in the quantum regime e.g. quantum simulation. Disturbing<br />
effects before and during a quantum simulation must be minimized in<br />
order to reach a suitable fidelity. In a quantum simulation using Mg<br />
ions in a linear Paul trap we were confronted with three types of disturbance<br />
mainly. Thermal motion of the ions is a handicap for gaining<br />
high precision in the most experiments but a knock-out criterion for<br />
experiments which require knowledge of the system’s exact motional<br />
state. Furthermore the radio-frequency fields used to confine the ions<br />
in the trap can lead to periodical motion of the ions (so called micromotion)<br />
which can be responsible for further heating effects. The<br />
third effect originates in fluctuations of the ion’s energy levels itself.<br />
Induced by Zeeman effect these level follow (periodical) disturbance in<br />
the applied magnetic fields. We present the impact of these effects on<br />
a feasibility study on quantum simulation and techniques to cope with<br />
them. Namely, these techniques are first and second sideband cooling<br />
to ground state (¯n < 0.05), a procedure minimizing micromotion and<br />
a setup reducing magnetic field fluctuation.<br />
Q 28.6 Di 16:30 Poster C2<br />
Quantum Information Processing with Atoms in Arrays of<br />
Dipole Potentials — •Malte Schlosser, Jens Kruse, Andre<br />
Lengwenus, Christian Gierl, Joost Sattler, and Gerhard Birkl<br />
— Institut für Angewandte Physik, TU Darmstadt, Schlossgartenstr.<br />
7, 64289 Darmstadt<br />
Quantum information processing with neutral atoms represents an<br />
important experimental approach complementing systems based on<br />
trapped ions. Especially the question of scalability might be easier addressed<br />
in the case of neutral atoms. By using ultra-cold atoms in optical<br />
dipole traps, one can realize highly controllable systems with long<br />
coherence times. In our experiment, we use two-dimensional arrays of<br />
optical micro-potentials created by micro-fabricated lens arrays as the<br />
architecture for a scalable quantum proecessor. Due to the large lateral<br />
separation of neighboring potential wells, each trap is individually<br />
addressable. For the qubit manipulation, we apply coherent Raman<br />
coupling to the hyperfine ground states of small ensembles of 85 Rb<br />
atoms. We demonstrate the transport of atoms from one trap position<br />
to another which is needed for a realization of a two-qubit gate based<br />
on ultracold collisions. The scalability of this transport process up to<br />
macroscopic distances is shown by performing a repeated hand over of<br />
atoms from trap to trap. We present investigations of the coherence of<br />
the system using Ramsey and spin-echo methods and observe nearly<br />
no loss of coherence while moving the atoms.<br />
We give a detailed overview of the experimental configuration, the<br />
experiments performed, and the results obtained.<br />
Q 28.7 Di 16:30 Poster C2<br />
Quantum cryptography with qudits using one- and two-way<br />
entanglement purification — •Kedar Ranade and Gernot Alber<br />
— Institut für Angewandte Physik, Technische Universität Darmstadt<br />
Well-known quantum cryptographic protocols can be generalised to<br />
qudits, i. e. to d-dimensional quantum systems. We analyse the security<br />
of these protocols using entanglement purification involving one-way<br />
and two-way classical communication, focussing on protocols which<br />
can be reduced to practically feasible prepare-and-measure schemes.<br />
We further attempt to provide precise bounds for the maximally tolerable<br />
error rates of these protocols using generic methods to determine<br />
such bounds.<br />
Q 28.8 Di 16:30 Poster C2<br />
Towards Einstein-Podolsky-Rosen quantum channel multiplexing<br />
— •Aiko Samblowski, Boris Hage, and Roman Schnabel<br />
— Institut für Gravitationsphysik, Leibniz Universität Hannover<br />
und Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-<br />
Institut), Callinstraße 38, 30167 Hannover, Germany<br />
We present an experiment to utilize a single broadband squeezed field<br />
as a source for a large number N of quantum channels, based on<br />
distributed Einstein-Podolsky-Rosen (EPR) entangled states. Each of<br />
those channels can serve as a resource for independent quantum communication<br />
protocols. N-fold channel multiplexing can be realized by<br />
accessing 2N squeezed modes at different Fourier frequencies of a single<br />
squeezed field. We demonstrate the experimental implementation<br />
of the N = 1 case through the interference of two squeezed modes.<br />
Q 28.9 Di 16:30 Poster C2<br />
Fiber based Quantum Cryptography with Continuous Variables<br />
— •Josef Fürst 1 , Carlos H. Wiechers M. 1,3 , Dominique<br />
Elser 1 , Christoffer Wittmann 1 , Ulrik L. Andersen 1,2 , and<br />
Gerd Leuchs 1 — 1 Institut für Optik, Information und Photonik,<br />
Max-Planck-Forschungsgruppe, Universität Erlangen-Nürnberg,<br />
Günther-Scharowsky-Str. 1 / Bau 24, 91058 Erlangen, Germany —<br />
2 Department of Physics, Technical University of Denmark, Building<br />
309, 2800 Kgs. Lyngby, Denmark — 3 Instituto de Física de la Universidad<br />
de Guanajuato, Lomas del Bosque 103, 37150 León, Guanajuato,<br />
Mexico<br />
Quantum Key Distribution (QKD) offers a secure method of sharing<br />
a secret key between two parties, commonly called Alice and Bob. In<br />
general, there are two different kinds of QKD protocols either with<br />
discrete variables or with continuous variables. We implement a continuous<br />
variable protocol with binary encoded coherent states, which<br />
offers convenient state preparation and measurement. No entanglement<br />
source is present in our prepare and measure scheme. However,<br />
the nonorthogonality of the signal states, encoded by discrete phase<br />
and amplitude modulation, leads to effective entanglement [1]. The<br />
encoded states (ES) and the Local Oscillator (LO) are sent from Alice<br />
to Bob via a single optical fiber using time multiplexing. Thereby, scattering<br />
from the LO into the ES, which generates noise, is prevented.<br />
Subsequently, we measure both conjugate quadratures of the ES by<br />
homodyne detection and generate the raw key using postselection.<br />
[1] S. Lorenz et al., Phys. Rev. A 74, 042326 (2006)<br />
Q 28.10 Di 16:30 Poster C2<br />
Free Space Quantum Key Distribution with Coherent Polarization<br />
States — •Tim Bartley 1 , Dominique Elser 1 , Christoffer<br />
Wittmann 1 , Ulrik L. Andersen 1,2 , and Gerd Leuchs 1 — 1 Institut<br />
für Optik, Information und Photonik (Max-Planck-Forschungsgruppe),<br />
Universität Erlangen-Nürnberg, Günther-Scharowsky-Str. 1, Bau 24,<br />
91058 Erlangen — 2 Department of Physics, Technical University of<br />
Denmark, Building 309, 2800 Kgs. Lyngby, Denmark<br />
Quantum key distribution (QKD) is the process of establishing a secret<br />
shared key between two parties, traditionally named Alice and Bob.<br />
The security is based on the laws of quantum mechanics, in contrast to<br />
classical schemes, where security relies only on unproven mathematical<br />
assumptions.<br />
In our free space QKD setup we encode the signal in coherent states<br />
which allow for convenient and fast state preparation and measurement.<br />
We utilize a pair of conjugate polarization variables (Stokes parameters)<br />
as signal carriers. This produces an excellent interference<br />
between signal and local oscillator without the need for stabilization.<br />
After the successful demonstration of this QKD scheme in the laboratory<br />
[1], we now present a proof-of-principle experiment under real<br />
free space conditions: the quantum states are transmitted over 100 m<br />
on the roof of our institute’s building. The use of a retro-reflector enables<br />
us to place Alice’s and Bob’s station on the same optical table.<br />
In the future, we plan to establish a QKD link between two distinct<br />
buildings 1.5 km apart.<br />
[1] S. Lorenz et al., Phys. Rev. A 74, 042326 (2006).<br />
Q 28.11 Di 16:30 Poster C2<br />
QKD Decoy Protocol with Photon Number Measurement
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
— •Malte Avenhaus 1 , Wolfgang Mauerer 1 , Patrick Bronner 2 ,<br />
and Christine Silberhorn 1 — 1 Max Planck Research Group IOIP,<br />
Günther-Scharowsky-Str. 1 / Bau 24, 91058 Erlangen — 2 Friedrich-<br />
Alexander-Universität Erlangen Nürnberg, Staudtstr. 7, 91058 Erlangen<br />
Quantum decoy protocols provide an advantageous alternative to various<br />
conventional QKD protocols. Decoy protocols feature a lower<br />
threshold for detecting a potential eavesdropper and thus increase the<br />
secure communication distance. The principle of operation is that Alice<br />
uses photons as quantum carriers and interposes a decoy photon<br />
distribution within the signal.<br />
We investigate the experimental implementation of a decoy protocol.<br />
On Alice’s side, a pulsed laser beam pumps a PDC process in a<br />
PPKTP wave-guide. The PDC process shows high source brightness<br />
and converts photons from the pump mode at 1550nm in signal and<br />
idler mode of 800nm and 1550nm respectively. The signal mode is particularly<br />
apt for photon number measurements on Alice’s side, whereas<br />
the idler mode is used for low loss transmission via telecommunication<br />
fibre to recipient Bob. The decoy subset during communication may<br />
be chosen a posteriori while performing a classical communication.<br />
Q 28.12 Di 16:30 Poster C2<br />
Spectral effects in Quantum Key Distribution — •Wolfram<br />
Helwig, Wolfgang Mauerer, and Christine Silberhorn — University<br />
Erlangen-Nuremberg, Max-Planck Research Group IOIP, Integrated<br />
Quantum Optics Group<br />
In recent years tremendous research progress was made in the field<br />
of quantum key distribution (QKD). By now a variety of protocols<br />
exists for which security has been proven even for realistic imperfect<br />
devices. The proofs based on the idea of Shor and Preskill, provide<br />
us with a lower bound on the secure key generation rate. The security<br />
of BB84 relies on the fact, that well defined single-mode photonic<br />
states are prepared by the sender and used as information carriers.<br />
However, potential sources for QKD implementations like parametric<br />
down conversion (PDC) sources emit states with a multi-mode spectral<br />
distribution. These states have to be described in a higher-dimensional<br />
Hilbert space. We investigate to what extent these spectral properties<br />
affect the security considerations.<br />
We further present a comparison of the theoretical bounds on the<br />
secure key rates for different protocols and the dependence on various<br />
experimental imperfections, e.g., dark-counts, detector efficiency, channel<br />
attenuation etc. Only single-photon signals contribute to the secure<br />
key, but unfortunately such sources don’t exist at present. Hence we<br />
consider different photon statistics in our simulations.<br />
Q 28.13 Di 16:30 Poster C2<br />
Beyond the three-partite GHZ and W states using a bimodal<br />
cavity — •Denis Gonta 1 , Thomas Radtke 2 , and Stephan<br />
Fritzsche 1,3 — 1 Max–Planck–Institut für Kernphysik, Postfach<br />
103980, D–69029 Heidelberg — 2 Institut für Physik, Universität Kassel,<br />
Heinrich-Plett-Str. 40, D-34132 Kassel — 3 Physikalisches Institut<br />
der Universität Heidelberg, Philosophenweg 12, D-69120 Heidelberg<br />
In the framework of cavity QED, we propose two novel schemes to<br />
engineer the four-partite entangled GHZ and W states. The entangled<br />
states are produced between the two-level Rydberg atoms in a deterministic<br />
way. In contrast to standard (single-mode) cavity schemes,<br />
our proposal is based on a bimodal cavity that possesses two independent<br />
modes of the light field. In addition, we suggest two schemes<br />
to reveal the non-classical correlations of the entangled states and to<br />
ensure that no statistical (uncorrelated) mixtures of states have been<br />
produced. An extension of the schemes to produce N-partite entangled<br />
GHZ and W states is also possible.<br />
Q 28.14 Di 16:30 Poster C2<br />
Wigner-Ionenkristalle für Quanteninformationsverarbeitung<br />
— •Jens Baltrusch 1 , Jacob Taylor 2 und Tommaso Calarco 1<br />
— 1 Institut für Quanteninformationsverarbeitung, Universität Ulm,<br />
89079 Ulm — 2 Department of Physics, Massachusetts Institute of<br />
Technology, Cambridge, MA 02139<br />
In einer Penningfalle gefangene Ionen formieren sich bei geeignet<br />
gewählten Fallenparametern und Temperaturen zu 2D- oder 3D-<br />
Wigner-Kristallen. Typische Ionenabstände in einem solchen Wigner-<br />
Kristall sind in der Größenordnung von 10 µm, so dass Adressierung<br />
und Quantenkontrolle einzelner Ionen mit Hilfe von stark fokussierten<br />
Lasern realisierbar sind. Weiter sind bei thermischen Phononenanregungen<br />
robuste Zwei-Qubit-Quantengatter genauso implementier-<br />
bar wie hochverschränkte Zustände, sogenannte Cluster-States, so dass<br />
dieses System ein vielversprechenden und skalierbaren Zugang für zahlreiche<br />
Anwendungen in der Quanteninformationsverarbeitung bietet.<br />
Der Schwerpunkt unserer theoretischen Untersuchungen liegt dabei<br />
in der Bestimmung der für eine experimentelle Umsetzung geeigneten<br />
Übergänge und Laserkonfigurationen, um insbesondere eine möglichst<br />
hohe Genauigkeit der Gatteroperationen bei gleichzeitig kurzen Gatterzeiten<br />
zu erzielen. Offene Fragestellungen betreffen unter anderem<br />
die Ausweitung bisheriger Konzepte auf 3D-Kristalle sowie den Einfluß<br />
der Zyklotronbewegung auf die Genauigkeit und Stabilität der implementierten<br />
Gatter.<br />
Q 28.15 Di 16:30 Poster C2<br />
Towards long distance atom-atom entanglement — •Wenjamin<br />
Rosenfeld 1 , Florian Henkel 1 , Michael Krug 1 , Christian<br />
Jakob 1 , Andreas Deeg 1 , Fredrik Hocke 1 , Jürgen Volz 1 , Markus<br />
Weber 1 , and Harald Weinfurter 1,2 — 1 Fakultät für Physik der<br />
LMU, 80799 München — 2 Max-Planck Institut für Quantenoptik,<br />
85748 Garching<br />
Entanglement is a central part of quantum information and communication<br />
applications. Of special interest is entanglement between different<br />
quantum objects like photons and atoms. It allows to combine the<br />
advantages of long atomic coherence times with the ability of photons<br />
to transport quantum information over large distances.<br />
In our experiment we generate entanglement between the spin of a<br />
single optically trapped Rb87 atom and the polarization of a photon<br />
in a spontaneous decay process in a lambda-type transition[1]. Based<br />
on this entanglement we performed a first demonstration of a quantum<br />
communication protocol between an atomic qubit and a photonic<br />
communication channel[2]. More recently we have demonstrated faithful<br />
distribution of entanglement over a 300 m long optical fiber. Here<br />
we report on the realization of a second atom trap and on the progress<br />
towards generating entanglement between two distant atoms via entanglement<br />
swapping.<br />
[1] J. Volz et al., PRL 96, 030404 (2006)<br />
[2] W. Rosenfeld et al., PRL 98, 050504 (2007)<br />
Q 28.16 Di 16:30 Poster C2<br />
Single-Atom Single-Photon Quantum Interface — •Tatjana<br />
Wilk 1 , Simon C. Webster 1 , Axel Kuhn 2 , and Gerhard Rempe 1<br />
— 1 Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1,<br />
D-85748 Garching — 2 Clarendon Laboratory, University of Oxford,<br />
Parks Road, Oxford OX1 3PU, UK<br />
Atom-cavity systems with the ability to generate single photons provide<br />
an ideal toolbox for quantum networks. Atoms stored in an intracavity<br />
dipole trap act as quantum memories, whereas photons can be<br />
used to interconnect distant atom-cavity nodes. The cavity provides<br />
an interface between the stationary and flying qubits that boosts the<br />
overall efficiency of single photon generation compared to freespace,<br />
thus allowing quantum state transfer from a single atom onto a single<br />
photon [1]. This is demonstrated by entangling a single atom with<br />
a single photon emitted into the cavity mode and subsequently mapping<br />
the quantum state of the atom onto a second photon. The latter<br />
step disentangles the atom from the light and results in an entangled<br />
photon pair. [1] Wilk et al., Science 317, 488 (2007).<br />
Q 28.17 Di 16:30 Poster C2<br />
Observing Free-Space and Cavity Emission of one Atom in<br />
a High-Finesse Optical Cavity — •Holger Specht, Bernhard<br />
Weber, Tobias Müller, David Moehring, and Gerhard Rempe —<br />
Max-Planck-Institute for Quantum Optics, Hans-Kopfermann-Str. 1,<br />
D-85748 Garching, Germany<br />
Using state of the art trapping techniques and cavity cooling schemes<br />
we are able to trap a single neutral atom inside a high-finesse cavity<br />
for several tens of seconds. In [1] we showed that our coupled atomcavity<br />
system can be used to generate single photons in a controlled<br />
way. With our long trapping times and a single-photon production<br />
efficiency of 9% we produced on average 10ˆ5 single photons with a<br />
single trapped atom. The non-classical properties of the emitted light<br />
has been shown in the photon correlations of just one trapping event.<br />
With a new high-resolution camera system we are now able to monitor<br />
the atom within the cavity mode from the side, allowing the simultaneous<br />
observation of free-space emission and scattering into the<br />
cavity. Finally, we also discuss new insights into the dynamics of the<br />
system with single and multiple trapped atoms.<br />
[1] Hijlkema et al, Nature Physics 3, 253-255 (2007).
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
Q 28.18 Di 16:30 Poster C2<br />
Cooling, storing, and manipulating single atoms in an optical<br />
cavity — •Jörg Bochmann, Martin Mücke, David Moehring,<br />
and Gerhard Rempe — Max-Planck-Institut für Quantenoptik, 85748<br />
Garching, Germany<br />
Single atoms coupled to high finesse cavities provide unique systems to<br />
study light-matter interactions in the quantum regime. Deterministic<br />
generation of single photons and application as a single photon server<br />
has been demonstrated [1]. Naturally, these systems are well suited for<br />
generation of entangled states between atoms and photons [2].<br />
Efficient operation of these experiments relies on cavity-mediated<br />
cooling of the atom within the cavity mode [3]. In our new setup, we<br />
reliably trap and cool Rb atoms in a cavity using a 2D-optical lattice of<br />
far detuned dipole traps. The cavity parameters put the system at the<br />
boundary of the strong coupling regime and we have observed constant<br />
coupling of atoms to the cavity over many seconds. Photons generated<br />
inside the cavity are outcoupled to an optical fiber and transmitted to<br />
a detection setup with ca. 50% efficiency. Improvements regarding a<br />
3D-dipole trap configuration and fast photon generation schemes are<br />
in progress.<br />
[1] M. Hijlkema, et al., Nature Physics 3, 253 (2007)<br />
[2] T. Wilk, et al., Science 317, 488 (2007)<br />
[3] S. Nußmann, et al., Nature Physics 1, 122 (2005)<br />
Q 28.19 Di 16:30 Poster C2<br />
Experimental techniques for quantum information processing<br />
with trapped 40 Ca + ions — •Michael Brownnutt 1 , Felicity<br />
Splatt 1,2 , Max Harlander 1 , Wolfgang Hänsel 1 , and Rainer<br />
Blatt 1,2 — 1 Institut für Experimentalphysik, Universität Innsbruck,<br />
Österreich — 2 Institut für Quantenoptik und Quanteninformation,<br />
Österreichische Akademie der Wissenschaften, Innsbruck, Österreich<br />
One of the outstanding requirements for realising quantum computing<br />
with trapped ions is the implementation of a truly scalable trap architecture.<br />
Proposals for such architectures include segmented linear Paul<br />
traps, where the segmentation allows the axial confining potential to<br />
be varied. Ions can thereby be independently held in - and moved between<br />
- separate trapping regions. We present numerical models of linear<br />
shuttling of ions in such traps, and of optimised shuttling through<br />
junctions. We also report on developments in fabrication and testing<br />
of various segmented trap designs. Finally, work regarding practical<br />
aspects of vacuum chamber design will be outlined.<br />
Q 28.20 Di 16:30 Poster C2<br />
Application of optimal control techniques in scalable ion trap<br />
quantum logic — •Ulrich Poschinger, Kilian Singer, and Ferdinand<br />
Schmidt-Kaler — Institut für Quanteninformationsverarbeitung,<br />
Universität Ulm, Albert-Einstein-Allee 11, 89069 Ulm<br />
Strings of laser cooled ions in a Paul trap provide a yet unmatched<br />
degree of quantum control[1]. The drawback of this concept lies in the<br />
limited scalability, which can be overcome by operating a microstructured<br />
array of Paul traps and shuttling the ions between different trap<br />
sites. The shuttling operations are carried out by dynamically changing<br />
the confining voltages at the trap segments. They have to be fast,<br />
robust and should not contribute excess energy to the ion qubit as this<br />
would spoil subsequent quantum logic operations. This setting suggests<br />
the application of optimal control (OCT) techniques. We present<br />
numerical results showing that OCT should indeed make such shuttling<br />
operations possible[2]. Furthermore, quantum logic logic gates can<br />
benefit from OCT as well since achieving high fidelities is crucial for<br />
attaining the quantum error correction threshold[3]. We demonstrate<br />
numerically that shaped pulse sequences obtained by OCT allow for<br />
the implicit compensation of parameter offsets. Analogously to NMR<br />
experiments, the logic operations can therefore be robustified[4].<br />
[1] H.Häffner et al., Nature 438, 643 (2005)<br />
[2] S. Schulz et al., Progress of Physics, Wiley 54, No. 8-10, 648<br />
(2006)<br />
[3] C. Roos, arXiv:0710.1204v3 (2007)<br />
[4] N. Timoney et al. quant-ph/0612106 (2006)<br />
Q 28.21 Di 16:30 Poster C2<br />
HC-PCF based Rubidium vapor cell — •wenjia zhong 1 ,<br />
christoph marquardt 1 , ulrik l. andersen 2 , and gerd leuchs 1<br />
— 1 Institute of Optics, Information and Photonics, University of<br />
Erlangen-Nuremberg, 91058 Erlangen, Germany — 2 Department of<br />
Physics, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark<br />
Using hollow core photonic crystal fiber as a vapor cell has the advantage<br />
of long interaction length and small laser beam area. We filled the<br />
core of a HC-PCF with liquid Rubidium using microfluidic methods<br />
and put the fiber ends inside vacuum chambers to prevent oxidization<br />
and quenching. With a constant temperature along the entire length<br />
of the fiber, the rubidium will be evaporated to prevent bulk condensation.<br />
The Rb density will be monitored by the help of absorption<br />
spectroscopy.<br />
We plan to use the D1 transition of Rb and a femtosecond laser<br />
beam to achieve the sharp-line limit of self-induced transparency. The<br />
nonlinearity inherent in detuned SIT will then be exploited for the<br />
generation of squeezed states.<br />
Q 28.22 Di 16:30 Poster C2<br />
Controlled dynamic generation of entanglement — •Thomas<br />
Häberle 1 , Kilian Singer 2 , and Matthias Freyberger 1 — 1 Institut<br />
für Quantenphysik, Universität Ulm, 89069 Ulm — 2 Institut für Quanteninformationsverarbeitung,<br />
Universität Ulm, 89069 Ulm<br />
We discuss two compact particles in a harmonic trap which interact via<br />
pointlike collisions. The interaction can be modelled by a δ-potential<br />
in the relative coordinate of the particles. Each collision will dynamically<br />
entangle the particles by a certain amount. Therefore, the time<br />
evolution of entanglement will show a step-like behaviour [1]. We now<br />
study if it is possible to maximize the entanglement at an arbitrarily<br />
fixed time by dynamically varying the trap frequency. We approach<br />
this problem by using appropriate techniques [2] from optimal control<br />
theory.<br />
[1] M. Bußhardt and M. Freyberger, Phys. Rev. A 75, 052101 (2007).<br />
[2] T. Calarco et al., Phys. Rev. A 70, 012306 (2004).<br />
Q 28.23 Di 16:30 Poster C2<br />
Optimiertes Atom-Ion-Quantengatter — •Hauke Doerk-<br />
Bendig 1 , Zbigniew Idziaszek 2 und Tommaso Calarco 1 — 1 Institut<br />
für Quanteninformationsverarbeitung, Universität Ulm, 89079 Ulm,<br />
Deutschland — 2 Center for Theoretical Physics, Polish Academy of<br />
Science, 02-668 Warschau, Polen<br />
Die gleichzeitige Verwendung von neutralen Atomen und Ionen in der<br />
Quanteninformationsverarbeitung ist durch die Kombination der Vorteile<br />
beider Spezies motiviert. Einerseits ist die Dekohärenzzeit von<br />
Atomen in optischen Gittern lang, andererseits lassen sich Gatteroperationen<br />
mit Ionen wegen ihrer relativ starken Wechselwirkung mit<br />
hoher Geschwindigkeit durchführen.<br />
Wir wollen die theoretische Grundlage für ein solches Quantengatter<br />
schaffen, indem wir die von der inneren Struktur abhängigen Wechselwirkung<br />
gefangener Atome mit gefangenen Ionen studieren und<br />
mit Hilfe einer durch ein externes Magnetfeld gesteuerten Feshbach-<br />
Resonanz kontrollieren.<br />
Unsere weitere Arbeit besteht darin, geeignete Hyperfeinzustände<br />
von Atom und Ion für die Kodierung von Qubits zu finden und Fidelity<br />
und Laufzeit eines Quantengatters mittels Quantum Optimal<br />
Control zu optimieren.<br />
Q 28.24 Di 16:30 Poster C2<br />
Photo-ionization studies of Calcium atoms — •Carsten<br />
Schuck, Marc Almendros, Felix Rohde, Francois Dubin, Markus<br />
Hennrich, and Jürgen Eschner — ICFO - Institut de Ciencies Fotoniques,<br />
08860 Castelldefels (Barcelona), Spain<br />
We present a novel method for the efficient ionization of neutral Calcium<br />
atoms, which is used in our ion trap experiment. The atoms are<br />
resonantly excited from the ground state via the intermediate 4s4p<br />
1 P1 level close to the continuum, where they are ionized in the strong<br />
electric fields of the Paul trap [1]. For the first step a laser source at<br />
423 nm is used while an incoherent source around 390 nm is sufficient<br />
for the second step [2]. We use a temperature-stabilized periodically<br />
poled KTiOPO4 crystal to create coherent 423 nm light in second harmonic<br />
generation from a 170 mW extended cavity diode laser in single<br />
pass [3]. A hollow cathode lamp is used to tune the laser to the 40 Ca<br />
resonance. The 390 nm light is obtained from a high power indium gallium<br />
nitride LED, which emits approximately 85 mW of optical output<br />
power around its 380 nm peak wavelength. Using achromatic doublet<br />
lenses we focus the light from both sources into a multimode fiber and<br />
then image the fiber end to a 200 µm spot at the center of the trap,<br />
where they are overlapped with the atomic beam.<br />
[1] S. Gulde, et al., Appl. Phys. B 73, 861 (2001),<br />
[2] D.M. Lucas, et al., Phys. Rev. A 69, 012711 (2004),<br />
[3] F. Torabi-Goudarzi, E. Riis, Opt. Comm. 227, 389 (2003).
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
Q 28.25 Di 16:30 Poster C2<br />
Counterpropagating PDC photon source with PPLN waveguides<br />
— •Andreas Christ, Andreas Eckstein, and Christine Silberhorn<br />
— Günther-Scharowsky-Str. 1, Bau 24<br />
We investigate the properties of a quasi-phasematched parametric<br />
downconversion process in a periodically poled LiNbO3 waveguide.<br />
Our aim is to provide a bright source of pure single photon pairs at<br />
the telecom wavelength, i.e. 1550 nm. To quantify the amount of frequency<br />
entanglement we perform a Schmidt-decomposition of the joint<br />
spectrum.<br />
Our focus lies on the creation of counterpropagating photon-pairs<br />
and applications in integrated quantum networks:<br />
Firstly these counterpropagating and uncorrelated photons enable us<br />
to design a photon source without spatial and spectral filtering. Combined<br />
with the application of a waveguide instead of a bulk crystal, we<br />
propose an ultrabright source of decorrelated photon pairs.<br />
Secondly we investigate one of the most interesting aspects of counterpropagating<br />
photon pairs: The included separation between the signal<br />
and idler beams, offering the possibility to separately access the<br />
signal and idler photons even for degenerate type-I phasematching.<br />
Q 28.26 Di 16:30 Poster C2<br />
Maple tools for teaching and exploring quantum computation<br />
and information protocols — •Thomas Radtke 1 and Stephan<br />
Q 29: Poster Quanteneffekte<br />
Fritzsche 2 — 1 Institut für Physik, Universität Kassel, 34132 Kassel,<br />
Germany — 2 Gesellschaft für Schwerionenforschung (GSI), 64291<br />
Darmstadt, Germany<br />
During the last decade, the field of quantum information and computation<br />
has been growing rapidly. Beside of the great promise and the<br />
potential of various quantum information protocols, such as Shor’s factorization<br />
algorithm, quantum teleportation and others, however, there<br />
are still many open problems to be solved. Although entanglement has<br />
been recognized today as a crucial resource for quantum information,<br />
it is still not fully understood, especially in the multipartite setting [1].<br />
To assist in the teaching and study of multi-qubit quantum states<br />
and algorithms, several software tools have been presented and discussed<br />
in the web. More often than not, however, these tools only<br />
implement a rather limited set of features or they were focused on<br />
special protocols. Therefore, in order to provide a flexible toolbox, we<br />
developed the FEYNMAN program within the framework of MAPLE<br />
[2]. Apart from a catalogue of frequently used quantum gates and noisy<br />
channels this program implements a variety of separability criteria as<br />
well as entanglement measures. In this poster, we show how this toolbox<br />
can be utilized for teaching basic but also more advanced topics<br />
in quantum information theory.<br />
[1] R. Horodecki et al., quant-ph/0702225v2<br />
[2] T. Radtke, S. Fritzsche, Comput. Phys. Commun. 176 (2007) 617<br />
Zeit: Dienstag 16:30–19:00 Raum: Poster C2<br />
Q 29.1 Di 16:30 Poster C2<br />
A single photon source with a Ca + cavity-QED system<br />
— •Andreas Stute 1,2 , Carlos Russo 1,2 , Helena G. Barros 1,2 ,<br />
François Dubin 1 , Piet O. Schmidt 1 , and Rainer Blatt 1,2 —<br />
1 Institut für Experimentalphysik, Universiät Innsbruck, Technikerstr.<br />
25, A-6020 Innsbruck — 2 Institut für Quantenoptik und Quanteninformation,<br />
Österreichische Akademie der Wissenschaften, Otto-Hittmair-<br />
Platz 1, A-6020 Innsbruck<br />
Linear optics quantum computation as well as quantum cryptography<br />
require a source of single, indistinguishable photons. We realize a deterministic<br />
source of single photons in a setup consisting of a single<br />
trapped 40 Ca + ion coupled to a single mode of a high finesse optical<br />
resonator. A single trapped ion can be stored for days and can be<br />
precisely positioned in the cavity mode.<br />
Photons are generated in a vacuum-stimulated Raman process<br />
driven by a pulsed pump laser and the cavity vacuum field. During<br />
the pump pulse a photon is emitted into the cavity mode, subsequently<br />
leaves the cavity and is detected with a Hanbury Brown & Twiss setup.<br />
The system is initialized again by repumping the ion back to the ground<br />
state and the sequence is repeated.<br />
The resulting intensity correlation g (2) (τ) reveales the signature of a<br />
single photon source. The experimental results are in excellent agreement<br />
with numerical simulations of the process.<br />
Q 29.2 Di 16:30 Poster C2<br />
Towards controlled Cavity-QED experiments with toroidal<br />
microresonators — •Rico Henze 1 , Markus Gregor 1 , Tim<br />
Schröder 1 , Helmar Kostial 2 , Edith Wiebicke 2 , and Oliver<br />
Benson 1 — 1 AG Nano-Optik, Institut für Physik, Humboldt-<br />
Universität zu Berlin, Hausvogteiplatz 5-7, 10117 Berlin — 2 Paul-<br />
Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117<br />
Berlin<br />
Optical microresonators are interesting systems to study the lightmatter<br />
interaction on the nanometer scale. The so-called Whispering<br />
Gallery Modes (WGM) in spherical resonators offer high spatial<br />
and temporal light confinement, a prerequisite for Cavity-QED experiments.<br />
We report the production and optical characterization of<br />
chip-based SiO2 toroidal microresonators which we produce by standard<br />
clean room techniques. A tapered optical fiber is implemented as<br />
an efficient light coupler. Combined with scanning probes (SNOM and<br />
AFM) a versatile setup is created that allows to study the optical mode<br />
structure of the WGMs in a toroidal cavity or to position nanoscopic<br />
emitters on the resonator surface at will.<br />
Q 29.3 Di 16:30 Poster C2<br />
Double-Slit Light Diffraction in Strong Electromagnetic<br />
Fields — •Ben King, Antonino Di Piazza, and Christoph H. Keitel<br />
— Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117<br />
Heidelberg<br />
In [1] the vacuum-polarisation effects of change in ellipticity and polarisation<br />
of a laser probe beam passing through an ultra-intense standing<br />
wave, were calculated. We further develop these results to increase<br />
the measurable polarisation and ellipticity, by calculating diffraction<br />
effects from the double-slit-like setup of two parallel and off-centre,<br />
gaussianly-focused, strong field waves propagating against each other.<br />
We move towards a measurable set-up through calculations of the offaxis<br />
effects on a focused probe beam, allowing alternative detection of<br />
these vacuum effects.<br />
[1] A. Di Piazza, K. Z. Hatsagortsyan, and C. H. Keitel, Phys. Rev.<br />
Lett. 97, 083603 (2006)<br />
Q 29.4 Di 16:30 Poster C2<br />
Thermodynamics and quantum effects — •Stefanie Hilt 1 and<br />
Eric Lutz 2 — 1 Institut für Quantenphysik, Universität Ulm, Deutschland<br />
— 2 Institut für Physik, Universität Augsburg, Deutschland<br />
We consider a system coupled to a heat reservoir modelled by a harmonic<br />
chain and discuss the influence of quantum effects on the equilibrium<br />
properties of the system. Special emphasis is put on the low<br />
temperature regime where quantum fluctuations play an important<br />
role. In particular, we use the negativity to quantify the entanglement<br />
created between the system and the reservoir.<br />
Q 29.5 Di 16:30 Poster C2<br />
Dekohärenz molekularer Konfigurationszustände —<br />
•Johannes Trost und Klaus Hornberger — Arnold Sommerfeld<br />
Center for Theoretical Physics, Ludwig-Maximilians-Universität,<br />
München<br />
Superpositionszustände von Enantiomeren, d.h. von isomeren Molekülen<br />
mit unterschiedlicher Konfiguration, werden bei komplexeren<br />
Molekülen nicht beobachtet. Bei einfachen chiralen Molekülen<br />
wie Dihydrogendisulfid, HSSH, (oder der deuterierten Form DSSD)<br />
ist zu erwarten, dass die Kohärenz solcher quantenmechanischer Superpositionen<br />
durch Streuprozesse mit Molekülen des Umgebungsgases<br />
beschränkt wird. Wir entwickelten ein Modell, das dispersive<br />
Wechselwirkungen des chiralen Moleküls mit einfachen Hintergrundgasen<br />
realistisch und konsistent beschreibt. Anhand dieser chiralitätsabhängigen<br />
Wechselwirkungen lässt sich die Dekohärenzrate<br />
durch Stöße streutheoretisch berechnen und eine Abhängigkeit spektroskopischer<br />
Übergangslinien von der Stoßrate demonstrieren.
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
Q 29.6 Di 16:30 Poster C2<br />
Creating and Ascertaining Entanglement of Atoms by Photon<br />
Scattering — •Torsten Scholak and Cord A. Müller —<br />
Physikalisches Institut, Universität Bayreuth, 95440 Bayreuth, Germany<br />
We study the light-scattering dynamics of two tightly trapped atoms<br />
with internal spin degrees of freedom. The aim is to manipulate populations<br />
and coherences by a selective tuning of photon field parameters<br />
like polarization. We are particularly interested in the preparation of<br />
entanglement and its subsequent witnessing [1] by interaction with the<br />
driving laser field.<br />
[1] arXiv:0710.0825<br />
Q 29.7 Di 16:30 Poster C2<br />
Coherent beam splitting with a single spontaneously emitted<br />
photon — •Jiri Tomkovic 1 , Michael Schreiber 1 , Inka<br />
Benthin 1 , Arne Schietinger 1 , Jörg Schmiedmayer 2 , and Markus<br />
Oberthaler 1 — 1 Kirchhoff Institut für Physik,Universität Heidelberg,<br />
69120 Heidelberg — 2 Atominstitut der Österreichischen Universitäten,<br />
TU-Wien, Stadionallee 2, A-1020 Vienna, Austria<br />
Spontaneous emission of a photon leads to a momentum transfer to<br />
the emitting atom. In free space this leads to a incoherent momentum<br />
distribution of the atom which is typically used in laser cooling<br />
schemes. In case the atom is close to a mirror, the situation can drastically<br />
change since directly emitted and reflected light can principally<br />
not be distinguished in certain directions. Thus at distances of few<br />
micrometers the spontaneous emission of a single photon leads to a<br />
coherent superposition of two momentum states of the atom. We will<br />
present our experimental results revealing the expected coherence.<br />
Q 29.8 Di 16:30 Poster C2<br />
Electromagnetically induced transparency and retrieval of<br />
light pulses in a Pr 3+ :Y2SiO5 crystal — •Georg Heinze, Fabian<br />
Beil, Jens Klein, and Thomas Halfmann — Institut für Angewandte<br />
Physik, TU Darmstadt, Hochschulstraße 6, 64289 Darmstadt<br />
Recent research on coherent interactions between light and matter already<br />
led to a large variety of applications. In particular electromagnetically<br />
induced transparency (EIT) and the closely related concepts of<br />
slow light and light storage play an important role in quantum information<br />
processing and optical data storage. A very promising approach is<br />
the implementation of these techniques in solids, e.g. in particular rare<br />
earth doped solids. These media offer the advantages of solids, i.e. high<br />
density and scalability, while still exhibiting sharp optical transitions<br />
- like free atoms in the gas phase. We apply EIT and related techniques<br />
in a Pr 3+ :Y2SiO5 crystal, cooled to cryogenic temperatures.<br />
The dopant ions are prepared by optical pumping and spectral holeburning.<br />
This permits the generation of spectrally isolated Λ-type or Vtype<br />
systems within the inhomogeneous bandwidth of the 3 H4 ↔ 1 D2<br />
transition of the Pr 3+ ions. We observe and compare cancellation of<br />
absorption due to EIT in the Λ-type coupling scheme as well as in the<br />
V-type coupling scheme. By EIT, we also excite persistent nuclear spin<br />
coherences between the hyperfine levels of the ground state (Λ-System)<br />
or the excited state (V-system). These coherences are probed by time<br />
delayed retrieval of light pulses. Hereby we determine the dephasing<br />
times of the nuclear spin coherences of the Pr 3+ ions, either in the<br />
ground state or in the optically excited state.<br />
Q 29.9 Di 16:30 Poster C2<br />
Negative refraction in atomic two-component media —<br />
•Bastian Jungnitsch and Jörg Evers — Max-Planck-Institut für<br />
Kernphysik, Saupfercheckweg 1, 69117 Heidelberg<br />
We discuss the feasibility of obtaining negative refraction with low<br />
losses or even gain in an atomic gas consisting of two different species<br />
of atoms [1]. The two components yield electrical and magnetical responses,<br />
respectively, which are individually tailored via external fields<br />
to give the desired negative index of refraction. Using different atoms<br />
for magnetic and electric response allows to relax the stringent requirements<br />
to achieve negative refraction in single species systems [2]. For<br />
this, several few-level systems with different combinations of coherent<br />
and incoherent driving fields are compared with an emphasis on the<br />
problem of obtaining a sufficiently large magnetic response. Based on<br />
these results, we discuss potential candidate systems in real atoms.<br />
[1] B. Jungnitsch and J. Evers, in preparation<br />
[2] P. P. Orth, J. Evers, and C. H. Keitel, arXiv:0711.0303<br />
Q 29.10 Di 16:30 Poster C2<br />
Pulse propagation in a medium with time-dependent refractive<br />
index — •Martin Kiffner 1 and Tarak N. Dey 1,2 — 1 Max-<br />
Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg,<br />
Germany — 2 Indian Institute of Technology Guwahati, Guwahati- 781<br />
039, Assam, India<br />
The phenomenon of electromagnetically induced transparency (EIT)<br />
gives rise to counterintuitive effects like the slowing and stopping of<br />
light and is of great importance, e.g., for the fields of quantum information<br />
theory and nonlinear optics [1]. Here we consider a standard EIT<br />
medium comprised of three-level Λ-type atoms and investigate the influence<br />
of a polychromatic control field on the propagation of the probe<br />
pulse. Our results are analyzed in terms of a time-dependent refractive<br />
index.<br />
[1] M. Fleischhauer, A. Imamoglu, and J. P. Marangos, Rev. Mod.<br />
Phys. 77, 633 (2005).<br />
Q 29.11 Di 16:30 Poster C2<br />
Stationary light in cold gases — •Gor Nikoghosyan and Michael<br />
Fleischhauer — Fachbereich Physik, TU Kaiserslautern<br />
One of the challenging problems of practical quantum information processing<br />
with photons is to achieve a strong nonlinear coupling between<br />
two single-photon pulses. A promising approach for its realizations<br />
is based on so-called stationary light in resonant Λ-type media with<br />
electromagnetically induced transparency. Here a weak probe pulse is<br />
trapped in the medium by a stationary coupling field. Previous theoretical<br />
studies considered room-temperature ensemble where atomic<br />
motion leads to a rapid dephasing of high-frequency components of<br />
the ground-state coherence allowing for a secular approximation. In<br />
the present work we study the dynamics of the probe pulse in cold<br />
media where this approximation no longer holds. We show that in the<br />
case of one-photon resonance forward and backward components of the<br />
probe field are decoupled and no stationary light pattern is formed.<br />
Q 29.12 Di 16:30 Poster C2<br />
Stationary light and Klein tunneling — •Razmik Unanyan and<br />
Michael Fleischhauer — Fachbereich Physik, TU Kaiserslautern<br />
We discuss the generation and coherent manipulation of stationary<br />
pulses of light in atomic ensemble with electromagnetically induced<br />
transparency with two counterpropagating control fields. In particular<br />
we discuss the limits on the spatial confinement of these pulses<br />
when the latter becomes comparable to the absorption length of the<br />
medium. In this case the stationary field in the dilute gas can be described<br />
by a two-component spinor which obeys the two-dimensonal<br />
Dirac-Weyl equation in an external potential generated by a spatially<br />
varying two-photon detuning. We show that a fundamental lower limit<br />
to the spatial confinement arises from Klein tunneling. We determine<br />
the linewidth of the resonances in the effective potential and discuss<br />
conditions for optimizing spatial confinement and tunneling losses.<br />
Q 29.13 Di 16:30 Poster C2<br />
Efficient coherent population transfer to highly excited vibrational<br />
states in NO molecules by Stark-chirped rapid adiabatic<br />
passage — •Holger Münch, Martin Oberst, and Thomas<br />
Halfmann — Institute for Applied Physics, TU Darmstadt, Schlossgartenstr.<br />
7, 64289 Darmstadt, Germany<br />
The interaction of strong, coherent radiation fields with quantum states<br />
permit the efficient and selective manipulation of population distributions.<br />
Adiabatic processes, e.g. rapid adiabatic passage (RAP), allow<br />
to prepare complete population inversion between two quantum<br />
states. An extension of RAP is Stark-chirped rapid adiabatic passage<br />
(SCRAP). This process uses dynamic stark-shifts to drive the transition<br />
frequency through resonance with an initially detuned laser field<br />
and thereby realize a RAP process. The implementation of SCRAP<br />
in a L-type three state system rather than application of other coherent<br />
techniques, e.g. STIRAP, offers e.g. advantages in inhomogeneous<br />
broadened media. We demonstrate the experimental realization<br />
of SCRAP among three states in nitric oxide (NO) molecules. SCRAP<br />
permits complete population inversion between a vibrational ground<br />
state and a highly excited vibrational state. Both states are coupled<br />
through strong, pulsed laser fields (pump and Stokes laser) to an electronically<br />
excited intermediate state. An intense Stark laser pulse induces<br />
dynamic stark-shifts of the transition frequencies. Appropriate<br />
choice of laser detunings and time delays between the laser pulses permits<br />
complete and robust population inversion in the NO molecules<br />
and efficient storage of large amounts of internal energy.
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
Q 29.14 Di 16:30 Poster C2<br />
Stimulated Raman Adiabatic Passage (STIRAP) in a<br />
Pr 3+ :Y2SiO5 crystal — •Fabian Beil, Jens Klein und Thomas<br />
Halfmann — Institute for Applied Physics, TU Darmstadt, Schlossgartenstr.<br />
7, 64289 Darmstadt, Germany<br />
STIRAP is a well-established, efficient and robust technique to manipulate<br />
population distributions in atoms and molecules. Among others,<br />
STIRAP found applications in optical data storage and quantum information<br />
processing. Experimental studies of STIRAP have been mainly<br />
constricted to media in the gas phase. However, it is solid media which<br />
are (due to their high density and scalability) of special interest for applications.<br />
Usually, ultra-fast decoherence processes in solids prevent<br />
the implementation of coherent excitations. This obstacle is overcome<br />
in rare earth ion doped inorganic crystals, which combine the advantages<br />
of solids and the coherent properties of atoms. We implemented<br />
STIRAP in a Pr 3+ :Y2SiO5 crystal (Pr:YSO). The experiment yielded<br />
striking data on complete adiabatic population transfer in a solid. Population<br />
is transferred between two hyperfine levels of the 3 H4 ground<br />
state of a selected ensemble of Pr 3+ ions. Efficient transfer is observed<br />
for negative pulse delay (STIRAP) as well as for positive delay.<br />
The latter is due to an alternative adiabatic passage process, i.e.b-<br />
STIRAP, which is closely related to conventional STIRAP. We record<br />
the population dynamics for both adiabatic processes by time-resolved<br />
absorption measurements. In addition to the experimental investigations,<br />
we performed numerical simulations. The results are in good<br />
qualitative agreement with the experimental observations.<br />
Q 29.15 Di 16:30 Poster C2<br />
Adaptive quantum estimation of continuous systems —<br />
•Sabine Wölk and Matthias Freyberger — Institut für Quantenphysik,<br />
Universität Ulm, D-89069 Ulm, Germany<br />
We propose an adaptive scheme to reconstruct unknown quantum<br />
states of light via quantum comparison with certain classes of reference<br />
or ruler states. This comparison is realized by joint measurements<br />
of EPR variables on both states. The arising probability distribution<br />
contains the complete information of the unknown quantum state. Different<br />
ruler states allow us to estimate different representations of the<br />
unknown state. As an example, we have developed an adaptive algorithm<br />
to determine the quadrature representation using Gaussian<br />
states as ruler states.<br />
Q 29.16 Di 16:30 Poster C2<br />
Quantum theory of atom lasers — •Tobias Kramer 1 , Mirta<br />
Rodríguez 2 , and Christian Bracher 3 — 1 Institut I: Theoretische<br />
Physik, Universität Regensburg, Germany — 2 Institut de Ciències<br />
Fotòniques, Barcelona, Spain — 3 California State University, Long<br />
Beach, USA<br />
We present a three-dimensional, quantum mechanical and largely analytical<br />
theory for the properties of atomic laser beams in the gravitational<br />
field. The results describe both the total emission rate and the<br />
beam profile. Depending on the trapping frequencies and the strength<br />
of interactions, the theory predicts a transverse substructure in the<br />
atomic beam. Recent experiments on atom laser beam profiles are in<br />
good agreement with the model.<br />
T. Kramer and M. Rodriguez Quantum theory of an atom laser orig-<br />
inating from a Bose-Einstein condensate or a Fermi gas in the presence<br />
of gravity, Phys. Rev. A, 74, 013611-1-13, (2006)<br />
Q 29.17 Di 16:30 Poster C2<br />
Simultaneous measurements in quantum optics — •Michael<br />
Bußhardt and Matthias Freyberger — Institut für Quantenphysik,<br />
Universität Ulm, 89069 Ulm, Germany<br />
Various possibilities for simultaneous measurements of conjugate variables<br />
in the optical domain are investigated. Here, for example, the<br />
quadratures of the electromagnetic field do not commute and therefore<br />
cannot be precisely measured simultaneously. Possible setups, necessary<br />
for measuring such non-commuting observables simultaneously by<br />
allowing the system to interact with certain classes of ruler systems,<br />
are reviewed and discussed. The question arises, which states of the<br />
ruler systems are optimal to gain specific information about the investigated<br />
system. This leads to generalized versions of the Heisenberg<br />
uncertainty relation.<br />
Q 29.18 Di 16:30 Poster C2<br />
Riemann’s Zeta Function in Phase-Space — •Cornelia Feiler,<br />
Rüdiger Mack, and Wolfgang P. Schleich — Institut für Qunatenphysik,<br />
Universität Ulm<br />
The Riemann hypothesis is at the very heart of number theory. We<br />
propse a novel approach where the Riemann Zeta function emerges in<br />
a quantum system. For that, we consider states, which provide us with<br />
the Riemann Zeta function when we take appropriate scalar products.<br />
Moreover, we present the corresponding Wigner and Q-functions and<br />
discuss their behaviour in phase space.<br />
Q 29.19 Di 16:30 Poster C2<br />
Nicht-klassische Lichtquellen für die Zweiphotonenabsorption<br />
— •Axel Heuer, Benjamin Freyer, Andreas Jechow und Ralf<br />
Menzel — Institut für Physik, AG Photonik Universität Potsdam, Am<br />
Neuen Palais 10, 14469 Potsdam<br />
Für die Beobachtung der Zweiphotonenabsorption (TPA) von nichtklassischem<br />
Licht, wird eine Lichtquelle benötigt, die eine genügend<br />
hohe Anzahl an Photonenpaaren mit einem hohen Grad an zeitlicher<br />
und räumlicher Korrelation emittiert. Es werden zwei Lichtquellen vorgestellt,<br />
die jeweils auf der parametrischen Fluoreszenz (PDC) beruhen.<br />
Die eine Quelle besteht aus einem BBO Kristall, der für die kollineare<br />
PDC mit Typ I Phasenanpassung geschnitten ist. Der Kristall<br />
wird gepumpt mit der dritten Harmonischen eines modengekoppelten<br />
Nd:YVO4-Laser. Bei einer mittleren Pumpleistung von 120 mW konnten<br />
Zählraten korrelierter Photonenpaare von über 1010 Photonen/s<br />
detektiert werden. Die Photonen erstreckten sich über eine spektrale<br />
Bandbreite von über 200 nm. Bei dieser Lichtquelle verteilen sich die<br />
korrelierten Photonen jedoch auch über ein Winkelspektrum von mehreren<br />
Grad, was eine geeignete Fokussierung für die Zweiphotonenabsorption<br />
schwierig macht. Daher wurde eine weitere Lichtquelle realisiert,<br />
bei der die beiden korrelierten Photonen sich in einer räumlichen<br />
Mode befinden. Dieses lässt sich realisieren, wenn ein periodisch gepolter<br />
Kristall mit Wellenleiterstruktur verwendet wird. Es werden Ergebnisse<br />
präsentiert, die mit einem 10 mm langen PPLN Kristall erzielt<br />
wurden<br />
Q 30: Poster Präzisionsmessungen und Metrologie<br />
Zeit: Dienstag 16:30–19:00 Raum: Poster C2<br />
Q 30.1 Di 16:30 Poster C2<br />
Cold Atom Sagnac Interferometer — •Christian Schubert,<br />
Thijs Wendrich, Michael Gilowski, Ernst Rasel, and Wolfgang<br />
Ertmer — Institut für Quantenoptik, Leibniz Universität Hannover<br />
Cold atom fountains and mater-wave interferometry have enabled<br />
many very sensitive measurements methods for fundamental physics<br />
and metrology [1]. We report on the status of our dual atom interferometer<br />
for the precise determination of inertial forces. Our device<br />
is based on synchronous operation of two counter propagating atom<br />
interferometers to discriminate between accelerations and rotations.<br />
The atomic source units are horizontal fountains each consisting of<br />
a 2D-MOT which loads a 3D-MOT with cold 87 Rb atoms [2]. The<br />
3D-MOT uses a moving molasses technique to launch the atoms with<br />
about 4.4 m/s with a temperature of about 8 µK. The interferometer<br />
sequence itself has a Mach-Zehnder configuration realized with three<br />
optical Raman pulses for the coherent manipulation of the atoms. The<br />
atomic interference signal is measured using the fluorescence light of<br />
both output states of each interferometer, allowing normalized results<br />
that are insensitive to changes in the number of atoms in both directions.<br />
With this compact and transportable setup we aim to reach<br />
sensitivities of 2 ∗ 10 −9 rad/s for 1 ∗ 10 8 atoms per shot and a velocity<br />
of 3 m/s. This work is supported by DFG SFB407 and FINAQS. [1] C.<br />
Jentsch, T. Müller, E.M. Rasel, W. Ertmer, Gen. Rel. Grav. 36(10),<br />
2197(2004). [2] T. Müller, T. Wendrich, M. Gilowski, C. Jentsch, E.M.<br />
Rasel, W. Ertmer, arXiv:0705.4544v1, accepted by Phys. Rev. A.<br />
Q 30.2 Di 16:30 Poster C2<br />
Laser Doppler Interferometry Mission for Determination of
Fachverband Quantenoptik und Photonik (Q) Dienstag<br />
the Earth’s Gravity Field — •Marina Dehne, Ben Sheard, Gerhard<br />
Heinzel, and Karsten Danzmann — Albert-Einstein-Institut<br />
Hannover, Max-Planck-Institut für Gravitationsphysik und Universität<br />
Hannover, Callinstr. 38, D-30167 Hannover<br />
The aim of a future GRACE follow-on mission is to map with high<br />
resolution the gravitational field of the Earth. The space segment consists<br />
of two spacecraft in a Low- Earth Orbit (LEO), following each<br />
other with a seperation of about 10 km. The variations of that distance<br />
in the frequency range 1...100 mHz are to be monitored by the interferometer<br />
with nanometer precision. Data analysis to be performed on<br />
the ground will recover the information about the gravitational field<br />
from those measurements, in the form of the spherical harmonics from<br />
degree 6 to 240.<br />
One possible orbit is a circular sun-synchronous orbit (i = 96.78 ◦ ) in<br />
order to provide a constant thermal environment and to avoid sunlight<br />
entering the optical axis between the two spacecraft. The atmospheric<br />
drag in a Low-Earth Orbit is significant and must be compensated.<br />
For this purpose, drag-free technology such as developed for LISA<br />
Pathfinder is ideally suited. The proposed interferometer makes use<br />
of technologies developed for LISA and LISA Pathfinder.<br />
The goal of this work is to develop an interferometer breadboard<br />
which fulfills the requirements (2.5 nm/ √ Hz from 10 to 100 mHz, increasing<br />
as 1/f between 10 and 1 mHz) under the given other constraints<br />
of the mission.<br />
Q 30.3 Di 16:30 Poster C2<br />
A quantum radiation-pressure noise dominated interferometer<br />
— •Stefan Goßler, Yanbei Chen, Stefan Danilishin, Daniel<br />
Friedrich, Kentaro Somiya, Tobias Westphal, Kazuhiro Yamamoto,<br />
Karsten Danzmann, and Roman Schnabel — MPI für<br />
Gravitationsphysik (AEI) und Institut für Gravitationsphysik der<br />
Leibniz Universität Hannover, Callinstr.38, 30167 Hannover<br />
The second generation of interferometric gravitational-wave detectors<br />
will be limited by quantum noise of the light field in most of the detection<br />
band: while shot noise will limit the sensitivity at high frequencies<br />
it is quantum radiation-pressure noise that will be limiting at<br />
low frequencies. Despite the effort of various groups all over the world<br />
so far no interferometric measurement that is dominated by quantum<br />
radiation-pressure noise has been obtained yet. A mechanical device<br />
to couple the quantum fluctuations of the light field to displacement<br />
of a sensor is crucial to these measurements. We present our design<br />
of such a sensor and the general concept to accomplish the first ever<br />
measurement of quantum radiation-pressure noise.<br />
Q 30.4 Di 16:30 Poster C2<br />
Frequenzmessung eines optischen Frequenznormals über ein<br />
Glasfasernetz — •Osama Terra 1 , Burghard Lipphardt 1 , Gesine<br />
Grosche 1 , Jan Friebe 2 , Ernst Rasel 2 und Harald Schnatz 1<br />
— 1 Physikalisch Technische Bundesanstalt, Braunschweig — 2 Institut<br />
für Quantenoptik, Universität Hannover , Hannover<br />
Im Rahmen des SFB 407 untersuchen die Physikalisch-Technische Bundesanstalt<br />
(PTB) in Braunschweig und das Institut für Quantenoptik<br />
(IQO) der Universität Hannover eine neue Methode zur Messung<br />
des Uhrenübergangs des Mg Frequenznormals. Bisher wurde diese Frequenz<br />
mit Hilfe einer transportablen Cs Uhr oder einem auf GPS stabilisierten<br />
Quarz vermessen. Um das Mg Normal besser charakterisieren<br />
zu können und dessen Potenzial voll auszuschöpfen, ist es erforderlich,<br />
kurzzeitstabilere Oszillatoren als Referenz zu benutzen. Mit optische<br />
Uhren, wie sie in Staatsinstituten betrieben werden, lassen sich<br />
wesentlich kleinere Unsicherheiten und höhere Kurzzeitstabilitäten erreichen<br />
als mit Mikrowellennormalen. Dazu ist es aber erforderlich,<br />
dass die hohe Stabilität und Genauigkeit der optischen Uhren auch an<br />
weit entfernten Standorten zur Verfügung gestellt werden kann. Hierzu<br />
wird ein Laser bei 195 THz (1,55 µm) mit Hilfe eines Frequenzkammes<br />
auf die optische Referenzfrequenz stabilisiert und dessen Frequenz<br />
über einen 70 km langen Glasfaserlink nach Hannover gesendet. Anschließend<br />
wird das trägerfrequente cw-Signal dort mittels zweitem<br />
Frequenzkamm mit der Frequenz des Mg Frequenznormals verglichen.<br />
Die Gesamtverbindung wird zur Zeit schrittweise aufgebaut und cha-<br />
rakterisiert. Wir berichten über den Stand des Projektes.<br />
Q 30.5 Di 16:30 Poster C2<br />
High reflectivity grating waveguide coatings — •Daniel<br />
Friedrich 1 , Oliver Burmeister 1 , Michael Britzger 1 , Tina<br />
Clausnitzer 2 , Frank Brückner 2 , Ernst-Bernhard Kley 2 , Andreas<br />
Tünnermann 2 , Karsten Danzmann 1 , and Roman Schnabel 1<br />
— 1 Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-<br />
Institut) und Institut für Gravitationsphysik der Leibniz Universität<br />
Hannover, Callinstr. 38, 30167 Hannover — 2 Institut für Angewandte<br />
Physik der Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1,<br />
07743 Jena<br />
Thin single-layer grating structures can be used as a high reflectivity,<br />
but low thermal noise, alternative to conventional multilayer coatings.<br />
Grating waveguide (GWG) coatings should have low mechanical loss<br />
due to the reduced coating thickness, resulting in low thermal noise.<br />
Since the coating provides the interface between a light field and a<br />
mirror device, coating thermal noise is an important design concern<br />
for various high precision experiments such as gravitational wave detection.<br />
We present concepts and ongoing investigations of different<br />
types of GWG’s.<br />
Q 30.6 Di 16:30 Poster C2<br />
Testing the Isotropy of the Speed of Light using ULE Optical<br />
Resonators — •Christian Eisele 1 , Maxim Okhapkin 2 , Alexander<br />
Yu. Nevsky 1 , and Stephan Schiller 1 — 1 Institut für Experimentalphysik,<br />
Heinrich-Heine-Universität, 40225 Düsseldorf — 2 Institute for<br />
Laser Physics, Novosibirsk, Russia<br />
Modern Michelson-Morley-type experiments with ultra-stable resonators<br />
are aiming to measure a possible violation of Lorentz invariance<br />
for electromagnetic waves.<br />
We will report about the latest results of our measurements using<br />
optical high finesse resonators (F = 190000) orthogonally embedded in<br />
a rectangular ULE (ultra low expansion coefficient glass) block. This<br />
design gives a certain amount of common mode rejection for several<br />
disturbances. A monolithic Nd:YAG laser at 1064 nm is frequency<br />
stabilized to the resonance frequencies of the resonators, and the difference<br />
frequency between the resonators is measured as a function of<br />
the orientation of the cavities in space. To improve the short term frequency<br />
stability of the laser system, we use an active vibration isolation<br />
system. For active rotation of the setup a highly-accurate air-bearing<br />
rotation table is used.<br />
Q 30.7 Di 16:30 Poster C2<br />
Thermal noise limit of the Fabry-Perot cavities used for<br />
laser stabilisation at sub-Hz level — •Janis Alnis, Nikolay Kolachevsky,<br />
Arthur Matveev, Thomas Udem, and Theodor Hansch<br />
— Max Planck Institute of Quantum Optics, 85748 Garching,<br />
Germany<br />
Precision optical spectroscopy experiments require lasers with extremely<br />
narrow spectral line widths that can be achieved by stabilising<br />
the laser to a high-finesse Fabry-Perot (FP) cavity. We have developed<br />
two independent external-cavity diode laser systems at 972 nm with<br />
0.5 Hz spectral line width that is limited by the thermal noise properties<br />
of the FP cavity spacer and mirrors [1]. The thermal noise limit is<br />
reached thanks to a mid-plane mounting of the cavities making them<br />
insensitive to ambient vibrations. The line drift is always smaller than<br />
0.5 Hz/s as the cavities are made from Ultra-Low-Expansion (ULE)<br />
glass possessing a zero expansion temperature. Our new design with<br />
Peltier coolers in vacuum allows us to keep any ULE FP cavity at this<br />
particularly advantageous temperature.<br />
With this narrow laser source after amplification and frequency quadrupling<br />
to 243 nm we excite the 1S-2S two-photon transition in atomic<br />
hydrogen [2]. The diode laser has an unusually long (20 cm) resonator<br />
that significantly reduces the high-frequency noise typical to diode<br />
lasers and allows efficient doubling of the narrow optical carrier.<br />
References<br />
1. J. Alnis et al., in preparation for Appl. Phys. B.<br />
2. N. Kolachevsky et al., Phys. Rev. A 73, 021801(R) (2006).
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
Q 31: Quanteninformation (Konzepte und Methoden I)<br />
Zeit: Donnerstag 8:30–10:30 Raum: 1B<br />
Q 31.1 Do 8:30 1B<br />
Effective Spin Systems in Coupled Arrays of Cavities<br />
— •Michael Hartmann 1,2 , Fernando Brandão 1,2 , and Martin<br />
Plenio 1,2 — 1 Institute for Mathematical Sciences, Imperial College<br />
London, 53 Exhibition Road, London, SW7 2PG, United Kingdom —<br />
2 QOLS, Blackett Laboratory, Imperial College London, Prince Consort<br />
Road, London, SW7 2BW, United Kingdom<br />
We show that atoms trapped in micro-cavities that interact via the<br />
exchange of virtual photons can model an anisotropic Heisenberg spin-<br />
1/2 lattice in an external magnetic field. All parameters of the effective<br />
Hamiltonian can individually be tuned via external lasers. Since the<br />
occupations of excited atomic levels and photonic states are strongly<br />
suppressed, the effective model is robust against decoherence mechanisms,<br />
has a long lifetime and its implementation is feasible with<br />
current experimental technology. The model provides a feasible way to<br />
create cluster states in these devices.<br />
Q 31.2 Do 8:45 1B<br />
Possibility, Impossibility and Cheat-Sensitivity of Quantum<br />
Bit String Commitment — Harry Buhrman 1 , •Matthias<br />
Christandl 2 , Patrick Hayden 3 , Hoi-Kwong Lo 4 , and Stephanie<br />
Wehner 1 — 1 CWI Amsterdam, The Netherlands — 2 University of<br />
Cambridge, United Kingdom — 3 McGill University, Montreal, Canada<br />
— 4 University of Toronto, Canada<br />
Unconditionally secure non-relativistic bit commitment is known to<br />
be impossible in both the classical and the quantum worlds. But when<br />
committing to a string of n bits at once, how far can we stretch the<br />
quantum limits? In this paper, we introduce a framework for quantum<br />
schemes where Alice commits a string of n bits to Bob in such a way<br />
that she can only cheat on a bits and Bob can learn at most b bits of<br />
information before the reveal phase.<br />
Our results are two-fold: we show by an explicit construction that<br />
in the traditional approach, where the reveal and guess probabilities<br />
form the security criteria, no good schemes can exist: a + b is at least<br />
n. If, however, we use a more liberal criterion of security, the accessible<br />
information, we construct schemes where a = 4 log 2 n + O(1) and<br />
b = 4, which is impossible classically.<br />
We furthermore present a cheat-sensitive quantum bit string commitment<br />
protocol for which we give an explicit tradeoff between Bob’s<br />
ability to gain information about the committed string, and the probability<br />
of him being detected cheating.<br />
Q 31.3 Do 9:00 1B<br />
Complementarity, Privacy, and Entanglement — •Joseph M.<br />
Renes 1 and Jean-Christian Boileau 2 — 1 Institut für Angewandte<br />
Physik, TU Darmstadt, Germany — 2 Center for Quantum Information<br />
and Quantum Control, University of Toronto, Canada<br />
We develop a complementary information tradeoff which bounds the<br />
amount of information about complementary observables that can be<br />
simultaneously extracted from a quantum system. This leads directly<br />
to a simple characterization both private states (the quantum version<br />
of secret keys) and maximally-entangled states, revealing these to be a<br />
direct manifestation of the quantum mechanical phenomenon of complementarity.<br />
Furthermore, we conjecture a strengthened version of the<br />
tradeoff and show how these ideas can be adapted to create protocols<br />
for distilling secret keys or entangled states.<br />
Q 31.4 Do 9:15 1B<br />
Maximally entangled fermions — •Dirk-Michael<br />
Schlingemann 1,2 , Lorenzo Campos Venuti 1 , Marco Cozzini 1 ,<br />
and Michael Keyl 1,2 — 1 ISI Foundation Torino, Quantum information<br />
theory unit, Torino, Italy — 2 Institut f. Mathematische Physik,<br />
TU-Braunschweig, Germany<br />
Fermions play an essential role in many areas of quantum physics and<br />
it is desirable to understand the nature of entanglement within systems<br />
that consists of fermions. Whereas the issue of separability for<br />
bipartite fermions has extensively been studied in the present literature,<br />
this talk reports on our recent paper [arXive:0711.3394] that is<br />
concerned with maximally entangled fermions. A complete characterization<br />
of maximally entangled quasifree (gaussian) fermion states is<br />
given in terms of the covariance matrix. This result can be seen as a<br />
step towards distillation protocols for maximally entangled fermions.<br />
Q 31.5 Do 9:30 1B<br />
Evolution equation for quantum entanglement — •Markus<br />
Tiersch 1,2 , Thomas Konrad 3 , Fernando de Melo 1,2 , Christian<br />
Kasztelan 4 , Adriano Aragao 5,2 , and Andreas Buchleitner 1,2<br />
— 1 Albert–Ludwigs–Universität Freiburg, Physikalisches Institut,<br />
Hermann–Herder–Str. 3, D–79104 Freiburg, Germany — 2 Max–<br />
Planck–Institut für Physik komplexer Systeme, Nöthnitzer Str. 38,<br />
D–01187 Dresden, Germany — 3 Quantum Research Group, School of<br />
Physics, University of KwaZulu-Natal, Private Bag X54001, Durban<br />
4000, South Africa — 4 Institut für Theoretische Physik C, RWTH<br />
Aachen, D–52056 Aachen, Germany — 5 Instituto de Física, Universidade<br />
Federal do Rio de Janeiro, Caixa Postal 68.528, CEP 21945-970,<br />
Rio de Janeiro, RJ, Brazil<br />
Quantum systems composed of two qubits consitute the starting point<br />
for the study of quantum entanglement. The evolution of entanglement<br />
when such a system is subject to open system dynamics will be examined<br />
in this talk. We will derive a simple factorization relation which<br />
describes the system’s final entanglement after one of the qubits has<br />
undergone an arbitrary physical process.<br />
Q 31.6 Do 9:45 1B<br />
Bound Entanglement and Entanglement Bounds — •Simeon<br />
Sauer 1,2 , Fernando de Melo 2,3 , Joonwoo Bae 4 , Florian<br />
Mintert 2,3 , Beatrix Hiesmayr 5 , and Andreas Buchleitner 2,3 —<br />
1 Physikalisch-Astronomische Fakultät, Friedrich-Schiller-Univesität<br />
Jena, Germany — 2 Physikalisches Institut, Albert-Ludwigs-<br />
Universität Freiburg, Hermann-Herder-Strasse 3, D-79104 Freiburg,<br />
Germany — 3 Max-Planck-Institut für Physik komplexer Systeme,<br />
Nöthnitzer Str.38, D-01187 Dresden, Germany — 4 School of Computational<br />
Sciences, Korea Institute for Advanced Study, Seoul 130-012,<br />
Korea — 5 Faculty of Physics, University of Vienna, Boltzmanngasse<br />
5, A-1090 Vienna, Austria<br />
We investigate the separability of Bell-diagonal states of two qutrits.<br />
By using lower bounds to algebraically estimate concurrence, we find<br />
convex regions of bound entangled states. Some of these regions exactly<br />
coincide with the obtained results when employing optimal entanglement<br />
witnesses, what shows that the lower bound can serve as<br />
a precise detector of entanglement. Some hitherto unknown regions of<br />
bound entangled states were discovered with this approach, and delimited<br />
efficiently.<br />
Q 31.7 Do 10:00 1B<br />
Indirect control of open system dynamics — •Raffaele Romano<br />
— Max Planck Research Group, Institute of Optics, Information<br />
and Photonics, Staudstr. 7/B2, 91058 Erlangen, Germany<br />
Although conceptually simpler, the standard open loop approach to<br />
the control of a quantum mechanical system offers a limited ability to<br />
drive the state of the system when the interaction with the external<br />
environment cannot be neglected. With this motivation in mind, closed<br />
loop approaches have been proposed (quantum feedback). In this contribution,<br />
we show that open loop controllability of an open system<br />
can be obtained if non standard control scenarios are adopted [1]. In<br />
particular, we consider the {\it indirect control} technique [2], based<br />
on the use of an auxiliary system whose initial state can be arbitrarily<br />
prepared. In our model, the environmental action can be engineered to<br />
give complete controllability, and it does not only represent a source<br />
of noise and decoherence.<br />
[1] R. Romano, D. D’Alessandro, Phys. Rev. Lett. 97, 080402(2006)<br />
[2] R. Romano, D. D’Alessandro, Phys. Rev. A 73, 022323 (2006)<br />
Q 31.8 Do 10:15 1B<br />
Wave particle duality in a two atom interferometer — •Uwe<br />
Schilling 1 , Christoph Thiel 1 , Thierry Bastin 2 , and Joachim von<br />
Zanthier 1 — 1 Institut für Optik, Information und Photonik, Max-<br />
Planck-Forschungsgruppe, Universität Erlangen-Nürnberg, Germany<br />
— 2 Institut de Physique Nucléaire, Atomique et de Spectroscopie, Université<br />
de Liège, Belgium<br />
In 1996 Englert investigated the wave-particle duality in a Ramsey<br />
interferometer and derived a quantitative complementarity relation<br />
between the contrast of the interference pattern and the maximum<br />
obtainable which-way (WW) information [1].
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
We examine the duality relation in a system of two two-level atoms<br />
which are coherently excited by a resonant laser pulse. The atoms subsequently<br />
scatter a single photon which is recorded by a detector in the<br />
far field region. By applying Englert’s definition of the distinguishability<br />
D of the two pathes in this interferometer, we find that D becomes<br />
a function of where the photon is detected. As a result we derive that<br />
in this system, by choosing the detector position and the Bloch angle<br />
Q 32: Quantengase (Gitter III)<br />
of the exciting laser pulse accordingly, full WW information becomes<br />
available after the detection of the photon while the contrast of the<br />
interference pattern remains close to 100 %. By introducing a quantity<br />
which describes the average WW information per scattered photon, it<br />
is possible to derive a quantitative relation between the wave and the<br />
particle properties of the photon in this system.<br />
[1] B.-G. Englert, Phys. Rev. Lett. 77, 2154 (1996)<br />
Zeit: Donnerstag 8:30–10:15 Raum: 1C<br />
Q 32.1 Do 8:30 1C<br />
Coexistence of bosonic and fermionic atoms in a 3d optical<br />
lattice — •Thorsten Best, Sebastian Will, Ulrich Schneider,<br />
Lucia Hackermüller, Dries van Oosten, and Immanuel Bloch —<br />
Johannes Gutenberg-Universität Mainz<br />
The investigation of mixtures of ultracold gases of distinct atomic<br />
species has gained a lot of attention recently. Depending on interaction<br />
strength and particle numbers, these systems can display rich phase<br />
diagrams with interesting analogies to condensed matter physics, especially<br />
in the presence of a periodic potential. We investigate a mixture<br />
of bosonic 87 Rb and fermionic 40 K atoms in a 3d optical lattice potential.<br />
Depending on the ratio of potassium to Rubidium atoms, the<br />
particle mobility in the lattice and the strength of interspecies interactions,<br />
we find evidence for coexistence or phase separation of the two<br />
species. We will present a characterization of the mixture in terms of<br />
both long-range coherence and onsite density distribution.<br />
Q 32.2 Do 8:45 1C<br />
Direct Observation and Control of Superexchange Interactions<br />
with Ultracold Atoms in Optical Lattices — •Stefan<br />
Trotzky 1 , Patrick Cheinet 1 , Simon Fölling 1,2 , Michael Feld 1,3 ,<br />
Ute Schnorrberger 1 , Ana Maria Rey 4 , Anatoli Polkovnikov 5 ,<br />
Eugene Demler 2,4 , Mikhail Lukin 2,4 , and Immanuel Bloch 1 —<br />
1 Johannes Gutenberg Universität Mainz — 2 Harvard University, USA<br />
— 3 Technische Universität Kaiserslautern — 4 Harvard-Smithsonian<br />
Center of Astrophysics, USA — 5 Boston University, USA<br />
Quantum mechanical superexchange interactions form the basis of<br />
quantum magnetism in strongly correlated media. We report on the<br />
first direct observation of such superexchange processes with ultracold<br />
atoms in optical lattices. Our lattice set-up consists of a bichromatic<br />
superlattice along one spatial direction and two perpendicular<br />
monochromatic lattices, thus providing a three-dimensional array of<br />
double-wells. After preparing a spin-mixture of 87 Rb atoms in an antiferromagnetic<br />
order along the superlattice axis, we record the spin<br />
dynamics within the double-wells. In the regime of strong interaction,<br />
coherent superexchange oscillations are observed which can be described<br />
by an effective Heisenberg Hamiltonian. We demonstrate, how<br />
the effective coupling parameter can be controlled in magnitude and<br />
sign, thus enabling the system to be switched between ferromagnetic<br />
or antiferromagnetic spin interactions. The experimental results show<br />
very good agreement with the predictions of a two-site Bose-Hubbard<br />
model, however, we are also able to identify corrections, which can be<br />
explained by the inclusion of direct nearest-neighbor interactions.<br />
Q 32.3 Do 9:00 1C<br />
In situ studies of ultracold fermions in a blue detuned optical<br />
lattice — •Ulrich Schneider, Lucia Hackermüller, Thorsten<br />
Best, Sebastian Will, Dries van Oosten, and Immanuel Blocj<br />
— Institut für Physik, Johannes Gutenberg-Universität, 55099 Mainz,<br />
Germany<br />
Ultracold atoms in optical lattices are a versatile system to study topics<br />
ranging from ultracold molecules to solid state physics. The rich<br />
phase diagram of ultracold fermions in a lattice includes both metallic<br />
and insulating phases, e.g the fermionic Mott-Insulator and antiferromagnetically<br />
ordered states.<br />
In our experiment we sympathetically cool fermionic 40 K with<br />
bosonic 87 Rb in an optically plugged quadrupole trap and subsequently<br />
in a dipole trap to quantum degeneracy. After removing the rubidium<br />
atoms from the trap, the fermionic 40 K is loaded into a blue detuned<br />
3D optical lattice. The combination of a dipole trap and a blue lattice<br />
allows for an independent control of lattice depth and harmonic con-<br />
finement. We use in situ imaging to study fermionic clouds in different<br />
regimes varying from noninteracting spinpolarized clouds to strongly<br />
interacting spin mixtures.<br />
Q 32.4 Do 9:15 1C<br />
Controlling interaction-induced dephasing of Bloch oscillations<br />
— •Elmar Haller, Mattias Gustavsson, Manfred Mark,<br />
Johann Danzl, Gabriel Rojas-Kopeinig, and Hanns-Christoph<br />
Nägerl — Institut für Experimentalphysik, Universität Innsbruck,<br />
Austria<br />
A BEC in an optical lattice undergoes Bloch oscillations when subject<br />
to an external force. However, interactions lead to dephasing, limiting<br />
the number of oscillations one can observe.<br />
By tuning the interaction strength using a Feshbach resonance, we<br />
quantitatively characterize the dephasing and compare with numerical<br />
simulations. The zero crossing of the scattering length can be precisely<br />
determined by minimizing dephasing. In the weakly interacting limit,<br />
we observe more than 20000 oscillations over 12 s.<br />
For non-zero interaction strength, we find that the momentum distribution<br />
of a dephased condensate develops structure on a scale much<br />
smaller than the Bloch momentum. This structure becomes visible<br />
when the interaction is quickly switched off during release from the<br />
lattice and the time-of-flight detection is aided by magnetic levitation<br />
to allow for long expansion times.<br />
Q 32.5 Do 9:30 1C<br />
Exact phase-space dynamics of the M-site Bose-Hubbard<br />
model — •Friederike Trimborn, Dirk Witthaut, and Hans<br />
Jürgen Korsch — FB Physik, TU Kaiserslautern, 67663 Kaiserslautern<br />
The dynamics of M-site, N-particle Bose-Hubbard systems is described<br />
in quantum phase space constructed in terms of generalized SU(M)<br />
coherent states. These states have a special significance for these systems<br />
as they are equivalent to the fully condensed states. Based on the<br />
differential algebra developed by Gilmore, we derive an explicit evolution<br />
equation for the (generalized) Husimi (Q) and Glauber-Sudarshan<br />
(P) distributions. Most remarkably, these evolution equations turn out<br />
to be second order differential equations where the second order terms<br />
scale as 1/N with the particle number. For large N the evolution reduces<br />
to a (classical) Liouvillean dynamics. The phase space approach<br />
thus provides a distinguished instrument to explore the mean-field<br />
many-particle crossover.<br />
Q 32.6 Do 9:45 1C<br />
Mott-insulator states of ultracold atoms in optical resonators<br />
— Jonas Larson 1 , Sonia Fernandez-Vidal 2 , •Giovanna Morigi 2 ,<br />
and Maciej Lewenstein 1 — 1 ICFO - Institut de Ciencies Fotoniques,<br />
Castelldefels (Barcelona), Spain — 2 Departament de Fisica, Universitat<br />
Autonoma de Barcelona, 08193 Bellaterra, Spain<br />
We investigate a paradigm example of cavity quantum electrodynamics<br />
with many body systems: an ultracold atomic gas inside a pumped optical<br />
resonator, confined by the mechanical potential emerging from the<br />
cavity-field spatial mode structure. When the optical potential is sufficiently<br />
deep, the atomic gas is in the Mott-insulator state as in open<br />
space. Inside the cavity, however, the potential depends on the atomic<br />
distribution, which determines the refractive index of the medium, thus<br />
altering the intracavity-field amplitude. We derive the effective Bose-<br />
Hubbard model describing the physics of the system in one dimension<br />
and study the crossover between the superfluid – Mott-insulator quantum<br />
states. We predict the existence of overlapping stability regions<br />
corresponding to competing insulator-like states. Bistable behavior,<br />
controlled by the pump intensity, is encountered in the vicinity of the
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
shifted cavity resonance.<br />
Q 32.7 Do 10:00 1C<br />
Dynamics of the Ising chain coupled to a Markovian bath<br />
— •Birger Horstmann, Tommaso Roscilde, Michael Wolf, and<br />
Ignacio Cirac — Max-Planck-Institut für Quantenoptik, Garching<br />
Q 33: Ultrakalte Atome II [gemeinsam mit A]<br />
In this talk we discuss the dynamics of an Ising chain coupled to a<br />
Markovian bath. We simulate the dynamics of the system with a Lindblad<br />
master equation and study the decoherence of the ground state<br />
of the Ising chain in time focussing on the effect of the quantum phase<br />
transition of the Ising chain on the decoherence rates. We propose to<br />
simulate such a system in an optical lattice.<br />
Zeit: Donnerstag 8:30–10:00 Raum: 2F<br />
Q 33.1 Do 8:30 2F<br />
Towards laser cooling of negative ions — •Raoul Heyne, Jan<br />
Meier, Ulrich Warring, and Alban Kellerbauer — Max-Planck-<br />
Institut für Kernphysik, Postfach 103980, 69029 Heidelberg<br />
Currently available ion cooling techniques do not allow the cooling of<br />
negatively charged particles confined in an ion trap to a temperature<br />
lower than that of the (cryogenic) environment. The proposed laser<br />
cooling of negative osmium ions [1] holds the prospect of achieving<br />
temperatures well below 1 mK. Cooling antiprotons with this technique<br />
might open the door to forming antihydrogen at ultra-cold temperatures,<br />
thus allowing precision antimatter studies. We will outline<br />
the unique techniques and challenges involved in this cooling scheme<br />
and report intermediate results on Os − production, manipulation, and<br />
spectroscopy.<br />
[1] A. Kellerbauer and J. Walz, “A novel cooling scheme for antiprotons,”<br />
New J. Phys. 8 (2006) 45.<br />
Q 33.2 Do 8:45 2F<br />
Slicing a Bose-Einstein Condensate: Direct observation of<br />
number squeezing — •Christian Gross, Jerome Esteve, Andreas<br />
Weller, Stefano Giovanazzi, and Markus K. Oberthaler<br />
— Kirchhoff Institut für Physik, Universität Heidelberg<br />
Todays interferometers are very often limited by the standard quantum<br />
limit. Pushing the performance beyond this limit demands the use<br />
of number squeezed states.<br />
We report on the direct observation of number squeezed states in<br />
Bose-Einstein Condensates (BEC). These are produced by ramping<br />
up a one dimensional optical lattice adiabatically, slicing an initially<br />
almost pure condensate of 87 Rb atoms into seven pieces.<br />
Our system can be described as an array of Josephson junctions. The<br />
effective interaction between the atoms increases with barrier height<br />
and their motion is more and more restricted to single wells since the<br />
tunneling coupling across the junctions decreases. In this regime the<br />
ground state of the Josephson junction array is characterized by a loss<br />
of phase coherence and sub shot noise atom number fluctuations across<br />
the junctions.<br />
Q 33.3 Do 9:00 2F<br />
Observation of dark soliton oscillations in a harmonic trap<br />
— •Andreas Weller, Christian Groß, Jens Philipp Ronzheimer,<br />
Jerome Esteve, and Markus K. Oberthaler — Kirchhoff Institut<br />
für Physik, Universität Heidelberg<br />
We experimentally create dark solitons in a Bose Einstein Condensate<br />
confined in a harmonic optical dipole trap by releasing atoms from a<br />
double well potential into a harmonic potential. The two clouds collide<br />
and form a dark soliton train. We observe the consequent dynamics<br />
(oscillations) with a novel imaging system. Furthermore we confirm<br />
that the oscillation frequency deviates from the harmonic trapping<br />
frequency and is close to the prediction of the one dimensional Gross<br />
Pitaevskii Equation (GPE): ωds = ωtrap/ √ 2. The deviations are consistent<br />
with the results obtained by integration of the three dimensional<br />
GPE.<br />
We will further discuss the status of the experiment creating intrinsically<br />
localized modes and bright solitons by starting with a single<br />
occupied well in an optical lattice.<br />
Q 33.4 Do 9:15 2F<br />
Quantum State Engineering via Dissipation — •H.P.<br />
Büchler 1 , S. Diehl 2 , A. Kantian 2 , B. Kraus 3 , A. Micheli 2 , and P.<br />
Zoller 2,3 — 1 Institut für Theoretische Physik, Universität Stuttgart<br />
— 2 Institut für Quantenoptik und Quanteninformation, Universität<br />
Innsbruck — 3 Insitut für Theoretische Physik, Universität Innsbruck<br />
An open quantum system, whose time evolution is governed by a master<br />
equation, can be driven in steady state into a given pure quantum<br />
state by an appropriate design of the system-reservoir coupling.<br />
This points out a route towards preparing many body states and nonequilibrium<br />
quantum phases by quantum reservoir engineering. Here<br />
we discuss in detail the example of a driven dissipative Bose Einstein<br />
Condensate (BEC), where atoms in an optical lattice are coupled to<br />
a bath of Bogoliubov excitations via the atomic current representing<br />
local dissipation. In the absence of interactions the lattice gas is driven<br />
into a pure state with long range order. Weak interactions lead to a<br />
weakly mixed state, which in 3D can be understood as a depletion<br />
of the condensate, and in 1D and 2D exhibits properties reminiscent<br />
of a Luttinger liquid or a Kosterlitz-Thouless critical phase at finite<br />
temperature, with the role of the “finite temperature” played by the<br />
interactions.<br />
Q 33.5 Do 9:30 2F<br />
Light propagation in ultracold atomic gases confined by optical<br />
lattices — •Stefan Rist and Giovanna Morigi — Departament<br />
de Fisica, Universitat Autonoma de Barcelona, 08193 Bellaterra, Spain<br />
We develop a theory which describes photon propagation in a medium<br />
constituted by ultracold atoms confined by an optical lattice. We discuss<br />
in particular the input-output relations taking into account the<br />
finite size of the optical lattice and the atoms quantum motion and<br />
statistics. This work extends previous studies [1,2] by considering the<br />
atomic vibrations at the lattice sites, the finite tunneling matrix elements,<br />
and saturation effects of the atomic transitions. The coherence<br />
properties of the transmitted light are discussed as a function of the<br />
quantum state of the gas.<br />
[1] Deutsch et al. Phys. Rev. A 52, 1394 (1995).<br />
[2] Chong et al. Phys. Rev. B 75, 235124 (2007).<br />
Q 33.6 Do 9:45 2F<br />
Superfluid properties of a Bose-Einstein condensate in an optical<br />
lattice confined in a cavity — •Aranya bhuti Bhattacherjee<br />
— Max Planck-Institute for Physics of Complex System, Noethnitzer<br />
Str.38, 01187 Dresden, Germany<br />
In this work, we study the effect of a one dimensional optical lattice in<br />
a cavity field with quantum properties on the superfluid dynamics of a<br />
Bose-Einstein condensate(BEC). In the cavity the influence of atomic<br />
backaction and the external driving pump become important and modify<br />
the optical potential. Due to the coupling between the condensate<br />
wavefunction and the cavity modes, the cavity light field develops a<br />
band structure. This study reveals that the pump and the cavity now<br />
emerges as a new handle to control the coherence properties of the<br />
BEC, which offer the potential for improved interferometric technique,<br />
quantum information processing and efficient control of nonlinear excitations<br />
such as solitons. A wealth of new phenomena can be expected<br />
in the many-body physics of quantum gases with pump-cavity mediated<br />
interaction. Expressions for the tunneling parameter, the Bloch<br />
energy, the Bogoliubov spectrum and the effective mass in a quantum<br />
optical lattice are new results, derived here for the first time.
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
Q 34: Ultrakalte Rydberggase [gemeinsam mit A]<br />
Zeit: Donnerstag 8:30–10:00 Raum: 2G<br />
Q 34.1 Do 8:30 2G<br />
Rydberg excitation of a Bose-Einstein condensate — •Ulrich<br />
Raitzsch, Rolf Heidemann, Vera Bendkowsky, Björn Butscher,<br />
Robert Löw, and Tilman Pfau — 5. Physikalisches Institut, Pfaffenwaldring<br />
57, 70569 Stuttgart, Germany<br />
We present our latest results on Rydberg excitation of a Bose-Einstein<br />
condensate [1]. Crossing the critical temperature Tc, a signature of the<br />
phase transition to Bose condensation is observed in the fraction of<br />
excited Rydberg atoms. The main features in the experimental data<br />
were reproduced by a simulation using a superatom model. A superatom<br />
is formed by N ground state atoms in a sphere with the blockade<br />
radius rb ∝ 6p C6/Ω due to the van der Waals interaction [2].<br />
The Rydberg excitation is proven to be coherent despite strong interactions<br />
with a rotary echo technique known from nuclear magnetic<br />
resonance physics [3]. The rotary echo experiment was done for various<br />
densities of ground state atoms and excitation times, giving insight<br />
into the dephasing caused by the van der Waals interaction.<br />
References<br />
[1]R. Heidemann, et al., arXiv:0710.5622 (2007)<br />
[2]R. Heidemann, et al., Phys. Rev. Lett. 99(16), 163601(2007)<br />
[3]U. Raitzsch, et al., arXiv:0706.3869 (2007)<br />
Q 34.2 Do 8:45 2G<br />
Universal Scaling in a Strongly Interacting Rydberg gas —<br />
•Hendrik Weimer 1 , Hans Peter Büchler 1 , Rolf Heidemann 2 , Ulrich<br />
Raitzsch 2 , Vera Bendkowsky 2 , Björn Butscher 2 , Robert<br />
Löw 2 , and Tilman Pfau 2 — 1 Institut für Theoretische Physik<br />
III, Universität Stuttgart — 2 5. Physikalisches Institut, Universität<br />
Stuttgart<br />
We analyze the van der Waals blockade and the quantum evolution of<br />
an atomic gas resonantly driven by a laser into a strongly interacting<br />
Rydberg state. Such a system has recently been studied experimentally<br />
by Heidemann et al. [1]. The main mechanism behind the van der<br />
Waals blockade is that once a Rydberg atom is excited, the van der<br />
Waals interaction shifts the surrounding atoms out of resonance with<br />
the driving laser and therefore suppresses the excitation of additional<br />
Rydberg atoms. The combination of the van der Waals interaction<br />
with the Rabi frequency of the resonant laser gives rise to a single dimensionless<br />
parameter. We show that the experimental data exhibits a<br />
data collapse with a universal scaling function in this single dimensionless<br />
parameter. A numerical analysis of the effective theory provides<br />
excellent agreement for the scaling function with the experiment, and<br />
is evidence for universality in a strongly interacting Rydberg gas undergoing<br />
coherent quantum evolution.<br />
[1] R. Heidemann et. al. Phys. Rev. Lett. 99, 163601 (2007).<br />
Q 34.3 Do 9:00 2G<br />
Many-particle mechanical effects of an interacting Rydberg<br />
gas — •Thomas Amthor, Markus Reetz-Lamour, Christian<br />
Giese, and Matthias Weidemüller — Physikalisches Institut, Universität<br />
Freiburg, Hermann-Herder-Str. 3, 79104 Freiburg<br />
Gases of ultracold Rydberg atoms have been found to spontaneously<br />
ionize and form plasmas [1]. Recent experiments showed that the initial<br />
ionization is mainly due to collisions induced by long-range forces between<br />
the cold Rydberg atoms. The acceleration and subsequent Penning<br />
ionization of Rydberg atoms has been investigated under different<br />
conditions, the underlying interactions being either of dipole-dipole [2]<br />
or van der Waals type [3]. For attractive interaction potentials, atoms<br />
excited to Rydberg states on the red-detuned wing of the resonance<br />
are observed to ionize first, as more atom pairs are prepared at short<br />
distances and experience strong attractive forces. Here we discuss the<br />
ionization dynamics of gases initially prepared in states with purely<br />
repulsive interaction. This requires a more detailed model including<br />
many-particle aspects and mechanisms for state redistribution to overcome<br />
the repulsive forces. A Monte Carlo model for the description of<br />
such a system is presented and agrees well with experimental observations<br />
[4].<br />
[1] M. P. Robinson et al., Phys. Rev. Lett. 85, 4466 (2000)<br />
[2] W. Li et al., Phys. Rev. Lett. 94, 173001 (2005)<br />
[3] T. Amthor et al., Phys. Rev. Lett. 98, 023004 (2007)<br />
[4] T. Amthor et al., Phys. Rev. A 76, 054702 (2007)<br />
Q 34.4 Do 9:15 2G<br />
Prospects for resonant energy transfer in structured ultracold<br />
Rydberg gases — •Christian Giese, Christoph Sebastian<br />
Hofmann, Wendelin Sprenger, Janne Denskat, Thomas<br />
Amthor, Markus Reetz-Lamour, and Matthias Weidemüller —<br />
Physikalisches Intitut, Universität Freiburg, Hermann-Herderstr. 3,<br />
79104 Freiburg<br />
Dynamics in cold Rydberg gases are entirely determined by long-range<br />
dipole-dipole and van der Waals interactions due to the negligible<br />
translational energy. A unique feature of the system is the tunability of<br />
these interactions in both strength and character. In this manner, two<br />
Rydberg pair states can be made energetically degenerate. This leads<br />
to energy and population transfer known as resonant energy transfer<br />
(RET) which plays an important role in the process of photosynthesis.<br />
In recent work , we have compared Monte Carlo simulations of this<br />
process to density dependent population measurements[1]. Coherent<br />
energy transfer occurs, but the signature is washed out by many-body<br />
diffusion and disorder. To overcome this, we plan to use beamshaping<br />
techniques for structuring the atomic cloud. Recently, the theoretical<br />
and experimental prospects of coherent exciton transport in linear<br />
chains in the presence of excitation traps were discussed[2]. We propose<br />
an experimental way of using cold, structured Rydberg gases as a<br />
model system for investigating the coherent and incoherent properties<br />
of this process when introducing different degrees of disorder.<br />
[1] S. Westermann et al., Eur. J. Phys. D 40, 37 (2006)<br />
[2] O. Mülken et al., Phys. Rev. Lett. 99, 090601 (2007)<br />
Q 34.5 Do 9:30 2G<br />
High-resolution spectroscopy of an ultracold Rydberg gas<br />
— •Christoph S. Hofmann, Thomas Amthor, Christian Giese,<br />
Wendelin Sprenger, Markus Reetz-Lamour, and Matthias Weidemueller<br />
— Physics Institute, Albert-Ludwig University Freiburg,<br />
79104 Freiburg, Germany<br />
The exaggerated properties of Rydberg atoms provide a fertile ground<br />
for investigating atomic interaction phenomena. Due to the long-range<br />
character of the interaction between highly excited atoms, the dynamics<br />
of an ultracold gas of Rydberg atoms are entirely determined<br />
by van-der-Waals and dipole-dipole interactions. Rydberg excitationspectra<br />
reveal valuable information over a wide range of characteristic<br />
phenomena occurring in ultracold Rydberg samples, which are the<br />
scope of this talk. For instance, effects like suppression of excitation due<br />
to Rydberg-Rydberg interaction [1] can be traced back by analysing<br />
these spectra. Spectral features such as line shapes and broadening provide<br />
information on interaction potentials. Furthermore highly resolved<br />
spectra also permit the observation of long-range molecular resonances<br />
[2]. High-resolution spectroscopy requires sophisticated experimental<br />
techniques like careful electric and magnetic stray field control, frequency<br />
stabilized excitation and probe lasers with narrow line widths<br />
as well as sensitive ion detection schemes. An overview about these<br />
techniques is given in this talk.<br />
[1] D. Tong et al.,Phys. Rev. Lett. 93, 063001 (2004); K. Singer et<br />
al., Phys. Rev. Lett. 93, 163001 (2004)<br />
[2] S. M. Farooqi et al., Phys. Rev. Lett. 91, 183002 (2003)<br />
Q 34.6 Do 9:45 2G<br />
Rydberg excitations in an Ion Trap — •Igor Lesanovsky 1 ,<br />
Markus Müller 1 , Lin-Mei Liang 1,2 , and Peter Zoller 1 —<br />
1 Institute for Theoretical Physics, University of Innsbruck, and Institute<br />
for Quantum Optics and Quantum Information of the Austrian<br />
Academy of Sciences, Innsbruck, Austria — 2 Department of Physcis,<br />
National University of Defense Technology, Changsha 410073, China<br />
We investigate Rydberg excitations of ions which are trapped in a<br />
linear Paul trap. In such trap the ions are confined by an electric<br />
quadrupole field and a ponderomotive potential due to an oscillating<br />
quadrupole. We employ a two-body approach in order to model the<br />
Rydberg ions and derive the Hamiltonian governing Rydberg excitations<br />
in a linear ion crystal. We show how a strong state-dependent<br />
dipole-dipole interaction among the ions can be achieved by coupling
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
Rydberg states of different parity using a microwave field. This system<br />
offers the possibility to study Rydberg excitation dynamics of a<br />
Q 35: Laseranwendungen (Optische Messtechnik)<br />
mesoscopic ensemble in a structured environment and permits the experimental<br />
realization of strongly interacting spin models.<br />
Zeit: Donnerstag 8:30–10:00 Raum: 3H<br />
Q 35.1 Do 8:30 3H<br />
Photoakustische NO-Detektion mittels gepulstem Quantenkaskadenlaser<br />
— •Markus Germer 1 , Marcus Wolff 1,3 , Hermann<br />
Harde 2 und Hinrich G. Groninga 3 — 1 Hochschule für Angewandte<br />
Wissenschaften Hamburg — 2 Helmut-Schmidt-Universität — 3 PAS-<br />
Tech GmbH<br />
Ziel unserer Untersuchungen ist es, einen auf photoakustischer Spektroskopie<br />
basierenden Sensor für Stickstoffmonoxid (NO) zur Asthmadiagnose<br />
zu entwickeln. Als Anregungsquelle wird ein gepulster DFB-<br />
Quantenkaskadenlaser verwendet, der bei Raumtemperatur betrieben<br />
wird. Es wurden Untersuchungen am Grundvibrationsübergang 1-0<br />
von NO bei einer Wellenlänge von 5,27 µm durchgeführt. Zur Optimierung<br />
des photoakustischen Signals wurden verschiedene Betriebsparameter<br />
des Lasers wie Pulsbreite und Repetitionsrate untersucht.<br />
Weiter wurden die Puls-Gate-Modulation und die Repetitionsfrequenzmodulation<br />
bezüglich ihrer Eignung miteinander verglichen.<br />
Q 35.2 Do 8:45 3H<br />
Erzeugung mehrerer spektral getrennter Femtosekundenpulse<br />
und deren Anwendung zur Formvermessung schnell bewegter<br />
Objekte — •Thomas Hansel 1 , Ruediger Grunwald 1 ,<br />
Günter Steinmeyer 1 , Uwe Griebner 1 , Jens Bonitz 2 und Christian<br />
Kaufmann 2 — 1 Max-Born-Institut, Max-Born-Straße 2a, D-12489<br />
Berlin — 2 Technische Universität Chemnitz, Reichenhainer Straße 70,<br />
D-09107 Chemnitz<br />
Die digital holografische 3D–Formvermessung sehr schnell bewegter<br />
Objekte erfordert die simultane Erzeugung von mindestens zwei<br />
spektral getrennten optischen Pulsen. Neben einem hohen spektralen<br />
Kontrast der Pulse ist zur Vermessung ausgedehnter Objekte eine<br />
Einzelpulsenergie > 1 µJ erforderlich [1]. Das breitbandige Spektrum<br />
eines Ti:Saphir–Laserverstärkersystems um 800 nm wird so modifiziert,<br />
dass dieser bis zu 5 Pulse mit einer Dauer von ca. 500 fs und<br />
einem spektralen Abstand von ca. 10 nm simultan emittiert. Mit dieser<br />
Quelle wurden Form– und Deformationsmessungen von MEMS<br />
mit Resonanzfrequenzen im kHz-Bereich durchgeführt. Dazu wurde<br />
ein Michelson–Interferometer mit zwei spektral um 15 nm separierten<br />
Pulsen gespeist. Die Trennung der Interferenzmuster beider Spektralanteile<br />
erfolgte durch Polarisationskodierung und der simultanen<br />
Aufnahme mit zwei CCD–Kameras. Konturplots der schnell bewegten<br />
MEMS mit Deformationen im Bereich von 10 nm wurden erstellt.<br />
[1] T. Hansel et al., Appl. Phys. B, in press<br />
Q 35.3 Do 9:00 3H<br />
Interferometric testing of a deep parabolic mirror —<br />
•Hildegard Konermann, Johannes Schwider, Klaus Mantel,<br />
Norbert Lindlein, Markus Sondermann, Ulf Peschel, and Gerd<br />
Leuchs — Institut für Optik, Information und Photonik, Max-Planck-<br />
Forschungsgruppe, Staudtstraße 7 B2, Universität Erlangen-Nürnberg,<br />
91058 Erlangen, Germany<br />
We present the results of the testing of a deep parabolic mirror that is<br />
to be used for excitation of single atoms by single photons with high<br />
efficiency. For this purpose, the aberrations of the mirror have to be<br />
known with less than 0.1 wavelengths precision. For such a deep mirror<br />
with an aperture angle of 135 degree, i.e. nearly 4Pi solid angle, this will<br />
be at the limit of the highest possible precision which can be achieved<br />
in practice. For the characterization of the parabolic mirror, we use an<br />
interferometer of the Fizeau type. We perform a null-test with a metal<br />
sphere at the focal point of the parabolic mirror, thus circumventing<br />
ambiguities in the localization of surface errors. In order to rule out<br />
polarization dependent phase jumps upon reflection off the mirror surface,<br />
the parabolic mirror is illuminated with radially polarized light<br />
which is also the polarization of the light in the final application for the<br />
excitation of single atoms. The results of the measurements are needed<br />
for the creation of a phase plate that compensates the deviations of<br />
the mirror from an ideal parabola.<br />
Q 35.4 Do 9:15 3H<br />
Dreiport-Gitter-Resonator mit Power-Recycling — •Michael<br />
Britzger 1 , Oliver Burmeister 1 , Daniel Friedrich 1 , Alexander<br />
Bunkowski 1 , Tina Clausnitzer 2 , Ernst-Bernhard Kley 2 , Andreas<br />
Tünnermann 2 , Karsten Danzmann 1 und Roman Schnabel 1 —<br />
1 MPI für Gravitationsphysik (AEI) und Institut für Gravitationsphysik<br />
der Leibniz Universität Hannover, Callinstr. 38, 30167 Hannover<br />
— 2 Institut für Angewandte Physik der Friedrich-Schiller-Universität<br />
Jena, Max-Wien-Platz 1, 07743 Jena<br />
Dielektrische Reflexionsgitter können so konzeptioniert werden, dass<br />
sie als Einkoppler in einem Resonator dazu führen, dass resonantes<br />
Licht vollständig zum Eingang zurückreflektiert wird. Mit Hilfe eines<br />
Spiegels, der das reflektierte Licht erneut in den Resonator zurückleitet<br />
entsteht ein gittergekoppelter Doppelresonator. Bei einem Resonator<br />
auf Basis eines sogenannten Dreiport-Gitters als niedereffizientem Einkoppler,<br />
existiert ein weiterer Ausgang, der nichtresonante Moden aus<br />
dem Resonator auskoppelt. Diese Modenselektivität des gekoppelten<br />
Gitterresonators kann genutzt werden um mit Verwendung eines Lasermediums<br />
im Resonator Laserstrahlung mit geringer Modenfluktuation<br />
zu erzeugen. Dadurch, dass keine transmissiv genutzen Optiken<br />
verwendet werden und somit bei hohen Leistungen keine thermischen<br />
Effekte, wie thermische Linsen in Substraten verursacht werden, besteht<br />
eine weitere Anwendungsmöglichkeit in der Hochleistungslaserphysik.<br />
Es wird die erste experimentelle Realisierung eines Dreiport-<br />
Gitter-Resonators mit Power-Recycling vorgestellt und ein Ausblick<br />
auf zukünftige Anwendungsmöglichkeiten gegeben.<br />
Q 35.5 Do 9:30 3H<br />
Silizium als Testmassenmaterial für zukünftige Gravitationswellendetektoren<br />
— •Jessica Dück, Stefan Goßler, Sebastian<br />
Steinlechner, Karsten Danzmann und Roman Schnabel — Max-<br />
Planck-Institut für Gravitationsphysik (AEI) und Institut für Gravitationsphysik,<br />
Leibniz Universität Hannover<br />
Um das thermische Rauschen in erdgebundenen Gravitationswellendetektoren<br />
(GWD) zu reduzieren, ist das Kühlen der Testmassen, für<br />
welche die Materialien Fused Silica, Saphir und Silizium (Si) in der<br />
engeren Auswahl stehen, der erfolgversprechendste Weg.<br />
Fused Silica, welches in der ersten Generation von GWD verwendet<br />
wurde, besitzt eine gute optische Qualität für die verwendete Wellenlänge<br />
von 1064 nm. Die mechanischen Eigenschaften bei niedrigen<br />
Temperaturen entsprechen jedoch nicht den Anforderungen. Si hingegen<br />
besitzt insbesondere bei kryogenen Temperaturen die erforderlichen<br />
mechanischen Eigenschaften, bei einer Wellenlänge von 1064 nm<br />
weist es allerdings eine inakzeptabel hohe Absorption auf. Bei größeren<br />
Wellenlängen zeigt es aber ein ausgeprägtes Absorptionsminimum. Innerhalb<br />
dieses Minimums liegt die Wellenlänge von 1550 nm und wurde<br />
zur weiteren Untersuchung ausgewählt. Grund für diese Wahl sind die<br />
hinsichtlich Leistung und Stabilität vielversprechenden Laser, welche<br />
angetrieben durch kommerzielle Anwendungen (z.B. Telekommunikation)<br />
in den letzten Jahren entwickelt worden sind.<br />
Wir präsentieren Methoden zur Vermessung des vermutlich im<br />
Bereich von 10 −8 /cm liegenden Absorptionskoeffizienten von Si bei<br />
1550 nm.<br />
Q 35.6 Do 9:45 3H<br />
Neuartiger THz Detektor auf Basis des Nachweises des Photonenimpulses<br />
— •Ulrike Willer 1,2 , Andreas Pohlkötter 1 und<br />
Wolfgang Schade 1,2 — 1 TU Clausthal, Institut für Physik und<br />
Physikalische Technologien, Clausthal-Zellerfeld, Deutschland — 2 TU<br />
Clausthal, LaserAnwendungsCentrum, Clausthal-Zellerfeld, Deutschland<br />
Eine Quarzstimmgabel wird zur Detektion von elektromagnetischer<br />
Strahlung verwendet. Dazu wird die Strahlung moduliert und auf die<br />
Seitenfläche einer Zinke der Stimmgabel fokussiert. Der übertragene<br />
Photonenimpuls regt die Stimmgabel zur Schwingung an. Wird als<br />
Modulationsfrequenz die Resonanzfrequenz des Oszillators gewählt,<br />
kann die Schwingung direkt über den erzeugten Piezostrom nachge-
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
wiesen werden. Eine Beschreibung des Systems mit dem Modell des<br />
getriebenen harmonischen Oszillators ist möglich. Messungen, die mit<br />
einem THz Quantenkaskadenlaser durchgeführt wurden, werden mit<br />
Simulationen verglichen, der neuartige Detektor charakterisiert und<br />
die Einsatzmöglichkeiten diskutiert.<br />
Q 36: Quanteninformation (Konzepte und Methoden II)<br />
Zeit: Donnerstag 11:00–13:00 Raum: 1B<br />
Q 36.1 Do 11:00 1B<br />
Disentanglement in qubit-qutrit systems — •Mazhar Ali 1 ,<br />
Gernot Alber 1 , Kedar Ranade 1 , and A. R. P. Rau 2 — 1 Institut<br />
für Angewandte Physik, Technische Universität Darmstadt, D-64289,<br />
Germany — 2 Department of Physics and Astronomy, Louisiana State<br />
University, Baton Rouge, Louisiana 70803, USA<br />
The interaction of a quantum system with an environment leads to<br />
decoherence. This decoherence gradually degrades quantum entanglement.<br />
In particular, there are situations in which entanglement can<br />
vanish after some finite time. This phenomenon has been named entanglement<br />
sudden death. We examine this phenomenon induced by<br />
local spontaneous emission for 2 × 3-dimensional systems [1]. Similar<br />
to 2 × 2-dimensional systems, the negativity of quantum states can<br />
vanish in finite time. It is possible to hasten, delay or even avert this<br />
sudden death phenomenon [2].<br />
[1] Mazhar Ali, A. R. P. Rau and K. Ranade, arXiv:quantph/0710.2238.<br />
[2] A. R. P. Rau, Mazhar Ali and G. Alber, arXiv:quantph/0711.0317.<br />
Q 36.2 Do 11:15 1B<br />
2D Multipartite Valence Bond States in Quantum Antiferromagnets<br />
— Enrique Rico 1 , •Robert Hübener 1 , and Hans<br />
Briegel 1,2 — 1 Institut für Quantenoptik und Quanteninformation<br />
Innsbruck, Technikerstraße 21a, A-6020 Innsbruck, Austria —<br />
2 Institut für Theoretische Physik, Universität Innsbruck, Technikerstraße<br />
25, A-6020 Innsbruck, Austria<br />
A quantum anti-ferromagnetic spin-model on a lattice is characterized<br />
via projections of the Hilbert space of a spin-1/2-model on a 2D lattice<br />
into suitable subspaces. We implement the following requirements<br />
to the resulting state space: a) the states are homogeneous, translationally<br />
and rotationally invariant; b) the states are real singlet states<br />
(non-chiral); c) the states have a local spin-1 representation. We investigate<br />
the properties (e.g., decay of correlations) of this class of states,<br />
which is a set of ground states of certain Heisenberg-like Hamiltonians,<br />
and then relax the requirements to obtain more general models. Ref.:<br />
arXiv:0710.2349v1<br />
Q 36.3 Do 11:30 1B<br />
The structure and properties of symmetric and antisymmetric<br />
maximally entangled multidimensional bipartite states —<br />
•Denis Sych — Institute of Optics, Information and Photonics, University<br />
of Erlangen-Nuremberg, Germany<br />
A multidimensional generalization of the Bell states and the Pauli matrices<br />
is considered. It is shown that in the case when the dimension<br />
of the Hilbert space is equal to a power of 2, a basis of multidimensional<br />
maximally entangled bipartite states can be chosen similarly to<br />
the Bell states and constructed of only symmetric and antisymmetric<br />
states. It preserves all basic properties of the standard Bell states. An<br />
iterative method for its construction is presented and its properties<br />
are discussed. Antisymmetric states turn out to be analogous to the<br />
singlet Bell state, namely they deliver perfect anticorrelations while<br />
being rotationally invariant. The latter property is shown to be tightly<br />
connected with antisymmetry. The generalized Bell states are used to<br />
show the upper bounds of possible correlations between two quantum<br />
systems and to prove the “no-copying” principle, which is a stronger<br />
version of the “no-cloning” principle.<br />
Q 36.4 Do 11:45 1B<br />
Discussion of generalized monogamy relations for multipartite<br />
entanglement — •Andreas Osterloh 1 , Christopher<br />
Eltschka 2 , and Jens Siewert 2 — 1 Institut für Theoretische Physik,<br />
Universität Hannover, D-30167 Hannover, Germany — 2 Institut für<br />
Theoretische Physik, Universität Regensburg, D-93040 Regensburg,<br />
Germany<br />
The analytic convex roof expression for the entanglement of pairs of<br />
qubits marked a major breakthrough in the quantification of entanglement.<br />
An equally remarkable ”momogamy” relation limits the way of<br />
distibuting such pairwise qubit entanglement over a multi-qubit system<br />
and gave rise to the definition of a tri-partite entanglement measure.<br />
Already for this reason would it be desirable to have an extension of<br />
this monogamy relation in order to include multipartite entanglement<br />
beyond pairs. We discuss possible extensions of the monogamy relation<br />
for pairwise qubit entanglement. Based on recent advances for mixed<br />
state threetangle and known invariants for four qubits we systematically<br />
analyze pure states of four qubits. Though a class of states exists<br />
for which the manogamy relation can be extended in some form, we<br />
give a family of counterexamples where no monogamy equality does<br />
exist including the three- and/or some four-tangle.<br />
Q 36.5 Do 12:00 1B<br />
Unambiguous discrimination of many mixed states —<br />
•Matthias Kleinmann, Hermann Kampermann, and Dagmar<br />
Bruß — Heinrich-Heine-Universität Düsseldorf, Institut für Theoretische<br />
Physik III, Universitätsstraße 1, 40225 Düsseldorf<br />
While the optimal unambiguous discrimination of two mixed states<br />
has already attracted considerable attention, only a few results [1,2]<br />
are known for the optimal case of more than two mixed states. We<br />
show that many concepts and some classes of optimal solutions known<br />
from the two-state case [3] can be generalized to the many-state case.<br />
[1] Y.C. Eldar, M. Stojnic, and B. Hassibi, Phys. Rev. A 69, 062318<br />
(2004), [2] Y. Feng, R. Duan, and M. Ying, Phys. Rev. A 70, 012308<br />
(2004), [3] M. Kleinmann, H. Kampermann, and D. Bruß (in preparation)<br />
Q 36.6 Do 12:15 1B<br />
Characterization of superposition states via STIRAPtype<br />
back transfer — •Ruth Garcia-Fernandez 1,2 , Frank<br />
Vewinger 1,3 , David Dzsotjan 1 , and Klaas Bergmann 1 — 1 FB<br />
Physik, TU Kaiserslautern, Kaiserslautern — 2 Current address: Institut<br />
für Physik, Johannes-Gutenberg Universität, Mainz — 3 Current<br />
address: Institut für Angewandte Physik, Universität Bonn, Bonn<br />
We present results of an experimental technique for the characterization<br />
of coherent superposition states between magnetic sublevels. The<br />
technique is based on a multistate variant of the stimulated Raman<br />
adiabatic passage (STIRAP) method [1]. The determination of the<br />
parameters of the superposition (phases and amplitudes) is achieved<br />
using the reverse process, i.e., the transfer of the population in the<br />
superposition state back to the initial state by means of a second interaction<br />
zone with the laser beams. The experiments are carried out in<br />
a collimated supersonic beam of Neon atoms. The superposition states<br />
involves two or more degenerate levels in the J = 2 metastable state.<br />
The population in the initial state J = 0 is monitored as a function of<br />
the phase. The parameters of the unknown initial superposition state<br />
are determined from the properties of the laser radiation which lead<br />
to a maximum flow of atoms in J = 0.<br />
[1] F. Vewinger et al., Phys. Rev. A 75, 043407, 2007.<br />
Q 36.7 Do 12:30 1B<br />
Experimental Demonstration of near-Optimal Discrimination<br />
of Optical Coherent States — •Christoffer Wittmann 1 ,<br />
Katiuscia N. Cassemiro 2 , Masahiro Takeoka 3 , Masahide Sasaki 3 ,<br />
Ulrik L. Andersen 1 , and Gerd Leuchs 1 — 1 Institut für Optik,<br />
Information und Photonik, Max-Planck Forschungsgruppe, Universität<br />
Erlangen-Nürnberg, — 2 Instituto de Fìsica, Universidade de São<br />
Paulo, Caixa Postal 66318, — 3 National Institute of Information and<br />
Communications Technology, 4-2-1 Nukui-kitamachi, Koganei, Tokyo<br />
184-8795, Japan<br />
Optimal discrimination of non-orthogonal quantum states is one of the<br />
fundamental tasks in quantum detection theory. For weak coherent<br />
states, the standard detection schemes, namely homodyne detection<br />
and the Kennedy receiver, are not able to achieve error free sensitivity
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
in principle. Both schemes do not even reach the optimal bound for<br />
the minimum average error.<br />
We propose and experimentally realize a novel detection strategy<br />
for the discrimination of two optical coherent states. We present the<br />
experimental comparison of the new strategy with standard detection<br />
schemes and demonstrate, that the new receiver surpasses both standard<br />
approaches for any signal amplitude.<br />
Q 36.8 Do 12:45 1B<br />
Quantum evolution from a snapshot — •Michael Wolf 1 ,<br />
Jens Eisert 2 , Toby Cubitt 3 , and Ignacio Cirac 1 — 1 Max-Planck-<br />
Institut für Quantenoptik, Hans-Kopfermann-Str.1, 85748 Garching<br />
— 2 Institute for Mathematical Sciences, Imperial College London —<br />
3 Department of Mathematics, University of Bristol<br />
Q 37: Quantengase (Wechselwirkungseffekte I)<br />
We investigate what a snapshot of a quantum evolution - a quantum<br />
channel reflecting open system dynamics - reveals about the underlying<br />
continuous time evolution. Remarkably, from such a snapshot,<br />
and without imposing additional assumptions, it is possible to decide<br />
whether or not a channel is consistent with a time (in)dependent<br />
Markovian evolution, for which we provide computable necessary<br />
and sufficient criteria. Based on these, a computable measure of<br />
’Markovianity’ is introduced which quantifies the Markovian part of<br />
a quantum channel. We discuss the consistency with Markovian dynamics<br />
as encountered in quantum process tomography for physical<br />
non-Markovian processes. The results clarify the geometry of<br />
the set of quantum channels with respect to being solutions of time<br />
(in)dependent master equations or (in)divisible channels.<br />
Zeit: Donnerstag 11:00–13:15 Raum: 1C<br />
Q 37.1 Do 11:00 1C<br />
A number filter for matter-waves — •Reinhold Walser 1 ,<br />
Andreas Sizmann 2 , Gerrit Nandi 1 , and József Fortágh 3<br />
— 1 Institut für Quantenphysik, Universität Ulm — 2 Ludwig-<br />
Maximilians-Universität München — 3 Physikalisches Institut der Universität<br />
Tübingen<br />
In current Bose-Einstein condensate experiments, the shot-to-shot<br />
variation of atom number fluctuates up to 10%. In here, we present<br />
a procedure to suppress such fluctuations by using a nonlinear p − ¯p<br />
matter wave interferometer for a Bose-Einstein condensate with two<br />
internal states and a high beam-splitter asymmetry (p, ¯p = 0.5). We<br />
analyze the situation for an inhomogeneous trap within the Gross-<br />
Pitaevskii mean-field theory, as well as a quantum mechanical Josephson<br />
model, which addresses complementary aspects of the problem<br />
and agrees well otherwise.<br />
[1] M. Kitagawa and M. Ueda, Phys. Rev. A, 47, 5138 (1993).<br />
[2] S. Schmitt, J. Ficker, M. Wolff, F. König, A. Sizmann and G.<br />
Leuchs, Phys Rev. Lett. 81, 2446 (1998).<br />
[3] A. Sørensen and L.-M. Duan and J. I. Cirac and P. Zoller, Nature,<br />
409, 63 (2001).<br />
[4] U. V. Poulsen and K. Mølmer, Phys. Rev. A, 65, 033613, (2002).<br />
[5] G. Nandi, A. Sizmann, J. Fortágh, and R. Walser, arXiv:0710.1737<br />
(2007).<br />
Q 37.2 Do 11:15 1C<br />
Are there semi-fluxons in cold atomic gases? — •Michael<br />
Eckart 1 , Reinhold Walser 1 , Wolfgang P. Schleich 1 , Dieter<br />
Koelle 2 , Reinhold Kleiner 2 , and Edward Goldobin 2 — 1 Institut<br />
für Quantenphysik, Universität Ulm, 89069 Ulm — 2 Physikalisches<br />
Institut-Experimentalphysik II, Universität Tübingen, 72076 Tübingen<br />
Fluxons are single quanta of magnetic flux (Φ0 ≈ 2.07 × 10 −15 Wb)<br />
which may exist in superconducting long Josephson junctions [1]. By<br />
making a Josephson junction out of two parts with a phase difference of<br />
π between the tunneling supercurrents, one can construct a so-called<br />
0-π junction, where the ground state may correspond to a spontaneously<br />
created magnetic flux of Φ0/2 localized at the 0-π boundary.<br />
Such semifluxons are intensively investigated in superconducting structures<br />
[2-4].<br />
In this contribution we propose a technique to create and study<br />
similar 0-π junctions in cold atomic gases [5,6]. We investigate the<br />
interaction of single atoms as well as BECs with laser light to gain<br />
insight into the fundamental physics that eventually also sheds light<br />
on the macroscopic behavior of the semifluxons in superconductors.<br />
[1] W. Buckel and R. Kleiner, Superconductivity: Fundamentals and<br />
applications, Wiley-VCH, Berlin (2004)<br />
[2] E. Goldobin et al., Phys. Rev. B 72, 054527 (2005)<br />
[3] K. Buckenmaier et al., Phys. Rev. Lett. 98, 117006 (2007)<br />
[4] H. Hilgenkamp et al., Nature 422, 50 (2003)<br />
[5] V.M. Kaurov and A.B. Kuklov, Phys. Rev. A 73, 013627 (2006)<br />
[6] E. Goldobin et al., New J. Phys., in preparation<br />
Q 37.3 Do 11:30 1C<br />
Atom-molecule oscillations in a Mott insulator — •Matthias<br />
Lettner, Niels Syassen, Dominik M. Bauer, Daniel Dietze,<br />
Thomas Volz, Stephan Dürr, and Gerhard Rempe — Max Planck<br />
Institut für Quantenoptik, Hans-Kopfermann-Str. 1, D-85748 Garching,<br />
Germany<br />
Near a Feshbach resonance an unbound state of two ultracold atoms is<br />
coherently coupled to a molecular one. This realizes a coupled two level<br />
system. We report on the observation of large-amplitude oscillations.<br />
The damping is so weak that 29 cycles are observed. The experiment<br />
uses 87 Rb in an optical lattice and a Feshbach resonance near 414 G.<br />
The frequency and amplitude of the oscillations depend on the magnetic<br />
field in a way that is well described by a two-level model. Also the<br />
observed density dependence of the oscillation frequency agrees with<br />
the theoretical expectation. We confirmed that the state produced after<br />
a half-cycle contains exactly one molecule at each lattice site. In addition,<br />
we show that for energies in a gap of the lattice band structure,<br />
the molecules cannot dissociate.<br />
[1] N.Syassen PRL 99, 033201 (2007).<br />
Q 37.4 Do 11:45 1C<br />
Coherent backscattering of Bose-Einstein condensates in two<br />
dimensional disorder potentials — •Michael Hartung, Klaus<br />
Richter, and Peter Schlagheck — Institute for Theoretical Physics,<br />
University of Regensburg, Germany<br />
The rapid progress in the experimental techniques for Bose-Einstein<br />
condensates permits detailed studies of mesoscopic transport dynamics<br />
of interacting matter waves with rather high accuracy and high<br />
flexibility in the control of parameters. We particularly focus on quasistationary<br />
transport processes of Bose-Einstein condensates through<br />
two dimensional disorder potentials by integrating the time-dependent<br />
Gross-Pitaevskii equation.<br />
In the limit of vanishing atom-atom interaction we observe coherent<br />
backscattering, which leads to a sharp cone, centered around the backward<br />
direction, in the angle resolved density of the scattered condensate.<br />
This is a characteristic signature of weak localization and arises<br />
due to the constructive interference of semiclassical scattering paths<br />
with their time reversed counterparts. This coherent backscattering<br />
peak is transformed into a pronounced dip for weak repulsive interaction,<br />
and eventually vanishes for strong interaction. In this latter<br />
regime we find intrinsic time-dependent behavior of the condensate<br />
wavefunction, which effectively suppresses the interference phenomena<br />
that give rise to the coherent backscattering signal.<br />
Q 37.5 Do 12:00 1C<br />
Bifurcations in Bose-Einstein condensates with dipolar interactions<br />
— •Patrick Wagner, Jörg Main, and Günter Wunner<br />
— 1. Institut für Theoretische Physik, Universität Stuttgart, 70550<br />
Stuttgart<br />
We study Bose-Einstein condensates with dipolar and contact interaction<br />
within Gross-Pitaevskii theory. As an interesting novel phenomenon<br />
we find two ground-state solutions for negative as well as<br />
for positive scattering lengths. Below a critical value of the scattering<br />
length, no solution exists. We also discuss the dependence of physical<br />
properties of the condensate on the trap frequencies.<br />
Q 37.6 Do 12:15 1C<br />
Linear stability of Bose-Einstein condensates with attractive<br />
1/r-interaction — •Jörg Main, Holger Cartarius, Tomaˇz Fabčič,
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
and Günter Wunner — 1. Institut für Theoretische Physik, Universität<br />
Stuttgart, 70550 Stuttgart<br />
We investigate the stability of the two nodeless stationary solutions,<br />
which are created in a tangent bifurcation in the Gross-Pitaevskii equation<br />
for condensates with attractive 1/r-interaction. Using the Fréchet<br />
derivative of the time-dependent nonlinear integro-differential equation,<br />
we calculate the eigenvalues of the linearized system. The two<br />
stationary solutions are found to be an elliptic and a hyperbolic fixed<br />
point. The numerically exact solutions are compared with the results<br />
of an approximative variational approach, which leads to analytic expressions<br />
for the eigenmodes of the linearized time-dependent equation.<br />
There are quantitative differences between both approaches, however,<br />
qualitatively they agree very well.<br />
Q 37.7 Do 12:30 1C<br />
Dynamics of Bose-Einstein condensates with inter-particle interaction<br />
— •Tomaˇz Fabčič, Jörg Main, Holger Cartarius, and<br />
Günter Wunner — 1. Institut für Theoretische Physik, Universität<br />
Stuttgart, 70550 Stuttgart<br />
The time-dependent extended Gross-Pitaevskii equation for Bose-<br />
Einstein condensates with attractive inter-atomic interaction is investigated.<br />
The two stationary solutions created in a tangent bifurcation are<br />
shown to be elliptic and hyperbolic, respectively. The stable stationary<br />
state is surrounded by solutions periodically oscillating in time whereas<br />
wave functions in the unstable region undergo a collapse within finite<br />
time. Below the tangent bifurcation no stationary solutions exist, i.e.,<br />
the condensate is always unstable and collapsing. Computations are<br />
presented for atomic 1/r as well as dipolar interactions.<br />
Q 37.8 Do 12:45 1C<br />
Discovery of exceptional points in stationary states of Bose-<br />
Einstein condensates — •Holger Cartarius, Jörg Main, and<br />
Günter Wunner — 1. Institut für Theoretische Physik, Universität<br />
Stuttgart, 70550 Stuttgart<br />
The stationary Gross-Pitaevskii equation exhibits a nodeless solution<br />
which is born together with the ground state in a tangent bifurcation.<br />
The phenomenon has been demonstrated for condensat es in a harmonic<br />
trap and, recently, has also been found for condensates with<br />
attractive 1/r-interaction and condensates with dipole-dipole interaction.<br />
At the bifurcation point both states coalesce, i.e. the energies<br />
and the wave functions are identical, a situation known from exceptional<br />
points in linear non-Hermitian Hamiltonians. We point out that<br />
the mean field energy, the chemical potential, and the wave functions<br />
in the cases mentioned above show the same behavior as an exceptional<br />
point in a linear quantum system. For the self-trapping case of<br />
a condensate with 1/r-interaction we find analytic expressions directly<br />
demonstrating the branch point singularity structure of the states.<br />
Q 37.9 Do 13:00 1C<br />
Dynamics of strongly-correlated bosons in ladder-like optical<br />
lattices — •Arturo Argüelles and Luis Santos — Appelstraße 2,<br />
30167 Hannover, Germany<br />
We analyze the physics of strongly-correlated bosons in ladder-like<br />
optical lattices out of equlibrium formed by two connected onedimensional<br />
wires. In particular, we investigate Josephson-like oscillations<br />
between initially unbalanced wires, and study the effect of the<br />
in-wire correlations on the transversal dynamics between the wires. In<br />
absence of interactions, the system would perform standard Josephsonlike<br />
oscillations of the relative population. Due to strong interactions,<br />
strong correlations lead to a significant damping of such population oscillations.<br />
In our analysis we study by means of matrix-product state<br />
techniques the dependence of the damping ratio as a function of the<br />
interation regime.<br />
Q 38: Quanteneffekte (Verschränkung und Dekohärenz)<br />
Zeit: Donnerstag 11:00–13:15 Raum: 2D<br />
Gruppenbericht Q 38.1 Do 11:00 2D<br />
Operational monitoring of multi-qubit entanglement classes<br />
via tuning of local operations — •Thierry Bastin 1 , Christoph<br />
Thiel 2 , Joachim von Zanthier 2 , Lucas Lamata 3 , Enrique<br />
Solano 4 , and Girish S. Agarwal 5 — 1 Institut de Physique<br />
Nucléaire, Atomique et de Spectroscopie, Université de Liège,<br />
Belgium — 2 Institut für Optik, Information und Photonik,Max-<br />
Planck Forschungsgruppe, Universität Erlangen-Nürnberg, Germany<br />
— 3 Max-Planck-Institut für Quantenoptik, Garching, Germany<br />
— 4 Physics Department, ASC, and CeNS, Ludwig-Maximilians-<br />
Universität, Munich, Germany — 5 Department of Physics, Oklahoma<br />
State University, Stillwater, USA<br />
We introduce a physical setup consisting of N emitters, incoherently<br />
radiating single photons that may be absorbed remotely by detectors<br />
equipped with polarizers and producing long-lived multiqubit entangled<br />
states in the internal ground levels of the emitters. By using optical<br />
fibers our system offers also access to remote entangled matter qubit<br />
states.<br />
We show that it is possible to associate well-defined sets of locally<br />
tuned polarizer orientations with multiqubit entanglement classes, allowing<br />
their monitoring in an operational manner. Our method is not<br />
restricted to two or three particles but can monitor entanglement<br />
classes even for a four particle system. Hereby, multipath quantum<br />
interference, associated with qubit permutation symmetry, plays a key<br />
role in explaining the underlying physics.<br />
Q 38.2 Do 11:30 2D<br />
Entanglement screening by nonlinear resonances — •Ignacio<br />
Garcia-Mata 1 , Andre R. R. Carvalho 2 , Florian Mintert 3,4,5 ,<br />
and Andreas Buchleitner 3,4 — 1 Laboratoire de Physique Theorique,<br />
UMR 5152 du CNRS, Universite Toulouse III — 2 Department of<br />
Physics, Faculty of Science, Australian National University ACT 0200,<br />
Australia — 3 Albert-Ludwigs-Universitaet Freiburg, Physikalisches Institut,<br />
Hermann-Herder-Str. 3, D-79104 Freiburg, Germany — 4 Max-<br />
Planck-Institut fur Physik komplexer Systeme, Noethnitzerstrasse 38,<br />
D-01187, Dresden, Germany — 5 Department of Physics, Harvard University,<br />
17 Oxford Street, Cambridge Massachusetts, USA<br />
We show that nonlinear resonances in a classically mixed phase space<br />
allow us to define generic, strongly entangled multipartite quantum<br />
states. The robustness of their multipartite entanglement increases<br />
with the particle number, i.e., in the semiclassical limit, for those<br />
classes of diffusive noise which assist the quantum-classical transition.<br />
Numerical results are shown for the quantum Harper map.<br />
Q 38.3 Do 11:45 2D<br />
Estimation of multipartite entanglement — •Florian<br />
Mintert 1 , Leandro Aolita 2 , and Andreas Buchleitner 1 —<br />
1 Albert-Ludwigs-Universität Freiburg, Hermann-Herder-Str. 3, 79104<br />
Freiburg — 2 Universidade Federal do Rio de Janeiro, Caixa Postal<br />
68528, 21941-972 Rio de Janeiro, RJ, Brasil<br />
We present an efficient estimation of the multipartite entanglement of<br />
mixed quantum states in terms of simple parity measurements. Similarly<br />
to the bipartite case [1] also multipartite generalizations of concurrence<br />
can be bounded by expectation values of simple parity projections<br />
on two identically prepared quantum states [2].<br />
[1] F. Mintert and A. Buchleitner, Phys. Rev. Lett. 98, 140505 (2007)<br />
[2] L. Aolita, A. Buchleitner and F. Mintert, quant-ph/0710.3529<br />
Q 38.4 Do 12:00 2D<br />
The role of atom-cavity detuning in cavity QED experiments<br />
— •Denis Gonta 1 and Stephan Fritzsche 1,2 — 1 Max–<br />
Planck–Institut für Kernphysik, Postfach 103980, D–69029 Heidelberg<br />
— 2 Physikalisches Institut der Universität Heidelberg, Philosophenweg<br />
12, D-69120 Heidelberg<br />
Cavity QED provides an excellent control of the atom-field interaction,<br />
when Rydberg atoms reside or pass through the cavity. This opens up a<br />
way to obtain the coherent coupling of the atomic and photonic qubits<br />
as associated with the two-level Rydberg atoms and the cavity field<br />
states, respectively.<br />
In this contribution, we explore the coherent evolution of the cavity<br />
states superposition in bimodal cavities and how this evolution is affected<br />
if a realistic atom-cavity detuning is considered. Comparison of<br />
our model computations has been made with experiment [1] in which<br />
the entanglement of the two field modes has been demonstrated using
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
a bimodal cavity. A better agreement with experiment is obtained if<br />
a ‘finite switch’ of the atomic resonance frequency from one to the<br />
second mode of a bimodal cavity is combined with the mutual interaction<br />
between the cavity modes. We shall consider also experimental<br />
setup [2] in which the entanglement of two Rydberg atoms has been<br />
demonstrated by the cavity assisted collision.<br />
[1] A. Rauschenbeutel et al., Phys. Rev. A 64, 050301 (2001).<br />
[2] S. Osnaghi et al., Phys. Rev. Lett. 87, 037902 (2001).<br />
Q 38.5 Do 12:15 2D<br />
Semiclassical simulation of open quantum systems — •Florian<br />
Mintert 1,2 and Eric Heller 2 — 1 Albert-Ludwigs-Universität<br />
Freiburg, Hermann-Herder-Str. 3, 79104 Freiburg — 2 Department of<br />
Physics, Harvard University, 17 Oxford Street, Cambridge, MA 02138,<br />
USA<br />
We present an approach for the semiclassical treatment of open quantum<br />
systems. An expansion into localized states allows to restrict a<br />
simulation to a fraction of the environment that is located within a<br />
predefined vicinity of the system. Our approach allows to add and<br />
drop environmental particles during the simulation what provides the<br />
basis for an effective reduction of the size of the system that is being<br />
treated.<br />
Q 38.6 Do 12:30 2D<br />
Generation of arbitrary Dicke states in remote qubits using<br />
linear optics — •Andreas Maser 1 , Christoph Thiel 1 , Uwe<br />
Schilling 1 , Thierry Bastin 2 , Enrique Solano 3 , and Joachim von<br />
Zanthier 1 — 1 Institut für Optik, Information und Photonik, Max-<br />
Planck-Forschungsgruppe, Universität Erlangen-Nürnberg, Germany<br />
— 2 Institut de Physique Nucléaire, Atomique et de Spectroscopie, Université<br />
de Liège, Belgium — 3 Physics department, ASC, and CeNS,<br />
Ludwig-Maximilians-Universität, Munich, Germany<br />
We propose a method for generating any state out of the whole family<br />
of Dicke states (symmetric and non-symmetric) for an arbitrary number<br />
of remote qubits: The method uses the long-lived internal ground<br />
levels of remote particles as qubits and is based on linear optics and<br />
single photon detection. The scheme offers thus access to the complete<br />
basis of the Hilbert space of an N spin-1/2 particle compound system<br />
and its not yet investigated entanglement classes.<br />
In particular, we consider a system of N localized atoms, e.g. ions<br />
stored in a Paul trap, where each of them is characterised by a Λconfiguration.<br />
All atoms are initially coherently excited into the upper<br />
state and the spontaneously emitted photons are collected by photonic<br />
fibres which are connected to photon detectors with polarization sensitive<br />
analyzers placed in front. The latter determine the polarization<br />
state of the registered photons.<br />
Q 38.7 Do 12:45 2D<br />
Single-Particle Interference Can Witness Bipartite Entanglement<br />
— •Torsten Scholak 1 , Florian Mintert 2,3 , and<br />
Cord A. Müller 1 — 1 Physikalisches Institut, Universität Bayreuth,<br />
95440 Bayreuth, Germany — 2 Max-Planck-Institut für Physik Komplexer<br />
Systeme, Nöthnitzerstraße 38, 01187 Dresden, Germany —<br />
3 Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, 79104<br />
Freiburg, Germany<br />
Q 39: Ultrakurze Laserpulse (Erzeugung I)<br />
We propose to realize entanglement witnesses in terms of the interference<br />
pattern of a single quantum probe [1]. After giving a conceptional<br />
recipe, we discuss possible realizations both with electrons in mesoscopic<br />
Aharonov-Bohm rings and with photons in standard Young’s<br />
double-slit or coherent-backscattering interferometers.<br />
[1] arXiv:0710.0825<br />
Q 38.8 Do 13:00 2D<br />
Decoherence properties of entangled single nuclear spins and<br />
one electron spin at room temperature in diamond — •Philipp<br />
Neumann, Torsten Gaebel, Florian Rempp, Christian Zierl, Fedor<br />
Jelezko, and Jörg Wrachtrup — 3. Physikalisches Institut,<br />
Universität Stuttgart, Germany<br />
Generation of long-lived entanglement between single qubits is at the<br />
heart of quantum information processing. Since the coherence between<br />
single qubits in solid state systems is rather fragile one is looking for<br />
qubits with long coherence lifetimes. Those could be nuclear spins.<br />
In our case we use the electron spin of the NV-center in diamond to<br />
generate Bell States between two qubits associated with two proximal<br />
13 C nuclear spins. Eventually the electron spin itself is used as a qubit<br />
and 3-particle entanglement is generated. The decoherence properties<br />
of these entangled states are investigated.<br />
Zeit: Donnerstag 11:00–13:00 Raum: 3H<br />
Q 39.1 Do 11:00 3H<br />
Kurzpulslaserbasierte Erzeugung von 120 Attosekunden<br />
XUV Pulsen mit breitbandiger XUV Optik — •Martin<br />
Schultze 1 , Eleftherios Goulielmakis 1 , Matthias Uiberacker 2 ,<br />
Michael Hofstetter 1 , Ulf Kleineberg 2 und Ferenc Krausz 1,2<br />
— 1 MPI f. Quantenoptik, Garching, Germany — 2 LMU, Dept. Physik,<br />
München, Germany<br />
Durch Ionisierung von Neon mit phasenstabilisierten Infrarotlaserpulsen<br />
mit einer Dauer von weniger als 2 Lichtzyklen und anschliessender<br />
spektraler Filterung der enstehenden Harmonischenstrahlung<br />
durch Reflektion an einem breitbandigen, gechirpten Molybdän-<br />
Silizium Multilayerspiegel wird die Erzeugung isolierter 120 Attosekunden<br />
Pulse im Energiebereich um 100 eV (XUV - Extreme Ultra<br />
Violet) mit ˜10ˆ6 Photonen/Puls bei einer Wiederholrate von 3 kHz<br />
demonstriert<br />
Q 39.2 Do 11:15 3H<br />
Diodenlasergepumpter Nd:YVO4-Ultrakurzpulslaser mit aktiver<br />
Modenkopplung und spektraler Kontrolle der Bandbreite<br />
der Verstärkung — •Markus Lührmann, Christian Theobald<br />
und Richard Wallenstein — TU Kaiserslautern, Fachbereich Physik,<br />
Erwin-Schrödinger-Straße 46, 67663 Kaiserslautern<br />
Diodenlasergepumpte Festkörperlaser mit hoher Impulsenergie, -<br />
wiederhohlrate und -dauer im Bereich von mehreren hundert Pikosekunden<br />
können als Pumplaser eine Basiskomponente für kompakte<br />
hochrepetierende Femtosekundenverstärker darstellen. Die<br />
Schlüsselkomponente eines solchen Pumplasers ist ein modengekoppelter<br />
Masteroszillator der Impulse mit entsprechender Dauer liefert.<br />
Laser, die direkt solche vergleichsweise langen fourierlimitierten Impulse<br />
emittieren, sind jedoch bisher nicht verfügbar. Daher wurde die<br />
Erzeugung langer Pikosekundenimpulse durch die spektrale Einengung<br />
der Verstärkung in einem herkömmlichen aktiv akustooptisch modengekoppelten<br />
Nd:YVO4 Festkörperlaser untersucht. Dieser liefert direkt<br />
Impulse von 34 ps Dauer mit 6,4 W Ausgangsleistung bei einer Impulswiederhohlrate<br />
von 108 MHz und einem M 2 < 1,1. Zur Reduktion der<br />
spektralen Bandbreite der Verstärkung und somit der Erhöhung der<br />
Impulsdauer wurden Etalons im Resonator eingesetzt. Erreicht werden<br />
konnten modengekoppelte Impulse mit einstellbarer Impulsdauer<br />
im Bereich von 34 ps bis über 1 ns und Ausgangsleistungen von<br />
typisch 3 W. Bei fourierlimitierten Impulsen und Impulsdauern von<br />
350 ps wurden Ausgangsleistungen von 5,1 W mit beugungsbegrenztem<br />
Strahl in einem stabilen Betrieb erreicht.<br />
Q 39.3 Do 11:30 3H<br />
Single-walled carbon nanotube saturable absorber modelocked<br />
Yb:KLuW laser — •Andreas Schmidt 1 , Simon Rivier 1 ,<br />
Günter Steinmeyer 1 , Valentin Petrov 1 , Uwe Griebner 1 , Jong<br />
H. Yim 2 , Won B. Cho 2 , Soonil Lee 2 , and Fabian Rotermund 2 —<br />
1 Max-Born-Institut, Max-Born-Straße 2a, D-12489 Berlin, Germany<br />
— 2 Division of Energy Systems Research, Ajou University, 443-749<br />
Suwon, Korea<br />
Recently, single-walled carbon nanotube saturable absorbers<br />
(SWCNT-SA) have gained much attention as a potential replacement<br />
for semiconductor-based ultrafast passive mode-lockers and limiters<br />
[1]. So far, SWCNT-SAs have been utilized to mode-lock lasers in the<br />
1.5 µm wavelength range. Here we compare the mode-locked performance<br />
of an Yb:KLuW laser in the 1 µm spectral range employing a<br />
SWCNT-SA and a semiconductor saturable absorber mirror (SAM).<br />
Using an end-pumped configuration and placing the SAM in a z-shaped<br />
laser cavity, pulses as short as 83 fs are generated at a repetition rate
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
of 94 MHz with a time-bandwith product of 0.32. Implementing the<br />
SWCNT-SA instead of the SAM in the cavity, nearly transform-limited<br />
pulses with a duration of 115 fs at 1047 nm in a soliton-like regime are<br />
obtained. The achieved pulse durations demonstrate the high potential<br />
of the low cost SWCNT-SA to serve as fast saturable absorber for<br />
mode locking applications in the 1–µm spectral range.<br />
[1] Y.-C. Chen, et. al., Appl. Phys. Lett. 81, 975 (2002).<br />
Q 39.4 Do 11:45 3H<br />
Selbstkompression und asymptotische Pulsformen in Filamenten<br />
— •Carsten Krüger 1,2 , Ayhan Demircan 1 und Günter<br />
Steinmeyer 2 — 1 Weierstraß-Institut für Angewandte Analysis und<br />
Stochastik — 2 Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie<br />
Die Propagation von Femtosekunden-Laserpulsen in Filamenten ist ein<br />
bislang noch nicht vollständig verstandenes Phänomen. Im stationären<br />
Fall ist die Selbststabilisierung des transversalen Strahlprofils im Filament<br />
als Folge einer Balance der konkurrierenden Einflüsse von Kerrinduzierter<br />
Selbstfokussierung sowie plasmainduzierter Defokussierung<br />
durch verschiedene experimentelle und theoretische Arbeiten hingegen<br />
recht gut erklärt. Jedoch deuten experimentelle Daten darauf hin, dass<br />
sich zusätzlich zum selbststabilisierenden transversal-räumlichen Profil<br />
im Filament eine stabile Pulsform in der Zeitdomäne einstellt, um<br />
eine optimale Kompensation der konkurrierenden fokussierenden sowie<br />
defokussierenden Effekte zu jedem Zeitpunkt zu garantieren. Die sich<br />
einstellende charakteristisch asymmetrische, selbststabilisierende Pulsform<br />
ist bereits im Vergleich zum Eingangspuls auf wenige Zyklen der<br />
Trägerfrequenz komprimiert und bedarf keiner weiteren Dispersionskompensation,<br />
sondern weist im Gegenteil nach normaler Materialdispersion<br />
eine flache spektrale Phase auf. Wir führen den experimentell<br />
gefundenen negativen Chirp auf die Dispersion der Gruppengeschwindigkeit<br />
im Plasma zurück und zeigen, dass sich im Filament gegen<br />
Störungen stabile charakteristisch asymmetrische Pulsformen bilden<br />
können.<br />
Q 39.5 Do 12:00 3H<br />
Ytterbium Kurzpulsfaserlaser ohne Dispersationskompensation<br />
— •Heike Karow, Michael Schultz, Dieter Wand und Dietmar<br />
Kracht — Laserzentrum Hannover e.V., Hannover, Germany<br />
In aktuellen Arbeiten über modengekoppelte Ytterbium Faserlaser<br />
wurden verschiedene Aufbauten vorgestellt und untersucht, die auf<br />
eine Kompensation der normalen Gruppengeschwindigkeitsdispersion<br />
der verwendeten Fasern vollständig verzichten [1]. Damit konnten sehr<br />
einfache all-fiber Aufbauten realisiert werden, allerdings mit Pulsdauern<br />
im Bereich von etwa 1 ps. Kürzere Pulse (170 fs) wurden kürzlich<br />
auch ohne Dispersionskompensation mit einem Faseroszillator erreicht,<br />
der mit einem resonatorinternen Interferenzfilter versehen war [2].<br />
Wir stellen einen passiv modengekoppelten Ytterbium Faserringlaser<br />
mit resonatorinternem spektralem Filter vor, der ohne Komponenten<br />
mit anomaler Dispersion arbeitet. Der Einfluß der Bandbreite und<br />
Zentralwellenlänge des Filters auf die Lasereigenschaften wie spektrale<br />
Breite, komprimierte Pulsdauer und Energiequantisierung wird diskutiert.<br />
Erste Ergebnisse zeigen spektrale Pulshalbwertsbreiten von 25 nm<br />
bei einer Filterbandbreite von 8 nm. Die Pulse sind stark gechirpt und<br />
können mit einer externen Gitteranordnung auf eine Halbwertsbreite<br />
von 130 fs komprimiert werden.<br />
[1] Prochnow, et.al., Opt. Express, 15, 6889-6893, (2007)<br />
[2] Chong, et.al., Opt. Express, 14, 10095-10100, (2006)<br />
Q 39.6 Do 12:15 3H<br />
Q 40: Quantengase (Bosonen I)<br />
Verkürzung hochenergetischer Laserpulse durch Selbstkompression<br />
in einem Filament — Emilia Schulz, •Thomas Binhammer,<br />
Stefan Rausch, Milutin Kovacev und Uwe Morgner — Institut<br />
für Quantenoptik, Universität Hannover<br />
Das Streben nach immer kürzeren Laserpulsen ist ein andauerndes Forschungsgebiet.<br />
So ist für viele Experimente wie z.B. für die Erzeugung<br />
eines einzelnen Attosekunden-Pulses nicht nur eine hohe Pulsenergie,<br />
sondern auch eine sehr geringe Pulsdauer im Bereich von wenigen optischen<br />
Zyklen wesentlich. Filamentation in einer Edelgaszelle ist ein<br />
kürzlich erstmalig demonstriertes Verfahren, um mit geringem Aufwand<br />
hoch-energetische Pulse spektral zu verbreitern. Wir berichten<br />
hier über die Verkürzung von Pulsen aus einem Millijoule-Ti:Saphir-<br />
Verstärkersystem mittels Filamentation. Es werden systematische Untersuchungen<br />
bezüglich der verschiedenen Parameter wie Druck und<br />
Gassorte und die Strahleigenschaften nach dem Filament vorgestellt.<br />
Durch das Zusammenspiel unterschiedlicher nichtlinearer Effekte bei<br />
der Führung des Strahls im Filament gelingt es auf diese Weise, Pulse<br />
einer Dauer unter 10 fs zu erzeugen, ohne dass eine anschließende<br />
Kompression nötig war.<br />
Q 39.7 Do 12:30 3H<br />
Charakterisierung der Wellenfront von Hoher Harmonischer<br />
Strahlung — •Christian Kern, Stefan Eyring, Jan Lohbreier,<br />
Robert Spitzenpfeil und Christian Spielmann — Physikalisches<br />
Institut, Universität Würzburg, Am Hubland, 97074 Würzburg<br />
Im Bereich der Physik auf Attosekunden-Zeitskalen spielt die Erzeugung<br />
von kohärenter, extrem-ultravioletter (XUV) Strahlung durch<br />
den Prozess der Hohen Harmonischen Erzeugung (HHG) eine wichtige<br />
Rolle. Der komplexe nichtlineare Mechanismus der HHG macht eine exakte<br />
Berechnung der Strahlqualität der erzeugten Strahlung durch Simulationen<br />
nahezu unmöglich. Es werden zwei Methoden der Charakterisierung<br />
vorgestellt: die M2-Messung durch einen Knife-Edge-Scan<br />
und die Vermessung der Wellenfront durch einen Hartmann-Sensor.<br />
Mit den so gewonnenen Daten wird die Wellenfront in der Darstellung<br />
durch Zernike-Polynome eindeutig beschrieben. Eine solche quantitative<br />
Analyse von Hoher Harmonischer Strahlung ist unseres Wissens<br />
noch nicht durchgeführt worden. Desweiteren werden Möglichkeiten<br />
diskutiert, die gewonnene Charakterisierung als Kontrollsignal für die<br />
Formung der zur Erzeugung verwendeten kurzen Laserpulse zu verwenden.<br />
In ersten Experimenten wurde so zum Beispiel eine deutliche<br />
Steigerung der detektierten Ausbeute an Hohen Harmonischen erzielt.<br />
Q 39.8 Do 12:45 3H<br />
Fokussierung Hoher Harmonischer — •Christian Ott, Sebastian<br />
Jung, Nico Franke, Jan Henneberger und Christian Spielmann<br />
— Physikalisches Institut, Universität Würzburg, Am Hubland,<br />
97074 Würzburg<br />
Die Erzeugung Hoher Harmonischer (HHG) hat sich als Methode zur<br />
Herstellung ultrakurzer Laserpulse im XUV (extreme ultraviolet) etabliert.<br />
Allerdings sind die Intensitäten der dabei erzeugten XUV-Pulse<br />
gering, was eine erhebliche Einschränkung im Bereich der experimentellen<br />
Anwendung zur Folge hat. Für eine Vielzahl von Experimenten<br />
ist es daher erforderlich, die erzeugten XUV-Pulse auf einen Interaktionsbereich<br />
zu fokussieren, um höhere Intensitäten zu erhalten. Eine<br />
bereits erfolgreich eingesetzte Technik ist die Verwendung eines Toroidalspiegels<br />
in streifendem Einfall. In diesem Vortrag werden insbesondere<br />
die durch die Strahlgeometrie verursachten Abbildungsfehler<br />
des Spiegels diskutiert. Neben einer Vorstellung der experimentellen<br />
Umsetzung wird auch die Beeinflussung der Form und Lage des Fokus<br />
diskutiert, welche durch eine schlechte Ausrichtung der verwendeten<br />
Optiken hervorgerufen werden kann.<br />
Zeit: Donnerstag 14:00–16:00 Raum: 1A<br />
Q 40.1 Do 14:00 1A<br />
Differences between mean-field dynamics and N-particle<br />
quantum dynamics as a signature of entanglement —<br />
Christoph Weiss1,3 and •Niklas Teichmann2,3 — 1Laboratoire Kastler Brossel, École Normale Supérieure, Université Pierre et Marie-<br />
Curie-Paris 6, CNRS, Paris, France — 2Institut Henri Poincaré, Centre<br />
Emile Borel, Paris, France — 3Institut für Physik, Carl von Ossietzky<br />
Universität, Oldenburg, Germany<br />
A Bose-Einstein condensate in a tilted double-well potential under<br />
the influence of time-periodic potential differences is investigated in<br />
the regime where the mean-field (Gross-Pitaevskii) dynamics become<br />
chaotic. For some parameters near stable regions, even averaging over<br />
several condensate oscillations does not remove the differences between<br />
mean-field and N-particle results. While introducing decoherence via<br />
piecewise deterministic processes reduces those differences, they are<br />
due to the emergence of mesoscopic entangled states in the chaotic
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
regime.<br />
Q 40.2 Do 14:15 1A<br />
Anisotropic scattering of Bogoliubov quasi particles —<br />
•Christopher Gaul and Cord A. Müller — Universität Bayreuth<br />
In order to study the interplay of disorder and interaction in atomic<br />
BECs, we investigate scattering of Bogoliubov quasi particles (BQP)<br />
by the spatial fluctuations of an external optical potential. We first<br />
calculate the amplitude for a single scattering event. In contrast to<br />
the case of noninteracting particles, the scattering amplitude of BQPs<br />
has a sign change and consequently a node at a certain angle. In the<br />
long-wavelength limit, we understand this as a fundamental soundwave<br />
property, which becomes apparent in a hydrodynamic formulation.<br />
This scattering anisotropy has the curious consequence that in<br />
the 2D multiple-scattering regime the diffusive Boltzmann transport<br />
length becomes shorter than the scattering mean free path for particlelike<br />
excitations scattered by short-range correlated potentials.<br />
Q 40.3 Do 14:30 1A<br />
Commuting Heisenberg operators in the Wigner representation<br />
— •Bettina Berg 1 , Lev Plimak 1 , Murray K. Olsen 2 ,<br />
Michael Fleischhauer 3 , and Wolfgang P. Schleich 1 — 1 Institute<br />
of Quantum Physics, Ulm University, Germany — 2 School of Physical<br />
Sciences, University of Queensland, Australia — 3 Fachbereich Physik,<br />
Technische Universität Kaiserslautern, Germany<br />
We discuss commuting Heisenberg operators as a response problem in<br />
the phase space. In the Wigner representation one calculates averages<br />
of symmetrically ordered two-time operator pairs [1]. As the quantities<br />
that are experimentally measured are the time-normally ordered correlation<br />
functions, we need a way of commuting Heisenberg operators at<br />
different times. For an operator pair, solution to this problem is given<br />
by Kubo’s linear response relation [2] expressing the commutator as<br />
a linear response function. This quantity can be found in the Wigner<br />
representation simply by adding sources to the “Langevin” equations<br />
in the phase space. By using the truncated Wigner representation [3],<br />
one can calculate the normally-ordered correlation functions approximately<br />
yet with relative ease. These techniques are demonstrated for<br />
the Bose-Hubbard model [4].<br />
[1] L. I. Plimak, M. K. Olsen, M. Fleischhauer, M. J. Collett, Europhys.<br />
Lett. 56, 372 (2001). [2] R. Kubo, Lectures in Theoretical<br />
Physics, v. 1 (Wiley, New York, 1959). [3] M. J. Werner, P. D. Drummond,<br />
J. Comput. Phys. 132, 312 (1997). [4] D. Jaksch, C. Bruder,<br />
J. I. Cirac, C. W. Gardiner, P. D. Zoller, Phys. Rev. Lett. 81, 3108<br />
(1998).<br />
Q 40.4 Do 14:45 1A<br />
Transverse instability of straight vortex lines in dipolar Bose-<br />
Einstein condensates — •Michael Klawunn 1 , Rejish Nath 1 ,<br />
Paolo Pedri 2 , and Luis Santos 1 — 1 Institut für Theoretische Physik<br />
, Leibniz Universität Hannover, Appelstr. 2, D-30167, Hannover, Germany<br />
— 2 Laboratoire de Physique Theorique et Modeles Statistiques,<br />
Universite Paris Sud, 91405 Orsay Cedex, France<br />
The physics of vortex lines in dipolar condensates is studied. Due to the<br />
nonlocality of the dipolar interaction, the 3D character of the vortex<br />
plays a more important role in dipolar gases than in typical shortrange<br />
interacting ones. In particular, the dipolar interaction significantly<br />
affects the stability of the transverse modes of the vortex line.<br />
Remarkably, in the presence of a periodic potential along the vortex<br />
line, the spectrum of transverse modes shows a roton minimum, which<br />
eventually destabilizes the straight vortex when the BEC as a whole<br />
is still stable, opening the possibility for new scenarios for vortex-line<br />
configurations in dipolar gases.<br />
Q 40.5 Do 15:00 1A<br />
The spectrum of a non-Hermitian two-mode Bose-Hubbard<br />
system — •Eva-Maria Graefe 1 , Uwe Guenther 2 , Astrid<br />
Niederle 1 , and Hans Jürgen Korsch 1 — 1 TU Kaiserslautern, Germany<br />
— 2 Forschungszentrum Dresden Rossendorf, Germany<br />
We study an N-particle, two-mode Bose-Hubbard system, modelling<br />
a Bose-Einstein condensate in a double-well potential. By introduc-<br />
ing effective complex energies to the modes we describe a coupling<br />
to a continuum. The eigenvalues of the resulting non-Hermitian matrix<br />
model are in general complex where the imaginary parts describe<br />
the decay rate into the continuum. In dependence on the systems parameters,<br />
the eigenvalues show intricate patterns of avoided and real<br />
crossings, as well as characteristic bifurcations. In the present talk the<br />
effect of the interplay between the particle interaction and the non-<br />
Hermiticity on characteristic features of the spectrum is analysed and<br />
its peculiarities are clarified by perturbational methods.<br />
Q 40.6 Do 15:15 1A<br />
Phase fluctuations in one-dimensional quasi-condensates<br />
— •Stephanie Manz, Thomas Betz, Christian Koller,<br />
Robert Bücker, Wolfgang Rohringer, Aurélien Perrin,<br />
Thorsten Schumm, and Jörg Schmiedmayer — Atominstitut der<br />
Österreichischen Universitäten, Technische Universität Wien, Stadionallee<br />
2, A-1020 Vienna, Austria<br />
Due to the possibility to fabricate wire structures down to the micrometer<br />
scale, atomchips are ideally suited to examine ultracold onedimensional<br />
systems. In contrast to the three-dimensional case, onedimensional<br />
sytems do not exhibit long-range order. The respective<br />
phase fluctuations can either be seen in interference experiments with<br />
split one-dimensional Bose-Einstein condensates [1,2] or by directly<br />
observing density modulations in time-of-flight images [3].<br />
We study the ballistic expansion of tightly confined atomic clouds<br />
and compare the results to theory.<br />
[1] S. Hofferberth et al., Nature Phys. 2 710 (2006).<br />
[2] G.-B. Jo et al., arXiv:0706.4041v3<br />
[3] D. Hellweg et al., Appl. Phys. B 73 173 (2001).<br />
Q 40.7 Do 15:30 1A<br />
Bose-Einstein condensates and optical waveguides — •J. Nes,<br />
S. Hertsch, M. Krutzik, T. Lauber, O. Wille, and G. Birkl —<br />
Institut für Angewandte Physik, Technische Universität Darmstadt,<br />
Schlossgartenstr. 7, 64289 Darmstadt<br />
Achieving Bose-Einstein condensation in optical potentials has been<br />
tried since the early days of laser cooling. The first BEC in a dipole<br />
trap was created with a CO2 laser. Since then, achieving BEC in optical<br />
potentials is routine. However, using a CO2 laser to trap and<br />
evaporate atoms is favourable for some, but might be inconvenient for<br />
other implementations. Therefore, several groups have been trying to<br />
create BECs by trapping atoms with lasers with lower wavelengths. So<br />
far, only few groups have reached condensation with a laser having a<br />
wavelength in the one micron range by simple means.<br />
Our work aims at creating ultracold atom samples in the submicroKelvin<br />
temperature range and especially BECs, in a crossed optical<br />
dipole trap made with a laser with a wavelength of 1030 nm.<br />
After reaching these temperatures, the atoms are transferred into an<br />
optical guiding or storing structure created by microfabricated optical<br />
elements, so that the coherence properties can be studied. One of our<br />
projects is to guide the atoms along a waveguide and past a corrugated<br />
optical potential surface, such as an optical lattice, in order to investigate<br />
the modification of the wavepacket dynamics as compared to an<br />
uncorrugated guiding structure.<br />
Q 40.8 Do 15:45 1A<br />
Quantum chaos limits DMRG efficiency — •Hannah Venzl 1 ,<br />
Florian Mintert 1 , Andrew Daley 2 , and Andreas Buchleitner 1<br />
— 1 Physikalisches Institut, Albert-Ludwigs-Universität Freiburg,<br />
Hermann-Herder-Str. 3, 79104 Freiburg, Germany — 2 Institut für Theoretische<br />
Physik, Universität Innsbruck, Technikerstr. 25, 6020 Innsbruck,<br />
Austria<br />
The spectrum of the Bose-Hubbard Hamiltonian exhibits quantum<br />
chaos for certain ranges of the system parameters. One possible way<br />
to probe the chaos transition in this system is by tuning the strength<br />
of an additional static force. Likewise, the efficiency of time-dependent<br />
Density Matrix Renormalization Group (t-DMRG) simulations of the<br />
system dynamics depends strongly on the applied static field. We probe<br />
the connections between this loss of efficiency and the underlying spectral<br />
structure.
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
Q 41: Quanteninformation (Konzepte und Methoden III)<br />
Zeit: Donnerstag 14:00–16:00 Raum: 1B<br />
Q 41.1 Do 14:00 1B<br />
Channel Representation of Quantum Error-Correcting<br />
Codes — •Johannes Gütschow, Holger Vogts, and Reinhard<br />
Werner — Institut für Mathematische Physik, TU Braunschweig,<br />
www.imaph.tu-bs.de<br />
Quantum error-correcting codes (qeccs) are essential for most of the<br />
proposed realizations of quantum computation to correct errors due<br />
to decoherence. Quantum convolutional codes (qccs) are a promising<br />
candidate for on line encoding and decoding of a flow of quantum<br />
information thus enabling the sending party to begin with the transmission<br />
of quantum information before the end of the flow (or a block)<br />
is reached. Analogously the decoding process can begin before the end<br />
of the transmission. Until now, only the noise and interaction with<br />
the environment were described in the channel formalism. We investigate<br />
qeccs and describe their encoders as channels. Block encoders are<br />
represented by memoryless channels, whereas convolutional encoders<br />
are described by memory channels. Convolutional encoders need to be<br />
”non-catastrophic”, meaning an error on a single source qubit should<br />
only affect a finite number of target qubits. We investigate the relation<br />
between this condition and the ”forgetfulness”-property of quantum<br />
memory channels.<br />
Q 41.2 Do 14:15 1B<br />
Quasi-Free States on Clifford Quantum Cellular Automata<br />
— •Sonja Uphoff 1 , Zoltan Zimboras 2 , and Reinhard<br />
Werner 1 — 1 Institut für Mathematische Physik, TU Braunschweig,<br />
www.imaph.tu-bs.de — 2 Theoretische Physik, Universität des Saarlands,<br />
www.uni-saarland.de/fak7/rieger<br />
Clifford Quantum Cellular Automata (CQCA) are a particularly simple<br />
class of Quantum Cellular Automata that can be used for generating<br />
entanglement. We are interested in the asymptotics of states under<br />
CQCA action, one aspect being entanglement of invariant states. For<br />
a special class of CQCA it is possible to obtain these states on the spin<br />
chain by employing the Araki Jordan-Wigner transformation between<br />
the spin chain and the fermionic chain. In this case we can construct<br />
quasi-free states that are invariant under the time evolution of the<br />
CQCA.<br />
Q 41.3 Do 14:30 1B<br />
Completeness of classical spin systems and universal quantum<br />
computation — •Gemma De las Cuevas 1 , Robert Hübener 1 ,<br />
Maarten Van den Nest 1 , Wolfgang Dür 1,2 , and Hans J.<br />
Briegel 1,2 — 1 Institut für Quantenoptik und Quanteninformation der<br />
Österreichischen Akademie der Wissenschaften, Innsbruck, Austria —<br />
2 Institut für Theoretische Physik, Universität Innsbruck, Technikerstraße<br />
25, A-6020 Innsbruck, Austria<br />
It was recently shown [quant-ph/0708.2275] how classical spin models,<br />
such as the Ising and Potts models on arbitrary graphs, can be mapped<br />
onto the stabilizer formalism from quantum information theory. Moreover,<br />
by invoking the universality of the one-way quantum computer<br />
it was proven how the partition function on an arbitrary graph can<br />
be expressed as a special instance of the Ising partition function on a<br />
2D square lattice. However, in order to obtain this result the coupling<br />
strengths and local magnetic fields on the 2D square lattice had to be<br />
complex, and thus did not allow for a physical interpretation. In this<br />
talk, we will first present the completeness of the 2D Ising model with<br />
complex parameters and we will then show that a complete model with<br />
real parameters is obtained when the 3D Ising model is considered. We<br />
will further investigate how generalizations of the 2D Ising model allow<br />
us to strengthen the completeness results, and will consider other<br />
possible mappings between the partition function and the quantum<br />
stabilizer formalism.<br />
Q 41.4 Do 14:45 1B<br />
Three-tangle for mixtures of generalized GHZ and generalized<br />
W states — •Christopher Eltschka 1 , Andreas Osterloh 2 ,<br />
and Jens Siewert 1 — 1 Institut für theoretische Physik, Universität<br />
Regensburg, D-93040 Regensburg, Germany — 2 Institut für theoretische<br />
Physik, Leibnitz Universität Hannover, D-30167 Hannover, Germany<br />
The occurrence of entanglement in multipartite systems is one of the<br />
most important and distinctive features in quantum theory. While<br />
mixed state entanglement of two qubits is already well understood,<br />
for three qubits even for the simplest case of rank-2 mixed states, no<br />
general solution is known.<br />
We give analytic expressions for the three-tangle and corresponding<br />
optimal decompositions for a class of mixed states consisting of a<br />
generalized GHZ and an orthogonal generalized W state. We derive<br />
a characteristiic structure of the three-tangle function which is independend<br />
of the choice of the generalized GHZ and W states to be<br />
mixed. Especially we identify the “zero simplex” of all states inside<br />
the corresponding Bloch sphere with zero three-tangle.<br />
Moreover, as a special case we obtain a general solution for a family<br />
of states consisting of a generalized GHZ state and an orthogonal<br />
product state. For that case, we provide an analytic solution for all<br />
mixed states inside the Bloch sphere defined by those two states.<br />
Q 41.5 Do 15:00 1B<br />
Phase-space Characterization of Multipartite Entanglement<br />
— •Agung Budiyono 1 , Alejo Salles 1,2 , Fernando de Melo 1 ,<br />
Thomas Wellens 1 , and Andreas Buchleitner 1 — 1 Physikalisches<br />
Institut Albert-Ludwigs-Universität Freiburg, Hermann-Herder-Str. 3,<br />
D-79104, Freiburg, Germany — 2 Instituto de Física, Universidade Federal<br />
do Rio de Janeiro,<br />
We consider a sequence of two levels atoms interacting one by one<br />
resonantly with a cavity sustaining a single mode, according to the<br />
Jaynes-Cummings model. We evaluate the amount of entanglement in<br />
the initial atomic state which is needed to prepare certain classes of<br />
target field state. Furthermore, we investigate how this entanglement<br />
should be shared by the different subsystems in order to optimize the<br />
target field state creation. In this way, we explore how the multipartite<br />
entanglement of the initial atoms is mapped onto the phase-space of<br />
the field in the cavity.<br />
Q 41.6 Do 15:15 1B<br />
Entanglement Quantum Nondemolition Measurement —<br />
Bruno de Moura Escher 1 , •Fernando de Melo 2 , Ruynet L.<br />
de Matos Filho 1 , Andreas Buchleitner 2 , and Luiz Davidovich 1<br />
— 1 Instituto de Física, Universidade Federal do Rio de Janeiro,<br />
Caixa Postal 68528, Rio de Janeiro RJ 21941-972, Brazil<br />
— 2 Physikalisches Institut, Albert-Ludwigs-Universität Freiburg,<br />
Hermann-Herder-Strasse 3, D-79104 Freiburg, Germany<br />
We present a quantum circuit which allows for the nondemolition measurement<br />
of a two-qubit system. The protocol employs two simultaneous<br />
copies of the state, in order to give an operational meaning to<br />
the entanglement measure, an can thus be applied for all pure states.<br />
The complementarity relation between single particle characteristics<br />
and bipartite entanglement is scrutinized in the light of the proposed<br />
measurement.<br />
Q 41.7 Do 15:30 1B<br />
Decoherence protection for nuclear spin quantum memory<br />
in a quantum dot — •Zoltan Kurucz 1 , Martin Sørensen 2 , and<br />
Michael Fleischhauer 1 — 1 Fachbereich Physik, TU Kaiserslautern<br />
— 2 Nils-Bohr Institute, Kopenhagen<br />
We reconsider the possibility of storing quantum information in an<br />
ensemble of nuclear spins constituting a semiconductor quantum dot<br />
[1]. The nuclear magnetic moments are collectively interacting with an<br />
excess electron of the quantum dot through inhomogeneous hyperfine<br />
coupling. We present a configuration in which the collective nuclear<br />
spin states used as the qubit basis are energetically separated from the<br />
remaining states, thus protecting the quantum memory from various<br />
sources of decoherence.<br />
[1] J. Taylor, C. Marcus, M. Lukin, Phys. Rev. Lett. 90, 206803<br />
(2003)<br />
Q 41.8 Do 15:45 1B<br />
Covariance Matrices as a Tool in Entanglement Theory<br />
— •Oleg Gittsovich 1,2 , Otfried Gühne 1 , Philipp Hyllus 3 , and<br />
Jens Eisert 4 — 1 Institut für Quantenoptik und Quanteninformation,<br />
Österreichische Akademie der Wissenschaften, *Institut für<br />
Quantenoptik und Quanteninformation, Österreichische Akademie der<br />
Wissenschaften, Otto-Hittmair-Platz, 1, 6020 Innsbruck, Austria —<br />
2 Institut für Theoretische Physik,Universität Innsbruck, Techniker-
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
strasse 25, 6020 Innsbruck, Austria — 3 Institut für Theoretische<br />
Physik, Universität, Hannover, Appelstrasse 2, 30167 Hannover, Germany<br />
— 4 QOLS, Blackett Laboratory, Imperial College London,<br />
Prince Consort Road, London SW7 2BW, UK, Institute for Mathematical<br />
Sciences, Imperial College London, Prince’s Gate, London<br />
SW7 2PE, UK<br />
One of the most interesting features of a quantum state from the point<br />
of view of the quantum information theory is entanglement. Entangled<br />
states are used everywhere in this field and allow to achieve such<br />
tasks as teleportation of a quantum state, quantum communication for<br />
two or more parties and intensively used in quantum computation and<br />
quantum cryptography.<br />
In this talk we will have look at this problem from perspective of<br />
view, which uses familiar notions like variances and covariance matrix<br />
(CM).<br />
Q 42: Ultrakalte Atome (Manipulation und Detektion / Quantengase)<br />
Zeit: Donnerstag 14:00–16:00 Raum: 1C<br />
Gruppenbericht Q 42.1 Do 14:00 1C<br />
Direct observation of individual atoms in an optical lattice —<br />
•Tatjana Gericke, Peter Würtz, Daniel Reitz, Tim Langen, and<br />
Herwig Ott — Institut für Physik, Johannes Gutenberg-Universität,<br />
55099 Mainz<br />
Ultracold atoms in optical lattices have demonstrated to be an interesting<br />
system to study quantum phenomena such as quantum phase<br />
transitions and strongly correlated many-body systems. The lattice<br />
spacing in such systems ranges from 400 nm to 600 nm. Although many<br />
different detection schemes have been developed, a high resolution in<br />
situ imaging system with single atom sensitivity is still lacking. Our<br />
new imaging technique is based on the principles of scanning electron<br />
microscopy in combination with electron impact ionization. A 6 keV<br />
electron beam with a FWHM of around 200 nm is scanned across the<br />
atom cloud and ionizes an atom. The resulting ion is subsequently<br />
extracted with the aid of ion optics and detected by a channeltron<br />
detector.<br />
We use an all optical BEC approach in a single beam CO2 optical<br />
dipole trap and produce a 87 Rb condensate with up to 120000 atoms.<br />
The condensate is then loaded into an optical lattice. The optical lattice<br />
has a spacing of 604 nm and is formed by two focused laser beams<br />
with a wavelength of 854 nm intersecting each other under an angle<br />
of 90 degrees. We can observe single lattice sites of the optical lattice<br />
with the new imaging technique. The current status of the experiment<br />
is presented.<br />
Q 42.2 Do 14:30 1C<br />
State-selective microwave potentials on atom chips — •Max<br />
F. Riedel 1,2 , Pascal Böhi 1,2 , Johannes Hoffrogge 1,2 , Theodor<br />
W. Hänsch 1,2 , and Philipp Treutlein 1,2 — 1 Max-Planck-Institut<br />
für Quantenoptik, Garching — 2 Fakultät für Physik, Ludwig-<br />
Maximilians-Universität München<br />
We report on current results of our experiment with microwave nearfields<br />
on an atom chip.<br />
The integrated miniaturized microwave guiding structures on our<br />
chip allow the generation of microwave near-fields with unusually<br />
strong gradients. Through microwave dressing of hyperfine states, these<br />
can be used to create state-selective double-well potentials. Such potentials<br />
have applications in quantum information processing, the study<br />
of Josephson effects, and could be used to entangle atoms via stateselective<br />
collisions.<br />
Q 42.3 Do 14:45 1C<br />
Coupling of Bose-Einstein condensates to mechanical cantilevers<br />
on an atomchip — •David Hunger 1,2 , Stephan<br />
Camerer 1,2 , Daniel König 2 , Jörg P. Kotthaus 2 , Jakob Reichel 3 ,<br />
Theodor W. Hänsch 1,2 , and Philipp Treutlein 1,2 — 1 Max-Planck-<br />
Institut für Quantenoptik, Garching — 2 Fakultät für Physik, Ludwig-<br />
Maximilians-Universität, München — 3 LKB, E.N.S., Paris<br />
We report on the current status of our experiment which aims at coupling<br />
a BEC on an atomchip to the motion of mechanical oscillators.<br />
We have considered different coupling schemes to realize an interaction<br />
between the two systems. The strongest coupling can be realized<br />
by a magnetic interaction, which is mediated by a ferromagnetic island<br />
on the tip of a nanomechanical cantilever. In this scenario, the<br />
resonator motion causes an oscillating magnetic field that can drive<br />
atomic spin-flip transitions. In a first experiment we want to use this<br />
to probe the thermal motion of the cantilever with the atoms. [P.<br />
Treutlein et al., PRL 99, 140403 (2007)]<br />
In an alternative approach we consider a pure mechanical coupling,<br />
mediated by a standing wave dipole trap that is realized by reflecting<br />
a red detuned laser on the tip of an AFM cantilever. The motion of<br />
the cantilever causes motion of the standing wave, being the trap of a<br />
BEC. If the oscillation of the cantilever is resonant with the transition<br />
to the first excited motional state of the BEC, the transfer of atoms<br />
to the excited state can be used to probe the motion of the cantilever.<br />
Q 42.4 Do 15:00 1C<br />
Bose-Einstein Condensation of Dark-State Polaritons in<br />
Atomic Vapour — •Johannes Otterbach, Razmik Unanyan, and<br />
Michael Fleischhauer — TU Kaiserslautern, Germany<br />
We propose a mechanism for Bose-Einstein condensation (BEC) of<br />
dark-state polaritons in an atomic vapour. Dark-state polaritons<br />
(DSPs) are created in the Raman interaction of laser fields with atoms<br />
and are the basis of phenomena such as ultra-slow, stopped, and stationary<br />
light. In contrast to exciton-polaritons they have a very long<br />
intrinsic lifetime on the order of milliseconds. Stationary DSPs created<br />
by counter-propagating Raman pump fields have a quadratic dispersion<br />
profile with a variable mass tensor. Due to the small effective mass<br />
of these quasi-particles, the corresponding condensation temperature<br />
can be 4 orders of magnitude higher than that of the atomic vapour.<br />
After introduction of stationary light dark-state polaritons we discuss<br />
their incoherent generation and thermalization and analyze conditions<br />
for their condensation. Finally potential methods for an experimental<br />
observation of the Bose-Einstein condensation will be discussed.<br />
Q 42.5 Do 15:15 1C<br />
A Magnetic Ring Trap for Multiply Connected Quantum<br />
Gases and Atom Interferometry — Ryan Olf, Edward Marti,<br />
Enrico Vogt, •Anton Öttl, and Dan Stamper-Kurn — Department<br />
of Physics, University of California, Berkeley, CA 94720<br />
We are currently constructing a novel and improved experimental apparatus<br />
to create non-trivial, multiply connected trap geometries for<br />
quantum gases and atom interferometry.<br />
For this setup we employ specialized, microfabricated magnetic coils<br />
which will generate very smooth and tightly confining trapping fields of<br />
torroidal shape. The radius of the magnetic ring trap can be controlled<br />
and adjusted over a wide range, from tens of microns to millimeters.<br />
We aim to load the ring trap with both rubidium and lithium atoms.<br />
This will allow us to explore diverse regimes of matterwave interferometry<br />
with fermionic and bosonic atoms of differing interaction strengths<br />
and possibly overcome current limitations. A Sagnac-type atom interferometer<br />
in a mm-sized ring has the potential to greatly surpass the<br />
resolution of existing gyroscopes. However, working with smaller ring<br />
radii our goal is to fill the whole ring with degenerate quantum gases<br />
and to study the effects of this non-trivial topology on coherence and<br />
dynamics of Bose-Einstein condensates.<br />
The ongoing status of the experiment will be presented. We describe<br />
the performance of our dual-species oven and Zeeman slower design<br />
loading the double MOT and present measurements to demonstrate<br />
the quality of our magnetic ring trap.<br />
Q 42.6 Do 15:30 1C<br />
Kollektive Effekte in Ringresonatoren im Quantenregime —<br />
•Gordon Krenz, Simone Bux, Sebastian Slama, Philippe Courteille<br />
und Claus Zimmermann — Universität Tübingen, Auf der<br />
Morgenstelle 14, 72076 Tübingen, Germany<br />
In unserem Experiment untersuchen wir die Wechselwirkung zwischen<br />
ultrakalten thermischen und Bose-Einstein-kondensierten Atomen und<br />
dem Lichtfeld eines High-Finesse-Resonators. Dabei werden ultrakalte<br />
87 Rb-Atome in das Modenvolumen eines einseitig gepumpten Ringresonators<br />
geladen. Die Umstreuung von Pumplicht durch die Atome
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
gehorcht einer sichselbstverstärkenden Dynamik, die durch einen Anstieg<br />
der Intensität des Lichtfeldes in der nicht gepumpten Richtung<br />
zu beobachten ist. Dieses Verhalten ist als CARL-Effekt (Collective<br />
Atomic Recoil Lasing) bekannt und von unserer Arbeitsgruppe untersucht<br />
worden. Die Impulsverteilung der Atome wird durch den CARL-<br />
Effekt beeinflusst, da bei der Umstreuung eines Photons ein Impuls<br />
der Größe p = 2k übertragen wird. Beim CARL-Effekt gibt es verschiedene<br />
Regime, die sich unter anderem in der Anzahl bei einer Umstreuung<br />
gekoppelter Impulszustände unterscheiden. Unsere bisherigen<br />
Experimente beschränkten sich auf das semiklassische Regime, bei dem<br />
mehrere Impulszustände miteinander gekoppelt sind, was zu einer breiten<br />
Impulsverteilung führt. Ein verbesserter Experimentieraufbau soll<br />
uns nun die Untersuchung des Quantenregimes ermöglichen, bei dem<br />
ausschließlich benachbarte Impulszustände gekoppelt werden.<br />
Q 42.7 Do 15:45 1C<br />
Q 43: Photonik III<br />
Landau levels of cold atoms in non-Abelian gauge fields —<br />
•Andreas Jacob 1 , Patrik Öhberg 2 , Gediminas Juzeliunas 3 , and<br />
Luis Santos 1 — 1 Institut für Theoretische Physik, Leibniz Universität<br />
Hannover — 2 SUPA, Department of Physics, Heriot-Watt University,<br />
Edinburgh, UK — 3 Institute of Theoretical Physics and Astronomy of<br />
Vilnius University, Lithuania<br />
Recent proposals have shown that by properly designed laser arrangements<br />
or lattice setups it is possible to induce artificial gauge fields,<br />
which can even be non-Abelian. In this contribution, we will first discuss<br />
simple laser setups that allow the creation of non-Abelian gauge<br />
fields. Then the Landau levels of cold atomic gases in non-Abelian<br />
gauge fields are analyzed. In particular we identify effects on the energy<br />
spectrum and density distribution which are purely due to the<br />
non-Abelian character of the fields. In a second part, we discuss non-<br />
Abelian generalizations of both the Landau and the symmetric gauge,<br />
and how these can be generated.<br />
Zeit: Donnerstag 14:00–16:00 Raum: 2B/C<br />
Q 43.1 Do 14:00 2B/C<br />
Discreteness in Time — •Christoph Bersch, Georgy Onishchukov,<br />
and Ulf Peschel — Institut für Optik, Information<br />
und Photonik (Max-Planck Forschungsgruppe), Universität Erlangen-<br />
Nürnberg, Günther-Scharowsky-Str. 1 / Bau 24, 91058 Erlangen<br />
In the past nonlinear optics was restricted to homogenous systems.<br />
Only recently it was shown that periodically modulated transverse index<br />
structures can effectively discretize continuous space, thus allowing<br />
for the observation of completely new phenomena of wave propagation<br />
and soliton formation. We show that respective concepts can be<br />
transferred to the temporal domain. The idea is to launch a periodical<br />
amplitude-modulated field, which forms an effective potential for<br />
a signal wave propagating at a different wavelength. The advantage of<br />
temporal systems is that light can propagate in fibers over tens of kilometers,<br />
a span which can again be extended by several orders of magnitude<br />
by including optical amplification. In addition, time windows<br />
are basically not restricted thus providing almost unlimited space for<br />
transverse evolution. Although our main target is to reproduce spatial<br />
effects in the temporal domain, the controlled interaction of optical<br />
pulses with a temporal lattice could add new degrees of freedom to<br />
pulse shaping, regeneration and processing.<br />
Q 43.2 Do 14:15 2B/C<br />
Simulation und Herstellung von Subwellenlängengittern auf<br />
Basis von Aluminium und Aluminiumoxid — •Norbert Bergner,<br />
Jörg Petschulat, Ernst-Bernhard Kley, Thomas Pertsch<br />
und Andreas Tünnermann — Friedrich-Schiller-Universität Jena, Institut<br />
für Angewandte Physik (IAP)<br />
Die Lithographie tendiert seit Jahrzehnten dazu immer kleinere Strukturen<br />
herzustellen, wobei der Bereich von wenigen Nanometern Strukturbreite<br />
noch immer mit erheblichen Schwierigkeiten verbunden ist.<br />
Unter Einbeziehung der natürlichen Schichtdicke von Aluminiumoxid<br />
wird ein Ansatz verfolgt, der Strukturbreiten von etwa 1,5 bis 3 nm<br />
in Gitterstrukturen realisieren kann. Anwendungsbeispiel des Verfahrens<br />
sind metallische Nano-Gitter, die propagierende oder lokalisierte<br />
Oberflächenplasmonen unterstützen.<br />
Das Ziel der Untersuchung ist die Realisierung eindimensionaler Aluminiumgitter<br />
und deren gezielter Oberflächen- und Barrierenoxidation.<br />
Dies führt zur Entstehung von plasmonischen Wellenleitern, welche<br />
eine MIM (metal insulator metal) Konfigurationen darstellen. Die dabei<br />
auftretenden Resonanzen liegen im VIS / NIR. Nahfeldrechnungen<br />
mittels FDTD (finite difference time domain) und FMM (fourier modal<br />
method) zeigen, dass es sich dabei um Eigenmoden des plasmonischen<br />
Wellenleiters handelt.<br />
Dabei wird verstärkt an der experimentellen Umsetzung solcher Geometrien<br />
mittels RIE (reactive ionbeam etching) gearbeitet. Dazu ist<br />
es nötig, die Gitterparameter mittels verschiedener Messvorrichtungen<br />
während des Prozesses zu überprüfen.<br />
Q 43.3 Do 14:30 2B/C<br />
Surface States and Kramers-Kronig Relations in onedimensional<br />
Photonic Crystals — •Michael Bergmair and Kurt<br />
Hingerl — CD-Labor für oberflächenoptische Methoden, Institut für<br />
Halbleiter- und Festkörperphysik, Universität Linz, Austria<br />
Surface states provide very interesting features such as large field enhancement<br />
and are very sensitive to the geometry and dielectric behaviour<br />
of the investigated structure. A thin metallic sheet allows to<br />
investigate the near field and permits a design of a system with negative<br />
refracting behaviour.<br />
A one-dimensional photonic crystal consisting of layers which have a<br />
resonant dielectric behaviour in the infrared (photon-phonon coupling)<br />
show very interesting surface states: due to the coupling of bulk and<br />
surface states around the resonant frequency a dispersion with negative<br />
group velocity occurs. In this region the damping remains small<br />
yielding a large figure of merit n ′ /n ′′ which is the ratio of real and<br />
imaginary part of the dielectric function.<br />
In our work we will calculate the dispersion of such coupled surface<br />
states and unveil the mechanism that leads to this small damping<br />
values. Furthermore we investigate whether and how Kramers-Kronig<br />
relations can be applied to systems where the internal structure is on<br />
the order of the wavelength.<br />
Q 43.4 Do 14:45 2B/C<br />
Time-domain investigation of backward-wave formation in<br />
negative index materials — •Ulrich Dobramysl and Kurt<br />
Hingerl — Christian Doppler Labor für Oberflächenoptische Methoden,<br />
Institut für Halbleiter- und Festkörperphysik, Johannes Kepler<br />
Universität Linz, Austria<br />
We study the properties of negative index structures using the FDTD<br />
method by directly investigating the electromagnetic fields at the<br />
boundary between air and a region with negative µ and ɛ. The material<br />
consists of split ring resonator (SRR) structures[1] with negative<br />
permeability. These SRRs are embedded in a material exhibiting a<br />
Lorenz resonance and thus negative ɛ. The formation of a backward<br />
wave is studied. The FTDT simulation shows that it takes around 20-<br />
40 wavefronts until negative refraction is built up. During this initial<br />
time positive refraction exists and a damped wave propagates with a<br />
positive k-vector into the material.<br />
The effective material parameters are extracted by means of the the<br />
Fresnel equations. Using the Fresnel formulas it is possible to extract<br />
the effective permeability and permittivity by investigating the wave<br />
pattern at an interface without relying on reflection and transmission<br />
measurements. The field summation method[2] is used to complement<br />
this method.<br />
[1] J. B. Pendry, A. J. Holden, D. J. Robbins, and W. J. Stewart:<br />
IEEE Transactions on Microwave Theory and Techniques, 47, 2075<br />
(1999)<br />
[2] D. R. Smith, J. B. Pendry: J. Opt. Soc. Am. B, 23, 391 (2006)<br />
Q 43.5 Do 15:00 2B/C<br />
Räumliche photorefraktive Pikosekunden-Solitonen im Bereich<br />
hoher Lichtintensitäten — •Clemens Heese 1,2 , Jörg<br />
Imbrock 1,2 und Cornelia Denz 1,2 — 1 Institut für Angewandte Physik,<br />
Westfälische Wilhelms-Universität, 48149 Münster — 2 Center for<br />
Nonlinear Science, 48149 Münster<br />
Räumliche photorefraktive Solitonen sind aufgrund ihrer Möglichkeit,
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
selbstinduzierte Wellenleiter zu bilden, von großem Interesse. Ein fokussierter<br />
Laserstrahl führt in einem photorefraktiven Material zu einer<br />
Umverteilung von Ladungsträgern, so dass sich ein internes räumlich<br />
moduliertes Raumladungsfeld aufbaut, welches über den elektrooptischen<br />
Effekt den Brechungsindex verändert. Bei geeigneter Wahl der<br />
experimentellen Parameter kann die Dispersion des Laserstrahls durch<br />
die Selbstfokussierung kompensiert werden, so dass sich ein optisch<br />
räumliches Soliton bildet.<br />
Die hier vorgestellten Ergebnisse zeigen erstmals, dass sich räumliche<br />
Solitonen in SBN (Strontium Barium Niobat) Kristallen mit Hilfe von<br />
1 ps, 532 nm Laserpulsen großer optischer Intensität erzeugen lassen.<br />
Dazu wird der Kristall mit einem Hintergrundpuls gleicher Dauer beleuchtet,<br />
um die Sättigung der photorefraktiven Nichtlinearität einzustellen.<br />
Die zeitliche Verzögerung des Hintergrundpulses gegenüber<br />
dem Solitionenpuls hat einen entscheidenden Einfluss auf die Solitonenbildung.<br />
Genauere Untersuchungen betrachten das räumliche Intensitätsprofil<br />
und die zeitliche Dynamik der Solitonen in Abhängigkeit<br />
von den Pulsintensitäten, den Verhältnissen der Pulsintensitäten und<br />
der zeitlichen Verzögerungen von Soliton- zu Hintergrundpuls.<br />
Q 43.6 Do 15:15 2B/C<br />
Volumen-Holographie mit ultrakurzen Laserpulsen in photorefraktiven<br />
Kristallen — •Christian Nölleke 1,2 , Jörg<br />
Imbrock 1,2 und Cornelia Denz 1,2 — 1 Institut für Angewandte Physik,<br />
Westfälische Wilhelms-Universität, 48149 Münster — 2 Center for<br />
Nonlinear Science, 48149 Münster<br />
In photorefraktiven Kristallen lassen sich Volumen-Hologramme speichern,<br />
indem das Material mit einem räumlich modulierten Intensitätsmuster<br />
beleuchtet wird, welches dann in eine Brechungsindexänderung<br />
umgesetzt wird.<br />
In den hier präsentierten Experimenten wird gezeigt, wie sich Hologramme<br />
mit Piko-Sekunden Pulsen in LiNbO3 Kristallen speichern<br />
lassen, indem die Pulse interferometrisch räumlich und zeitlich innerhalb<br />
des Kristalls überlagert werden. Der Beugungswirkungsgrad<br />
der Hologramme wird in Abhängigkeit von der Intensität und Polarisation<br />
der Pulse bestimmt. Das Speichern der Hologramme kann<br />
entweder mit sichtbarem Licht oder mit infrarotem Licht bei gleichzeitiger<br />
Sensibilisierung der Kristalle mit blauen Licht (λ = 400 nm)<br />
durchgeführt werden. Dieses so genannte Zwei-Farben-Schreiben bietet<br />
den Vorteil, dass die Hologramme anschließend mit infrarotem Licht<br />
zerstörungsfrei ausgelesen werden können. Verantwortlich für diesen<br />
Prozess sind Polaronen, die durch das blaue Licht erzeugt werden. Die<br />
optimale Schreibwellenlänge für das Zwei-Farben-Schreiben kann experimentell<br />
zum ersten Mal bestimmt werden.<br />
Q 43.7 Do 15:30 2B/C<br />
High-Q whispering gallery mode resonators made of lithium<br />
Q 44: Quanteneffekte (Interferenz / Sonstige)<br />
niobate crystals* — •Judith R. Schwesyg, Anne S. Zimmermann,<br />
Daniel Haertle, and Karsten Buse — Physikalisches Institut, Universität<br />
Bonn, Wegelerstr. 8, 53115 Bonn<br />
Toroidally-shaped whispering-gallery-mode resonators made of amorphous<br />
or crystal materials are very promising for confining and trapping<br />
of light. The optical quality factor and the finesse reach very high<br />
values. Special fabrication techniques now enable to build such resonators<br />
from almost every material of interest. One useful crystalline<br />
material is lithium niobate which is widely used in integrated and<br />
guided-wave optics because of its favorable optical, piezoelectric, electrooptic,<br />
and photorefractive properties. In this talk we present the<br />
fabrication process of such resonators. Quality factors exceeding 10 7<br />
and finesses higher than 400 are achieved. Mode spectra enable to determine<br />
absorption values of the material as small as 5 × 10 −3 cm −1 .<br />
In a next step the resonators can be used as sensors maybe detecting<br />
single atoms.<br />
*Financial support of the Deutsche Forschungsgemeinschaft<br />
(FOR557) and the Deutsche Telekom Stiftung is gratefully acknowledged.<br />
Q 43.8 Do 15:45 2B/C<br />
Polarization Singularities from unfolding an Optical Vortex<br />
through a Birefrigent Crystal — •Ulrich Schwarz and Florian<br />
Flossmann — Institute for Experimental and Applied Physics, University<br />
of Regensburg, D-93040 Regensburg, Germany<br />
An optical vortex incident on a birefringent crystal unfolds into a complex<br />
topological structure of lines of circular polarization (C lines)<br />
and surfaces of linear polarization (L surfaces) [F. Flossmann, U.<br />
T. Schwarz, Max Maier, and M. R. Dennis, Phys. Rev. Letters 95,<br />
253901 (2005)]. The incident beam splits into two orthogonally polarized<br />
beams of ordinary and extraordinary polarization. Extraordinary<br />
refraction causes a shift of the extraordinarily polarized beam even<br />
under normal incidence. This shift together with the different phase<br />
velocities of both beams is the origin of an intriguing pattern of polarization<br />
singularities. We measure spatially resolved the full set of<br />
Stokes parameters after the beam passed the crystal to determine experimentally<br />
the spatial structure of the polarization singularities in<br />
three dimensions, two spatial directions (x, y) and one (L) corresponding<br />
to relative the phase retardation between ordinary and extraordinary<br />
beam. The observed unfolding of the initial phase singularity<br />
is the most generic case of the generation of polarization singularities<br />
in uniaxial or biaxial birefringent crystals. It can be describe in a<br />
very general way in terms of Stokes parameters where the polarization<br />
singularities arise naturally from the zeroes of the Stokes parameters<br />
[F. Flossmann, U. T. Schwarz, Max Maier, and M. R. Dennis, Optics<br />
Express 14, 11402 (2006)].<br />
Zeit: Donnerstag 14:00–16:15 Raum: 2D<br />
Q 44.1 Do 14:00 2D<br />
Vacuum-induced couplings of dipole moments in a pair of<br />
atoms — •Sandra Isabelle Schmid and Jörg Evers — Max-<br />
Planck-Institut für Kernphysik, Heidelberg, Deutschland<br />
In single atom systems, vacuum-coupling of different transition dipole<br />
moments can induce spontaneously generated coherences which give<br />
rise to a multitude of interesting effects. These couplings, however,<br />
only act between non-orthogonal dipole moments and thus rarely occur<br />
in real atoms. But in [1], they were demonstrated in a realistic<br />
four-level system in J=1/2 to J=1/2 configuration.<br />
Two nearby atoms can dipole-dipole interact by exchanging virtual<br />
photons via the vacuum. This dipole-dipole interaction can also couple<br />
transitions with orthogonal dipole moments, which crucially influences<br />
the system dynamics [2,3]. Even when averaging over different geometrical<br />
setups the effects resulting from these couplings do not vanish [4].<br />
Here, we investigate a system consisting of a pair of atoms in J=1/2<br />
to J=1/2 configuration where both types of couplings occur. In particular,<br />
we are interested in the interplay of the two vacuum-mediated<br />
interactions. As observables, we discuss the influence of the different<br />
couplings on the resonance fluorescence intensity and the spectrum.<br />
[1] M. Kiffner, J. Evers, and C. H. Keitel, Phys. Rev. Lett. 96, 100403<br />
(2006)<br />
[2] G. S. Agarwal and A. K. Patnaik, Phys. Rev. A 63, 043805 (2001)<br />
[3] J. Evers, M. Kiffner, M. Macovei, and C. H. Keitel, Phys. Rev. A<br />
73, 023804 (2006)<br />
[4] S. I. Schmid and J. Evers, arXiv:0709.2103 (2007)<br />
Q 44.2 Do 14:15 2D<br />
Phase space sub-Planck structures: experimental realization<br />
in time-frequency domain — •Ludmila Praxmeyer 1 , Piotr<br />
Wasylczyk 2 , Czeslaw Radzewicz 2 , and Krzysztof Wodkiewicz 2<br />
— 1 Optical Quantum Information Theory Group, Max Planck Research<br />
Group, Institute of Optics, Information and Photonics, 91058<br />
Erlangen, Germany — 2 Faculty of Physics, Warsaw University, Poland<br />
It was shown by Zurek [1] that sub-Planck structures in phase space<br />
play a surprisingly important role in the distinguishability of quantum<br />
states. A sub-Planck phase space shift applied to a superposition of coherent<br />
states is sufficient to produce a state which is orthogonal to the<br />
unshifted one! The effect was originally studied for a superposition of<br />
four coherent states [1], then it was shown that superpositions of just<br />
two coherent states lead to a similar result [2]. We present experimental<br />
data of the frequency resolved optical gating (FROG) measurements<br />
of light pulses revealing interference features which correspond to sub-<br />
Planck structures in phase space [3]. For superpositions of pulses a<br />
small, sub-Fourier shift in the carrier frequency leads to a state orthogonal<br />
to the initial one, although in the representation of standard
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
time-frequency distributions these states seem to have a non-vanishing<br />
overlap.<br />
[1] W. Zurek, Nature 412, 712 (2001).<br />
[2] L. Praxmeyer, K. Wodkiewicz, Laser Phys. Vol.15, No.10, 1477<br />
(2005); L. Praxmeyer, PhD thesis (2005).<br />
[3] L. Praxmeyer, P. Wasylczyk, Cz. Radzewicz, K. Wodkiewicz, Phys.<br />
Rev. Lett. 98, 063901 (2007).<br />
Q 44.3 Do 14:30 2D<br />
Interference of resonance fluorescence from two distant atoms<br />
— •Felix Rohde, Carsten Schuck, Marc Almendros, Roger<br />
Gehr, Francois Dubin, Markus Hennrich, and Jürgen Eschner<br />
— ICFO - Institut de Ciencies Fotoniques, Castelldefels (Barcelona),<br />
Spain<br />
We trap two single calcium ions simultaneously in two independent<br />
ion traps at a distance of about 1 m. The ions are continuously excited<br />
using lasers at 397 nm and 866 nm that are frequency-stabilised<br />
by a transfer locking scheme to an atomic reference line in cesium.<br />
The continuous resonance fluorescence from the two ions is coherently<br />
superimposed and recorded with photomultipliers in photon counting<br />
mode. We present results on classical and quantum interference in the<br />
detected light. Such interference will be used for entangling the two<br />
ions by conditional state preparation.<br />
Q 44.4 Do 14:45 2D<br />
Microwave driven Rydberg atoms: from strong localization<br />
to single-photon ionization — •Alexej Schelle 1,2 , Andreas<br />
Buchleitner 2 , and Dominique Delande 1 — 1 Laboratoire Kastler<br />
Brossel, 4, place Jussieu, F-75252 Paris, cedex 05 — 2 Institute of<br />
Physics, Department for Quantum Optics and Statistics, Albert-<br />
Ludwigs-Universität Freiburg, Hermann-Herder-Str. 3, 79104 Freiburg<br />
We study the atomic counterpart of Anderson localization in atomic<br />
driven Rydberg systems. By switching the initial Rydberg state from<br />
lower bound states, where destructive quantum interference suppresses<br />
the classically predicted ionization threshold, up to the single-photon<br />
absorption limit, we observe a transition in the scaling behavior of<br />
the ionization threshold field. Unlike in the strong localization regime,<br />
where the scaled ionization threshold shows a smooth and universal<br />
behavior for hydrogen and lithium atoms, strong oscillations in the<br />
few-photon absorption limit indicate the breakdown of the Anderson<br />
localization scenario.<br />
Q 44.5 Do 15:00 2D<br />
Quantum Phase Transitions with Polaritons and Photons<br />
— •Michael Hartmann 1,2 and Martin Plenio 1,2 — 1 Institute for<br />
Mathematical Sciences, Imperial College London, 53 Exhibition Road,<br />
London, SW7 2PG, United Kingdom — 2 QOLS, The Blackett Laboratory,<br />
Imperial College London, Prince Consort Road, London, SW7<br />
2BW, United Kingdom<br />
Artificial many-body systems that permit good experimental access<br />
and control have become an important tool for the study of quantum<br />
phase transitions in the laboratory.<br />
Here we show that arrays of coupled high-Q cavities doped with<br />
atoms can be employed to study quantum phase transitions with polaritons<br />
and photons. In particular, photons can be driven into a Mott<br />
insulator state which corresponds to light in a ”crystalized”form.<br />
An important advantage of our approach is that it allows to access<br />
and control individual lattice sites.<br />
Q 44.6 Do 15:15 2D<br />
Thermal equilibrium of coupled atom-light states in an ultrahigh<br />
pressure buffer gas cell — •Ulrich Vogl, Johannes Nipper,<br />
and Martin Weitz — Institut für Angewandte Physik, Wegelerstraße<br />
8, 53115 Bonn<br />
Thermal equilibrium is a prerequisite for most known phase transitions,<br />
as Bose-Einstein condensation of dilute atomic gases or many solid<br />
state physics concepts. Recently, phase transitions of coupled particle-<br />
light degrees of freedom have been investigated in the framework of<br />
polariton quasiparticle condensation, and exciton polariton systems<br />
gave compelling evidence for a condensation. However, the short polariton<br />
lifetimes of around a ps arose questions whether the system is<br />
fully thermalized. We investigate the statistical distribution of coupled<br />
atom-light excitations in an atomic rubidium gas cell subject to 500<br />
bar buffer gas pressure. The large collisional broadening of this system<br />
interpolates between usual atomic physics gas phase and solid/liquid<br />
phase conditions. An observed intensity-dependent blue asymmetry of<br />
spectra is interpreted as evidence for the approaching of thermal equilibrium<br />
of dressed atom-light states.<br />
Q 44.7 Do 15:30 2D<br />
Cooling of a nanomechanical resonator integrated into a superconducting<br />
box qubit — •Konstanze Jähne 1,2 and Margareta<br />
Wallquist 1,2 — 1 Institute for Theoretical Physics, University<br />
of Innsbruck, Innsbruck, Austria — 2 Institute for Quantum Optics and<br />
Quantum Information of the Austrian Academy of Sciences, Innsbruck,<br />
Austria<br />
We consider the following system: a nanomechanical resonator that<br />
is integrated into a superconducting loop of a current-biased superconducting<br />
qubit, in particular a Cooper pair box. One can apply<br />
a magnetic field to the nanoresonator, which together with the current<br />
flowing through it creates a Lorentz force, which gives rise to a<br />
switchable coupling between nanoresonator and qubit. Using methods<br />
of theoretical quantum optics, we show that it is possible to cool<br />
the nanoresonator, if one drives the qubit around its optimal working<br />
point with a drive frequency that is red detuned with respect to the<br />
qubit transition. Furthermore we investigate under which conditions<br />
the nanoresonator can be cooled to its quantum mechanical ground<br />
state.<br />
Q 44.8 Do 15:45 2D<br />
Inverse Scattering in Application to the Riemann Problem —<br />
•Rüdiger Mack and Wolfgang P. Schleich — Institut für Quantenphysik,<br />
Universität Ulm, 89073 Ulm<br />
We present a method to get the values of the Riemann Zeta-function<br />
by autocorrelation measure. Therefore we need a potential with specific<br />
energy eigenvalues. We calculate this potential with a variety of<br />
techniques, either numerical by the Numerov mehtod and analytically,<br />
with a JBKW approximation.<br />
Q 44.9 Do 16:00 2D<br />
Resonant Interferometric Lithography beyond the Diffraction<br />
Limit — •Jörg Evers 1 , Martin Kiffner 1 , and M. Suhail<br />
Zubairy 1,2 — 1 Max-Planck-Institut für Kernphysik, Heidelberg —<br />
2 Institute for Quantum Studies and Department of Physics, Texas<br />
A&M University, USA, and Texas A&M University at Qatar<br />
A fundamental limit to the spatial resolution of the interferometric<br />
lithography with classical uncorrelated light arises due to diffraction.<br />
To overcome this limit, several schemes have been proposed to improve<br />
the spatial resolution of interferometric lithography beyond the<br />
diffraction limit. These schemes are based on an N-photon absorption<br />
process and achieve a spatial resolution of λ/(2N), where λ is the<br />
wavelength of the light. The indispensable requirement of a multiphoton<br />
transition, however, is accompanied by the need for high light field<br />
intensities which makes an experimental realization of these schemes<br />
impractical.<br />
Here, we present a novel approach for the generation of subwavelength<br />
structures in interferometric optical lithography which only<br />
comprises resonant atom-field interactions, such that no multiphoton<br />
absorber is required [1]. Our scheme relies on the preparation of the system<br />
in a position dependent trapping state via phase shifted standing<br />
wave patterns. The contrast of the induced pattern does only depend<br />
on the ratios of the applied field strengths such that our method in<br />
principle works at arbitrarily low laser intensities.<br />
[1] M. Kiffner, J. Evers, and M. S. Zubairy, submitted
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
Q 45: Materiewellenoptik<br />
Zeit: Donnerstag 14:00–15:45 Raum: 3G<br />
Q 45.1 Do 14:00 3G<br />
Matter wave interferometry on potassium molecules — •Sha<br />
Liu, Ivan Sherstov, Horst Knöckel, Christian Lisdat, and Eberhard<br />
Tiemann — Institut für Qantenoptik, Gottfried Wilhelm Leibniz<br />
Universität Hannover, 30167 Hannover, Deutschland<br />
We operate a matter wave interferometer on K2 molecules in a<br />
Ramsey-Bordé configuration. The two exits of this interferometer with<br />
molecules in either the excited state or the ground state, give complementary<br />
detection schemes for the interference signal. Under certain<br />
geometric conditions, observed interference signal is composed of two<br />
interference patterns, the Ramsey interference formed by two laser<br />
beam splitters, the Ramsey-Bordé interference pattern with four laser<br />
beam splitters. These two interference patterns can be separated in frequency<br />
domain. For a better understanding, we observe Ramsey fringe<br />
alone directly and analyze the contrast dependence on the transversal<br />
velocity distribution. The Ramsey-Bordé interferometer will be used in<br />
further applications, thanks to its higher phase stability compared to<br />
the Ramsey interference. By introducing a near resonant laser field to<br />
the molecules in either the excited state or the ground state between<br />
the beam splitters, the transition matrix element can be determined.<br />
Furthermore, by changing the collision characteristics of the K atoms<br />
in the K2 molecular beam, the collision between potassium atoms and<br />
molecules can be investigated. The density of K atoms is varied by deflecting<br />
atoms through resonant laser field out of the molecular beam.<br />
The actual status of the experiment will be presented.<br />
Q 45.2 Do 14:15 3G<br />
Diffraction of helium atom beams from a micro-structured<br />
reflection grating — •Bum Suk Zhao 1 , Stephan Schulz 2 , Gerard<br />
Meijer 1 , and Wieland Schöllkopf 1 — 1 Fritz-Haber-Institut<br />
der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany<br />
— 2 Universität Ulm, Institut für Quanteninformationsverarbeitung,<br />
Albert-Einstein-Allee 11, 89069 Ulm, Germany<br />
We have observed high-resolution diffraction patterns of a thermalenergy<br />
helium-atom beam reflected from a micro-structured surface<br />
grating at grazing incidence. The grating has a periodicity of 20 µm<br />
and consists of 10-µm-wide Cr stripes patterned on a quartz substrate.<br />
Fully-resolved diffraction peaks up to the 7-th order are observed at<br />
grazing incidence angles up to 20 mrad. With changes in de Broglie<br />
wavelength or incidence angle the relative diffraction intensities show<br />
significant variations which are attributed to the atom-surface Casimirvan<br />
der Waals potential. In addition, the overall probability of coherent<br />
reflection is found to increase with increasing de Broglie wavelength<br />
and decreasing incidence angle. We discuss whether this behavior indicates<br />
quantum reflection at the long-range attractive branch of the<br />
atom-surface potential.<br />
Q 45.3 Do 14:30 3G<br />
Matter wave Talbot-Lau interferometry beyond the<br />
eikonal approximation — •Stefan Nimmrichter 1,2 and Klaus<br />
Hornberger 1 — 1 Arnold Sommerfeld Center for Theoretical Physics,<br />
Ludwig-Maximilians-Universität München — 2 Physikalisches Institut,<br />
Universität Wien<br />
We present a generalized phase-space description of matter wave<br />
Talbot-Lau interference experiments allowing to incorporate arbitrary<br />
grating interactions and realistic beam characteristics. These setups<br />
are being used to demonstrate the wave nature of complex molecules<br />
[1,2]. Typically they consist of three gratings and operate in the near<br />
field regime where the different diffraction orders interfere among each<br />
other. Unlike in far field diffraction, the interaction between the interfering<br />
particle and the grating crucially affects the interference contrast.<br />
The eikonal approximation used so far is expected to cease to<br />
be valid in upcoming experiments with more massive particles. Our<br />
theoretical model admits a general description of the grating interaction<br />
process using scattering theory. Based on this, we develop a<br />
semiclassical correction to the eikonal approximation.<br />
[1] L. Hackermüller et al, Phys. Rev. Lett. 91, 090408 (2003)<br />
[2] S. Gerlich et al, Nature Physics 3, 711 (2007)<br />
Q 45.4 Do 14:45 3G<br />
Bell test for the motional state of free massive particles —<br />
•Clemens Gneiting and Klaus Hornberger — Arnold Sommer-<br />
feld Center for Theoretical Physics, Ludwig-Maximilians-Universität<br />
München<br />
We propose a simple and robust way of generating and verifiying entanglement<br />
in the motional state of two free, macroscopically separated<br />
atoms. It is based on the concept of ‘dissociation-time entanglement’,<br />
allowing to formulate a special type of continuous variable entanglement<br />
in a two-dimensional state-space in analogy with the entangled<br />
spin-singlet state. We describe an interferometric setting, based only<br />
on linear elements of matter-wave optics, which reflects the general<br />
spin measurements required in the original spin-based Bell experiment.<br />
It thus allows to verify the entanglement by the violation of<br />
a Bell inequality using only single-particle interference without postselection.<br />
The dissociation-time entangled state can be generated by<br />
the Feshbach-induced dissociation of a molecular BEC. In particular,<br />
the shape of the magnetic pulse can be used to taylor the generated<br />
wave packets as to minimize the effect of dispersion.<br />
Q 45.5 Do 15:00 3G<br />
Decoherence in atom interferometry — •Scott Sanders 1,2,3 ,<br />
Florian Mintert 2,3 , and Eric Heller 2 — 1 Massachusetts Institute<br />
of Technology, Cambridge, MA, United States — 2 Harvard University,<br />
Cambridge, MA, United States — 3 Albert-Ludwigs-Universität<br />
Freiburg, Hermann-Herder-Str. 3, 79104 Freiburg<br />
We consider decoherence of an atom due to scattering from a free gas.<br />
Our analysis explains why a free gas can serve as a refractive medium<br />
that gives rise to a phase shift in atom interferometry, without acquiring<br />
which way information on the interfering particles.<br />
Q 45.6 Do 15:15 3G<br />
The relevance of internal states in molecular de Broglie interferometry<br />
— •Michael Gring 1 , Stefan Gerlich 1 , Lucia Hackermüller<br />
1,4 , Klaus Hornberger 2 , Hendrik Ulbricht 1 , Marcel<br />
Müri 3 , Jens Tüxen 3 , Marcel Mayor 3 , and Markus Arndt 1 —<br />
1 Faculty of Physics, University of Vienna, Boltzmanngasse 5, A-1090<br />
Wien, Austria — 2 Arnold Sommerfeld Center for Theoretical Physics,<br />
Ludwig-Maximilians-Universität München, Theresienstrasse 37, 80333<br />
München, Germany — 3 University of Basel, Department of Chemistry,<br />
St Johannsring 19, CH-4056 Basel, Switzerland — 4 Present address:<br />
Johannes Gutenberg-Universität Mainz, Staudingerweg 7, 55099<br />
Mainz, Germany<br />
We present recent matter wave interferometry results with<br />
perfluoroalkyl-functionalized azobenzene molecules. These long molecular<br />
chains are interesting for future decoherence and metrology experiments<br />
since they can be optically switched between two different<br />
conformers. We discuss the question under which conditions one can<br />
identify different molecular conformations using the Kapitza-Dirac-<br />
Talbot-Lau interference scheme that was recently developed in our<br />
group. We further examine the influence of state-dependent molecular<br />
properties such as the polarizability or dipole moment on the interference<br />
pattern and the experimental modifications required to reveal<br />
these properties also in various other molecular systems.<br />
Q 45.7 Do 15:30 3G<br />
Towards quantum optics with biomolecular clusters —<br />
•Philipp Haslinger, Markus Marksteiner, Hendrik Ulbricht,<br />
and Markus Arndt — Faculty of Physics, University of Vienna, Austria<br />
We present recent progress towards matter wave experiments with<br />
large biomolecular clusters. All successful experiments on macromolecule<br />
interferometry so far, with fullerenes [Nature1999], fullerene<br />
derivates [PRL2003] and large perfluoroalkyl-functionalized azobenzenes<br />
[Nature2007] used effusive beam sources. In order to prepare experiments<br />
with molecules of biological interest, we have implemented<br />
a pulsed laser desorption source. The combination of UV laser desorption<br />
into an intense noble gas jet and single-photon ionization by a<br />
VUV excimer laser (157nm) allows us to observe intense neutral jets<br />
of amino acids, nucleotides and polypeptides. We recently discovered<br />
a new method for producing large and neutral amino acid-metal complexes,<br />
such as for instance Ca@Trp2...Ca@Trp30, with masses exceeding<br />
6000 amu. The addition of alkaline Earth salts in the desorption<br />
process leads to the inclusion of at least one metal atom per complex<br />
and is sufficient to catalyze the cluster formation process. We discuss
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
how interferometric deflectometry might help in obtaining additional information about the structure of such large molecular compounds.<br />
Q 46: Ultrakurze Laserpulse (Erzeugung II / Anwendungen I)<br />
Zeit: Donnerstag 14:00–16:15 Raum: 3H<br />
Q 46.1 Do 14:00 3H<br />
Passiv modengekoppelter Thulium-dotierter Faserlaser mit<br />
3,45 nJ Pulsenergie — •Frithjof Haxsen, Martin Engelbrecht,<br />
Dieter Wandt und Dietmar Kracht — Laserzentrum Hannover<br />
e.V., Hollerithallee 8, 30419 Hannover<br />
Es wird ein Thulium-dotierter modengekoppelter Faserlaser mit interner<br />
Dispersionskompensation vorgestellt. Das vorliegende System wurde<br />
in Ringresonatorkonfiguration aufgebaut, bei dem eine bei 793 nm<br />
gepumpte Thulium-dotierte Doppelkernfaser als Verstärkungsmedium<br />
eingesetzt wurde. Die durch nichtlineare Polarisationsdrehung generierten<br />
Pulse hatten eine Zentralwellenlänge von 1985 nm mit 17 nm<br />
Halbwertsbreite und eine Pulsenergie von 3,45 nJ bei einer Repetitionsrate<br />
von 41,4 MHz. Aufgrund der negativen Dispersion der Faserstrecke<br />
bei der Emissionswellenlänge wurde zu deren Kompensation<br />
ein Gitteraufbau verwendet, bei dem durch eine 4-f-Abbildung positive<br />
Dispersion realisiert wurde. Die erzeugten Pulse wiesen einen deutlichen<br />
Chirp auf. Die Pulsdauer betrug 1,26 ps und konnte extern auf<br />
320 fs komprimiert werden. Sie lag damit 12 % über dem Bandbreitenlimit.<br />
Nach unserem Wissen ist dies die höchste Pulsenergie aus einem<br />
modengekoppelten Faseroszillator bei 2 µm Wellenlänge.<br />
Q 46.2 Do 14:15 3H<br />
Erbium-Faserlaser im positiven Dispersionsbereich mit Pulsenergien<br />
über 10 nJ — •Vincent Kuhn, Axel Rühl, Dieter<br />
Wandt und Dietmar Kracht — Laser Zentrum Hannover e.V., Hollerithallee<br />
8, 30419 Hannover<br />
Das Ziel dieser Arbeit war die Übertragung der von Ytterbium-<br />
Faserlasern bekannten selbstähnlichen Pulsformung* – und deren Potential<br />
zur Pulsenergieskalierung – auf Erbium-Faseroszillatoren. Der<br />
dazu entwickelte Laser wurde ohne resonatorinterne Dispersionskontrolle<br />
aufgebaut und selbststartende Modenkopplung über nichtlineare<br />
Polarisationsdrehung realisiert. Die erzielten Pulsenergien lagen über<br />
10 nJ und sind somit die, nach unserem Wissen, höchsten Pulsenergien<br />
die direkt aus einem Erbium-Faseroszillator gewonnen wurden. Die<br />
stark gechirpten Pulse (C > 50) konnten resonatorextern auf Pulsdauern<br />
unter 75 fs komprimiert werden. Die erreichten Spitzenleistungen<br />
lagen somit oberhalb von 135 kW.<br />
Ein deutlicher Unterschied zwischen Yb und Er dotierten Faserlasern<br />
ist die wesentlich geringere maximale Dotierungskonzentration im<br />
Fall von Erbium. Dies erfordert den Einsatz einer deutlich längeren<br />
Verstärkerfaser und verhindert die Möglichkeit einer Entkopplung von<br />
Verstärkung und Pulsformung. Zudem spielt auch Intrapuls-Raman-<br />
Streuung eine beträchtliche Rolle in der Strukturgebung der Pulse.<br />
Dies führt zu einer Pulsformung deren Analogien und Unterschiede<br />
zur selbstähnlichen Pulsevolution in diesem Beitrag diskutiert werden.<br />
* Ilday et al., Phys. Rev. Lett. 92, 213902 (2004)<br />
Q 46.3 Do 14:30 3H<br />
Front-end of Petawatt Field Synthesizer (PFS) — •Izhar Ahmad,<br />
Antonia Popp, Sergei Trushin, Tie-jun Wang, Zsuzsanna<br />
Major, and Stefan Karsch — Max-Planck Institue for Quantum<br />
Optics, Garching, Germany<br />
We are pursuing the development of a novel few-cycle ˜5fs, phase stabilized<br />
light source with a peak power ranging from 0.5 to 1.0 Petawatt. It<br />
is based on an ultrabroadband Optical-Parametric-Chirped-Pulse Amplification<br />
(OPCPA) technique, synchronously pumped with a highrepetition<br />
rate (10Hz) diode pumped Yb:YAG laser operating at ˜10<br />
ps pulse duration as a driver.<br />
The progress in the development of front end for this novel source<br />
will be presented. It involves seed generation for the pump source for<br />
optical synchronization based on soliton self stimulated emission in<br />
photonic crystal fibers, pulse compression of Ti:Sapphire amplifier using<br />
hybrid pulse compression technique and advancement towards ultrabroad<br />
band seed generation for OPCPA.<br />
Q 46.4 Do 14:45 3H<br />
Filamentation in air - poor man’s sub 7 fs setup — •Bruno<br />
Schmidt, Waldemar Unrau, Adlo Mirabal, Ludger Wöste, and<br />
Torsten Siebert — Institut für Experimentalphysik, Freie Universität<br />
Berlin, Arnimallee 14, 14195 Berlin, Germany<br />
An optical setup for generation and measurement of few cycle pulses is<br />
presented. It comprises spectral broadening via single filamentation in<br />
air, standard chirp mirrors for dispersion compensation and a transient<br />
grating FROG as characterization. This cheep and robust arrangement<br />
enables measuring of pulses as short as 6.4 fs and FROG traces with<br />
bandwidths reaching from (370-950) nm for uncompressed supercontinuum.<br />
Q 46.5 Do 15:00 3H<br />
Octave wide tunable UV-pumped NOPA: pulse durations<br />
down to 20 fs and repetition rates up to 2 MHz — •Christian<br />
Homann, Christian Schriever, Peter Baum, and Eberhard Riedle<br />
— Lehrstuhl für BioMolekulare Optik, LMU München<br />
For ultrafast spectroscopy, femtosecond laser pulses with wide tunability<br />
and high repetition rates are needed. Recently, amplified Yb-doped<br />
fiber systems became commercially available, delivering 10 µJ pulses at<br />
1035 nm and 2 MHz repetition rate. We demonstrate frequency conversion<br />
with a noncollinear optical parametric amplifier (NOPA), which is<br />
pumped by the frequency tripled (345 nm) output of the fiber-amplifier<br />
system and is seeded by a smooth continuum generated in bulk sapphire.<br />
The 3ω light is generated with 15% conversion efficiency in a<br />
novel and extremely simple setup consisting of two BBO crystals only.<br />
The NOPA is tunable between 460 and 990 nm, thus spanning over<br />
one octave. The output pulses show smooth Gaussian shaped spectra<br />
and pedestal-free autocorrelation traces. Nearly Fourier-limited pulse<br />
durations down to 19.8 fs are achieved. The remaining green 2ω light<br />
from the frequency tripling setup is used to pump an additional, independently<br />
tunable NOPA with a tuning range of 600-970 nm. Together,<br />
the two NOPAs provide powerful sources for tunable two-color pumpprobe<br />
spectroscopy. Interference experiments show that the two NOPA<br />
systems have a precisely locked relative phase, despite of being pumped<br />
by different harmonics with differing phase fluctuations. This directly<br />
proves that parametric amplification preserves the phase of the seed<br />
light.<br />
Q 46.6 Do 15:15 3H<br />
Optimierte Wavelet-basierte Algorithmen zur Phasenrekonstruktion<br />
ultrakurzer Lichtimpulse — •Jens Bethge und<br />
Günter Steinmeyer — Max-Born-Institut, Max-Born-Straße 2a, D-<br />
12489 Berlin<br />
Die Rekonstruktion der spektralen Phase von ultrakurzen Lichtimpulsen<br />
ist der Schlüssel zu ihrer Charakterisierung. Bei einer<br />
SPIDER-Messung [1] muss dazu die Periode eines Fringemusters in<br />
einem Interferogramm ausgewertet werden. Es wurde gezeigt, dass<br />
neben dem üblichen Takeda-Algorithmus [2] auch Wavelet-basierte<br />
Algorithmen benutzt werden können, ohne dass auf eine hohe Aktualisierungsrate<br />
verzichtet werden muss [3]. Dabei wird eine Gabor-<br />
Wavelet Transformation verwendet nach deren Anwendung sich eine<br />
sehr genaue Frequenzanalyse direkt durchführen lässt. Wir haben die<br />
vorgeschlagene Methode optimiert. Sowohl in numerischen Versuchen<br />
als auch bei der Anwendung auf experimentelle Daten konnte dabei<br />
die höhere Zuverlässigkeit und Genauigkeit, besonders bei schlechtem<br />
Signal-zu-Rausch-Verhältnis, nachgewiesen werden.<br />
[1] C. Iaconis and I.A. Walmsley, Opt. Lett. 23, 792 (1998).<br />
[2] M. Takeda et al., J. Opt. Soc. Am. A 72, 156 (1982).<br />
[3] J. Bethge et al., Opt. Express 15, 14313 (2007).<br />
Q 46.7 Do 15:30 3H<br />
Ein linear optisches Verfahren zur Mesung der Carrier-<br />
Envelope Phase modengekoppelter Laser — •Christian<br />
Grebing 1 , Karoly Osvay 1 , Mihaly Görbe 2 und Günter<br />
Steinmeyer 1 — 1 Max-Born-Institut, Max-Born-Straße 2a, D-12489<br />
Berlin — 2 Department of Optics and Quantum Electronics, University<br />
of Szeged, P.O.Box 406, H-6701, Szeged
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
Das f-2f Interferometer hat sich als Standard zur Messung der Carrier-<br />
Envelope Phasenänderung (CEP) von aufeinanderfolgenden Laserpulsen<br />
etabliert. Es beruht auf einem nichtlinearen Interferometer in dem<br />
die Fundamentale und die Frequenzverdoppelte des Pulsspektrums<br />
überlagert werden. Dieses Verfahren erfordert oktavbreite Pulse hoher<br />
Spitzenleistung und ist somit nicht für beliebige modengekoppelte Laser<br />
anwendbar. Wir schlagen eine neue lineare interferometrische Methode<br />
vor, die es erlaubt, die CEP eines Pulszuges über die Sichtbarkeit<br />
des Fringe-Musters in einem Mach-Zehnder Interferometer zu messen,<br />
in dessen einen Arm ein zusätzlicher Ringresonator eingefügt wurde.<br />
Die daraus resultierende Überlagerung aufeinanderfolgender Pulse mit<br />
unterschiedlicher CEP beeinflußt die Interferenz im Mach-Zehnder Interferometer<br />
und erzeugt eine Modulation des Interferenzkontrasts in<br />
Abhängigkeit von der CEP, was wir sowohl durch Messungen an einem<br />
Ti:Saphir-Laser als auch durch numerische Simulationen bestätigen<br />
konnten [1]. Da kein nichtlinearer Konversionsschritt erforderlich ist,<br />
erlaubt diese Methode auch CEP-Messungen für schmalbandige modengekoppelte<br />
Laser und solche mit geringer Laserleistung.<br />
[1] K. Osvay et al., Opt. Lett. 32, 3095-3097 (2007).<br />
Q 46.8 Do 15:45 3H<br />
Selbstreferenzierendes f-2f Interferometer zur Phasenstabilisierung<br />
von Femtosekundenlasern — •Sebastian Koke, Christian<br />
Grebing, Bastian Manschwetus und Günter Steinmeyer —<br />
Max-Born-Institut, Max-Born-Straße 2a, D-12489 Berlin<br />
Die Stabilisierung der sogenannten Carrier-Envelope Phase (CEP),<br />
d.h. der Phase zwischen dem Träger und der Einhüllenden eines ultrakurzen<br />
Laserpulses, ist eine wichtige Voraussetzung zur Erzeugung<br />
isolierter Attosekundenpulse sowie für die Untersuchung der CEP-<br />
Abhängigkeit verschiedenster Ionisierungsvorgänge. Für die Stabilisierung<br />
der CEP wird routinemäßig ein f-2f Interferometer verwendet,<br />
bei dem man die Struktur des Modenkamms ausnutzt, um die Wieder-<br />
Q 47: Quantengase (Bosonen II / Fermionen)<br />
holfrequenz gleicher CEP-Werte zu extrahieren [1]. Da jegliche Drifts<br />
und Störungen in den beiden Armen des Interferometers die Qualität<br />
der Stabilisierung verschlechtern, ist man bemüht, diese durch passive<br />
Stabiliserungsmaßnahmen zu reduzieren. Kürzlich ist es mittels einer<br />
aktiven Stabilisierung der optischen Weglänge in beiden Interferometerarmen<br />
gelungen, das Restrauschen der Phasenstabiliserung eines<br />
Lasersystems deutlich zu verringern [2]. In diesem Beitrag demonstrieren<br />
wir, dass schon durch die Wahl einer geeigneten Geometrie, in der<br />
beide Interferometerarme nahezu zusammenfallen, eine vergleichbare<br />
Reduktion des Restrauschens ohne aufwendige aktive Stabilisierung<br />
der optischen Weglänge erreicht werden kann.<br />
[1] H. Telle et al., Appl. Phys. B 69, 327-332 (1999).<br />
[2] E. Moon et al., Opt. Express 14, 9758-9763 (2006).<br />
Q 46.9 Do 16:00 3H<br />
High Harmonics Generation (HHG) from water droplets.<br />
— •Jan Henneberger, Nico Franke, Sebastian Jung, Christian<br />
Ott, and Christian Spielmann — Physikalisches Institut, Universität<br />
Würzburg, Am Hubland, 97074 Würzburg<br />
We experimentally study the interaction of ultrashort intense laser radiation<br />
with water microdroplets. In order to do this we build up a<br />
droplet source in a vacuum chamber, which allows us to produce liquid<br />
droplets with 30 µm diameter. We observe the HHG spectrum<br />
generated by a two pulse scheme.<br />
The HHG from molecules can be used to see fast nuclear dynamics<br />
in molecules. We exploit that the harmonic spectrum is temporally<br />
chirped. As a result each harmonic order is emitted at a different time<br />
and therefore it is possible to map frequency to a recollision time. In<br />
particular, by comparing the spectrum of two isotopes, information<br />
about the vibration dynamics can be obtained. We compare the high<br />
harmonic spectrum from H2O and D2O. First measurements of the<br />
spectrum of this isotopes will be presented.<br />
Zeit: Donnerstag 16:30–18:45 Raum: 1A<br />
Q 47.1 Do 16:30 1A<br />
Mean-field description of a decaying BEC — •Astrid Niederle,<br />
Eva-Maria Greafe, Hans Jürgen Korsch, Friederike Trimborn,<br />
and Dirk Witthaut — TU Kaiserslautern, Germany<br />
A quantum system with decay can be effectively described by a non-<br />
Hermitian Hamiltonian with complex energy eigenvalues, whose imaginary<br />
parts describe the decay rate. In this talk we focus on a non-<br />
Hermitian, two-mode Bose-Hubbard Hamiltonian, which serves as a<br />
model for a Bose-Einstein-condensate in a double-well potential with<br />
decay from one of the two wells. We discuss the dynamics of operators,<br />
which is governed by a generalized Heisenberg-equation. Taking<br />
expectation values of the operators, we obtain a mean-field approximation.<br />
The resulting dynamics described by a generalized nonlinear<br />
Bloch equation is mainly influenced by the (up to four) fixed points,<br />
which can be repulsive or attractive depending on the system parameters.<br />
The mean-field dynamics is compared with the full N-particle<br />
quantum evolution.<br />
Q 47.2 Do 16:45 1A<br />
Single atom detection on a magnetic microchip —<br />
•Helmar Bender 1 , Andreas Günther 1 , Alexander Stibor 1 , Sebastian<br />
Kraft 2 , József Fortágh 1 , and Claus Zimmermann 1 —<br />
1 Physikalisches Institut der Universität Tübingen, Auf der Morgenstelle<br />
14, D-72076 — 2 van der Waals-Zeeman Instituut, Universiteit<br />
van Amsterdam, Valckenierstraat 65, 1018 XE Amsterdam, The<br />
Netherlands<br />
The possibility to detect small amounts of atoms on a magnetic microchip<br />
opens the door to a variety of interesting fundamental experiments<br />
in the field of ultracold quantum gases. Standard absorption<br />
imaging requires a minimum number of several hundred atoms. Thus<br />
novel detection methods with single atom sensitivity are currently developed.<br />
Here, we present a single atom detector which is implemented<br />
in our magnetic microchip setup. The detection scheme is based on optical<br />
ionization of single atoms and subsequent counting of the ions in<br />
a channeltron. We discuss the characterization of the detector as well<br />
as our latest experimental data with ultracold atoms on a magnetic<br />
microchip.<br />
Q 47.3 Do 17:00 1A<br />
Dropping Bose-Einstein condensates over long times and<br />
large distances — •Endre Kajari, Stefan Arnold, Michael<br />
Eckart, Reinhold Walser, and Wolfgang P. Schleich for the<br />
QUANTUS-Collaboration — Institute of Quantum Physics, Universität<br />
Ulm, D-89069 Ulm<br />
Ultracold quantum gases have the potential to extend the limits of<br />
matter-wave interferometry beyond current precision standards. In<br />
particular, the QUANTUS project [1] aims for the creation of a Bose-<br />
Einstein condensate at the drop tower facility at the ”Center of Applied<br />
Space Technology and Microgravity” (ZARM) in Bremen. Such an experiment<br />
permits an unperturbed free fall of a condensate for up to<br />
10 s. In this talk we present our theoretical contributions [2] and provide<br />
three-dimensional numerical simulations of the time dependent<br />
Gross-Pitaevskii equation, including explicit time dependent trapping<br />
frequencies. Our results are compared with the scaling approach given<br />
in [3,4].<br />
[1] A. Vogel et al., Appl. Phys. B 84, 664 (2006).<br />
[2] G. Nandi et al., Phys. Rev. A (to be published 2007).<br />
[3] Yu. Kagan et al., Phys. Rev. A. 54, R1753 (1996).<br />
[4] Y. Castin and R. Dum, Phys. Rev. Lett. 77, 5315 (1996).<br />
Q 47.4 Do 17:15 1A<br />
Environment-induced dynamics in Bose-Einstein condensates<br />
— •Alexej Schelle 1,2 , Andreas Buchleitner 2 , Benoît<br />
Grémaud 1 , and Dominique Delande 1 — 1 Laboratoire Kastler<br />
Brossel, 4, place Jussieu, F-75252 PARIS, cedex 05 — 2 Institute<br />
of Physics, Department for Quantum Optics and Statistics, Albert-<br />
Ludwigs-Universität Freiburg, Hermann-Herder-Str. 3, 79104 Freiburg<br />
We develop a master equation theory for general Bose-Einstein condensates.<br />
Starting from first principles, we find that the condensate’s<br />
dynamics in the presence of the non-condensed component can be described<br />
by a Lindblad master equation, which accounts for all possible<br />
two-particle interaction processes. As a first application, we study the<br />
process of condensate formation in a 3-dimensional harmonic trap.<br />
Q 47.5 Do 17:30 1A
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
Fermion- and Spin-Counting in Strongly Correlated Systems<br />
— •Sibylle Braungardt 1 , Aditi Sen 1 , Ujjwal Sen 1 , Roy<br />
J. Glauber 2 , and Maciej Lewenstein 1 — 1 ICFO - Institut de Ciencies<br />
Fotoniques, Mediterranean Technology Park, 08860 Castelldefels<br />
(Barcelona), Spain — 2 Lyman Laboratory, Physics Department, Harvard<br />
University, 02138 Cambridge, MA, U.S.A.<br />
We apply the atom counting theory to strongly correlated Fermi systems<br />
and spin models, which can be realized with ultracold atoms.<br />
The counting distributions are typically sub-Poissonian and remain<br />
smooth at quantum phase transitions, but their moments exhibit critical<br />
behavior, and characterize quantum statistical properties of the<br />
system. Moreover, more detailed characterizations are obtained with<br />
experimentally feasible spatially resolved counting distributions.<br />
Q 47.6 Do 17:45 1A<br />
Interspecies Feshbach resonances and scattering properties<br />
of the ultracold Fermi-Fermi mixture 6 Li and 40 K — •Andreas<br />
Trenkwalder 1 , Eric Wille 1,2 , Frederik Spiegelhalder 1 ,<br />
Gabriel Kerner 1 , Devang Naik 1 , Gerhard Hendl 1 , Florian<br />
Schreck 1 , Rudolf Grimm 1,2 , Tobias Tiecke 3 , Jook Walraven 3 ,<br />
Servaas Kokkelmans 4 , Eite Tiesinga 5 , and Paul Julienne 5 —<br />
1 Institut für Quantenoptik und Quanteninformation, Österreichische<br />
Akademie der Wissenschaften, Innsbruck, Austria — 2 Institut für<br />
Experimentalphysik und Forschungszentrum für Quantenphysik, Universität<br />
Innsbruck, Austria — 3 Van der Waals-Zeeman Institute of the<br />
University of Amsterdam, The Netherlands — 4 Eindhoven University<br />
of Technology, The Netherlands — 5 Joint Quantum Institute, National<br />
Institute of Standards and Technology and University of Maryland,<br />
Gaithersburg, USA<br />
We present recent results on the observation of interspecies Feshbach<br />
resonances in the Fermi-Fermi mixture of 6 Li and 40 K. The mixture is<br />
stored in an optical dipole trap and is prepared in different combinations<br />
of spin states. At specific values of the magnetic field we observe<br />
enhanced atom loss which we can assign with the help of two theoretical<br />
models to s- or p-wave Feshbach resonances. The results from<br />
a simple model agree well with a full coupled channels analysis. The<br />
singlet and triplet scattering lengths are found to be 52.1(3) a0 and<br />
63.5(1) a0 respectively. Our next step will be the formation of bosonic<br />
molecules at the identified Feshbach resonances leading towards the<br />
creation of a heteronuclear molecular BEC. Preprint: arXiv:0711.2916<br />
Q 47.7 Do 18:00 1A<br />
Dissipative dynamics of a rotating, strongly-interacting<br />
Fermi gas. — •Edmundo R. Sánchez Guajardo, Stefan Riedl,<br />
Christoph Kohstall, Alexander Altmeyer, Johannes Hecker<br />
Denschlag, and Rudi Grimm — Institut für Experimentalphysik,<br />
Technikerstrasse 25/4, A-6020 Innsbruck<br />
We present our experiments on dissipative dynamics of a rotating ultracold<br />
gas of strongly interacting 6 Li atoms in a harmonic trap. In<br />
such a system both the superfluid core and the surrounding thermal gas<br />
are hydrodynamic, in contrast to weakly interacting BEC experiments<br />
where the thermal gas is collisionless. This leads to particularly long<br />
lifetimes of rotation of the thermal part, allowing for precise measurement<br />
of the angular momentum. We measure the lifetime of the angular<br />
momentum for different temperatures and trap anisotropies using collective<br />
oscillations. The measurements are in excellent agreement with<br />
the theoretical exponential decay previously predicted [Guéry-Odelin,<br />
2000].<br />
Q 47.8 Do 18:15 1A<br />
Finite-Temperature Collective Dynamics of a strongly interacting<br />
Fermi Gas — •Christoph Kohstall 1 , Stefan Riedl 1,2 ,<br />
Edmundo R. Sánchez Guajardo 1 , Alexander Altmeyer 1,2 , Johannes<br />
Hecker Denschlag 1 , and Rudolf Grimm 1,2 — 1 Inst. of Experimental<br />
Physics and Center for Quantum Physics, Univ. Innsbruck,<br />
6020 Innsbruck, Austria — 2 Inst. for Quantum Optics and Quantum<br />
Information, Acad. of Science, 6020 Innsbruck, Austria<br />
Collective excitations are a powerful tool to investigate the dynamics<br />
of a strongly interacting fermionic quantum gas.<br />
In a weakly interacting Bose gas hydrodynamic behavior coincides<br />
with superfluidity. According to BCS-theory superfluidity of fermions<br />
concurs with pairing. These two predictions are no more valid in the<br />
BEC-BCS crossover where interactions are strong; hydrodynamic behavior,<br />
superfluidity and pairing are established at different temperatures.<br />
The focus of this talk is our experimental data on collective oscillations<br />
of an ultracold, strongly interacting gas of 6 Li atoms showing<br />
the transition from hydrodynamic to nearly collisionless behavior as<br />
a function of temperature. The results are in agreement with recent<br />
calculations that take into account Pauli blocking and pairing.<br />
We find a novel feature of the scissors mode which might indicate<br />
the critical temperature for superfluidity.<br />
In addition, radiofrequency spectra reveal the existence of atom pairs<br />
up to a temperature where the gas behaves nearly collisionless.<br />
Q 47.9 Do 18:30 1A<br />
Dynamics of a trapped spinor Fermi gas — Nils Bornemann,<br />
•Philipp Hyllus, and Luis Santos — Institut für Theoretische<br />
Physik, Leibniz-Universität Hannover, Appelstr. 2, 30167 Hannover<br />
We investigate the spin dynamics of an atomic Fermi gas with a spin<br />
of f ≥ 3<br />
in a harmonic trap. Spin-changing collisions, which induce a<br />
2<br />
population tranfer between different spin components, are largely suppressed<br />
in the presence of a sufficiently large magnetic field due to the<br />
quadratic Zeeman effect.<br />
We derive the corresponding Master equation, and neglecting coherences,<br />
we simulate the equivalent rate equation for the populations<br />
including the supressing effects of the quadratic Zeeman effect, and the<br />
trap anharmonicity. We will show that the interplay between anharmonicity<br />
and quadratic Zeeman effect leads to a resonant enhancement<br />
of the spin-changing collisions as a function of the applied magnetic<br />
field. This effect should have clearly observable consequences especially<br />
for fermions in deep optical lattices, since for bosons under the same<br />
conditions the resonances would be absent.<br />
Q 48: Quanteninformation (Quantenkommunikation)<br />
Zeit: Donnerstag 16:30–19:00 Raum: 1B<br />
Q 48.1 Do 16:30 1B<br />
Two Photon Interference of Resonance Fluorescence Photons<br />
— •S. Gerber, D. Rotter, F. Dubin, and M. Mukherjee — Institut<br />
für Experimentalphysik, Universität Innsbruck, Austria<br />
We report on two photon interference measurements of resonance fluorescence<br />
photons from trapped ions. Two indistinguishable photons<br />
impinging at two input ports of a 50/50 beam splitter coalesce, i.e. they<br />
both are leaving the device in one of the output ports. This Hong-Ou-<br />
Mandel interference is quantified by measuring correlations between<br />
the two output channels. The visibility of the two-photon interference<br />
effect determines the degree of indistinguishability of the input photons.<br />
In a first experiment, a single trapped ion is converted into a pseudo<br />
two-photon source. The single ion resonance fluorescence is split in<br />
two parts, individually coupled into optical fibers of different length<br />
and then recombined on a beam splitter. A two-photon interference<br />
is observed with a contrast reaching 83%. The spectral brightness of<br />
our two-photon source is quantified and shown to be comparable to<br />
parametric down conversion devices [1].<br />
In a successive experiment two-photon interference between two ions<br />
located in two separate traps is measured with up to 87% contrast.<br />
Thus, two-photon interference is used as a building block for quantum<br />
network operations.<br />
[1] F. Dubin, D. Rotter, M. Mukherjee, S. Gerber, R. Blatt, Phys.<br />
Rev. Lett. 99, 183001 (2007)<br />
Q 48.2 Do 16:45 1B<br />
Quantum Repeaters using Coherent-State Communication —<br />
•Peter van Loock — Optical Quantum Information Theory Group,<br />
Max Planck Research Group, Institute of Optics, Information and Photonics,<br />
Staudtstr. 7/B2, 91058 Erlangen, Germany<br />
We investigate quantum repeater protocols based upon atomic qubitentanglement<br />
distribution through optical coherent-state communication.<br />
Various measurement schemes for an optical mode entangled with
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
two spatially separated atomic qubits are considered in order to nonlocally<br />
prepare conditional two-qubit entangled states. In particular,<br />
generalized measurements for unambiguous state discrimination enable<br />
one to completely eliminate spin-flip errors in the resulting qubit<br />
states, as they would occur in a homodyne-based scheme due to the<br />
finite overlap of the optical states in phase space [1]. As a result, by<br />
using weaker coherent states, high initial fidelities can still be achieved<br />
for larger repeater spacing, at the expense of lower entanglement generation<br />
rates. In this regime, the coherent-state-based protocols start<br />
resembling single-photon-based repeater schemes.<br />
[1] P. van Loock, T. D. Ladd, K. Sanaka, F. Yamaguchi, Kae Nemoto,<br />
W. J. Munro, and Y. Yamamoto, Phys. Rev. Lett. 96, 240501 (2006).<br />
Q 48.3 Do 17:00 1B<br />
Verbesserte Fehlerschwellen für das BB84 und 6-state Protokol<br />
— •Oliver Kern, Joseph M. Renes und Gernot Alber —<br />
Institut für Angewandte Physik, Technische Universität Darmstadt,<br />
64289 Darmstadt, Germany<br />
Es ist bekannt, dass lokale Randomisierung die Raten von Quantenkryptographie<br />
Protokollen welche Einwegkommunikation nutzen, verbessern<br />
kann. Ein noch größerer Vorteil kann für das BB84 Protokol<br />
erlangt werden, indem man eine Randomisierung mit struckturierten<br />
(nicht zufälligen) Blockcodes verknüpft. Wir zeigen, dass ein<br />
solcher Vorteil auch für das 6-state Protokol erlangt werden kann. Es<br />
ist möglich, die beste untere Schranke für die Bitfehlerrate von 14.12%<br />
mit Randomisierung auf mindestens 14.57% mit dem verknüpften Verfahren<br />
zu erhöhen.<br />
Q 48.4 Do 17:15 1B<br />
Continuous-variable quantum key distribution with qudits —<br />
•Ulrich Seyfarth and Gernot Alber — Institut für Angewandte<br />
Physik, Technische Universität Darmstadt, D-64289, Darmstadt<br />
A qudit generalization of the recently discussed two-state continuousvariable<br />
quantum key distribution protocol of Heid and Lütkenhaus<br />
[1] is presented. Secret key rates are evaluated for cases in which an<br />
eavesdropper can extract information by beam splitting attacks. Resulting<br />
key generation rates for direct and reverse reconciliation are<br />
compared.<br />
[1] M. Heid and N. Lütkenhaus, Phys. Rev. A 73, 052316 (2006).<br />
Q 48.5 Do 17:30 1B<br />
Measurement induced decoupling of Gaussian Noise for quantum<br />
communication — •Metin Sabuncu 1,2 , Radim Filip 3 , Gerd<br />
Leuchs 2 , and Ulrik L. Andersen 1,2 — 1 Department of Physics,<br />
Technical University of Denmark — 2 IOIP, Max-Planck Forschungsgruppe,<br />
Universität Erlangen-Nürnberg, Germany — 3 Department of<br />
Optics, Palacky University, Czech Republic<br />
Every communication link is affected by noise. In classical communication<br />
the noise does not have a very detrimental influence and can<br />
be removed. For quantum communication, however, the effect of this<br />
noise becomes much more devastating, normally preventing quantum<br />
information processing tasks from being realised. Therefore when performing<br />
quantum communication protocols it is crucial to have efficient<br />
noise erasing procedures that renders the protocols fault tolerant. We<br />
investigate a protocol used in quantum key distribution, where the information<br />
is encoded into conjugate continuous variables of a coherent<br />
state. We then consider a Gaussian noisy interaction with the environment<br />
and show that by performing environmental measurements<br />
it is possible to decouple the noise after some suitable measurement<br />
induced operations. Using this strategy, the quantum information content<br />
of conjugate variables can be ideally recovered independent of the<br />
amount of environmental excess noise provided that the state of the<br />
environment is fully accessible. We present an experiment in which coherent<br />
states are inflicted by Gaussian noise and we present different<br />
scenarios how to decouple the noise in the channel via measurement<br />
induced operations and compare it to the theory.<br />
Q 48.6 Do 17:45 1B<br />
Time-Bin Encoding for Narrow-Band Single Photons —<br />
•Nils Neubauer, Matthias Scholz, and Oliver Benson —<br />
Humboldt-Universität zu Berlin, Institut für Physik, AG Nanooptik,<br />
Hausvogteiplatz 5-7, 10117 Berlin<br />
For long-range applications in quantum information processing (e.g.,<br />
quantum key distribution QKD), time-bin encoding of single photons<br />
is the favorable choice since this scheme does not suffer from polarization<br />
degradation in optical fibers. In order to build larger quantum<br />
networks, coherent storage and retrieval of single photons in atomic<br />
ensembles has been suggested and realized, e.g., by using electromagnetically<br />
induced transparency in optically dense media. Therefore,<br />
the spectrum of these photons needs to match the narrow linewidth of<br />
atomic resonances.<br />
We realized a scheme for time-bin encoding of narrow-band single<br />
photons. The setup consists of two unbalanced Michelson interferometers<br />
acting as encoding and decoding units. Using a relative arm length<br />
difference of 100 m each, a path delay of 500 ns can be implemented,<br />
suitable for single photons with a bandwidth of 10 MHz. It is intended<br />
to show QKD via the BB84 protocol with attenuated light pulses of<br />
this bandwidth.<br />
Q 48.7 Do 18:00 1B<br />
Eavesdropping in quantum cryptography with six mixed<br />
states — •Zahra Shadman, Hermann Kampermann, Tim<br />
Meyer, and Dagmar Bruss — Institut für Theoretische Physik<br />
III,Düsseldorf,Germany<br />
For the case of the six state protocol in the presence of white noise<br />
(six mixed states) we express the optimal mutual information for both<br />
cases Alice/Bob and Alice/Eve in terms of the noise parameter and<br />
the quantum bit error rate. In comparison to the pure state case the<br />
crossing point of the two mutual information curves moves to a higher<br />
quantum bit error rate. We conclude that the six state protocol with<br />
mixed states is more robust against eavesdropping than for pure states.<br />
Q 48.8 Do 18:15 1B<br />
Optical Free-Space Quantum Key Distribution —<br />
•Sebastian Schreiner 1 , Henning Weier 1 , Martin Fürst 1 , Tobias<br />
Schmitt-Manderbach 1 , Christian Kurtsiefer 2 , and Harald<br />
Weinfurter 1,3 — 1 Department für Physik der LMU München,<br />
Schellingstr 4/III, 80799 München — 2 Department of Physics, National<br />
University of Singapore, 2, Science Drive 3, Singapore 117542<br />
— 3 Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1,<br />
85748 Garching<br />
The security of quantum key distribution, (QKD) is based on physical<br />
laws rather than assumptions about computational complexity: An<br />
adversary will necessarily disturb the communication by his quantum<br />
measurement. This leads to an error rate in the generated keys which<br />
allows to calculate an upper bound on the information eavesdropped.<br />
However, real implementations will be sensitive to side-channel attacks,<br />
i.e. to information losses due to distinguishabilities in other degrees of<br />
freedom, which an adversary can measure without causing errors.<br />
Here we report on progress of our implementation of the BB84 protocol<br />
installed on top of two university buildings in downtown Munich.<br />
Using attenuated laser pulses in combination with decoy states we can<br />
establish a key over a distance of 500˜m. Our system is fully remote<br />
controlled and allows for continuous and fast QKD. Additionally it is<br />
fully characterized with respect to spectral, temporal and spatial sidechannels<br />
and so can guarantee secure key exchange. Our experiments<br />
proof free-space QKD to be feasible, providing high key rates while<br />
still staying both robust and simple.<br />
Q 48.9 Do 18:30 1B<br />
Distillation of entangled state after a fading channel —<br />
•Ruifang Dong 1 , Mikael Lassen 2 , Christoph Marquardt 1 , Radim<br />
Filip 1 , Ulrik L. Andersen 2 , and Gerd Leuchs 1 — 1 Institute for<br />
Optics, Information and Photonics,Max-Planck Researchgroup, University<br />
Erlangen-Nuernberg, Guenther-Scharowsky-Str. 1, 91058, Erlangen,Germany<br />
— 2 Department of Physics, Technical University of<br />
Denmark, Building 309, 2800 Lyngby, Denmark<br />
We report on the experimental distillation of a continuous variable<br />
polarization entangled state which is affected by a fading channel. We<br />
produce a polarization entangled state by mixing two fiber-based polarization<br />
squeezing states at a beam splitter [1]. After the beam splitter,<br />
one part of the entangled beams is subject to a fading channel. Such<br />
channel may exhibit any kind of random distribution of the attenuation.<br />
In the experiment, to simulate the fading channel and implement<br />
the distillation, we insert a variable optical attenuator into one of the<br />
entangled beams and tap off a small portion of the attenuated beam for<br />
post selection [2], the joint measurement on the corrupted entangled<br />
beams is also made for verification. Then by setting various different<br />
attenuation levels, we achieve a series of data from tap measurements<br />
and verification measurements which are collected by A/D card into<br />
computer. Later, all the measured data can be mixed in the computer<br />
with certain distribution form and a destroyed entangled state after<br />
a certain fading channel is simulated. Based on such procedure, the
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
distillation can be succeeded and a recovery of the original entangled<br />
state is obtained with an accessible success probability.<br />
Q 48.10 Do 18:45 1B<br />
Experimental aspects of deterministic secure quantum<br />
key distribution — •Nino Walenta 1 , Dietmar Korn 1 ,<br />
Dirk Puhlmann 1 , Timo Felbinger 1 , Kim Boström 2 , Holger<br />
Hoffmann 1 , and Martin Ostermeyer 1 — 1 Universität Potsdam,<br />
Institut für Physik, 14469 Potsdam — 2 Universität Münster, 48149<br />
Münster<br />
Most common protocols for quantum key distribution (QKD) use nondeterministic<br />
algorithms to establish a shared key. But deterministic<br />
implementations can allow for higher net key transfer rates and eavesdropping<br />
detection rates. The Ping-Pong coding scheme by Boström<br />
Q 49: Ultrakurze Laserpulse (Anwendungen II)<br />
and Felbinger [1] employs deterministic information encoding in entangled<br />
states with its characteristic quantum channel from Bob to Alice<br />
and back to Bob.<br />
Based on a table-top implementation of this protocol [2] with<br />
polarization-entangled photons fundamental advantages as well as<br />
practical issues like transmission losses, photon storage and requirements<br />
for progress towards longer transmission distances are discussed<br />
and compared to non-deterministic protocols. Modifications of common<br />
protocols towards a deterministic quantum key distribution as in<br />
[3] are addressed.<br />
[1] K. Boström, T. Felbinger. Phys. Rev. Lett. 89 187902 (2002)<br />
[2] M. Ostermeyer, N. Walenta. arXiv:quant-ph/0703242v1<br />
[3] M. Lucamarini, J. S. Shaari, M.R.B. Wahiddin.<br />
arXiv:0707.3913v1<br />
Zeit: Donnerstag 16:30–19:15 Raum: 3H<br />
Q 49.1 Do 16:30 3H<br />
Exact description of self-focusing in highly nonlinear geometrical<br />
optics — •Larisa Tatarinova and Martin Garcia — University<br />
of Kassel, Kassel, Germany<br />
Problem of intense light propagation in a media exhibiting highly nonliner<br />
responce is studied in the geometrical optic approximation. We<br />
demonstrate that for big number of modern experiments and applications<br />
this approximation is appropriate. Particularly, for propagation<br />
of 5 nJ femtosecond pulse in air, the obtained analytically selffocusing<br />
distance deviates from the numerical solution of the nonlinear<br />
Schrodinger equation as 0.4%. We construct analytical solutions for<br />
several types of nonlinearities. The obtained solutions turn out to be<br />
exact on the beam axis and provide a benchmark for numerical simulations,<br />
and replace the widely used empirical Marburger formula. We<br />
show how the hight order nonlinearities can lead to dramatic changes<br />
in the self-focusing behaviour, and present a way for their experimental<br />
determination.<br />
Q 49.2 Do 16:45 3H<br />
Enhancement of the X-ray yield by adaptive shaping of<br />
ultrashort laser pulses — •Steffen Linden, Martin Silies,<br />
Henrik Witte, and Helmut Zacharias — Physikalisches Institut,<br />
Westfälische Wilhelms-Universität Münster<br />
A deformable mirror is implemented in a laser-based hard X-ray experiment<br />
in order to increase the hard X-ray yield. The imperfect wavefront<br />
from the Ti:Sapphire CPA laser system is spatially changed by<br />
means of a piezoelectric deformable mirror before th focusing optics<br />
of the laser-plasma experiment. The hard X-ray yield of the generation<br />
process is detected by an X-ray sensitive Schottky diode. This<br />
diode delivers the feedback signal for an evolutionary algorithm, that<br />
controls the piezovoltages of the deformable mirror. After a series of<br />
generations of the algorithm with an adjustable number of individuals<br />
(one individuum represents one mirror deformation) the F e−Kα yield<br />
is enhanced significantly.<br />
Q 49.3 Do 17:00 3H<br />
Auswirkungen von zeitverzögerten und geformten fs Laserpulsen<br />
auf das Abtragsverhalten von Werkstoffen — •Markus<br />
Schomaker, Holger Lubatschowski und Alexander Heisterkamp<br />
— Laser Zentrum Hannover e.V., Hollerithalle 8, 30419 Hannover<br />
Die laserinduzierte Strukturierung ist nicht nur für das Mikro- und<br />
Nanomachining von großer Bedeutung, sondern auch im Bereich der<br />
laserbasierten Zell- und Nanochirurgie sind definierte Strukturen für<br />
eine erfolgreiche Behandlung notwendig. Um solche Strukturen erzeugen<br />
zu können, sind Kenntnisse zur Wechselwirkung von Laserstrahlung<br />
und Material erforderlich. Ein tieferes Verständnis zum Ablationsprozess<br />
geben die durchgeführten Doppelpulsexperimente, bei<br />
denen gaußförmige fs- Doppelpulse mit unterschiedlicher, zeitlicher<br />
Verzögerung generiert werden. Dieses erfolgt durch das Aufsplitten<br />
eines Laserpulses in zwei Teilpulse und der anschließenden Leitung<br />
über verschieden lange Wegstrecken, bevor die beiden Teilpulse wieder<br />
überlagert werden. Durch das Fokussieren dieser Doppelpulse auf eine<br />
Probe können Abträge realisiert werden. Erfolgt das Auftreffen der<br />
Teilpulse zeitverzögert im Pikosekundenbereich, kommt es zu einer<br />
räumlichen Veränderung in den Abtragsdimensionen. Ebenfalls wird<br />
die Größe des Abtrags durch das Umwanden der Pulsform beeinflusst.<br />
Realisiert wird dieses durch das Einbringen einer Phasenplatte in den<br />
Strahlengang und einer Überlagerung der Teilpulse. Die erzielten Ergebnisse<br />
erlauben ein besseres Verständnis zur Puls- Materialwechselwirkung<br />
und geben Informationen zum gesamten Abtragsprozess.<br />
Q 49.4 Do 17:15 3H<br />
Adaptive Optik und deren Anwendung in biologischen Systemen<br />
— •Raoul-Amadeus Lorbeer, Holger Lubatschowski und<br />
Alexander Heisterkamp — Laser Zentrum Hannover e.V., Hollerithallee<br />
8, 30419 Hannover<br />
Die Echtzeitanpassung von Teleskopsekundärspiegeln an atmosphärische<br />
Turbulenzen hat die terrestrische Astronomie revolutioniert.<br />
Durch kompaktere Systeme könnte diese Technik nun auch Einzug<br />
in die Mikroskopie und Lasermedizin halten. Ein geeignetes System<br />
stellen so genannte Spatial Light Modulators (SLMs) dar. Mit einem<br />
Flüssigkristall SLM lassen sich die Wellenfronten von Laserlicht gezielt<br />
manipulieren und zur Verbesserungen der optischen Eigenschaften<br />
bzw. der Verringerung möglicher Aberrationen in biologischen Systemen<br />
einsetzen.<br />
Mögliche Anwendungsfelder sind daher zum einen die Augenheilkunde<br />
und zum anderen die Mikroskopie. Bei der Propagation des Lichtes<br />
durch Augenhornhaut, Augenlinse sowie Glaskörper werden diesem<br />
Aberrationen aufgeprägt. Um somit in der Augenheilkunde den Augenhintergrund<br />
genau abbilden und manipulieren zu können, ist es notwendig,<br />
die auftretenden Wellenfrontverkrümmungen zu korrigieren.<br />
Ebenso ist in der Mikroskopie beim Arbeiten mit hohen Numerischen<br />
Aperturen die detailgetreue Abbildung aus verschiedenen Probentiefen<br />
nicht mehr gewährleistet und eine Korrektur sinnvoll.<br />
Aus diesen Gründen wurde ein Versuchsaufbau realisiert, mit dem<br />
sowohl die Messung von Aberrationen als auch deren Korrektur<br />
möglich ist.<br />
Q 49.5 Do 17:30 3H<br />
Laser-Gewebe-Wechselwirkungen von ultrakurzen Laserpulsen<br />
bei unterschiedlichen Pulsfolgefrequenzen — •Kai<br />
Kütemeyer, Judith Baumgart, Holger Lubatschowski und Alexander<br />
Heisterkamp — Laser Zentrum Hannover e.V., Hollerithallee<br />
8, 30419 Hannover<br />
Oberhalb einer materialabhängigen Intensitätsschwelle erzeugt ein ultrakurzer<br />
Laserpuls in einem transparenten Medium einen optischen<br />
Durchbruch, der zu einem Abtrag des Materials führt. Für die Manipulation<br />
von einzelnen Zellorganellen in der Zellchirurgie ist die Minimierung<br />
der durch die Laserstrahlung eingebrachten Energie entscheidend,<br />
um die Vitalität der Zellen nach der Behandlung zu gewährleisten. Deshalb<br />
wird der Abtrag von einzelnen Zellorganellen im MHz Bereich<br />
mit Pulsenergien um 1 nJ unterhalb der Schwellenenergie für einen<br />
optischen Durchbruch durch kumulative chemische Effekte erzielt, die<br />
durch erzeugte freie Elektronen induziert werden. Zur Untersuchung<br />
dieser Mechanismen werden mit Hilfe eines akusto-optischen Modulators<br />
und eines mechanischen Shutters Pulszüge mit einer variablen<br />
Pulsfolgefrequenz zwischen 20 kHz und 4,5 MHz, einer Pulsdauer von<br />
100 fs und einer Pulsenergie von einigen nJ erzeugt. Durch ein Objektiv<br />
mit einer hohen numerischen Apertur von 1,3 werden die Pulse auf<br />
die Probe fokussiert. In Abhängigkeit der Pulsenergie, der Pulsfolgefre-
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
quenz und der Anzahl der eingestrahlten Pulse wird die Schädigung in<br />
transparenten biologischen Proben und künstlichen Modellsubstanzen<br />
bewertet, um eine Optimierung der Parameter für die Manipulation<br />
innerhalb einzelner Zellen zu erreichen.<br />
Q 49.6 Do 17:45 3H<br />
Zwei-Farben-Pump-Abfrage-Messungen von Quantenpunktstrukturen<br />
mit einem MHz-OPA — •Marcel Schultze, Andy<br />
Steinmann, Guido Palmer und Uwe Morgner — Institut für Quantenoptik,<br />
Leibniz Universität Hannover<br />
Da die zeitliche Auflösung von Pump-Abfrage-Messungen direkt mit<br />
der Pulsdauer der verwendeten Laserquelle korreliert, eignen sich<br />
Femtosekundenlaser hervorragend um z.B. einen direkten Einblick in<br />
die Ladungsträgerdynamik von Halbleiterstrukturen zu erlangen. Wir<br />
präsentieren die Messung der Relaxationsdynamik von Quantenpunktproben<br />
mit Hilfe einer Pump-Abfrage-Messung. Als Quelle dient ein<br />
optisch parametrischer Verstärker (OPA) mit MHz-Repetitionsrate.<br />
Im Vergleich zu kHz-Systemen ist dieser deutlich rauschärmer und<br />
ermöglicht durch die höheren Repetitionsraten eine Verbesserung<br />
des Signal-zu-Rausch-Verhältnisses. Dadurch lassen sich Transmissionsänderung<br />
bis herab zu 0,05 % messen. Ein passiv modengekoppelter<br />
Yb:KYW Oszillator mit Cavity-Dumping dient bei einer Zentralwellenlänge<br />
von 1040 nm als Pumpquelle für den OPA und wird gleichzeitig<br />
zur Anregung der Quantenpunktproben verwendet. Der durchstimmbare<br />
Idler des OPA-Systems wird im Wellenlängenbereich von<br />
1100 nm bis 1300 nm für die zeitliche Abfrage der Exzitonenniveaus<br />
der Halbleiterstrukturen genutzt. Durch eine zusätzliche Kühlung der<br />
Probe mit Hilfe eines Stickstoffkryostaten konnte eine weitere Zunahme<br />
der Transmissionsänderung erreicht werden.<br />
Q 49.7 Do 18:00 3H<br />
Femtosekunden Wellenform-Synthesizer — •Stefan Rausch,<br />
Thomas Binhammer, Anne Harth und Uwe Morgner — Institut<br />
für Quantenoptik, Leibniz Universität Hannover<br />
Die Formung der spektralen Phase ultrakurzer Laserpulse wird seit<br />
kurzem gezielt angewandt, um zeitliche Pulsprofile und -sequenzen<br />
auf Femtosekunden-Zeitskalen zu erzeugen. Durch eine zusätzliche<br />
Einflussnahme auf die spektrale Amplitude des Pulses eröffnen sich<br />
zahlreiche neue Möglichkeiten auf dem Gebiet der Femtosekunden-<br />
Pulsformung.<br />
Wir präsentieren hier einen Pulsformer-Aufbau bestehend aus einem<br />
Titan:Saphir-Oszillator, einem SPIDER-Messsystem und einem LCD-<br />
Pulsformer, der die unabhängige Manipulation von spektraler Pulsphase<br />
und -amplitude erlaubt. Das über-oktavbreite Spektrum des Lasers<br />
unterstützt eine Fourier-limitierte Pulsdauer von 3.7 fs, was ihn zur<br />
idealen breitbandigen Lichtquelle für Pulsformungsexperimente macht.<br />
Mit diesem Aufbau ist es möglich, Pulse mit variablen spektralen Formen,<br />
Pulsdauern unterhalb des Fourier-Limits und andere anspruchsvolle<br />
zeitliche Pulsformen zu generieren. Einige dieser Ergebnisse werden<br />
hier präsentiert.<br />
Um die totale Kontrolle über das E-Feld eines ultrakurzen Laserpulses<br />
zu erlangen, muss neben seiner spektralen Phase und Amplitude<br />
zusätzlich seine Träger-Einhüllende Phase beeinflusst werden, was über<br />
eine Phasenstabilisierung des Oszillators erreicht werden kann. Der<br />
dann realisierte Wellenform-Synthesizer erlaubt phasensensitive Experimente<br />
mit variablen Pulsformen im Bereich der kohärenten Kontrolle.<br />
Q 49.8 Do 18:15 3H<br />
Attosecond relative timing jitter from a two-branch femtosecond<br />
Er:fiber laser — •Alexander Sell 1 , Florian Adler 1,2 ,<br />
Rupert Huber 1 , and Alfred Leitenstorfer 1 — 1 Department of<br />
Physics, University of Konstanz, 78464 Konstanz, Germany — 2 JILA,<br />
University of Colorado, Boulder, Colorado 80309-0440, USA<br />
We present the first direct measurement of the relative timing jitter<br />
between the parallel pulse trains of two erbium-doped fiber amplifiers<br />
which share the same femtosecond seed oscillator. The system is operated<br />
without active stabilization. Each amplifier branch provides independently<br />
tunable pulses in the near infrared (tuning range: 1.0 µm to<br />
2.4 µm) with durations down to 12 fs, generated via four wave mixing<br />
in a highly nonlinear dispersion shifted bulk fiber. Employing an interferometric<br />
optical cross-correlator, the phase noise spectral density is<br />
measured with high sensitivity in a range from 1 Hz up to the Nyquist<br />
frequency of 24.5 MHz. The integrated timing jitter amounts to 11 attoseconds<br />
directly after the amplifier stages and 43 as after propagation<br />
through free-space optics and nonlinear fibers for frequency conversion.<br />
Multi-branch fiber lasers are thus promising seed sources for important<br />
applications such as phase stable, tunable difference frequency generation,<br />
field resolved spectroscopy or high-harmonic generation.<br />
Q 49.9 Do 18:30 3H<br />
Strong field control of molecular dynamics by resonant shaped<br />
ultrashort laser pulses — •Matthias Wollenhaupt, Tim Bayer,<br />
and Thomas Baumert — Universität Kassel, Institut für Physik and<br />
Center for Interdisciplinary Nanostructure Science and Technology<br />
(CINSaT), Heinrich-Plett-Str. 40, D-34132 Kassel, Germany<br />
Quantum control by tailored ultrashort light pulses is very successful<br />
to manipulate physical and chemical properties of matter. In many<br />
cases the underlying physical processes are not very well understood<br />
– particularly when shaped resonant intense pulses are applied. These<br />
pulses are of general importance because resonant control scenarios<br />
are the dominant pathways for pulses with ultra broad spectra. In this<br />
contribution the physical mechanism of strong field quantum control<br />
using tailored resonant pulses is investigated on small molecules [1-3].<br />
Switching among different final electronic states is realized by selective<br />
population of dressed states (SPODS). Our experiment is based<br />
on femtosecond pulse shaping and time-of-flight photoelectron spectroscopy.<br />
The spectrum of a femtosecond laser pulse is sinusoidally<br />
phase-modulated in frequency domain [4] to produce a sequence of<br />
pulses interacting with molecules in a beam. Our result show selectivity<br />
among different electronic states. Because SPODS is ultrafast our<br />
strategy might be operative in the presence of decoherence processes<br />
as well. [1] M. Wollenhaupt et al., Chem. Phys. Lett 419, 184 (2006)<br />
[2] M. Wollenhaupt and T. Baumert, J. Photochem. Photobiol. A 180,<br />
248 (2006) [3] M. Wollenhaupt et al., Ann. Rev. Phys. Chem. 56, 25<br />
(2005) [4] M. Wollenhaupt et al., Phys. Rev. A. 73, 063409 (2006)<br />
Q 49.10 Do 18:45 3H<br />
Ludwig-Maximilians-Universität, München, Deutschland —<br />
•Philipp von den Hoff, Dorothee Geppert, and Regina de Vivie-<br />
Riedle — Ludwig-Maximilians-Universität, München, Deutschland<br />
An efficient approach to describe electron dynamics in molecules is developed<br />
which exploits quantum dynamics and quantum chemistry in<br />
a new way. The photodissociation of D +<br />
2 , that can be controlled via the<br />
carrier-envelope phase of an ultrashort laser pulse, is chosen as a test<br />
system. In this system, the approach is checked against more rigorous<br />
theories as well as experiments which show excellent agreement. The<br />
electron dynamics is visualized in several ways including the phase information<br />
of the electronic wavefunction. The detailed analysis of the<br />
electron motion after different ionization events reveals the underlying<br />
complex dynamics which are hidden in the experiment. The interplay<br />
between the carrier-envelope phase and electron control is elucidated.<br />
The ansatz is based on the highly developed electronic structure theory<br />
and can be implemented quite easily. The method allows for a successive<br />
extension to multi-electron systems and simultaneously enables a<br />
quantum dynamical description of the nuclear motion.<br />
Q 49.11 Do 19:00 3H<br />
Strong-field control landscapes of coherent electronic excitation<br />
— •Tim Bayer, Matthias Wollenhaupt, and Thomas<br />
Baumert — Universität Kassel, Institut für Physik und CINSaT,<br />
Heinrich-Plett-Str. 40, D-34132 Kassel, Germany<br />
We study physical mechanisms of resonant strong-field coherent control.<br />
To this end, time-of-flight photoelectron spectra from multiphoton<br />
ionization of potassium atoms with intense shaped femtosecond<br />
laser pulses are measured and discussed in terms of Selective Population<br />
of Dressed States (SPODS). Recently, it was shown [1,2] that pulse<br />
sequences and chirped pulses provide efficient yet complementary realizations<br />
of SPODS. Combining these two approaches thus leads to<br />
a physically motivated pulse parametrization that opens up search<br />
spaces of manageable size. The SPODS control topology of these reduced<br />
search spaces is mapped out experimentally and presented in<br />
the form of strong-field control landscapes. Having revealed the landscape<br />
topologies we apply the same pulse parametrization to an adaptive<br />
optimization procedure in order to optimize SPODS on one of<br />
the mapped parameter spaces. The concept of control trajectories is<br />
introduced and serves to visualize the temporal evolution of the optimization<br />
on the measured landscape surface. The question whether<br />
such optimization procedures under experimentally constrained conditions<br />
in fact end up at the global optimum or eventually become<br />
trapped by suboptimal local extrema [3] is addressed.<br />
[1] M. Wollenhaupt et al.: PRA 73, 2006 [2] M. Wollenhaupt et al.:<br />
APB 82, 2006 [3] H. A. Rabitz et al.: PRA 74, 2006
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
Q 50: Poster Ultrakalte Atome<br />
Zeit: Donnerstag 16:30–19:00 Raum: Poster C2<br />
Q 50.1 Do 16:30 Poster C2<br />
Trapping and guiding neutral atoms using ultra-thin optical<br />
fibres. — •Guillem Sagué, Eugen Vetsch, Florian Warken,<br />
and Arno Rauschenbeutel — Institut für Physik, Staudingerweg 7,<br />
55128 Mainz<br />
We aim to optically trap and guide neutral atoms close to the surface<br />
of subwavelength-diameter optical fibres. For this purpose, we set up<br />
a two-colour surface trap which is based on light-induced dipole forces<br />
exerted on the atoms by a blue- and red-detuned evanescent light field<br />
[1], created by launching two co-propagating laser beams through the<br />
fibre. This results in a cylindrically symmetric trap around the fibre.<br />
It exhibits a trapping minimum about two hundred nanometers above<br />
the surface with expected radial trapping frequencies above 700 kHz.<br />
By launching a second, counter-propagating red-detuned laser beam<br />
through the fibre a red-detuned standing wave can be realized. This<br />
results in a periodic trapping potential along the fibre, thereby confining<br />
the atoms in all three dimensions.<br />
[1] G. Sagué, E. Vetsch, W. Alt, D. Meschede, and A. Rauschenbeutel,<br />
Phys. Rev. Lett. 99, 163602 (2007)<br />
Q 50.2 Do 16:30 Poster C2<br />
Optical Spectroscopy On Trapped Nanoparticles —<br />
•Alexander Kuhlicke, Stefan Schietinger, and Oliver Benson<br />
— AG Nano-Optik, Institut für Physik, Humboldt-Universität zu<br />
Berlin, Hausvogteiplatz 5-7, 10117 Berlin<br />
Linear radio frequency ion traps, so-called Paul traps, became widely<br />
used tools for high-resolution spectroscopy because of the absent interaction<br />
between particles and supporting surfaces or other particles.<br />
With their help it was possible to build up quantum registers and<br />
implement first operations for quantum computing. Also trapping of<br />
micrometer-sized particles in larger traps was demonstrated. Until today<br />
not much work was done for trapping particles in the span between<br />
these two size regimes of few atoms and microscopic particles. We have<br />
narrowed the gap by trapping single nanoparticles with sizes down to<br />
20 nm within a linear Paul trap. We observed Coulomb crystals within<br />
the trap and performed spectroscopy on single trapped dye-doped particles<br />
and N-V centers in nanodiamonds. Future experiments aim at<br />
the spectroscopy of single quantum emitters revealing their interaction<br />
with a mesoscopic environment.<br />
Q 50.3 Do 16:30 Poster C2<br />
Lasersystem zum Kühlen und Fangen von neutralem Quecksilber<br />
— •Patrick Villwock, Arne Schönhut, Mathias Sinther<br />
und Thomas Walther — TU Darmstadt, Institut für Angewandte<br />
Physik, AG Laser und Quantenoptik, Schlossgartenstr.7, 64289 Darmstadt<br />
Kalte Quecksilberatome in einer magneto-optischen Falle bieten die<br />
Möglichkeit der Erzeugung translatorisch kalter Moleküle durch Photoassoziation,<br />
sowie deren Laserkühlung in den vibratorischen Grundzustand.<br />
Zusätzlich erlaubt es die Untersuchung eines neuen Zeitstandards.<br />
Quecksilber hat stabile bosonische und fermionische Isotope,<br />
deren natürliche Häufigkeit im zweistelligen Prozentbereich liegen.<br />
Die Sättigungsintensität des Kühlübergangs bei 253,7 nm beträgt<br />
10,2 mW/cm 2 bei einer natürlichen Linienbreite von 1,27 MHz.<br />
Die Strahlung bei dieser Wellenlänge kann durch zweimalige Frequenzverdoppelung<br />
erreicht werden. Als Basis dient ein Yb:YAG Scheibenlaser<br />
der am Rand seines Verstärkungsmaximums bei 1014,8 nm betrieben<br />
wird. Die erste Verdopplungsstufe bildet ein geheizter LBO innerhalb<br />
eines Überhöhungsresonators. Als zweite Verdopplungseinheit<br />
folgt ein kommerzieller Überhöhungsresonator mit einem temperaturstabilisierten<br />
BBO. UV-Leistungen über 200 mW können so erreicht<br />
werden.<br />
Q 50.4 Do 16:30 Poster C2<br />
Clock laser for an optical lattice clock with strontium —<br />
•Thomas Legero, Fritz Riehle, and Uwe Sterr — Physikalisch-<br />
Technische Bundesanstalt, Braunschweig, Germany<br />
Ultrastable lasers with high spectral purity are a key technology in optical<br />
frequency metrology. We report on a 698 nm master-slave diode<br />
laser setup to probe the 1S0 - 3P0 clock transition of strontium atoms<br />
confined in a 1D optical lattice. The master laser is an extended cavity<br />
diode laser in Littman configuration which is locked to a high finesse<br />
optical cavity by the Pound-Drever-Hall stabilization technique. The<br />
temperature-stabilized and vibration-insensitive cavity is made of a<br />
100 mm long ULE spacer and shows a Finesse of 330 000. For probing<br />
the clock transition, the light from the injection locked slave laser is<br />
sent to the strontium atoms and to a femtosecond fiber-laser comb by<br />
two actively noise-cancelled optical fibers. We present the setup and<br />
the characteristics of the master-slave system and the performance of<br />
the fiber noise cancellation.<br />
Q 50.5 Do 16:30 Poster C2<br />
Vorbereitende Experimente zu einer magnetooptische Falle<br />
für Erbium — •Riad Bourouis, Benjamin Botermann und Martin<br />
Weitz — Universität Bonn, Institut für Angewandte Physik, 53115<br />
Bonn, Deutschland<br />
Wir zeigen, wie wir eine magnetooptische Falle für Erbium realisieren<br />
wollen. Die optischen Eigenschaften von Erbium werden<br />
präsentiert. Insbesondere erklären wir den Aufbau einer Erbium-<br />
Gasentladungszelle, mit deren Hilfe wir eine Spektroskopie zur Stabilisierung<br />
eines kommerzielles Lasersystem betreiben. Außerdem stellen<br />
wir Planung, Aufbau und Konzept eines Zeeman-Slowers vor. Dabei<br />
gehen wir speziell auf die Vereinbarkeit von theoretischer Vorarbeit<br />
und experimenteller Umsetzung ein. Wir berichten über aktuelle Fortschritte<br />
des Experiments.<br />
Q 50.6 Do 16:30 Poster C2<br />
Ion trap for efficient single ion-photon coupling — Robert<br />
Maiwald 1,2 , •Markus Sondermann 1 , Gerd Leuchs 1 , James C.<br />
Bergquist 2 , Dietrich Leibfried 2 , Joe Britton 2 , and David J.<br />
Wineland 2 — 1 Institut für Optik, Information und Photonik, Max<br />
Planck Forschungsgruppe, Universität Erlangen-Nürnberg, 91058 Erlangen,<br />
Germany — 2 National Institute of Standards and Technology,<br />
Boulder, CO 80305, USA<br />
We present the design of an ion trap that allows for the localization of<br />
an ion in the focal point of a deep parabolic mirror. The trap consists<br />
of a single radio frequency (RF) electrode and two ground electrodes.<br />
The RF electrode and one of the ground electrodes are placed concentrically<br />
on the optical axis of a conducting parabolic mirror that<br />
establishes the second ground electrode. This geometry results in a<br />
trapping potential that follows the axial symmetry of parabolic mirrors.<br />
Furthermore, the trap design enables minimally invasive optical<br />
access to the ion from almost the entire solid angle. The latter property<br />
is essential for efficient coupling of single ions to single photons in free<br />
space.<br />
The trap design can be adapted for other applications by replacing<br />
the mirror by a planar electrode. Using this more general design the<br />
ion can still be optically accessed from at least half to over 90% of the<br />
solid angle. First test results are presented.<br />
Q 50.7 Do 16:30 Poster C2<br />
Ultra-cold Strontium atoms in 1-D optical lattice for optical<br />
frequency metrology — •Joseph Sundar Raaj Vellore Winfred,<br />
Thomas Legero, Christian Lisdat, Fritz Riehle, and Uwe Sterr<br />
— Physikalisch-Technische Bundesanstalt, Braunschweig, Germany<br />
Recent advancement in optical frequency metrology promises to measure<br />
time with a fractional accuracy of 10 −17 . Such precise measurement<br />
of time is very important in technological and scientific endeavors.<br />
With a narrow transition linewidth of about 1 mHz and the existence<br />
of the magic wavelength in the NIR region for optical traps<br />
leading to cancellation of AC stark shift of the clock transition, strontium<br />
is an attractive candidate for such an optical clock. We report<br />
preliminary results of our Strontium optical clock experiment. 88 Sr<br />
atoms are cooled down to ultra cold temperature regime(∼ 1 µK) and<br />
trapped in a 1-D optical lattice with a potential depth around 120<br />
µK. Details of our experimental set up, characterization of atoms in<br />
the 1-D optical lattice with respect to different trap parameters and<br />
the status of spectroscopy of the magnetic field induced 1 S0- 3 P0 clock<br />
transition will be presented.<br />
Q 50.8 Do 16:30 Poster C2<br />
Chromium atoms in a very deep optical trap — •Jimmy Sebastian,<br />
Anoush Aghajani-Talesh, Markus Falkenau, Axel Griesmaier,<br />
and Tilman Pfau — 5. Physikalisches Institut, Universität
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
Stuttgart<br />
We study the properties of a very deep (∼4mK) optical dipole trap<br />
for ultracold chromium atoms that is generated by a single 300W fibre<br />
laser at a wavelength of 1070nm. We load the dipole trap directly from<br />
a magneto optical trap. Due to the high intensity of the laser field,<br />
the atoms in the region of the dipole trap experience differential light<br />
shifts between ground state and excited state much larger than the line<br />
width of the cooling transition. Additionally, the shifts depend on the<br />
polarization of the dipole trap beam and on the magnetic states which<br />
strongly influences the cooling and loading mechanism in the trap.<br />
We present spectroscopic measurements and calculations of the differential<br />
shifts and discuss strategies for optimal loading of optical traps<br />
in such a regime.<br />
Q 50.9 Do 16:30 Poster C2<br />
Ladedynamik optischer Dipolfallen bei Erdalkaliatomen —<br />
•Felix Vogt, Joseph Sundar Raaj Vellore Winfred, Uwe Sterr<br />
und Fritz Riehle — Physikalisch-Technische Bundesanstalt, Bundesallee<br />
100, D-38116 Braunschweig<br />
Vorgestellt wird die experimentelle Untersuchung des Transfers von<br />
Atomen aus einer magnetooptischen Falle in eine optische Dipolfalle<br />
für die Erdalkaliatome 40 Ca und 88 Sr. Beide Elemente werden in einer<br />
zweistufigen magnetooptischen Falle auf ∼12 µK (Ca) und ∼1 µK (Sr)<br />
abgekühlt und in eine optische Dipolfalle umgeladen. Als Dipolfallenlaser<br />
dient für Ca ein 25 W Yb:YAG-Scheibenlaser (1030 nm) und für<br />
Sr ein 1,1 W Ti:Sa-Laser (813 nm). Das durch das Lichtfeld des Dipolfallenlasers<br />
erzeugte Potential des Grund- ( 1 S0) und angeregten<br />
Zustands ( 3 P1) ist attraktiv, weist jedoch, abhängig von der Wellenlänge<br />
des Dipolfallenlasers eine unterschiedliche Tiefe für die atomaren<br />
Zustände auf. Dies beeinflusst die Effizienz der Laserkühlung<br />
innerhalb der Dipolfalle und damit auch die Laderate. Wir beobachten<br />
ein dynamisches Gleichgewicht im Transfer der Atome zwischen Dipolund<br />
magnetooptischer Falle, das durch ein Differentialgleichungsmodell<br />
gut beschrieben werden kann. Maximale Transferraten werden bei<br />
übereinstimmender Tiefe von Grund- und angeregtem Zustand erwartet.<br />
Der Einfluss des geometrischen Überlapps zwischen beiden Fallen<br />
auf die Laderate wird zusätzlich diskutiert und die optimalen Transferbedingungen<br />
für Ca und Sr miteinander verglichen.<br />
Q 50.10 Do 16:30 Poster C2<br />
Atom guiding in a photonic band gap fibre — •Stefan Vorrath,<br />
Sönke Möller, Kai Bongs, and Klaus Sengstock — Universität<br />
Hamburg, Institut für Laser-Physik, Hamburg, Germany<br />
In our project we investigate a promising new kind of atomic waveguide<br />
based on a 2D photonic band gap fibre which provides nearly lossless<br />
guiding of light and atoms in the central hole over long distances. Our<br />
guiding mechanism is realized by capturing, compressing and cooling<br />
rubidium atoms from a dark spot MOT into the guiding trap composed<br />
of several watts of laser power at 1064nm. After optimizing the<br />
loading process of our trap we capture about 3 million atoms in front<br />
of the fibre. Our newest results will be presented.<br />
Q 50.11 Do 16:30 Poster C2<br />
Status of the Hamburg Cavity Cooling Experiment — •Julian<br />
Klinner, Malik Lindholdt, Matthias Wolke, and Andreas Hemmerich<br />
— Institut für Laserphysik, Universität Hamburg, Hamburg,<br />
Germany<br />
We prepared a new experimental apparatus, which permits to trap a<br />
Bose-Einstein Condensate of rubidium atoms inside an optical cavity<br />
with 500.000 finesse and a mode volume greater than 0.1 cmm. The<br />
cavity displays a ratio between the scattering rate into the cavity mode<br />
and into all other modes well above 10 and a narrow bandwidth of a<br />
few kHz. We plan to explore cavity induced cooling mechanisms in the<br />
transition regime between thermal and quantum degenerate atomic<br />
dynamics. The poster presents the status of our experiments.<br />
Q 50.12 Do 16:30 Poster C2<br />
CO2-Laser Optical Dipole Trap for Fermionic Potassium<br />
Atoms — •Alexander Gatto, Christian Bolkart, Sylvi Händl,<br />
and Martin Weitz — Institut für Angewandte Physik, Rheinische<br />
Friedrich-Wilhelms-Universität Bonn, Wegelerstrasse 8, 53115 Bonn,<br />
Deutschland<br />
All optical techniques for the cooling of atoms toward quantum degeneracy<br />
are especially attractive for fermions, since in contrast to most<br />
magnetic trap techniques no additional atomic species for sympathetic<br />
cooling are required here. We here report on ongoing work aiming at an<br />
all-optical preparation of a 40K Fermi gas in a CO2-laser dipole trap,<br />
which will be used for the study of strongly correlated Fermi gases in<br />
optical lattices. Initially, we load a magneto-optical trap of 40K atoms<br />
from a two-dimensional MOT. Subsequently, the atomic density is increased<br />
in a compressed MOT, for which the magnetic field gradient<br />
is ramped towards higher values. Our CO2-laser dipole trap realized<br />
by a single mid-infrared focussed beam is loaded from this ensemble of<br />
cold atoms, in which further cooling by means of evaporative cooling<br />
will be performed. The present status of the work will be reported.<br />
Q 50.13 Do 16:30 Poster C2<br />
Continuous loading of calcium atoms into an optical dipole<br />
trap — •Purbasha Halder, Chih-Yun Yang, Oliver Appel, Dirk<br />
Hansen, and Andreas Hemmerich — Institut für Laserphysik, Universität<br />
Hamburg, Luruper Chaussee 149, 22761 Hamburg<br />
Alkaline-earth metals are interesting candidates for novel laser cooling<br />
schemes due to the presence of narrow intercombination lines in<br />
addition to strong principal fluorescence lines. We demonstrate an efficient<br />
scheme for continuously loading Ca atoms into a ground-state<br />
( 1 S0) optical dipole trap (ODT) at 532nm. The ODT is loaded from a<br />
MOT in the triplet metastable state ( 3 P2), by spatially selective optical<br />
pumping. This is done by careful superposition of the dipole trap<br />
laser on a depumping laser at 430 nm.<br />
With this setup we achieve a cold ensemble of 10 5 atoms at 40 µK<br />
and a phase space density of 4 · (10 −5 ). The loading and subsequent<br />
evaporation and cross-dimensional relaxation stages are well described<br />
by a simple model. We also point out that a comparable scheme could<br />
be employed to load a dipole trap with 3 P0 atoms.<br />
We are now setting up a new dipole laser at 1064 nm. We will be<br />
trying out a crossed dipole trap with which we hope to achieve efficient<br />
evaporative cooling and eventually reach quantum degeneracy.<br />
Here, we present the latest developments and the current status of our<br />
experiment.<br />
Q 50.14 Do 16:30 Poster C2<br />
Development and Characterization of a Multiple Species Zeeman<br />
Slower — Ryan Olf, Edward Marti, Enrico Vogt, •Anton<br />
Öttl, and Dan Stamper-Kurn — Department of Physics, University<br />
of California, Berkeley, CA 94720<br />
An increasing number of experiments cool and trap multiple atomic<br />
species both simultaneously and alternatively. Here we present a Zeeman<br />
slower design which is optimized for multiple species operation.<br />
Different sections of precision windings are targeted at individual<br />
species, with only marginally reduced performance than a slower designed<br />
for a single species only.<br />
We have constructed a Zeeman slower that is optimized for Lithium<br />
and Rubidium atoms emerging from a dual species oven. A combined<br />
Lithium-Rubidium magneto-optical trap is loaded with the slowed<br />
atomic beam. We will review design and construction of the setup<br />
and characterize the dual species operation of our system.<br />
Q 50.15 Do 16:30 Poster C2<br />
Imaging ultracold atoms with nanometer resolution — •Tim<br />
Langen, Tatjana Gericke, Peter Würtz, Daniel Reitz, and Herwig<br />
Ott — Institut für Physik, Johannes Gutenberg-Universität,<br />
55099 Mainz<br />
We present our experimental setup for high resolution imaging of individual<br />
atoms in ultracold quantum gases. The apparatus combines<br />
scanning electron microscopy with a standard all-optical approach to<br />
Bose-Einstein condensation of 87 Rb. A condensate of up to 120000<br />
atoms is produced inside a CO2 laser dipole trap 13 mm below the tip<br />
of an electron microscope. The focused 6 keV electron beam scanning<br />
through the cloud of atoms is able to locally produce ions that are<br />
subsequently detected with a channeltron ion detector. This allows a<br />
precise reconstruction of the atoms’ initial positions only limited by<br />
the width of the electron beam. We demonstrate the resolving power<br />
by imaging single sites of an optical lattice with a period of 604 nm.<br />
Q 50.16 Do 16:30 Poster C2<br />
Fringe-free imaging of BEC with spatially incoherent light —<br />
•Jochen Kronjäger 1 , Lars Neumann 1 , Christoph Becker 1 , Kai<br />
Bongs 2 , and Klaus Sengstock 1 — 1 Institut für Laser-Physik, Universität<br />
Hamburg — 2 Midlands Centre for Ultracold Atoms, University<br />
of Birmingham<br />
Imaging techniques of cold atomic gases, e.g. alkali Bose-Einstein condensates,<br />
critically rely on one atomic absorption line with a width
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
of a few MHz typically. Laser light from the same source used for<br />
e.g. Doppler cooling naturally provides the highly concentrated spectral<br />
power density needed for efficient absorption or phase contrast<br />
imaging. The drawback of using laser illumination in any application<br />
is interference fringes, originating from diffraction at optical apertures<br />
or dust particles and multiple reflections on optical surfaces in the light<br />
path.<br />
We have developed and tested an approach to neutralize these unwanted<br />
artefacts which is based on laser light scattered from an opaque<br />
fluid. In a simplified view, random scattering destroys the spatial coherence<br />
of the beam, while preserving its spectral narrowness. A more<br />
refined approach based on the properties of laser speckle allows to<br />
quantitatively analyze our setup and demonstrates its fitness for the<br />
purpose of fringe reduction.<br />
Q 50.17 Do 16:30 Poster C2<br />
Methods for High-Resolution Preparation of Bose-Einstein<br />
Condensates with Spatial Light Modulators — •Simon<br />
Stellmer, Mathis Baumert, Christoph Becker, Parvis Soltan-<br />
Panahi, Jochen Kronjäger, Kai Bongs, and Klaus Sengstock —<br />
Institut für Laserphysik, Uni Hamburg, Germany<br />
The use of Spatial Light Modulators (SLM) has developed into a common<br />
technique in the past years. The field of application ranges from<br />
biological use in the form of optical tweezers to optical manipulation<br />
of Bose-Einstein condensates. Splitting and transport of BECs [1] has<br />
been demonstrated, as well as the generation of oscillating solitons [2]<br />
and the observation of Josephson junctions in ultra-cold atoms [3].<br />
Here we present a method to manipulate BECs with an extraordinary<br />
high spatial resolution, leading e.g. to the generation of solitons in<br />
Bose-Einstein condensates. We achieve the accuracy by imaging computer<br />
generated structures on a spatial light modulator onto the BEC.<br />
Additional preparation methods are discussed regarding resolution<br />
and feasibility. We present holographic imaging in divergent laser<br />
beams allowing for an optical set-up with extremely high numerical<br />
aperture and therefore high resolution. Furthermore, we report on the<br />
possibilities of generating non-diffractive Bessel beams which may be<br />
employed in transport of atoms within quantum registers and atom<br />
guiding within photonic band gap fibres.<br />
[1] V. Boyer et al., Phys. Rev. A 73, 031402 (2006)<br />
[2] C. Becker et al., to be published<br />
[3] S. Levy et al., Nature 449, 579 (2007)<br />
Q 50.18 Do 16:30 Poster C2<br />
State-selective microwave potentials on atom chips — •Pascal<br />
Böhi 1,2 , Max F. Riedel 1,2 , Johannes Hoffrogge 1,2 , Theodor<br />
W. Hänsch 1,2 , and Philipp Treutlein 1,2 — 1 Max-Planck-Institut<br />
für Quantenoptik, Garching — 2 Fakultät für Physik, Ludwig-<br />
Maximilians-Universität München<br />
We present the status of our experiment with microwave near-fields<br />
on atom chips. Microwave near-fields are a key ingredient for atom<br />
chip applications such as quantum information processing, entanglement<br />
of Bose-Einstein condensates, atom interferometry, the study of<br />
Josephson effects and chipbased atomic clocks. We have integrated<br />
miniaturized microwave guiding structures on our atom chip. The micrometersized<br />
structures allow to generate microwave near-fields with<br />
unusually strong gradients. Through microwave dressing of hyperfine<br />
states, these can be used to create state-selective double-well potentials.<br />
Q 50.19 Do 16:30 Poster C2<br />
An ultracold gas of Rydberg atoms — •Wendelin Sprenger,<br />
Christoph Hofmann, Janne Denskat, Christian Giese, Thomas<br />
Amthor, and Markus Reetz-Lamour — Physikalisches Institut Universität<br />
Freiburg, Hermann-Herder-Str.3, 79104 Freiburg<br />
We report on the investigation of interaction phenomena in ultracold<br />
Rydberg gases. 87 Rb atoms are confined in a magneto-optical trap<br />
and excited into Rydberg levels via a two-photon process (780 nm and<br />
480 nm). We present experimental details and results of the latest work.<br />
This includes coherent Rabi oscillations between ground and Rydberg<br />
state [1] and stimulated rapid adiabatic passage, transferring 90% of<br />
the gas into Rydberg states [2], ionization induced by van der interatomic<br />
forces, even for systems initially exhibiting repulsive v.d.W.<br />
interaction [3,4] and the understanding of the coherent dynamics of<br />
resonant energy transfer processes [5] . We also present a proposal for<br />
studying energy transport in the presence of exciton traps [6] and for<br />
structuring the Rydberg gas.<br />
[1] M. Reetz-Lamour et al., submitted<br />
[2] J. Deiglmayr et al., Opt. Comm. 264, 293 (2006)<br />
[3] T. Amthor et al., Phys. Rev. Lett. 98, 023004 (2007)<br />
[4] T. Amthor et al., Phys. Rev. A 76, 054702 (2007)<br />
[5] S. Westermann et al., Eur. Phys. J. D 40, 37 (2006)<br />
[6] O. Mülken et al., Phys. Rev. Lett. 99, 090601 (2007)<br />
Q 50.20 Do 16:30 Poster C2<br />
Apparatus for all optical probing of Rydberg states —<br />
•Harald Kübler, Tim Van Boxtel, Stefan Müller, Robert Löw,<br />
and Tilman Pfau — 5. Physikalisches Institut, Universität Stuttgart,<br />
Pfaffenwaldring 57, 70550 Stuttgart, Germany<br />
We present an apparatus for all optical probing of Rydberg states in a<br />
dense atomic sample, trapped in a crossed CO2 laser trap. We implemented<br />
electrical field control which allows us to apply complex field<br />
configurations on the atoms.<br />
The apparatus offers an excellent numeric aperture for the detection<br />
of Rydberg states via light (in contrast to detection via field ionization).<br />
For this we will use electromagnetically induced transparency<br />
on the usual 5S-5P absorption line via coherent coupling to a highly<br />
excited Rydberg state[1]. We present first Rydberg EIT experiments.<br />
[1] A. K. Mohapatra, T. R. Jackson, C. S. Adams: Coherent optical<br />
detection of highly excited Rydberg states using electromagnetically<br />
induced transparency<br />
Q 50.21 Do 16:30 Poster C2<br />
State-Selective Transport of Single Caesium Atoms — •Leonid<br />
Förster, Micha̷l Karski, Daniel Döring, Florian Grenz, Arne<br />
Härter, Wolfgang Alt, Jai-Min Choi, Artur Widera, and Dieter<br />
Meschede — Institute for Applied Physics, University of Bonn<br />
The state-selective quantum transport of single neutral atoms in optical<br />
lattices offers a promising alternative to implement basic modules<br />
of advanced schemes in the context of quantum engineering. These<br />
range from the implementation of so called quantum walks, utilizing<br />
fundamental quantum effects involving spatial quantum interference to<br />
the preparation of so-called cluster states using coherent cold collisions<br />
as an inter-qubit interaction.<br />
We investigate systems of single Caesium atoms stored, one by one,<br />
in a state-dependent one-dimensional optical lattice. It is formed by a<br />
superposition of two standing wave dipole traps with right- and lefthanded<br />
circular polarisation respectively. They can be shifted with<br />
respect to each other. With an appropriate wave length, each of the<br />
two lattices couples to a different hyperfine state. Therefore, atoms prepared<br />
in these qubit states can be transported in opposite directions.<br />
Using microwave pulses in the presence of magnetic field gradients, the<br />
internal states can be separately manipulated.<br />
We present the current state of the experimental realisation of a onedimensional<br />
quantum transport for Caesium atoms, focussing on the<br />
experimental setup and the tools for the preparation and manipulation<br />
of individual qubit states and their spatial detection.<br />
Q 50.22 Do 16:30 Poster C2<br />
Measuring the coupling strength of single atoms to the field of<br />
a high-finesse optical resonator — •Tobias Kampschulte, Wolfgang<br />
Alt, Mkrtych Khudaverdyan, Karim Lenhard, Sebastian<br />
Reick, Karsten Schörner, and Dieter Meschede — Institut für<br />
Angewandte Physik, Wegelerstr. 8, D-53115 Bonn<br />
Cavity QED experiments provide unique possibilities for studying<br />
atom-photon interactions at a fundamental level. In our experiment we<br />
investigate the coupling of a small number of neutral caesium atoms<br />
to the mode of a high-finesse optical cavity (F = 10 6 ).<br />
Using a number-triggered loading process we transfer a predetermined<br />
number of atoms, ranging from a single atom to several atoms, from a<br />
magneto-optical trap into a standing wave dipole trap. Subsequently,<br />
the atoms are transported into the center of the cavity mode with submicrometer<br />
precision using the dipole trap as an optical conveyor belt.<br />
Of fundamental importance for the implementation of any controlled<br />
atom-cavity interaction is the knowledge of the atom-cavity coupling<br />
strength g(r). It is equivalent to the energy splitting of the cavity mode<br />
when an atom is present. The splitting can be measured by taking a<br />
transmission spectrum of a weak probe laser beam going through the<br />
cavity. A different approach is the detection of the change of the atomic<br />
state induced by the probe laser when it is resonant with a mode of<br />
the coupled atom-cavity system.<br />
The controlled and deterministic coupling of single atoms to the mode<br />
of a cavity is an important step towards cavity-enhanced atom-atom<br />
interaction, a basic ingredient of quantum information processing.
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
Q 50.23 Do 16:30 Poster C2<br />
Manipulation of a quantum particle in a rapidly oscillating<br />
potential by phase hops — Armin Ridinger1 and •Christoph<br />
Weiss1,2 — 1Laboratoire Kastler Brossel, École Normale Supérieure,<br />
Université Pierre et Marie-Curie-Paris 6, CNRS — 2Institut für<br />
Physik, Universität Oldenburg<br />
We show that the state and the energy of a quantum particle trapped<br />
by a rapidly oscillating potential can be significantly manipulated in<br />
a controlled fashion by instantaneously changing the phase of the potential<br />
(a phase hop). We demonstrate our results for the case of the<br />
ideal one-dimensional Paul-trap.<br />
Q 50.24 Do 16:30 Poster C2<br />
Spectroscopy of two-photon resonances in a single-atomcavity<br />
system — •Alexander Kubanek, Ingrid Schuster, Andreas<br />
Fuhrmanek, Thomas Puppe, Pepijn Pinkse, Karim Murr,<br />
and Gerhard Rempe — Max-Planck-Institut für Quantenoptik, Hans-<br />
Kopfermann-Str. 1, 85748 Garching<br />
Strong coupling of a single atom to a single mode of an optical cavity<br />
leads to an energy level structure consisting of a ladder of doublets,<br />
the lowest of which is known as the normal-mode splitting. Here we<br />
show additional resonances in the transmission spectrum stemming<br />
from multi-photon transitions to higher doublets, which exhibit a nonlinear<br />
response to a change of probe intensity. To explain the details<br />
of the spectra, we need to take into account the micromotion of the<br />
atom which is localized in the mode by means of an auxiliary intracavity<br />
dipole trap. For this reason, we perform Monte-Carlo simulations<br />
on the dynamics of a trapped atom in a driven cavity. We calculate<br />
atomic trajectories by combining the Langevin equation of motion for<br />
the atom’s center of mass with the internal dynamics of a two-state<br />
atom coupled to a quantized mode. In this way, we are able to match<br />
theory and experiment. Additionally, we show that a classical treatment<br />
of the field following Maxwell’s equations fails to reproduce the<br />
data, regardless of whether the atom is modelled as a harmonic oscillator<br />
or as a two-state particle. This shows that the observed nonlinearity<br />
cannot be attributed to saturation effects, but is of quantum origin.<br />
Q 51: Poster Ultrakalte Moleküle<br />
Q 50.25 Do 16:30 Poster C2<br />
A freely falling magneto-optical trap drop tower experiment<br />
— •Thorben Könemann 1 , Hansjörg Dittus 1 , Tim van Zoest 2 ,<br />
Ernst Maria Rasel 2 , Wolfgang Ertmer 2 , Wojciech Lewoczko-<br />
Adamczyk 3 , Achim Peters 3 , Anika Vogel 4 , Kai Bongs 4 , Klaus<br />
Sengstock 4 , Endre Kajari 5 , Reinhold Walser 5 , and Wolfgang<br />
Peter Schleich 5 — 1 ZARM, University of Bremen — 2 IQO, Leibniz<br />
University of Hanover — 3 QOM, Humboldt-University of Berlin<br />
— 4 Institute of Laser-Physics, University of Hamburg — 5 Institute of<br />
Quantum Physics, University of Hamburg<br />
We experimentally demonstrate the possibility of preparing ultracold<br />
atoms in the environment of weightlessness at the earth-bound shortterm<br />
microgravity laboratory Drop Tower Bremen. Our approach is<br />
based on a freely falling magneto-optical trap (MOT) drop tower experiment<br />
performed within the ATKAT collaboration (Atom-Catapult)<br />
as a preliminary part of the QUANTUS pilot project (Quantum Systems<br />
in Weightlessness) pursuing a Bose-Einstein condensate (BEC)<br />
in microgravity at the drop tower. We give a complete account of the<br />
specific drop tower requirements and present the results of the realized<br />
freely falling MOT and further accomplished experiments during<br />
several drops.<br />
Q 50.26 Do 16:30 Poster C2<br />
An Internet Controlled BEC Experiment — •Nadine Meyer,<br />
Anika Vogel, Kai Bongs, and Klaus Sengstock — Institut für<br />
Laserphysik, Universität Hamburg, Germany<br />
In our project we present the fascinating world of cold atoms and<br />
Bose-Einstein condensation to students all over the world. In the experiment<br />
all relevant parameters including laser locking, laser power<br />
monitoring are internet controllable. The setup has only little need of<br />
maintenance, as we use the laser system designed in our QUANTUS<br />
collaboration (talk Q22.7) and an atom chip for a compact setup. In<br />
addition to a theoretical introduction to the field, there are animations<br />
and simulations for the users to work on. The project is funded by the<br />
Multimedia Kontor Hamburg.<br />
Zeit: Donnerstag 16:30–19:00 Raum: Poster C2<br />
Q 51.1 Do 16:30 Poster C2<br />
Towards an ultracold gas of polar molecules — •Karin<br />
Mörtlbauer, Christian Glück, Jörg Lange, Johannes Deiglmayr,<br />
Anna Grochola, Roland Wester, and Matthias Weidemüller<br />
— Albert-Ludwigs Universität, Physikalisches Institut,<br />
Hermann-Herder-Str. 3, 79104 Freiburg i.Brsg., Germany<br />
We recently demonstrated the formation of ultracold LiCs molecules<br />
by the trapping light of a double species magneto optical trap [1] and<br />
also achieved the active photoassociation of dipolar LiCs molecules in<br />
the same setup. In order to create a stable and large ensemble of ultracold<br />
LiCs molecules, we will form the molecules in an optical dipole<br />
trap [2] and transfer them into the absolute ro-vibrational ground<br />
state relying on a Raman-type relaxation scheme and radiative decay.<br />
Estimates for the transfer efficiency are derived and the current status<br />
of the experimental setup is described.<br />
[1] S. D. Kraft et al., J. Phys. B 39, S993 (2006)<br />
[2] M. Mudrich et al., PRL 88, 253001 (2002)<br />
Q 51.2 Do 16:30 Poster C2<br />
Photoassociation of ultracold atoms by shaped ultrashort<br />
pulses — •Simone Götz 1 , Wenzel Salzmann 1 , Terry Mullins 1 ,<br />
Magnus Albert 1 , Judith Eng 1 , Roland Wester 1 , Matthias Weidemüller<br />
1 , Andrea Merli 2 , Fransizka Sauer 2 , Fabian Weise 2 ,<br />
Steffan Weber 2 , Mateusz Plewicki 2 , Ludger Wöste 2 , and Albrecht<br />
Lindinger 2 — 1 Physikalisches Institut, Universität Freiburg,<br />
Herrmann-Herder-Str.3, 79104 Freiburg — 2 Institut für Physik, Freie<br />
Universität Berlin, Arnimallee 14, D-14195 Berlin<br />
We present experiments on the photoassociation (PA) of ultracold<br />
atoms using shaped femtosecond laser pulses. In a pump-probe scheme,<br />
molecules are produced in am excited state from an ultracold gas of<br />
85 Rb atoms, are ionized and mass selectively detected. Pump-pulses<br />
are shaped to suppress atomic losses from the trap [1] and address<br />
only bound molecular states. The molecular ion signal shows rich coherent<br />
interactions between the molecules and the electric field. Quantum<br />
dynamical simulations accompany the data, providing detailed<br />
insight into the process. Wavepacket motion is a requirement for proposed<br />
PA into ground states [2] and was not observed due to rapid<br />
wavepacket dispersion. We circumvent this by the use of picosecond<br />
pulses with a more suitable bandwidth that is closely matched to the<br />
free-bound Franck-Condon factors. A new pulse-shaper design allows<br />
high-resolution shaping of such pulses and thus application of coherent<br />
control techniques to the PA process in the perturbative domain.<br />
[1] W. Salzmann et al., PRA 73, 023414 (2006)<br />
[2] C. Koch et al., PRA 73, 043409 (2006)<br />
Q 51.3 Do 16:30 Poster C2<br />
Formation of Ultracold Ground State Molecules with a Single<br />
Short Laser Pulse — •Ruzin Aˆganoˆglu and Christiane P.<br />
Koch — Freie Universität zu Berlin, Institut für Theoretische Physik,<br />
Arnimallee 14, 14195 Berlin<br />
Bringing ultracold systems and coherent control schemes together is<br />
a promising subject of current research. One method to combine ultracold<br />
and ultrafast is photoassociation where two colliding atoms<br />
are transferred to an electronically excited state coherently with a<br />
short laser pulse. Already after a single pulse, formation of ultracold<br />
molecules in their electronic ground state is also observed. This is due<br />
to the change of the initial scattering wavefunction which leads to<br />
molecules in very weakly bound levels of the electronic ground state.<br />
Here we study the creation of ground state molecules with a single<br />
short laser pulse. Since the molecule formation is desired only in<br />
the electronic ground state, an excited state is chosen with a repulsive<br />
potential and the short laser pulse is blue detuned for excitation.The<br />
laser parameters can be chosen such that atoms far from each other<br />
are blown away while atoms very close to each other are kept and form<br />
molecules.
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
The initial thermal probability density of atoms is expected to be<br />
very small at short internuclear distances. However, it can be manipulated<br />
by changing the scattering properties of the atoms. In this work<br />
an optically induced Feshbach resonance is employed to modify the<br />
initial atomic distribution prior to photoassociation by a single short<br />
pulse.<br />
Q 51.4 Do 16:30 Poster C2<br />
The Efimov Molecule with short and finite range potentials<br />
— •Bettina Berg 1 , Lev Plimak 1 , Misha Ivanov 2 und Wolfgang<br />
P. Schleich 1 — 1 Institute of Quantum Physics, Ulm University, Germany<br />
— 2 NRC, Ottawa, Canada<br />
The Efimov effect [1,2] has always been regarded somewhat of a mystery.<br />
As there is an evergrowing interest in this problem, a simple<br />
explanation of this effect utilizing only elementary quantum mechanics<br />
appears more than desirable. We investigate the so-called Efimov<br />
molecule formed by two heavy and one light particle in the Born-<br />
Oppenheimer limit, by applying an Ansatz from “Quantum Chemistry<br />
101” and assuming that the light particle interacts with the heavy ones<br />
via a short-range potential. The resulting molecular term exhibits the<br />
typical 1/R 2 behaviour of a Efimov potential [3]. An extention of our<br />
method to potentials of arbitrary radius is also discussed.<br />
[1] V. N. Efimov, Weakly Bound States of Three Resonantly-<br />
Interactiong Particles, Sov. J. Nucl. Phys. 12, 589-595 (1971).<br />
[2] T. Kraemer et al., Evidence for Efimov quantum states in an<br />
ultracold gas of caesium atoms, Nature 440, 315-318 (16 March 2006),<br />
cond-mat/0512394.<br />
[3] L. Plimak, B. Berg, M. Ivanov, W. Schleich, Quantum Chemistry<br />
of the Efimov Molecule, submitted.<br />
Q 51.5 Do 16:30 Poster C2<br />
Few-body physics with ultracold Cs atoms and molecules<br />
— •Steven Knoop 1 , Martin Berninger 1 , Francesca Ferlaino 1 ,<br />
Harald Schöbel 1 , Michael Mark 1 , Hanns-Christoph Nägerl 1 ,<br />
and Rudolf Grimm 1,2 — 1 Institut für Experimentalphysik, Universität<br />
Innsbruck, Austria — 2 Institut für Quantenoptik und Quanteninformation,<br />
Innsbruck, Austria<br />
Ultracold atomic gases are versatile systems to study few-body physics<br />
because of full control over the external and internal degrees of freedom<br />
and the magnetic tunability of the scattering properties using<br />
Q 52: Poster Materiewellenoptik<br />
Feshbach resonances. Here we experimentally study three- and fourbody<br />
physics by investigating ultracold (30-250 nK) atom-dimer and<br />
dimer-dimer collisions with Cs Feshbach molecules in various molecular<br />
states and Cs atoms in different hyperfine states. Resonant enhancement<br />
of the atom-dimer relaxation rate is observed in a system of three<br />
identical bosons and interpreted as being induced by a trimer state,<br />
possibly an Efimov state. A strong magnetic field dependence of the<br />
relaxation rate is also observed when the atoms are transferred to a<br />
different hyperfine sublevel [1]. For dimer-dimer collisions we have observed<br />
an unexpected temperature dependence and a suppression of<br />
the collisional loss rate [2].<br />
[1] S. Knoop et al., in preparation [2] F. Ferlaino et al., in preparation<br />
Q 51.6 Do 16:30 Poster C2<br />
Ultracold Cesium Feshbach Molecules — •Martin Berninger 1 ,<br />
Steven Knoop 1 , Francesca Ferlaino 1 , Harald Schöbel 1 ,<br />
Michael Mark 1 , Hanns-Christoph Nägerl 1 , and Rudolf<br />
Grimm 1,2 — 1 Institut für Experimentalphysik, Universität Innsbruck,<br />
Austria — 2 Institut für Quantenoptik und Quanteninformation, Innsbruck,<br />
Austria<br />
We present our recent work on ultracold Cesium Feshbach molecules in<br />
an optical dipole trap. We have implemented a new crossed-beam laser<br />
trap, which traps atoms and molecules simultaneously. By scanning<br />
one laser beam the ellipticity can be dynamically tuned for an optimal<br />
trap configuration. We routinely prepare ultracold mixed atomic and<br />
molecular or pure molecular samples at temperatures down to 30 nK<br />
[1]. We selectively populate Feshbach molecules in various s-, d-, g- and<br />
even l-wave states [2]. We have experimentally demonstrated that the lwave<br />
dimers can be stable against spontaneous decay on the timescale<br />
of one second well above the dissociation threshold [3]. We have recently<br />
implemented the technique of resonantly modulated magnetic<br />
field spectroscopy [4]. Transitions between the atomic continuum and<br />
dimer states, and vice versa, as well as dimer-dimer transitions can<br />
be driven. Our main motivation is to apply this technique to search<br />
for trimer and tetramer states, whose presence has been indicated by<br />
resonances in collisional loss measurements.<br />
[1] F. Ferlaino et al., in preparation; [2] M. Mark et al., Phys. Rev.<br />
A 76, 042514 (2007); [3] S. Knoop et al., arXiv:0710.4052; [4] T. M.<br />
Hanna et al., Phys. Rev. A 75, 013606 (2007)<br />
Zeit: Donnerstag 16:30–19:00 Raum: Poster C2<br />
Q 52.1 Do 16:30 Poster C2<br />
Berry phase in atom optics — •Polina V. Mironova, Maxim A.<br />
Efremov, and Wolfgang P. Schleich — Institut für Quantenphysik,<br />
Universität Ulm, Ulm, Germany<br />
We suggest a scheme to observe the Berry phase using the atomic external<br />
degrees of freedom. We consider two consecutive interactions of<br />
an atom with a near-resonant standing light waves. An atom is scattered<br />
by a standing wave, which is formed by two red-detuned traveling<br />
light waves, ∆ < 0, with wave vectors k1 and k2, |k1| = |k2| = k,<br />
Q 53: Poster Photonik<br />
∡(k1, k2) = 2α. Afterwards, the atom is scattered by a second standing<br />
wave, which is formed by two blue-detuned traveling light waves,<br />
∆ > 0, with wave vectors k ′ i/|k ′ i| = −ki/|ki|, i = 1, 2. We assume<br />
that both interactions turn-on and turn-off adiabatically. Within the<br />
rotating wave approximation and the adiabatic approximation on the<br />
atomic center-of-mass motion we obtain that the final state of the<br />
atom differs from the initial state of the atom only by twice the familiar<br />
Berry phase, which depends on the atomic external degrees of<br />
freedom. The dynamical phase is cancelled out and the scattering picture<br />
is determined only by the atomic center-of-mass position.<br />
Zeit: Donnerstag 16:30–19:00 Raum: Poster C2<br />
Q 53.1 Do 16:30 Poster C2<br />
Fluoreszenzlebensdauer von Quantenpunkten und Laserfarbstoffen<br />
in Photonic-Crystal-Fasern — •Peter Keller und Fedor<br />
Mitschke — Universität Rostock, Institut für Physik, Experimentalphysik:<br />
Optik, 18051 Rostock<br />
Photonic-Crystal-Fasern mit Hohlkern (HC-PCF) können für einige<br />
neue Anwendungen (z.B. Sensorik) mit Gasen oder Flüssigkeiten<br />
gefüllt werden [1]. In diesem Beitrag wird neben dem Fluoreszenzspektrum<br />
vor allem die Fluoreszenzlebensdauer von Quantenpunkten<br />
und Laserfarbstoffen untersucht, die in Lösungsmittel gelöst in den<br />
zentralen Kern, aber nicht in die Braggstruktur, einer HC-PCF eingebracht<br />
sind. Wir regen die befüllte Faser mit 250fs-Pulsen aus einem<br />
frequenzverdoppelten Ti:Sa-Laser an. Während die Laserfarbstoffe keinerlei<br />
verändertes Fluoreszenzverhalten zeigen, ist bei den Quantenpunkten<br />
zum Teil eine deutliche Verkürzung der Lebensdauer zu beobachten.<br />
Diese Verkürzung ist abhängig von der Pumpintensität und<br />
der Einwirkdauer.<br />
[1] J. M. Fini, Meas. Sci. Technol. 15, 1120 (2004)<br />
Q 53.2 Do 16:30 Poster C2<br />
Frequency Tripling and Interferometric Sensing with Ultra-<br />
Thin Optical Fibers — •Ulrich Wiedemann, Konstantin Karapetyan,<br />
Wolfgang Alt, and Dieter Meschede — Institut für Angewandte<br />
Physik, Universität Bonn, Wegelerstr. 8, 53115 Bonn
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
We present the first results and the perspectives of our work devoted<br />
to investigation of ultra-thin optical fiber applications.<br />
Our first goal is to achieve effective third harmonic generation<br />
(THG) using an ultra-thin fiber, which allows for light guidance over a<br />
large length while keeping the spot size small. In case of sub-wavelength<br />
fibers a significant portion of the power propagates outside the fiber, in<br />
the evanescent field. This high intensity light field in the space around<br />
the fiber is coupled to atoms with high third order nonlinearity to provide<br />
THG. To phase-match the fundamental and the frequency-tripled<br />
waves we compensate material dispersion with modal dispersion.<br />
The second goal is to create an interferometric fiber sensor, in which<br />
the two legs of Mach-Zehnder scheme are represented by two different<br />
transverse fiber modes. One mode has a smaller evanescent field intensity<br />
than the other one, leading to different degree of influence of<br />
the surrounding medium on the optical path length. The two coherent<br />
modes are obtained and recombined using either non-adiabatic taper<br />
transition or long period fiber gratings.<br />
For both experiments we are using standard single-mode fibers tapered<br />
down to diameters of about 500 nm at the length of 1–20 mm<br />
by flame-heating and stretching.<br />
Q 53.3 Do 16:30 Poster C2<br />
Einfluss von Belichtungsparametern bei schreibender Excimerlaserbelichtung<br />
auf die Indexmodifikation von PMMA<br />
— •Hauke Höppner, Sebastian Huber, Ortwin Siepmann, Volker<br />
Braun, Sabine Tiedeken, Ulrich Teubner und Hans Josef<br />
Brückner — FH OOW - Emden, Niedersachsen, Deutschland<br />
Die Absorption von UV-Strahlung führt in PMMA unterhalb von<br />
ca. 260 nm zum Aufbrechen von Molekülbindungen und zur Erhöhung<br />
des optischen Brechungsindexes. Es ist zu beobachten, dass sich bei<br />
Erhöhung der Leistungsdichte das Absorptionsverhalten und die Form<br />
eines lokal erzeugten Indexprofils ändert. Dies ist insbesondere bei der<br />
Herstellung optischer Wellenleiter durch schreibende Excimerlaserbelichtung<br />
kritisch, da zur Reduzierung der Herstellungszeit mit hohen<br />
Leistungsdichten unterhalb der Ablationsschwelle gearbeitet wird. Der<br />
Einfluss von Belichtungsparametern wie Gesamtdosis und Leistungsdichte<br />
auf die Indexmodifikation und die Führungseigenschaften von<br />
optischen Wellenleitern wird dargestellt.<br />
Q 53.4 Do 16:30 Poster C2<br />
Design von Mikroresonatoren in photonischen Kristallen in<br />
Diamant — •Janine Riedrich-Möller, Roland Albrecht, Elke<br />
Neu und Christoph Becher — Universität des Saarlandes, Fachrichtung<br />
7.3, Technische Physik, Campus E 2.6, 66123 Saarbrücken<br />
Optisch aktive Farbzentren in Diamant sind vielversprechende Kandidaten<br />
für die Realisierung von Konzepten der Quanteninformationsverarbeitung.<br />
Für den Einsatz in Quantencomputern [1], sowie in der<br />
Quantenkryptographie [2] ist die Ankopplung des Farbzentrums an<br />
die Mode eines Resonators hoher Güte wünschenswert. Zur Realisierung<br />
dieser Ankopplung betrachten wir Mikroresonatoren in zweidimensionalen<br />
photonischen Kristallen in Diamantfilmen. Die zeitliche<br />
und räumliche Lokalisierung der Feldverteilung ist sowohl abhängig<br />
von dem Design eines solchen Mikroresonators wie auch von der Absorption<br />
des verwendeten Materials. Wir stellen Strategien zur Optimierung<br />
des Gütefaktors Q verschiedener Resonatorstrukturen anhand<br />
von Simulationen zur Lösung der Maxwell-Gleichungen im Zeit- und<br />
Frequenzraum (FDTD) vor. Zudem diskutieren wir den Einfluss von<br />
Verlusten im Material, sowie die mögliche experimentelle Realisierung<br />
von photonischen Kristallen in Diamant.<br />
[1] Lim et al. Phys. Rev. A 73, 012304 (2006)<br />
[2] Beveratos et al. Phys. Rev. Lett. 89,187901(2002)<br />
Q 53.5 Do 16:30 Poster C2<br />
Selective excitation of magnetic and electric resonances<br />
in single split-ring resonators with polarization tailored<br />
light — •Peter Banzer 1 , Susanne Quabis 1 , Ulf Peschel 1 , Gerd<br />
Leuchs 1 , Stefan Linden 2 , Nils Feth 2 , and Martin Wegener 3<br />
— 1 Max Planck Research Group, Institute of Optics, Information<br />
and Photonics, Erlangen, Germany — 2 Institut für Nanotechnologie,<br />
Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft, Karlsruhe,<br />
Germany — 3 Institut für Angewandte Physik and DFG-Center<br />
for Functional Nanostructures, Universität Karlsruhe, Karlsruhe, Germany<br />
Metamaterials consist of building-blocks which can be seen as artificial<br />
atoms. Especially the magnetic response of these sub-structures<br />
is important if one wants to achieve extraordinary material properties<br />
like negative permeability. Therefore we investigate experimentally<br />
the pure magnetic coupling to the magnetic resonance of single splitring<br />
resonators (SRR) in the optical regime. Therefor we use strongly<br />
focused azimuthally polarized light. It provides an ideal polarization<br />
pattern on a sub-wavelength scale for studying the magnetic resonance<br />
behaviour of single SRRs. If a SRR is placed in the centre of the focal<br />
spot the pure longitudinal magnetic field component points perpendicular<br />
to the SRR plane. In the resonant case, the magnetic field can<br />
excite a magnetic dipole. By displacing the SRR in the focal spot,<br />
one can also couple to magnetic and electric resonances via transversal<br />
electric fields (for corresponding wavelengths). In the transmitted<br />
light, one can search for fingerprints of the excited magnetic dipole.<br />
Q 53.6 Do 16:30 Poster C2<br />
Spektroskopie und nichtlineare Optik in photonischen Hohlfasern<br />
— •Christoph Brenker, Jan Klärs, Frank Vewinger und<br />
Martin Weitz — Institut für Angewandte Physik, Wegelerstraße 8,<br />
53115 Bonn<br />
Photonische Hohlfasern erfahren in letzter Zeit ein wachsendes Interesse<br />
in der Spektroskopie [1] und der Untersuchung nichtlinearer Prozesse<br />
[2],[3]. Die kleine Strahltaille in der Faser von wenigen Mikrometern<br />
bei einer Wechselwirkungslänge von mehreren Metern ermöglicht eine<br />
sehr hohe Sensitivität. Für nichtlineare Prozesse bietet sie durch die<br />
Fokussierung über die gesamte Länge optimale Voraussetzungen.<br />
Wir berichten über Ergebnisse zur Spektroskopie in hohlen photonischen<br />
Fasern, die mit Stickstoffdioxid gefüllt wurden. Auch wird über<br />
den Stand von Experimenten zur Erzeugung von Seitenbändern durch<br />
Vier-Wellen Mischung berichtet. Wir stellen Faserstrukturen vor, deren<br />
optimierte Dispersionsrelation eine Überhöhung von nichtlinearen<br />
Prozessen erwarten lässt.<br />
[1] J.Henningsen, J.Hald and J.C.Petersen: Saturated absorption in<br />
acetylene and hydrogen in hollow-core photonic bandgap fibers, Optics<br />
Express 13,10475 (2005)<br />
[2] P.S. Light, F.Benabid and F.Couny Electromagetically induced<br />
transparency in Rb-filled coated hollow-core photonic crystal fiber, Optics<br />
Letters 32,1323 (2007)<br />
[3] S.O. Konorov, A.B.Fedotov and A.M. Zheltikov, Enhanced fourwave<br />
mixing in a hollow-core photonic-crystal fiber, Optics letters<br />
28,1448 (2003)<br />
Q 53.7 Do 16:30 Poster C2<br />
Linear and nonlinear optics in curved space — •Sascha Batz,<br />
Henrike Trompeter, and Ulf Peschel — Max Planck Research<br />
Group of Optics, Information and Photonics, Günther-Scharowsky-Str.<br />
1 / Bau 24, 91058 Erlangen<br />
In the past nonlinear optics was restricted to homogenous Euclidean<br />
space. However, completely new effects occur if the curvature of space<br />
starts to play a role. In optics we can investigate related phenomena<br />
if we abandon one spatial dimension and restrict wave propagation<br />
to a two-dimensional manifold. Using the tools provided by<br />
the theory of general relativity we established a mathematical model<br />
for the propagation of light on a curved surface with arbitary curvature.<br />
Here we focus on surfaces with constant Gaussian curvature.<br />
A sphere with a film waveguide on it is an example for a space of<br />
constant positive curvature. Here already the linear wave propagation<br />
deviates from that in flat space. It is characterized by periodic refocusing<br />
caused by a quantization into discrete modes with constant<br />
wavenumber spacing. If the power is increased solitons appear as nonlinear<br />
extension of these discrete linear modes. They show a distinct<br />
stability behavior deviating considerably from that of their counterparts<br />
in flat space. The theoretical model developed to describe wave<br />
propagation on curved surfaces shows some interesting similarities with<br />
nonlinear systems e.g. dispersion management in optical fibers and solitons<br />
in trapped Bose-Einstein condensates. Symmetry transformations<br />
derived for wave propagation in curved space can likewise be applied<br />
to other systems, thus generating new solutions.<br />
Q 53.8 Do 16:30 Poster C2<br />
Präparation von photonischen Hohlkernfasern zum selektiven<br />
Befüllen mit Materialien hoher optischer Nichtlinearität<br />
— •Dirk Puhlmann 1 , Markus Gregor 2 und Martin Ostermeyer 1<br />
— 1 Institut für Physik, Universität Potsdam, Am Neuen Palais 10,<br />
14469 Potsdam — 2 Institut für Physik, Humboldt-Universität zu Berlin,<br />
Hausvogteiplatz 5-7, 10117 Berlin<br />
Photonische Hohlkernfasern können mit Materialien hoher optischer<br />
Nichtlinearität befüllt werden. Auf diese Art werden sie zu interessanten<br />
Lichtquellen für eine Reihe von Anwendungen. Es ist jedoch beim<br />
Befüllen des Faserkerns mit z.B. einer Flüssigkeit Sorgfalt geboten,
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
um zu verhindern, daß die Löcher der Ummantelung mit befüllt werden<br />
und somit die lichtleitenden Eigenschaften der Faser stark modifiziert<br />
oder gar zerstört werden. Um dieses Problem zu lösen, haben<br />
wir einen alternativen Ansatz gewählt. Zunächst wurde ein Ende der<br />
Faser komplett (Kern und Ummantelung) mit einem positiv Fotolack<br />
befüllt. Daraufhin haben wir den Lack durch das andere, noch offene<br />
Ende der Faser belichtet. Da der geführte Mode in der photonischen<br />
Faser deutlich im Faserkern konzentriert ist, wird dabei nur der Lack<br />
belichtet, der den Kern verstopft. In der Folge kann der belichtete Lack<br />
mit Hilfe eines Entwicklers wieder ”ausgewaschen” werden. Die Faser<br />
ist nun bereit mit der gewünschten Flüssigkeit hoher Nichtlinearität<br />
befüllt zu werden, da der Kern ”frei” ist, die Löcher der Ummantelung<br />
jedoch noch durch den Lack besetzt sind. Die Probleme die bei dieser<br />
Technik auftreten sowie unsere Lösungsansätze werden präsentiert.<br />
Q 53.9 Do 16:30 Poster C2<br />
Optimierung eines nichtlinearen verstärkenden Schleifenspiegels<br />
zur Amplitudenregeneration phasenkodierter optischer<br />
Signale — •Tobias Röthlingshöfer 1 , Klaus Sponsel 1 , Kristian<br />
Cvecek 1 , Christian Stephan 1 , Georgy Onishchukov 1 , Bernhard<br />
Schmauss 2 und Gerd Leuchs 1 — 1 Institut für Optik, Information<br />
und Photonik, Abteilung I, Universität Erlangen-Nürnberg —<br />
2 Lehrstuhl für Hochfrequenztechnik, Universität Erlangen-Nürnberg<br />
In der optischen Datenübertragung werden mehr und mehr phasenkodierte<br />
Modulationsformate eingesetzt. Durch nichtlineare Effekte in<br />
Übertragungsfasern, wie Selbstphasenmodulation, wird jedoch Amplitudenrauschen<br />
in nichtlineares Phasenrauschen umgewandelt und beeinträchtigt<br />
so besonders phasenkodierte Signale.<br />
Es wird gezeigt, daß die Amplituden-Regeneration von phasenkodierten<br />
optischen Datenformaten, wie z.B. Differential Phase-Shift<br />
Keying” (DPSK), mit Hilfe eines modifizierten Faser-Sagnac Interferometer<br />
z.B. Nonlinear Amplifying Loop Mirror (NALM), möglich<br />
ist. Dadurch wird die Generation von nichtlinearem Phasenrauschen<br />
unterdrückt, ohne daß die Phasenkodierung der Daten zerstört wird.<br />
Q 53.10 Do 16:30 Poster C2<br />
Towards tunable high-Q whispering-gallery-mode resonators<br />
— •Michael Pöllinger, Danny O’Shea, Florian Warken, and<br />
Arno Rauschenbeutel — Institut für Physik, Universität Mainz,<br />
Staudingerweg 7, 55128 Mainz<br />
We present experimental results on the fabrication and characterization<br />
of tunable whispering-gallery-mode resonators. These so-called<br />
bottle resonators are highly prolate and exhibit an advantageous mode<br />
Q 54: Poster Laserentwicklung<br />
geometry and spectrum [1]. They are realized from glass fibers, which<br />
are flame heated and elongated to produce a 15 µm diameter waist.<br />
The resonator structure is then obtained by focused CO2 laser heating.<br />
The resonators are spectrally characterized in a setup where light is<br />
coupled in and out by means of micron sized coupling fibers. Furthermore,<br />
this setup allows us to tune the resonance frequency by applying<br />
mechanical strain. Tuning over more than one free spectral range and<br />
quality factors in the Q = 10 6 –10 7 range have been observed.<br />
Our current efforts aim at enhancing Q. Therefore, we fabricate resonators<br />
from different ultra-pure commercial glass fibers, investigate<br />
the surface properties by TEM imaging and quantitatively investigate<br />
the spatial mode structure of the resonator. Achieving Q-factors<br />
in the 10 8 –10 9 range together with the special features of the resonator<br />
would open interesting perspectives for cQED experiments and<br />
ultralow-power optical switches.<br />
We acknowledge financial support by the DFG research unit 557.<br />
[1] Y. Louyer, D. Meschede, and A. Rauschenbeutel, Phys. Rev. A 72,<br />
031801(R) (2005).<br />
Q 53.11 Do 16:30 Poster C2<br />
Evaneszente Felder von ZnO Nanodrähten und Nano-Fasern<br />
— •Sandra Börner, Marcel Bremerich, Farzaneh Fattahi und<br />
Wolfgang Schade — Insitut für Physik und Physikalische Technologien,<br />
Leibnizstr. 4, 38678 Clausthal-Zellerfeld<br />
Optische Fasern mit Durchmessern im Mikrometer-Bereich oder ATR-<br />
Elemente werden unter Ausnutzung einer evaneszenten Wechselwirkung<br />
mit umgebenden Medien, wie z.B. Gasen oder Flüssigkeiten, zur<br />
Detektion im nahen infraroten oder mittleren infraroten Spektralbereich<br />
genutzt. Nanodrähte oder -fasern bieten eine effiziente Alternative.<br />
Da sie in einer Dimension eine Ausdehnung im Nanometerbereich<br />
besitzen, sind sie kleiner als die üblich genutzten Wellenlängen.<br />
Ein großer Teil des Lichtes wird dadurch als evaneszentes Feld außerhalb<br />
der Strukturen geführt. Infolge dessen wird die Wechselwirkung<br />
mit dem umgebenden Medium erhöht. Die Wellenleitereigenschaften<br />
von ZnO Nanodrähten wurden simuliert und hinsichtlich ihrer evaneszenten<br />
Eigenschaften analysiert. Die theoretischen Resultate können<br />
mit Hilfe optischer Mikroskopie bestätigt werden. Zusätzlich wurden<br />
herkömmliche Quarz-Fasern durch systematisches Erhitzen und Ziehen<br />
bearbeitet, um eine Verjüngung in den nm-Bereich zu erreichen.<br />
Diese wurden hinsichtlich ihrer Transmissions- und Wellenleitungseigenschaften<br />
untersucht. In Zukunft sollen diese Erkenntnisse der Entwicklung<br />
und Verbesserung optischer Sensorsysteme dienen.<br />
Zeit: Donnerstag 16:30–19:00 Raum: Poster C2<br />
Q 54.1 Do 16:30 Poster C2<br />
Eine flexible, gepulste Lichtquelle auf Basis eines ns-<br />
Titan:Saphir Lasers — •Diana Wendland, Daniel Depenheuer,<br />
Thorsten Führer und Thomas Walther — TU Darmstadt, Institut<br />
für angewandte Physik, Laser- und Quantenoptik, Schlossgartenstr. 7,<br />
64297 Darmstadt<br />
Vorgestellt wird ein ns-Titan:Saphir Lasersystem, das als flexible Lichtquelle<br />
konzipiert ist. Durch die Verwendung eines kleinen Resonators<br />
konnten sehr kurze und konstante Buildup Zeiten erreicht werden. Dies<br />
ermöglicht es den Spektralbereich des Lasers nicht nur durch die Erzeugung<br />
höherer Harmonischer, sondern auch durch Summen- und Differenzfrequenzmischen<br />
mit dem Pumppuls stark zu erweitern. Dieser<br />
ist sowohl nach unten, als auch nach oben nur durch die Verfügbarkeit<br />
von Konversionskristallen beschränkt und ist Aufgrund des grossen<br />
Abstimmbereichs von Titan:Saphir nahezu lückenlos.<br />
Q 54.2 Do 16:30 Poster C2<br />
Ein schmalbandiger cw-Titan:Saphir Laser mit resonatorinterner<br />
Frequenzverdopplung — •Ulrich Jäger, Christoph Burandt<br />
und Thomas Walther — Laser- und Quantenoptik, Institut<br />
für Angewandte Physik, Technische Universität Darmstadt<br />
Vorgestellt wird ein cw-Titan:Saphir Laser in Bow-Tie Konfiguration.<br />
Eine Durchstimmbarkeit von 816 nm bis 873 nm ist mittels eines Lyotfilters<br />
möglich. Durch zusätzliches injection-seeding wird ein schmalbandiger<br />
Betrieb bei 871,6 nm erreicht. Eine Frequenzverdopplung auf<br />
435,8 nm wird resonatorintern mit einem BBO-Kristall realisiert. In<br />
der zweiten Harmonischen können Ausgangsleistungen von über 5 mW<br />
erreicht werden. Das System ist für spektroskopische Anwendungen an<br />
Quecksilber konzipiert. Berichtet wird über den aktuellen Entwicklungsstand.<br />
Q 54.3 Do 16:30 Poster C2<br />
Entwicklung eines regenerativen Ti:Saphir-Verstärkersystems<br />
auf 761 nm und 789 nm zum Nachweis von Hg in einer MOT<br />
— •Alexander Bertz, Andrea Golla und Thomas Walther — TU<br />
Darmstadt, Institut für angewandte Physik, Laser und Quantenoptik<br />
Wir stellen ein regeneratives Ti:Saphir-Verstärkersystem vor, welches<br />
für die synchrone Emission von fourierlimitierten ns-Pulsen der Wellenlängen<br />
761 nm und 789 nm ausgelegt ist. Durch resonatorexterne<br />
Frequenzkonversionsprozesse wird Strahlung der Wellenlängen 253,7<br />
nm bzw. 197,3 nm erzeugt, die für den Photoionisationsnachweis von<br />
Hg-Dimeren in einer magneto-optischen Falle mittels eines linearen<br />
Time-of-Flight-Massenspektrometers verwendet werden soll.<br />
Q 54.4 Do 16:30 Poster C2<br />
Spektroskopie Pr-dotierter Oxide — •Nicky Thilmann, André<br />
Richter, Friedjof Tellkamp, Klaus Petermann und Günter<br />
Huber — Institut für Laser-Physik, Universität Hamburg, Luruper<br />
Chaussee 149, 22761 Hamburg<br />
Es wurden mittels Czochralski-Zucht Praseodym (Pr) dotierte oxidische<br />
Kristalle hergestellt und spektroskopisch untersucht. Die Granatkristalle<br />
Y3Ga5O12 (YGG) und Gd3Ga5O12 (GGG) weisen eine ku-
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
bische Kristallstruktur auf und haben schon mit Nd als aktivem Ion<br />
effiziente Lasertätigkeit gezeigt. Daher erscheint die Nutzung dieser<br />
Wirtsmaterialien für diodengepumpte Pr-Laser aussichtsreich.<br />
Der Peakabsorptionswirkungsquerschnitt liegt in der<br />
Größenordnung von mehren 10 −20 cm 2 bei einer Wellenlänge<br />
von 450 nm. Die größten Emissionswirkungsquerschnitte betragen<br />
1·10 −19 cm 2 bei einer Wellenlänge von 742 nm. Diskrete strahlende<br />
Übergänge unter Laserdiodenanregung in das 3 P2 - Niveau erfolgen<br />
im gesamten Spektralbreich von 485 nm bis 750 nm. Die Lebensdauer<br />
des 3 P0- Multipletts beträgt bei Raumtemperatur 24 µs. Um eine<br />
Abschätzung der Laserschwelle vornehmen zu können, werden die<br />
spektroskopischen Daten mit denen Pr-dotierter Fluoride verglichen.<br />
Ferner wird über die ersten spektroskopischen Daten von Pr:GdScO3<br />
berichtet.<br />
Q 54.5 Do 16:30 Poster C2<br />
Optimierung und Verbesserung eines ECDLs durch nichtlineare<br />
Stromnachführung und Einsatz eines LC-Segments —<br />
•Denise Stang, Thorsten Führer und Thomas Walther — TU<br />
Darmstadt, Institut für Angewandte Physik, AG Laser und Quantenoptik,<br />
Schlossgartenstr. 7, D-64289 Darmstadt<br />
In der Spektroskopie und als Seed-Quelle für leistungsstarke Laser<br />
werden häufig ECDLs eingesetzt. Hierfür sind möglichst große modensprungfreie<br />
Abstimmbereiche und eine große Stabilität von Vorteil.<br />
Daher werden neben einer zuverlässigen Modensprung-Detektion<br />
Möglichkeiten zur Stabilisierung der Modenselektion benötigt. Damit<br />
während der Änderung der Wellenlänge stets die gleiche Mode dominiert,<br />
müssen die Modenabstände des internen und externen Resonators<br />
entsprechend geändert werden.<br />
Dies wird im präsentierten Aufbau für den externen Resonator durch<br />
eine Längenänderung mittels Piezoaktoren, für den internen Resonator<br />
mittels einer Änderung des Laserdiodenstroms realisiert. Da die Ausdehnung<br />
der Piezoaktoren nichtlinear von der Spannung abhängt, wird<br />
der Strom ebenfalls nichtlinear nachgeführt und dadurch der Durchstimmbereich<br />
vergrößert. Ferner wird gezeigt, dass auch eine gezielte<br />
Modulation der rückgekoppelten Intensität in die Laserdiode anstelle<br />
der Änderung des Laserdiodenstroms ein modensprungfreies Durchstimmen<br />
ermöglicht. Diese Modulation wird aufgrund der polarisationsabhängigen<br />
Beugungseffizienz des Gitters durch einen Polarisationsrotator<br />
auf Flüssigkristallbasis erreicht.<br />
Q 54.6 Do 16:30 Poster C2<br />
Untersuchung von getrennt kontaktierten Trapezlaserdioden<br />
im externen Resonator — •Andreas Jechow und Ralf Menzel<br />
— Universität Potsdam, Institut für Physik, Photonik, Am Neuen Palais<br />
10, 14469 Potsdam<br />
Trapezlaserdioden zeigen bei etwa gleicher Effizienz gegenüber Breitstreifenlaserdioden<br />
deutlich verbesserte räumliche Strahlqualität und<br />
liefern optischen Ausgangsleistungen von mehreren Watt [1].<br />
Mithilfe von externen Resonatoren ist es möglich auch die spektralen<br />
Eigenschaften des Trapezlasers weiter zu verbessern. Die dadurch erreichte<br />
schmalbandige spektrale Emission und ein weiter Durchstimmbereich<br />
erschließen nichtlineare Anwendungen wie Frequenzverdopplung.<br />
Durch die getrennte Kontaktierung von Ridge und Trapezsektion<br />
ist eine zusätzliche Leistungssteigerung bei verringertem Materialstress<br />
möglich geworden.<br />
[1] M.T. Kelemen, J. Weber, G. Kaufel, G. Bihlmann, R. Moritz, M.<br />
Mikulla, G. Weimann, “Tapered diode lasers at 976 nm with 8 W nearly<br />
diffraction limited output power”, Electronics Letters 41, 1011-13<br />
(2005)<br />
Q 54.7 Do 16:30 Poster C2<br />
Untersuchung der Auswirkung von Materialdispersion in<br />
spektral modengekoppelten Lasern (Fourier Domain Mode<br />
Locking - FDML) — •Benjamin Biedermann, Christoph Eigenwillig<br />
und Robert Huber — Lehrstuhl für BioMolekulare Optik,<br />
Fakultät für Physik, LMU München<br />
Bei Fourier Domain Mode Locking handelt es sich um einen neuen<br />
Operationsmodus von Lasern, bei dem nicht die Amplitude, sondern<br />
die Frequenz synchron zur Lichtumlaufzeit moduliert wird [1]. Dies<br />
ermöglicht die Realisierung von schnell abstimmbaren Lasern, welche<br />
sich mit bis zu 300kHz über einen Bereich von 150nm im nahen Infraroten<br />
abstimmen lassen. Durch diese hohe Geschwindigkeit sind FDML-<br />
Laserquellen ideal für die optische Kohärenztomographie (OCT) geeignet.<br />
Die OCT stellt ein optisches Bildgebungsverfahren dar, welches<br />
mit einer räumlichen Auflösung von wenigen Mikrometern die drei-<br />
dimensionale Darstellung von Brechzahlkontrasten erlaubt und damit<br />
für medizinische Anwendungen von Bedeutung ist [2]. Materialdispersion<br />
im Resonator ist ein Problem bei FDML-Laserquellen, da sie eine<br />
gleichzeitige, perfekte Synchronisation aller Frequenzkomponenten verhindert.<br />
Im Wellenlängenbereich um 1550nm werden FDML-Laser mit<br />
unterschiedlich großer Gesamtdispersion untersucht. Die Auswirkung<br />
von Dispersion auf Rauschen, instantane Kohärenzlänge und spektrale<br />
Bandbreite wird gezeigt. Die Eignung dieser Laserquellen für OCT<br />
wird untersucht.<br />
1. Huber R. et al. Optics Express 14:3225-3237 (2006).<br />
2. Huang D. et al. Science 254:1178-1181 (1991).<br />
Q 54.8 Do 16:30 Poster C2<br />
Enhanced Four-Wave Mixing in mercury isotopes, prepared<br />
by Stark-chirped rapid adiabatic passage — •Martin Oberst,<br />
Jens Klein, and Thomas Halfmann — Institute for Applied Physics,<br />
TU Darmstadt, Schlossgartenstr. 7, 64289 Darmstadt, Germany<br />
We demonstrate significant enhancement of four-wave mixing (FWM)<br />
in coherently driven mercury isotopes to generate vacuum-ultraviolet<br />
radiation at 125 nm. The enhancement is accomplished by preparation<br />
of the mercury atoms in a state of maximum coherence, i.e. maximum<br />
nonlinear-optical polarization, driven by Stark-chirped rapid adiabatic<br />
passage (SCRAP). In this technique a pump laser at 313 nm excites<br />
the two-photon transition between the ground state 6s 2 1 S0 and the<br />
target state 7s 1 S0 in mercury. A strong, off-resonant radiation field<br />
at 1064 nm generates dynamic Stark shifts. These Stark shifts induce<br />
a rapid adiabatic passage process on the two-photon transition. The<br />
maximum nonlinear-optical polarization induced by SCRAP permits<br />
efficient FWM of the pump laser and an additional probe laser at 626<br />
nm. The efficiency is further enhanced, as the SCRAP process stimulates<br />
the complete set of different mercury isotopes to participate in<br />
the FWM-process. This enlarges the effective atomic density of the<br />
medium. Thus, we observe the generation of vacuum-ultraviolet radiation<br />
at 125 nm enhanced by more than one order of magnitude with<br />
respect to conventional frequency conversion. Parallel to the FWMprocess,<br />
we monitored the evolution of the population in the medium<br />
by laser-induced fluorescence. These data demonstrate efficient coherent<br />
population transfer by SCRAP.<br />
Q 54.9 Do 16:30 Poster C2<br />
Nichtlineare parametrische Konversion zu RGB direkt aus<br />
einem gütegeschalteten Oszillator — •Tino Lang 1 , Matthias<br />
Pospiech 2 und Uwe Morgner 2,3 — 1 Westsächsischen Hochschule<br />
Zwickau, Deutschland — 2 Institut für Quantenoptik, Leibniz Universität<br />
Hannover, Deutschland — 3 Laserzentrum Hannover e.V.<br />
Aktiv gütegeschaltete Lasersysteme bieten aufgrund hoher Pulsenergien<br />
die Möglichkeit der parametrischen Konversion in diverse Wellenlängenbereiche<br />
mit hoher Effizienz. Die zweite und dritte Harmonische<br />
wurde mit den 10 ns-Pulsen mit einer Pulsenergie von 0,3 mJ<br />
(40 kHz) und einer Wellenlänge von 1064 nm erzeugt. Durch die Verwendung<br />
periodisch gepolter Kristalle in Kombination mit einem<br />
signal-resonanten optisch parametrischen Oszillator konnte mit dem<br />
übrigen fundamentalem Laserlicht von 100 nJ für die Konversion zu<br />
1,5 µm eine Effizienz von 75 % erreicht werden. Diese hohe Effizienz<br />
ermöglicht die anschließende Konversion zu Blau und Rot mit der zuvor<br />
generierten dritten Harmonischen und der restlichen Fundamentalen.<br />
Aufgrund numerischer Simulationen werden Leistung größer 1 W<br />
pro Farbe erwartet. Wir stellen die Ergebnisse und den Vergleich mit<br />
Simulationen vor.<br />
Q 54.10 Do 16:30 Poster C2<br />
Tunable mid-IR CW narrowband laser source for molecular<br />
spectroscopy — •Sergey Vasilyev 1 , Alexander Nevsky 1 ,<br />
Stephan Schiller 1 , Arnaud Grisard 2 , Eric Lallier 2 , David<br />
Faye 2 , Zhaowei Zhang 3 , Deyuan Shen 3 , Andrew Clarkson 3 ,<br />
Morten Ibsen 3 , Peter Geiser 4 , Axel Bohman 4 , Peter<br />
Kaspersen 4 , and Juan Jiménez 5 — 1 Institute for Experimental<br />
Physics, Düsseldorf, Germany — 2 Thales Research and Technology,<br />
Palaiseau Cedex, France — 3 Optoelectronics Research Centre, University<br />
of Southampton, UK — 4 Norsk Elektro Optikk, Lørenskog,<br />
Norway — 5 University of Valladolid, Spain<br />
The objective of our research project is the development of a widely<br />
tunable (5 - 15 µm) narrowband mid-IR laser source based on a nonlinear<br />
down conversion of 1.5 - 2.0 µm laser radiation using difference<br />
frequency generation (DFG) and optical parametric generation (OPO)<br />
in a Orientation-Patterned Gallium Arsenide (OP-GaAs) crystal. The<br />
OP-GaAs combines a high nonlinearity, wide transparency range, and
Fachverband Quantenoptik und Photonik (Q) Donnerstag<br />
high thermal conductivity with merits of a quasi-phase-matching technique.<br />
Recently a method was developed for fabrication of large-size<br />
OP-GaAs structures.<br />
Tunable mid-IR source based on the DFG between a narrowband<br />
broadly tunable EDFA (10 W) and thulium doped fiber laser MOPA<br />
(1 W) has been developed. DFG output wavelength was tunable from<br />
7.5 µm to 8.2 µm with pm precision. Mid-IR output power of 0.1 -<br />
0.3 mW has been measured. Spectroscopic capabilities of the mid-IR<br />
source were tested by measuring of CH4 absorption spectra.<br />
Q 54.11 Do 16:30 Poster C2<br />
Emissionsrauschen eines Festkörperlasers mit resonatorinterner<br />
Frequenzverdoppelung — •Oliver Back, René Hartke,<br />
Ernst Heumann, Günter Huber, Klaus Sengstock und Valeri<br />
Baev — Institut für Laserphysik, Universität Hamburg<br />
Das Emissionsrauschen eines frequenzverdoppelten Festkörperlasers<br />
wird durch die Anregung der Summenfrequenz bei zwei- oder mehrmodigem<br />
Laserbetrieb verursacht [1]. Wir haben festgestellt, dass die<br />
Q 55: Poster Laseranwendungen<br />
Bedingung für die Entstehung des Rauschens eine partielle Entkopplung<br />
der verfügbaren Inversion für verschiedene Moden z.B. durch<br />
räumliche Inhomogenität in der Verstärkung ist. Es ist bekannt, dass<br />
eine Verringerung des Rauschens möglich ist, wenn die Effizienz der<br />
Summenfrequenzbildung gegenüber der Frequenzverdoppelung reduziert<br />
wird [2]. Eine andere Methode zur Unterdrückung des Rauschens<br />
beruht auf der Reduzierung der Modenentkopplung, z.B. durch die<br />
Verringerung des Modenabstandes [3]. Die numerische Modellierung<br />
eines Zweimodenlasers unter der Berücksichtigung der räumlichen Inhomogenität<br />
der Verstärkung hat unsere experimentellen Ergebnisse<br />
bestätigt. Die Steuerung des Emissionsrauschen eines frequenzverdoppelten<br />
Festkörperlasers kann sowohl mit der Effizienz der Summenfrequenzbildung<br />
als auch mit der Modenentkopplung effizient erfolgen.<br />
[1] T.Baer, J. Opt. Soc. Am. B 3, 1175 (1986)<br />
[2] C.Czeranowsky, V.Baev, G.Huber, Opt. Lett. 28, 2100 (2003)<br />
[3] R.Hartke, V.Baev, K.Seger, O.Back, E.Heumann, G.Huber,<br />
M.Kühnelt, U.Steegmüller, Appl. Phys. Lett. (submitted)<br />
Zeit: Donnerstag 16:30–19:00 Raum: Poster C2<br />
Q 55.1 Do 16:30 Poster C2<br />
Absorption spectroscopy of isolated molecules using subwavelength<br />
diameter optical fibres — •Ariane Stiebeiner, Ruth<br />
García Fernández, and Arno Rauschenbeutel — Institut für<br />
Physik, Universität Mainz, Staudingerweg 7, 55128 Mainz<br />
Particles on the surface of sub-wavelength diameter air-clad fibres are<br />
strongly coupled to the pronounced evanescent field of the fibre guided<br />
modes. This makes such fibres a powerful tool for absorption spectroscopy<br />
of surface-adsorbed molecules, based upon the measurement<br />
of the reduction in fibre transmission. We have shown that the corresponding<br />
detection sensitivity for a given surface coverage of molecules<br />
can be orders of magnitude higher than for conventional techniques [1].<br />
We present an improved setup for the detection of small numbers of<br />
isolated molecules at room temperature. The measurements are carried<br />
out on different species of organic molecules in a dry nitrogen<br />
atmosphere, thus permitting spectroscopy of molecules that are not<br />
stable under ambient conditions. Also, due to the absence of water in<br />
this atmosphere, reordering processes to monolayer islands or even a<br />
polycrystalline phase, which are possible for some molecular species,<br />
will be slowed down, enabling us to prepare and observe molecules on<br />
the fibre surface for extended periods of time.<br />
[1] F. Warken et al., Opt. Express, 15, 11952-11958 (2007)<br />
Q 55.2 Do 16:30 Poster C2<br />
Laserspektroskopie an Farbzentren in CVD-Diamantfilmen —<br />
•David Steinmetz, Elke Neu und Christoph Becher — Universität<br />
des Saarlandes, Technische Physik, Campus E2.6, 66123 Saarbrücken<br />
Eine zentrale Voraussetzung für die Realisierung verschiedener Konzepte<br />
in der Quanteninformationsverarbeitung ist die Verfügbarkeit<br />
von Einzelphotonenquellen, die photostabil sind und über eine schmale<br />
Linienbreite verfügen [1]. Als Einzelphotonenemitter eignen sich Farbzentren<br />
in künstlich hergestellten Diamanten, die sehr schwach an den<br />
umgebenden Kristall koppeln, was schmale Fluoreszenzlinien zur Folge<br />
hat. Ein Beispiel ist das aus einem Silizium-Atom und zwei Gitterfehlstellen<br />
aufgebaute Si-V Zentrum [2]. Farbzentren aus Übergangsmetallen<br />
wie Wolfram, Tantal oder Nickel sind weitere vielversprechende<br />
Möglichkeiten für Einzelphotonenemitter [3].<br />
Die von uns untersuchten Farbzentren liegen in Diamantfilmen vor,<br />
die in einem so genannten Chemical Vapor Deposition-Verfahren<br />
(CVD) hergestellt werden. Die Farbzentren entstehen dabei im Wachstumsprozess<br />
der Filme oder durch Ionenimplantation. Sie lassen sich<br />
mit Hilfe konfokaler Laser-Fluoreszenzmikroskopie analysieren und zur<br />
Einzelphotonenemission anregen. Wir stellen Ergebnisse von temperaturabhängigen<br />
spektroskopischen Untersuchungen an verschiedenen<br />
Farbzentren vor und diskutieren deren Eignung als Einzelphotonenemitter.<br />
[1] B. Lounis et al., Rep. Prog. Phys. 68, 1129-1179 (2005)<br />
[2] C. Wang et al., J. Phys. B 39, 37-41 (2006)<br />
[3] A. Zaitsev, Phys. Rev. B 61, 12909-12922 (2000)<br />
Q 55.3 Do 16:30 Poster C2<br />
Spektroskopie an CVD-Diamantfilmen im ultravioletten,<br />
sichtbaren und nahinfraroten Spektralbereich — •Christian<br />
Hepp, David Steinmetz, Elke Neu und Christoph Becher — Universität<br />
des Saarlandes, Technische Physik, Campus E2.6, 66123 Saarbrücken<br />
Aktuelle Forschung der Quanteninformationstechnologie beschäftigt<br />
sich mit dem Ankoppeln von Einzelphotonenemittern an Mikroresonatoren.<br />
Die von uns untersuchten Emitter sind Farbzentren in Diamantfilmen<br />
verschiedener Kristallitgrößen. Für dieses Materialsystem<br />
bietet sich die Realisierung von Mikroresonatoren in photonischen<br />
Kristallstrukturen an [1]. Die Güte dieser Mikroresonatoren hängt<br />
jedoch kritisch von den Absorptionsverlusten des Materials ab. Deshalb<br />
liegt ein besonderes Interesse unserer Forschung auf den Untersuchungen<br />
der Absorption in Diamantfilmen. Diese Absorption wird<br />
hauptsächlich durch sp 2 -gebundenen Kohlenstoff in den Korngrenzen<br />
des Diamanten und die dadurch ermöglichten Übergänge innerhalb<br />
der Bandlücke verursacht [2]. Wir untersuchen die Transmissionseigenschaften<br />
von Diamantfilmen mit Hilfe von UV/Vis/NIR-Spektroskopie.<br />
Um Mehrfachreflexionen und den Einfluss der Oberflächenrauhigkeit<br />
zu berücksichtigen, wird das Mehrschichtsystem aus CVD-Diamant<br />
und Substrat mit Hilfe der Wellen-Transfer-Matrixmethode simuliert.<br />
Aus den Messdaten kann der Absorptionskoeffizient der Diamantfilme<br />
bestimmt und mit einem theoretischen Modell verglichen werden.<br />
[1] C.F. Wang et al., Appl. Phys. Lett. 91, 201112 (2007)<br />
[2] P. Achatz et al., Appl. Phys. Lett. 88, 101908 (2006)<br />
Q 55.4 Do 16:30 Poster C2<br />
Detection of NO isotopologues with a Quantum Cascade<br />
Laser based Faraday Modulation Spectroscopy — •X Sabana,<br />
Thomas Fritsch, Peter Hering, and Manfred Mürtz — Institut<br />
für Lasermedizin, 40225 Düsseldorf<br />
The detection of 14 NO and 15 NO enables to analyse endogenous as well<br />
as exogenous sources. Faraday Modulation Spectroscopy (FAMOS) is<br />
a method used to detect NO with high sensitivity and without any<br />
cross-interferences.<br />
FAMOS uses a Quantum Cascade Laser (QCL) because of its narrow<br />
linewidth and high optical output. It is also able to be frequency<br />
modulated up to about hundred MHz. This allows to improve the sensitivity<br />
of the detection using the double modulation technique. The<br />
double modulation technique is a combination of the laser frequency<br />
modulation and magnetic field frequency modulation with detection<br />
at the sum frequency.<br />
The QCL used in our laboratory operates between 1839.9 cm −1 and<br />
1851.9 cm −1 at a temperature between −30 o C and 30 o C and a maximum<br />
power of 27.4 mW . The laser power at the wavelength of the<br />
used NO transition is in the 1 mW range.<br />
The NO transitions are in the frequency range of the QCL at 1842.94<br />
cm −1 ( 14 NO) and 1841.76 cm −1 ( 15 NO) and the detection limits are<br />
70 ppb (parts per billion) for 15 NO and 380 ppb for 14 NO with an<br />
integration time of 300 ms.<br />
Because of its high selectivity, the FAMOS technique is an excellent
Fachverband Quantenoptik und Photonik (Q) Freitag<br />
method for measuring NO production from aqueous solutions.<br />
Q 55.5 Do 16:30 Poster C2<br />
Integrated Cavity Output Spectroscopy für die Atemgasanalytik<br />
— •Jón Mattis Hoffmann, Sven Thelen, Peter Hering<br />
und Manfred Mürtz — Institut für Lasermedizin, Heinrich-Heine-<br />
Universität, Düsseldorf, www.ilm.uni-duesseldorf.de/tracegas<br />
Der Nachweis bestimmter Spurengase im Atem spielt in der Medizin<br />
eine immer größere Rolle. Für die quantitative Analyse von Spurengasen<br />
im ppb-Bereich ist die Cavity Ring Down Spectroscopy (CRDS) als<br />
empfindliches und spezifisches Messverfahren etabliert. Als eine Alternative<br />
wird in der Literatur die Integrated Cavity Output Spectroscopy<br />
(ICOS) diskutiert, die ebenfalls die Verlängerung des Absorptionsweges<br />
in einer Cavity ausnutzt, aber als robuster und leichter handhabbar<br />
gilt.<br />
In diesem Beitrag soll die Anwendbarkeit von ICOS für die Atemgasanalyse<br />
im Wellenlängenbereich um 3 µm untersucht und mit der<br />
CRDS verglichen werden. Hierzu wird ein neues System aufgebaut,<br />
welches aus einer 56 cm langen Absorptionszelle mit zwei hochreflektierenden<br />
Spiegel sowie einem CO-Obertonlaser besteht. Der Laserstrahl<br />
wird in diesem System im Off-Axis-Verfahren in die Zelle eingekoppelt,<br />
wobei der Aufbau durch Simulationen unterstützt wird.<br />
Q 55.6 Do 16:30 Poster C2<br />
Absorptionsmessungen im Resonator eines Tm-dotierten Faserlasers<br />
von 1730 nm bis 2040 nm — •Matthias Höh 1 ,<br />
Benjamin Löhden 1 , Klaus Sengstock 1 , Valeri Baev 1 und Bera<br />
Pálsdóttir 2 — 1 Institut für Laserphysik, Universität Hamburg, Germany<br />
— 2 OFS Fitel, Brondby, Denmark<br />
Die Nutzung Thulium-dotierter Silikatglasfasern mit höherer Dotierung<br />
und besserer Qualität konnte den Durchstimmbereich eines damit<br />
realisierten Thulium-Faserlasers um insgesamt 50% gegenüber<br />
früheren Experimenten [1] erweitern. Das Emissionsspektrum wird mit<br />
einer asphärischen Linse im Resonator zwischen 1730 nm und 2040<br />
nm durchgestimmt. Der erweiterte Spektralbereich ermöglicht hochempfindliche<br />
Absorptionsmessungen wichtiger atmosphärischer Gase<br />
wie H2O, H2S, NH3, HCl, HBr, NO, N2O, CO, 12 CO2, 13 CO2,<br />
CH4, die für Medizin, Prozesstechnik und Umweltanalyse von Relevanz<br />
sind. Dabei entspricht die Messempfindlichkeit einer Absorptionsweglänge<br />
von mehreren Kilometern bezogen auf konventionelle Messverfahren.<br />
Zur Aufnahme der Spektren wurde wahlweise ein Fourier-<br />
Spektrometer oder ein Gitterspektrometer mit Diodenzeile verwendet.<br />
Die nichtstationäre Modendynamik des Lasers bewirkt bei den Messungen<br />
mit dem Fourier Spektrometer einen Rauschuntergrund. Die<br />
Diodenzeile dagegen ermöglicht deutlich schnellere und rauscharme<br />
Aufnahmen.<br />
[1]. A.Stark, L.Correia, M.Teichmann, S.Salewski, C.Larsen,<br />
V.M.Baev, P.E.Toschek, Opt. Commun., 215, 113 (2003)<br />
Q 55.7 Do 16:30 Poster C2<br />
Entwicklung eines ultra-temperaturstabilen Zerodur-<br />
Masterlasers — •Alexandra Dwenger, Anika Vogel, Kai Bongs<br />
und Klaus Sengstock — Institut für Laserphysik der Universität<br />
Hamburg, Germany<br />
In unserem Projekt entwickeln wir ein neuartiges Laserkonzept, welches<br />
hohen Anforderungen hinsichtlich mechanischer Stabilität, Temperaturunempfindlichkeit,<br />
Größe und Gewicht genügen muss.<br />
Das mobile und flexible Lasersystem ist mit seinen Abmessungen<br />
von 103 x 103 x 90 mm 3 ultraklein. Es muss Beschleunigungen bis zu<br />
50 g standhalten, wie sie bei den Experimenten unserer QUANTUS-<br />
Kollaboration (Q 22.7) erreicht werden.<br />
Um diese Eigenschaften zu gewährleisten sind alle Komponenten des<br />
Systems aus der Glaskeramik Zerodur gefertigt und mittels einer von<br />
uns entwickelten Klebetechnik justierbar.<br />
Q 55.8 Do 16:30 Poster C2<br />
Polarization dependent light transmission through single<br />
nanoscopic apertures — •Jochen Kindler née Mueller, Peter<br />
Banzer, Susanne Quabis, Ulf Peschel, and Gerd Leuchs —<br />
Max Planck Research Group of Optics, Information and Photonics,<br />
Günther-Scharowsky-Str. 1 / Bau 24, 91058 Erlangen<br />
In the recent years the investigation of transmission through sub wavelength<br />
holes in thin metal films has intensified in order to gain a better<br />
understanding at a fundamental level. Much work has been published<br />
studying arrays of holes. In contrast, we experimentally study the<br />
transmission of a single aperture and compare our results to rigorous<br />
numerical calculation based on FDTD algorithm. We concentrate on<br />
investigating the influence of polarization distributions which are nonhomogeneous<br />
on a scale of less than one wavelength. For this purpose<br />
we generate radially and azimuthally polarized beams at wavelengths<br />
of 775 nm and 532 nm which are focussed by a high numerical aperture<br />
microscope objective onto each aperture. As samples we use glass<br />
substrates covered with different metals (Ag, Pt, Cr) which are structured<br />
with apertures of different types and sizes. For holes as well as<br />
for annular rings with diameters smaller than the wavelength we find<br />
a strong polarization effect on the transmitted power. In this contribution,<br />
we will apply the concept of cylindrically symmetric waveguide<br />
Eigenmodes to our results. Furthermore, the FDTD model calculation<br />
reveals the excitation of surface plasmons to play an important role.<br />
Q 55.9 Do 16:30 Poster C2<br />
Polarization effects on metal edges — •Pavel Marchenko, Susanne<br />
Quabis, Ulf Peschel, and Gerd Leuchs — Max Planck Research<br />
Group, Insitute of Optics, Information and Photonics, University<br />
Erlangen-Nuremberg, Günther-Scharowsky-Str. 1 / Bau24, 91058<br />
Erlangen<br />
To image the intensity distribution of laser beams the so-called ”knifeedge”<br />
method can be applied. The principle is to move the spot across<br />
differently oriented metal edges and reconstruct the intensity distribution<br />
by analyzing the slope of the photocurrents. But at nanoscale<br />
dimensions the modification of the electric field by the metal edge cannot<br />
be neglected, so in general the reconstruction of a strongly focused<br />
beam is not possible any more. However, understanding the mechanisms<br />
of how various parameters (wavelength, metal properties, input<br />
polarization) influence this field modification offer a way to overcome<br />
this problem.<br />
In our experiment linearly, radially and azimuthally polarized beams<br />
at 532, 633 and 780 nm are focused by a high numerical aperture onto<br />
a sample. The sample is a p-i-n photodiode covered with metal objects<br />
consisting of an Zn/Au alloy with various mixing ratios. We move the<br />
spot over the metal edges and for each one record the photocurrent as<br />
a function of the position.<br />
The measurements reveal ”push” and ”pull” effects the metal edge<br />
exerts on the field where the direction of the polarization vector plays<br />
an important role. Moreover, we can determine conditions where these<br />
effects compensate.<br />
Q 56: Quanteninformation (Photonen und nichtklassisches Licht I)<br />
Zeit: Freitag 11:00–13:00 Raum: 1A<br />
Q 56.1 Fr 11:00 1A<br />
Two-mode single-atom laser as a source of entangled light<br />
— •Martin Kiffner 1 , M. Suhail Zubairy 1,2 , Jörg Evers 1 , and<br />
Christoph H. Keitel 1 — 1 Max-Planck-Institut für Kernphysik,<br />
Saupfercheckweg 1, 69117 Heidelberg, Germany — 2 Institute for<br />
Quantum Studies and Department of Physics, Texas A&M University,<br />
College Station, Texas 77843, USA and Texas A&M University at<br />
Qatar, Education City, P. O. Box 23874, Doha, Qatar<br />
Continuous variable entanglement is a key resource in many applications<br />
of quantum information and quantum computation theory. We<br />
theoretically investigate a single atom trapped inside a doubly resonant<br />
cavity as a source of entanglement in macroscopic light. The four-level<br />
gain medium atom interacts with two (nondegenerate) cavity modes<br />
on separate transitions, while the two other transitions are driven by<br />
control laser fields. Spontaneous decay of the atomic levels as well as<br />
cavity losses are included in our model. We employ an inequality [1]<br />
based on the correlation of the field operators as a sufficient criterion<br />
for the entanglement of the cavity field. It is shown that the considered<br />
two-mode single-atom laser gives rise to an entangled state of the<br />
cavity modes with a macroscopic number of photons over a wide range<br />
of control parameters and initial states of the cavity field [2].<br />
[1] L.-M. Duan, G. Giedke, J. I. Cirac, and P. Zoller,
Fachverband Quantenoptik und Photonik (Q) Freitag<br />
Phys. Rev. Lett. 84, 2722 (2000).<br />
[2] M. Kiffner, M. S. Zubairy, J. Evers, and C. H. Keitel,<br />
Phys. Rev. A 75, 033816 (2007).<br />
Q 56.2 Fr 11:15 1A<br />
Aperture imaging beyond the classical resolution limit by using<br />
incoherent photons — •Christoph Thiel 1 , Thierry Bastin 2 ,<br />
Joachim von Zanthier 1 , and Girish S. Agarwal 3 — 1 Institut für<br />
Optik, Information und Photonik, Max- Planck-Forschungsgruppe,<br />
Universität Erlangen-Nürnberg, Germany — 2 Institut de Physique<br />
Nucléaire, Atomique et de Spectroscopie, Université de Liège, Belgium<br />
— 3 Department of Physics, Oklahoma State University, Stillwater,<br />
OK, USA<br />
We propose a technique to image arbitrary objects, e.g. an aperture,<br />
with sub-wavelength resolution using incoherent light. The method<br />
employs two photons spontaneously emitted by two atoms acting as<br />
the light source of our setup. The photons irradiate an aperture and<br />
are subsequently detected by two detectors in the far field region. We<br />
demonstrate that for certain detector positions r1 and r2 the second<br />
order correlation function G (2) (r1, r2) offers full information of the<br />
aperture, even if of size λ/2. The result corresponds thus to a 2-fold<br />
increase in spatial resolution in comparison with the classical intensity<br />
pattern. Unlike in the classical case, the two photons can take different<br />
but indistinguishable quantum paths. Our method makes explicit use<br />
of the second order interferences between these paths and it is thereby<br />
able to obtain a resolution beyond the classical limit.<br />
Q 56.3 Fr 11:30 1A<br />
Realization of two indistinguishable Fourier-limited solid<br />
state single-photon sources — Robert Lettow 1 , Ville Ahtee 2 ,<br />
Alois Renn 1 , Erkki Ikonen 2 , •Stephan Götzinger 1 , and Vahid<br />
Sandoghdar 1 — 1 Laboratory of Physical Chemistry, ETH Zürich,<br />
CH-8093 Zürich, Switzerland — 2 Metrology Research Institute,<br />
Helsinki University of Technology , FI-02015 TKK, Finland<br />
Single-photon sources comprise an important building block in many<br />
quantum information processing schemes. The feasibility of such<br />
sources has been demonstrated in various systems. Single photons have<br />
also already been successfully used for applications in quantum cryptography.<br />
However, complex schemes of quantum information processing<br />
require a large number of indistinguishable photons from independent<br />
sources.<br />
We demonstrate indistinguishable Fourier-limited single-photon<br />
sources based on two single molecules [1]. High resolution laser spectroscopy<br />
and optical microscopy were combined to identify individual<br />
molecules in two independent microscopes. The Stark effect was exploited<br />
to shift the transition frequency of a given molecule and thus<br />
obtain single-photon sources with perfect spectral overlap. The solidstate<br />
aspect of our system offers many advantages including well defined<br />
polarization and a nearly indefinite measurement time using the<br />
same single emitters. Our experimental arrangement sets the ground<br />
for the realization of quantum interference experiments with two independent<br />
solid state single-photon sources.<br />
[1] R. Lettow et al., Optics Express 15, 15842 (2007).<br />
Q 56.4 Fr 11:45 1A<br />
Gequetschtes Licht bei 1550 nm — •Sebastian Steinlechner,<br />
Jessica Dück, Stefan Goßler, Moritz Mehmet, Karsten Danzmann<br />
und Roman Schnabel — Max-Planck-Institut für Gravitationsphysik<br />
(AEI) und Institut für Gravitationsphysik, Leibniz Universität<br />
Hannover<br />
Die Empfindlichkeit von Gravitationswellendetektoren der zweiten Generation<br />
wird durch thermisches Rauschen sowie durch Quantenrauschen<br />
des Lichtfeldes limitiert sein.<br />
Empfindlichkeiten unter dem Quantenrauschen können durch den<br />
Einsatz von nichtklassischem (gequetschtem) Licht erreicht werden.<br />
Entsprechende Experimente mit gequetschtem Licht wurden erfolgreich<br />
durchgeführt und die Umsetzung für den Detektor GEO 600 befindet<br />
sich derzeit im Aufbau. Vielversprechender Ansatz zur Verminderung<br />
des thermischen Rauschens ist die Kühlung der Interferometer-<br />
Testmassen. Die bisher verwendeten Fused-Silica-Substrate besitzen<br />
hohe optische Qualität, zeigen jedoch bei niedrigen Temperaturen inakzeptable<br />
mechanische Verluste. Aussichtsreichster Kandidat für kryogene<br />
Testmassen ist Silizium, das jedoch bei der bisher verwendeten Laserwellenlänge<br />
von 1064 nm nicht transparent ist. Dagegen wird im Bereich<br />
von 1550 nm ein extrem niedriger Absorptionskoeffizient erwartet.<br />
Vorhandene Techniken für die Erzeugung von gequetschtem Licht werden<br />
auf 1550 nm übertragen, um zusammen mit Silizum-Testmassen<br />
die Grundlage für kommende, kryogene Detektoren zu bilden.<br />
Wir stellen das Konzept und erste Ergebnisse einer Quetschlichtquelle<br />
bei 1550 nm vor.<br />
Q 56.5 Fr 12:00 1A<br />
An entangled-pair photon source for single-photon singleatom<br />
interaction — •Albrecht Haase, Nicolas Piro, Morgan<br />
Mitchell, and Jürgen Eschner — ICFO - Institut de Ciencies Fotoniques,<br />
08660 Castelldefels (Barcelona), Spain<br />
We present a narrow-bandwidth source of entangled photon pairs,<br />
which will allow us to address the transitions D3/2-P3/2 and D5/2-<br />
P3/2 in single 40Ca+ ions at 850 and 854 nm wavelength, respectively.<br />
The source has been designed to emit photons with a high spectral<br />
power density into the absorption window of the Calcium ions, which<br />
has a bandwidth of ˜20 MHz. We describe the setup and characterize<br />
the performance of the source. Its applications will be experiments towards<br />
the probabilistic entanglement of distantly trapped single atoms.<br />
As a first step we employ the temporal correlation of the photon pairs<br />
to study the triggered excitation of an ion. Additionally the source<br />
provides entanglement in the polarization degree of freedom of the<br />
photons, which we have observe with over 91% visibility. We propose<br />
schemes to transfer the entanglement to the internal states of<br />
the trapped ions.<br />
Q 56.6 Fr 12:15 1A<br />
Observation of polarization squeezing in PPKTP waveguides<br />
— Malte Avenhaus 1 , Maria Chekhova 2 , •Leonid Krivitsky 1 ,<br />
Gerd Leuchs 1 , and Christine Silberhorn 1 — 1 University of<br />
Erlangen-Nurnberg, Institute for Optics Information and Photonics<br />
— 2 M.V. Lomonosov Moscow State University<br />
We study the experimental configuration of generation of polarizationsqueezed<br />
states based on interference effect involving two nonlinear<br />
crystals. Our experiment represents a generalization of the well developed<br />
method of polarization-entangled state generation at the single<br />
photon level for the case of high parametric gain. The high gain regime<br />
is achieved by using an efficient source based on periodically poled<br />
KTP crystal waveguide pumped by a femtosecond laser. We show that<br />
the effect of polarization entanglement observed at a single photon<br />
level transforms in observation of polarization squeezing at a high gain<br />
regime.<br />
Q 56.7 Fr 12:30 1A<br />
Spatial modes and spectral entanglement in PDC — •Andreas<br />
Eckstein, Andreas Christ, Thomas Lauckner, and Christine<br />
Siblerhorn — University Erlangen-Nuremberg, Max-Planck Research<br />
Group IOIP, Integrated Quantum Optics Group<br />
We present the observation of a picosecond beating in a Hong-Ou-<br />
Mandel (HOM) type experiment. To study the HOM interference, we<br />
implemented a PDC process in a PPKTP waveguide, pumped by a<br />
picosecond laser at 404nm. Both signal and idler photons are fed into<br />
a balanced beamsplitter, and coincident photons from its output ports<br />
are detected. Instead of a gaussian HOM dip, we observe a gaussianenveloped<br />
beating signature of coincidence events. Unlike the experiment<br />
in [1], our setup exhibits anti-bunching without spectrally restricting<br />
the detector response function.<br />
We attribute this behavior the fact that our waveguide is multimoded<br />
in the pump regime. The superposition of spatial pump modes<br />
inside the waveguide is translated into a frequency correlation between<br />
signal and idler photons via modal dispersion. Owing to the broadband<br />
nature of the PDC-generated photons, we propose a definition<br />
for broadband mode entanglement and explore the feasibility of this<br />
anti-bunching effect as an entanglement witness.<br />
[1] Hong, C. K., Ou, Z. Y., and Mandel, L. Phys. Rev. Lett. 59(18),<br />
2044*2046 (1987).<br />
Q 56.8 Fr 12:45 1A<br />
Photon pair generation in photonic crystal fibres —<br />
•Christoph Söller, Leyun Zang, Myeong Soo Kang, Philip Russell,<br />
and Christine Silberhorn — Max Planck Research Group<br />
IOIP, Günther-Scharowsky-Str. 1 / Bau 24, 91058 Erlangen<br />
Spontaneous four-wave mixing in photonic crystal fibres (PCF) is a<br />
new promising approach to generate photon pairs for quantum information<br />
applications. Tailoring of the PCF microstructure allows the realisation<br />
of a wide variety of dispersion profiles and offers the prospect<br />
to control the spectral properties of the generated photons to a high degree.<br />
We are working on the implementation of a PCF source optimized
Fachverband Quantenoptik und Photonik (Q) Freitag<br />
for quantum networks. By manufacturing appropriate fibres, we aim<br />
to realise a source that provides heralded single photon states without<br />
narrow bandpass filtering. The heralding signal photon is emitted at a<br />
wavelength in the Si-APD range to ensure efficient detection. The idler<br />
photon of the pair is generated at 1.55µm and can thus be transmitted<br />
Q 57: Quanteneffekte (QED / Lichtstreuung)<br />
with very low losses by telecom fibres. Spectral decorrelation of the pair<br />
photons ensures the indistinguishability of idler photons from different<br />
sources and permits quantum interference without narrow bandpass<br />
filters.<br />
Zeit: Freitag 11:00–13:00 Raum: 2D<br />
Q 57.1 Fr 11:00 2D<br />
Jaynes-Cummings Ladder in Quantum-Dot Microcavities —<br />
•Lukas Schneebeli, Mackillo Kira und Stephan Koch — Department<br />
of Physics and Materials Sciences Center, Philipps-University<br />
Marburg, Renthof 5, 35032 Marburg, Germany<br />
The quantum-optical hierarchy problem for dots in microcavities in the<br />
strong-coupling regime is analyzed using a cluster-expansion approach<br />
[1]. Resonance fluorescence spectra are discussed for several excitation<br />
conditions.<br />
[1] M. Kira, S.W. Koch/Progress in Quantum Electronics 30 (2006),<br />
155-296<br />
Q 57.2 Fr 11:15 2D<br />
From a single-photon emitter to a single ion laser —<br />
•Helena G. Barros 1,2 , François Dubin 1 , Carlos Russo 1,2 , Andreas<br />
Stute 1,2 , Piet O. Schmidt 1 , and Rainer Blatt 1,2 —<br />
1 Institut für Experimentalphysik, Universiät Innsbruck, Technikerstr.<br />
25, A-6020 Innsbruck — 2 Institut für Quantenoptik und Quanteninformation,<br />
Österreichische Akademie der Wissenschaften, Otto-Hittmair-<br />
Platz 1, A-6020 Innsbruck<br />
A single atom interacting with a single mode of a cavity is the building<br />
block of a laser from a fundamental point of view. In this work, we<br />
study a single 40 Ca + ion coupled to a high finesse optical resonator.<br />
In particular, we evaluate the statistical properties of emitted cavity<br />
photons for different regimes of operation.<br />
In the experiment, a drive laser together with an optical cavity excites<br />
an off-resonant Raman transition that connects the S 1/2 and<br />
D 3/2 levels of the 40 Ca + ion. Population gets transferred from S 1/2<br />
to D 3/2 while emitting a photon into the cavity. The excitation cycle<br />
is closed by a recycling laser that brings the atomic population<br />
back to the initial state S 1/2 via resonant excitation of the P 1/2 state.<br />
The photons leave the cavity at a rate of 54 kHz and are sent to a<br />
Hanbury-Brown & Twiss setup, where photon-photon correlations are<br />
measured. For weak recycling laser intensity, the system is operating<br />
as a single-photon source. In this regime, we can tune the statistics<br />
of the photon arrival times from sub-Poissonian to super-Poissonian<br />
behaviour. For faster recycling rates, we observe a single-atom laser at<br />
threshold. Different criteria for lasing in such a system are discussed.<br />
Q 57.3 Fr 11:30 2D<br />
Non-perturbative vacuum-polarization effects in proton-laser<br />
collisions — •Antonino Di Piazza, Karen Z. Hatsagortsyan,<br />
and Christoph H. Keitel — Max-Planck-Institut für Kernphysik,<br />
Saupfercheckweg 1, 69117 Heidelberg<br />
Merging of laser photons can occur due to the polarization of vacuum<br />
in the collision of a high-energy proton beam and an intense laser field<br />
[1]. The photon merging rate is calculated by exactly accounting for<br />
the laser field which involves a highly non-perturbative dependence<br />
on the laser field parameters, namely its intensity and frequency. It<br />
is shown that even non-perturbative vacuum-polarization effects could<br />
be in principle experimentally measured by combining proton accelerators<br />
presently available with the next generation of table-top petawatt<br />
lasers.<br />
[1] A. Di Piazza, K. Z. Hatsagortsyan, and C. H. Keitel, Phys. Rev.<br />
Lett. (in press). See also arXiv:0708.0475 [hep-ph].<br />
Q 57.4 Fr 11:45 2D<br />
Slow light in inhomogeneous and transverse magnetic fields —<br />
•Leon Karpa and Martin Weitz — Institut für Angewandte Physik<br />
der Universität Bonn, Wegelerstr. 8, 53115 Bonn, Germany<br />
Electromagnetically induced transparency allows for light transmission<br />
through dense atomic media by means of quantum interference of absorption<br />
amplitudes[1]. Media exhibiting electromagnetically induced<br />
transparency have interesting properties, such as very slow group ve-<br />
locities[2]. Associated with the slow light propagation are quasiparticles,<br />
so-called dark polaritons, which are mixtures of a photonic and<br />
an atomic contribution[3]. We have carried out experiments, where<br />
circularily polarized light traversing a rubidium gas cell under EIT<br />
conditions is deflected by an inhomogeneous magnetic field. The obtained<br />
results can be described in terms of dark state polaritons having<br />
a nonzero effective magnetic moment[4]. In subsequent experiments,<br />
electromagnetically induced transparency and slow light have also been<br />
observed with a transverse magnetic field orientation. Such a configuration<br />
can be used in further studies of the quasiparticle nature of<br />
slow light, as in a planned Aharonov-Casher experiment.<br />
[1] See e.g.: E. Arimondo, Prog. Opt. 35, 257 (1996).<br />
[2] See e.g.: L. V. Hau et al. Nature (London) 397, 594 (1999).<br />
[3] M. Fleischhauer and M. D. Lukin, Phys. Rev. Lett. 84, 5094 (2000).<br />
[4] L. Karpa and M. Weitz, Nature Physics 2, 332 (2006).<br />
Q 57.5 Fr 12:00 2D<br />
Nonlinear Effects in Pulse Propagation through Doppler-<br />
Broadened Closed-Loop Atomic Media — •Robert<br />
Fleischhaker and Jörg Evers — Max-Planck-Institut für Kernphysik,<br />
Heidelberg<br />
Nonlinear effects in pulse propagation through a medium consisting of<br />
four-level double-Λ-type systems are studied theoretically. We apply<br />
three continous-wave driving fields and a pulsed probe field such that<br />
they form a closed interaction loop. Due to the closed loop and the<br />
finite frequency width of the probe pulses the multiphoton resonance<br />
condition cannot be fulfilled, such that a time-dependent analysis is<br />
required. By identifying the different underlying physical processes we<br />
determine the parts of the solution relevant to calculate the linear and<br />
nonlinear response of the system. We find that the system can exhibit<br />
a strong intensity dependent refractive index with small absorption<br />
over a range of several natural linewidths. For a realistic example we<br />
include Doppler and pressure broadening and calculate the nonlinear<br />
selfphase modulation in a gas cell with Sodium vapor and Argon buffer<br />
gas. We find that a selfphase modulation of π is achieved after a propagation<br />
of few centimeters through the medium while the absorption<br />
in the corresponding spectral range is small.<br />
Q 57.6 Fr 12:15 2D<br />
Lossless Negative Refraction in An Active Dense Gas of<br />
Atoms — •Jörg Evers, Peter P. Orth, and Christoph H. Keitel<br />
— Max-Planck-Institut für Kernphysik, Heidelberg<br />
Negative index materials promise far-reaching applications in a broad<br />
range of areas from sub-wavelength imaging to antenna design. Since<br />
current designs are passive, however, negative index materials suffer<br />
from losses, prohibiting applications in particular towards optical frequencies.<br />
Here we predict lossless negative refraction in an active, i.e.<br />
amplifying, dense gas of atoms [1]. External laser fields are used to tune<br />
the medium’s electromagnetic response and an additional weak pumping<br />
field controls the absorption properties. We identify metastable<br />
Neon as a suitable experimental candidate at infrared frequencies. Our<br />
approach provides negative refraction without losses as required for<br />
applications and offers the unique opportunity to study the controlled<br />
transition to active negative index material.<br />
[1] P. P. Orth, J. Evers, and C. H. Keitel, arXiv:0711.0303<br />
Q 57.7 Fr 12:30 2D<br />
Controlled Coupling of Counterpropagating Whispering-<br />
Gallery Modes by a Single Rayleigh Scatterer: A Classical<br />
Problem in a Quantum Optical Light — Andrea<br />
Mazzei 1 , •Stephan Götzinger 2 , Leonardo Menezes 1 , Gert<br />
Zumofen 2 , Oliver Benson 1 , and Vahid Sandoghdar 2 — 1 Institut<br />
für Physik, Humboldt-Universität zu Berlin, 10117 Berlin, Germany<br />
— 2 Laboratory of Physical Chemistry, ETH Zürich, CH-8093 Zürich,<br />
Switzerland
Fachverband Quantenoptik und Photonik (Q) Freitag<br />
It is well established that the radiative properties of atoms can be<br />
strongly modified by coupling them to resonators. A corner stone<br />
of such modifications is the change of the photonic density of states<br />
caused by the boundary conditions imposed by a cavity. We investigate<br />
the analogy between this quantum optical scenario and the classical<br />
phenomenon of Rayleigh scattering in the presence of a high-finesse<br />
cavity.<br />
We present experiments where a single subwavelength scatterer is<br />
used to examine and control the backscattering induced coupling between<br />
counterpropagating high-Q modes of a microsphere resonator<br />
[1]. Our measurements reveal the standing wave character of the resulting<br />
symmetric and antisymmetric eigenmodes, their unbalanced<br />
intensity distributions, and the coherent nature of their coupling. We<br />
discuss our findings and the underlying classical physics in the framework<br />
common to quantum optics and provide a particularly intuitive<br />
explanation of the central processes.<br />
[1] A. Mazzei et al., Phys. Rev. Lett. 99, 173603 (2007).<br />
Q 57.8 Fr 12:45 2D<br />
Q 58: Ultrakalte Atome (Einzelne Atome)<br />
Improving High-Finesse Cavities: Corrections beyond the<br />
Paraxial Approximation — •Martin Zeppenfeld, Michael<br />
Motsch, Pepijn W.H. Pinkse, and Gerhard Rempe — Max-Planck-<br />
Institut für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching,<br />
Germany<br />
Increased atom-light interactions in a cavity due to many degenerate<br />
modes are of great interest for many experiments in quantum optics.<br />
While every second transverse mode of a confocal resonator is degenerate<br />
within the framework of the paraxial approximation, it is by no<br />
means to be expected that this remains the case when taking into<br />
account corrections to the paraxial approximation.<br />
Spheroidal coordinates and the associated spheroidal wave functions<br />
can be used to construct a set of exact solutions to Maxwell’s equations<br />
in free space which reduce to the Laguerre-Gaussian modes in<br />
the short wavelength limit. Using these solutions, we calculated firstorder<br />
corrections to the resonance frequencies of modes in a two-mirror<br />
Fabry-Perot resonator. For a confocal resonator, the mode degeneracy<br />
is lifted. The calculations are supported by measurements with a high<br />
finesse cavity.<br />
Zeit: Freitag 11:00–12:30 Raum: 3B<br />
Gruppenbericht Q 58.1 Fr 11:00 3B<br />
Quantum nonlinearity with one atom dressed by two photons<br />
— •Ingrid Schuster, Alexander Kubanek, Andreas Fuhrmanek,<br />
Thomas Puppe, Pepijn Pinkse, Karim Murr, and Gerhard Rempe<br />
— Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1,<br />
85748 Garching<br />
The strong-coupling regime of cavity QED has proven to be a rich<br />
pond of optical phenomena at the level of single atoms and photons.<br />
We experimentally demonstrate that such a system exhibits a nonlinear<br />
intensity response when a single atom is made to interact not<br />
with one, but with two photons at the same time. This nonlinearity<br />
is explained by quantum mechanics and is expected to vanish in<br />
the limit of many intracavity atoms. It originates from the energylevel<br />
structure of the system, which consists of a ladder of doublets<br />
with anharmonic level splitting. The first doublet is visible in lowintensity<br />
spectroscopy, where it leads to the well-known vacuum-Rabi<br />
or normal-mode splitting. For stronger driving, we find a resonance<br />
stemming from excitation of the second doublet, at a frequency which<br />
is distinct from the normal modes because of the anharmonicity of the<br />
energy level spectrum. Since we access the resonance by driving a twophoton<br />
transition, we see a mainly quadratic response with respect<br />
to the probe intensity. Our experiment opens up new avenues for the<br />
controlled generation of multi-photon states.<br />
Q 58.2 Fr 11:30 3B<br />
Experimentelle Demonstration einer deterministischen Einzelionenquelle<br />
für die nm-genaue Implantation von Ionen in<br />
Festkörper — •Wolfgang Schnitzler, N. M. Linke, J. Eble, F.<br />
Schmidt-Kaler und K. Singer — Universität Ulm, Institut für Quanteninformationsverarbeitung,<br />
Albert-Einstein-Allee 11, D-89069 Ulm<br />
Wir haben mittels einer Ionenfalle eine universelle deterministische<br />
Einzelionenquelle realisiert [1]. In einer segmentierten linearen Falle<br />
werden zunächst kalte 40 Ca + Ionenkristalle gefangen, anschließend deterministisch<br />
aus der Falle extrahiert und mit einer Erfolgsquote von<br />
über 90% auf einen 25cm entfernten Detektor geschossen. Die Streuung<br />
der kinetischen Energie der Ionen liegt dabei unter 0,1%. Auch<br />
das Laden und Extrahieren gemischter Kristalle wurde bereits erfolgreich<br />
durchgeführt. Für die nm-genaue Implantation planen wir, die<br />
räumliche Auflösung der extrahierten Ionen mittels einer elektrostatischen<br />
Einzellinse weiter zu optimieren. Diese können dann zur Implantation<br />
von P in Si oder zur Erzeugung von NV-Farbzentren in<br />
Diamant genutzt werden, welche optisch manipuliert werden können.<br />
Solche Systeme stellen Kandidaten zur Realisierung eines skalierbaren<br />
Festkörper-Quantencomputers dar [2,3]. Die elektrischen Eigenschaften<br />
von Halbleiterbauelementen können durch die deterministische Implantation<br />
einzelner Ionen ebenfalls verbessert werden [4].<br />
[1] J. Meijer et. al., Appl. Phys. A 83, 321 (2006)<br />
[2] B. Kane, Nature 393, 133 (1998)<br />
[3] F. Jelezko et. al., Phys. Rev. Lett. 93, 130501 (2004)<br />
[4] T. Shinada et. al., Nature 437, 1128 (2005)<br />
Q 58.3 Fr 11:45 3B<br />
State-Selective Transport of Single Caesium Atoms —<br />
•Micha̷l Karski, Leonid Förster, Daniel Döring, Florian Grenz,<br />
Arne Härter, Wolfgang Alt, Jai-Min Choi, Artur Widera, and<br />
Dieter Meschede — Institute for Applied Physics, University of Bonn<br />
The state-selective quantum transport of single neutral atoms in optical<br />
lattices offers a promising alternative to implement basic modules<br />
of advanced schemes in the context of quantum engineering. These<br />
range from the implementation of so called quantum walks, utilizing<br />
fundamental quantum effects involving spatial quantum interference to<br />
the preparation of so-called cluster states using coherent cold collisions<br />
as an inter-qubit interaction.<br />
We investigate systems of single Caesium atoms stored, one by one,<br />
in a state-dependent one-dimensional optical lattice. It is formed by a<br />
superposition of two standing wave dipole traps with right- and lefthanded<br />
circular polarisation respectively. They can be shifted with<br />
respect to each other. With an appropriate wave length, each of the<br />
two lattices couples to a different hyperfine state. Therefore, atoms prepared<br />
in these qubit states can be transported in opposite directions.<br />
Using microwave pulses in the presence of magnetic field gradients, the<br />
internal states can be separately manipulated.<br />
We present the current state of the experimental realisation of a onedimensional<br />
quantum transport for Caesium atoms, focussing on the<br />
experimental setup and the tools for the preparation and manipulation<br />
of individual qubit states and their spatial detection.<br />
Q 58.4 Fr 12:00 3B<br />
Measuring the coupling strength of single atoms to the field<br />
of a high-finesse optical resonator — •Sebastian Reick, Wolfgang<br />
Alt, Tobias Kampschulte, Mkrtych Khudaverdyan, Karim<br />
Lenhard, Karsten Schörner, and Dieter Meschede — Institut für<br />
Angewandte Physik, Wegelerstr. 8, -53115 Bonn<br />
The long-term goal of our experiment is the realisation of quantum<br />
information processing using neutral atoms. Since they are not coupled<br />
to each other or to the environment by a dipole force, which is<br />
an advantage in terms of coherence times, coherent interaction of two<br />
or more atoms has to be achieved by other means, e.g. by photon<br />
exchange.<br />
In our experiment, we store atoms in a standing wave dipole trap,<br />
which can be utilised as an optical conveyor belt to move the atoms<br />
into the mode of a high-finesse optical resonator. We control the<br />
number of atoms loaded into the dipole trap and - with sub-micron<br />
precision - the transport distance. We aim at the realisation of coherent<br />
interaction between two atoms, placed both at the centre of<br />
the cavity field. The calculated parameters of our experimental setup<br />
((gmax, κ, γ) = 2π(18, 0.43, 2.61)MHz, g 2 /(2κγ) = 146) show that we<br />
are in the strong coupling regime.<br />
An important prerequisite for this experiment is the precise knowledge<br />
of the coupling strength between one atom and the cavity field g.<br />
Furthermore, g should be maximised and kept constant over the inter-
Fachverband Quantenoptik und Photonik (Q) Freitag<br />
action time. We report on our results to measure the coupling strength<br />
between single atoms and the field of our high-finesse resonator.<br />
Q 58.5 Fr 12:15 3B<br />
Cold Atoms On Nanostructures — •Carsten Weiß 1,2 , Reinhold<br />
Walser 1 , Wolfgang P. Schleich 1 , and József Fortágh 2 —<br />
1 Institut für Quantenphysik, Universität Ulm — 2 Physikalisches Institut,<br />
Universität Tübingen<br />
A single-walled carbon nanotube (SWCNT) mounted on a lithographically<br />
fabricated chip defines a nearly perfect mechanical nano-<br />
oscillator. At common temperatures of a cryogenically cooled chip surface<br />
it performs large classical oscillations. By exposing it to ultra-cold<br />
alkali atoms we want to study the elastic and inelastic scattering by the<br />
SWCNT. In particular, we will present simulations for the interaction<br />
between a nanotube and a polarizable 87 Rb atom.<br />
[1] J. Fortágh, and C. Zimmermann, Rev. Mod. Phys.79, 235 (2007)<br />
[2] R. A. Jishi et al., Chem. Phys. Lett. 209, 77 (1993)<br />
[3] R. Fermani et al., arXiv:quant-ph/0703155v2<br />
[4] I. Wilson-Rae et al., Phys. Rev. Lett. 92, 75507 (2004)<br />
[5] M. D. LaHaye et al., Science 304, 74 (2004)<br />
Q 59: Transport in ultrakalten Gasen und Plasmen [gemeinsam mit A]<br />
Zeit: Freitag 11:00–12:30 Raum: 3C<br />
Hauptvortrag Q 59.1 Fr 11:00 3C<br />
Nonlinear coherent transport of waves in disordered media<br />
— •Thomas Wellens 1 and Benoît Grémaud 2 — 1 Physikalisches Institut,<br />
Universität Freiburg, Hermann-Herder-Str. 3a, 79104 Freiburg<br />
— 2 Laboratoire Kastler Brossel, Université Pierre et Marie Curie, 4<br />
place Jussieu, 75252 Paris Cedex 05<br />
In general, transport of waves in disordered media cannot fully be described<br />
as a simple diffusion process, since wave interference effects<br />
lead to a reduction or even complete suppression of the diffusion constant<br />
(weak or strong localization) and the appearance of a coherent<br />
backscattering peak.<br />
In this talk, I present a diagrammatic theory for treating the impact<br />
of nonlinearities on such disorder-induced localization phenomena<br />
[1]. The theory is applied to describe propagation of weakly interacting<br />
Bose-Einstein condensates in disordered potentials, on the<br />
one hand, and multiple scattering of light in nonlinear media, on the<br />
other one. In particular, the conditions under which nonlinear effects<br />
diminish or enhance the height of the coherent backscattering peak,<br />
and the consequences for the occurrence of Anderson localization of<br />
light and cold matter are discussed. Finally, I also talk about the possibility<br />
to incorporate quantum-mechanical many-body effects (for example<br />
multi-photon scattering processes from strongly driven two-level<br />
atoms), which generally lead to decoherence, thereby reducing the localization<br />
effects.<br />
[1] T. Wellens and B. Grémaud, PRL (in press)<br />
Q 59.2 Fr 11:30 3C<br />
One-Dimensional Rydberg Gas in a Magnetoelectric Trap<br />
— •Bernd Hezel 1 , Michael Mayle 2 , Igor Lesanovsky 3 , and Peter<br />
Schmelcher 1,2 — 1 Physikalisches Institut, Universität Heidelberg,<br />
69120 Heidelberg, Germany — 2 Theoretische Chemie, Universität<br />
Heidelberg, 69120 Heidelberg, Germany — 3 Institut für Theoretische<br />
Physik, Universität Innsbruck, 6020 Innsbruck, Austria<br />
We study the quantum properties of Rydberg atoms in a magnetic<br />
Ioffe-Pritchard trap superimposed by a homogeneous electric field.<br />
Trapped Rydberg atoms in long-lived electronic states can be created<br />
with permanent electric dipole moments of several hundred Debye. The<br />
resulting dipole-dipole interaction in conjunction with the radial confinement<br />
gives rise to an effectively one-dimensional ultracold Rydberg<br />
gas with a macroscopic interparticle distance. Analytical expressions<br />
for the electric dipole moment and the required linear density of Rydberg<br />
atoms can be derived.<br />
Q 59.3 Fr 11:45 3C<br />
Structural phase transitions in low-dimensional ion crystals<br />
— •Gabriele De Chiara 1 , Shmuel Fishman 2 , Tommaso Calarco 3 ,<br />
and Giovanna Morigi 1 — 1 Departament de Fisica, Universitat Autonoma<br />
de Barcelona, 08193 Bellaterra, Spain — 2 Physics Department,<br />
Technion, 32000 Haifa, Israel — 3 Institut für Quanteninformationsverarbeitung,<br />
Universität Ulm, D89069 Ulm, Germany<br />
A chain of singly-charged particles, confined by a harmonic potential,<br />
exhibits a sudden transition to a zigzag configuration when the radial<br />
potential reaches a critical value, depending on the particle number.<br />
This structural change is a phase transition of second order, whose<br />
order parameter is the crystal displacement from the chain axis. We<br />
study analytically the transition using Landau theory and find full<br />
agreement with numerical predictions by J. Schiffer [Phys. Rev. Lett.<br />
70, 818 (1993)] and Piacente et al. [Phys. Rev. B 69, 045324 (2004)].<br />
Our theory allows us to determine analytically the system’s behaviour<br />
at the transition point.<br />
Q 59.4 Fr 12:00 3C<br />
Damped Bloch Oscillations of Bose Einstein Condensates<br />
in disordered gradient fields — •Sascha Drenkelforth, Georg<br />
Kleine Büning, Johannes Will, Wolfgang Ertmer, and Jan Arlt<br />
— Institut für Quantenoptik, Universität Hannover, Welfengarten 1,<br />
30167 Hannover<br />
Optical lattices are excellent tools to probe the nature of quantum degenerate<br />
Bose gases and serve as an ideal testing ground for theories<br />
originating in solid state physics.<br />
One of the most peculiar effects in the framework of periodic potentials<br />
is the well known Bloch Oscillation (BO) of quantum particles.<br />
Under the influence of a constant force they undergo an oscillatory<br />
motion instead of a linear acceleration.<br />
We report on our investigations of damped BO in optical lattices.<br />
The addition of disorder to the prior perfect optical lattice leads to<br />
an dephasing and therefore to a damping of the BO [1]. The experimental<br />
results show increased damping with stronger disorder and a<br />
strong broadening of the quasimomentum distribution during the time<br />
evolution of the BO.<br />
These results promise a better understanding of the role of disorder<br />
in quantum transport experiments.<br />
[1] Schulte et al., cond-mat/0707.3131(2007)<br />
Q 59.5 Fr 12:15 3C<br />
Sympathetic Cooling of Ions using Laser-Cooled One-<br />
Component Plasmas — •Michael Bussmann 1 , Ulrich Schramm 2 ,<br />
Peter Thirolf 1 , Veli Kolhinen 1 , Jerzy Szerypo 1 , Juergen<br />
Neumayr 1 , Michael Sewtz 1 , and Dietrich Habs 1 — 1 Ludwig-<br />
Maximilians-Universitaet Muenchen, Am Coulombwall 1, 85748<br />
Garching — 2 Forschungszentrum Dresden-Rossendorf, Bautzner Landstraße<br />
128, 01328 Dresden<br />
We present new simulation results on sympathetic cooling of ions for<br />
precision experiments. Using a laser-cooled one-component plasma of<br />
10 5 24 Mg + ions it is possible to stop and sympathetically cool ions to<br />
mK temperatures. With the proposed cooling scheme fast and efficient<br />
cooling of rare nuclei for precision in-trap physics, e.g. subsequent<br />
mass measurements in Penning traps, becomes possible. In the talk<br />
we will give an overview of previous results before presenting new<br />
results on the stopping dynamics, especially the interplay of collective<br />
dynamics, plasma stability and recooling efficiency.<br />
[1]Bussmann M. et al., European Physical Journal D 45(1) (2007)<br />
129-132.<br />
[2]Bussmann M. et al., Hyperfine Interactions 173(1-3) (2007) 27-34.
Fachverband Quantenoptik und Photonik (Q) Freitag<br />
Q 60: Quantengase (Gemische / Tunneleffekte)<br />
Zeit: Freitag 11:00–13:00 Raum: 3G/H<br />
Q 60.1 Fr 11:00 3G/H<br />
Interacting Rubidium and Caesium Atoms — •Claudia Weber,<br />
Michael Haas, Shincy John, Nicolas Spethmann, Lars Steffens,<br />
Artur Widera, and Dieter Meschede — Institut für Angewandte<br />
Physik, Universität Bonn, Wegelerstr. 8, 53115 Bonn<br />
In our experimental set up we magnetically trap a mixture of Rubidium<br />
and a few Caesium atoms simultaneously. We selectively cool only<br />
Rubidium atoms by a microwave field tuned to the Rubidium ground<br />
state hyperfine transition. Caesium is sympathetically cooled via elastic<br />
collisions with Rubidium. We are able to cool down the mixture to<br />
temperatures below 1µK. Analysing the dynamics of sympathetic cooling<br />
we have estimated a lower limit for the Rubidium-Caesium s-wave<br />
scattering length to 150 a0. Our next step is to load the mixture in an<br />
optical dipole trap. Using an external homogeneous magnetic field we<br />
intend to tune the inter-species interaction. We will present our latest<br />
results.<br />
Q 60.2 Fr 11:15 3G/H<br />
Self-Trapping of Bosons and Fermions in Optical Lattices<br />
— •Dirk-Sören Lühmann 1 , Kai Bongs 2,3 , Klaus Sengstock 2 , and<br />
Daniela Pfannkuche 1 — 1 I. Institut für Theoretische Physik, Universität<br />
Hamburg, Jungiusstr. 9, 20355 Hamburg, Germany — 2 Institut<br />
für Laser-Physik, Universität Hamburg, Luruper Chaussee 149, 22761<br />
Hamburg, Germany — 3 Midlands Centre for Ultracold Atoms, School<br />
of Physics and Astronomy, University of Birmingham, Edgbaston,<br />
Birmingham B15 2TT, United Kingdom<br />
The superfluid to Mott insulator transition is one of the paradigms<br />
of solid state physics that maps onto ultra cold atomic systems. The<br />
interaction between different kinds of atoms adds an additional degree<br />
of freedom to two-component atomic systems not present in the solid<br />
state counterpart.<br />
We numerically investigate the enhanced localisation of bosonic<br />
87Rb by fermionic 40K atoms in three-dimensional optical lattices<br />
and find a self-trapping of bosons and fermions. Due to the mutual<br />
interaction the fermion orbitals are substantially squeezed which results<br />
in a strong deformation of the bosonic effective potential. We<br />
show that orbital effects in attractively interacting atomic mixtures<br />
are non-negligible as they lead to a large shift of the critical point of<br />
the transition from a superfluid to a Mott-insulator, which is of direct<br />
relevance to recent experiments with 87Rb and 40K atoms.<br />
Q 60.3 Fr 11:30 3G/H<br />
Heteronuclear Feshbach resonances in a mixture of ultracold<br />
87 Rb and 133 Cs atoms — •Andrea Prantner 1 , Almar Lange 1 ,<br />
Karl Pilch 1 , Gabriel Kerner 2 , Francesca Ferlaino 1 , Hanns-<br />
Christoph Nägerl 1 , and Rudolf Grimm 1,2 — 1 Institut für Experimentalphysik,<br />
Innsbruck, Austria — 2 Institut für Quantenoptik und<br />
Quanteninformation,<br />
In the last few years there has been a growing interest in the in the<br />
area of heteronuclear ultracold quantum gases and the production of<br />
heteronuclear molecules via Feshbach resonances. We present the first<br />
observation of heteronuclear Feshbach resonances in a mixture of ultracold<br />
87 Rb and 133 Cs. We give an overview about our experimental<br />
setup and the procedure of sample preparation. One of the key ingredients<br />
to reach the ultracold limit is the implementation of simultaneous<br />
degenerate Raman sideband cooling on both species. This cooling<br />
technique allows us to get around 10 8 atoms, fully polarized in the lowest<br />
magnetic sublevel at a temperature of ∼1µK in a crossed dipole<br />
trap. We discuss the next steps towards double degeneracy and present<br />
our approach to produce ground state RbCs molecules starting from<br />
weakly bound Feshbach molecules.<br />
Q 60.4 Fr 11:45 3G/H<br />
Feshbach Resonances in a Lithium Rubidium Mixture —<br />
•Carsten Marzok, Benjamin Deh, Philippe W. Courteille, and<br />
Claus Zimmermann — Physikalisches Institut, Universität Tübingen,<br />
Auf der Morgenstelle 14, D-72076<br />
Ultracold atomic gases are a versatile instrument allowing to study the<br />
rich field of many body physics with unprecedented control. Indeed the<br />
coupled dynamics is governed by few parameters only, namely temperature,<br />
masses of the constituents and the interactions between them.<br />
In ultracold gases these interactions are ruled by the s-wave scattering<br />
length. Control over this parameter is provided by magnetic Feshbach<br />
resonances. The physics involved can be enriched by choosing a mixture<br />
of different atomic species with different masses and different quantum<br />
statistics i.e. Bose-Fermi mixtures. The lithium-rubidium system is remarkable<br />
among these because of its large mass difference. In recent<br />
experiments we were able to detect two heteronuclear Feshbach resonances<br />
in the 6 Li- 87 Rb system, that now make it possible to study<br />
the physics of this rich system in more detail. The characterization<br />
of these resonances and further experiments will be discussed in this<br />
presentation.<br />
Q 60.5 Fr 12:00 3G/H<br />
Do mixtures of bosonic and fermionic atoms adiabatically<br />
heat up in optical lattices? — •Marcus Cramer 1 ,<br />
Silke Ospelkaus 2 , Christian Ospelkaus 2 , Kai Bongs 2 , Klaus<br />
Sengstock 2 , and Jens Eisert 1 — 1 Blackett Laboratory, Imperial<br />
College London — 2 Institut für Laser-Physik, Universität Hamburg<br />
Mixtures of bosonic and fermionic atoms in optical lattices provide<br />
a promising arena to study strongly correlated systems. In experiments<br />
realizing such mixtures in the quantum degenerate regime the<br />
temperature is a key parameter. We investigate the intrinsic heating<br />
and cooling effects due to an entropy-preserving raising of the optical<br />
lattice, identify the generic behavior valid for a wide range of parameters<br />
and discuss it quantitatively for the recent experiments with<br />
87 Rb and 40 K atoms. In the absence of a lattice, we treat the bosons<br />
in the Hartree-Fock-Bogoliubov-Popov approximation, including the<br />
fermions in a self-consistent mean field interaction. In the presence of<br />
the full three-dimensional lattice, we use a strong coupling expansion.<br />
We find the temperature of the mixture in the lattice to be always<br />
higher than for the pure bosonic case, shedding light onto a key point<br />
in the analysis of recent experiments.<br />
Q 60.6 Fr 12:15 3G/H<br />
Heteronuclear Feshbach molecules in an ultracold Bose-Fermi<br />
Mixture — •Carsten Klempt, Thorsten Henninger, Oliver<br />
Topic, Lisa Kattner, Eberhard Tiemann, Wolfgang Ertmer, and<br />
Jan Arlt — Institut für Quantenoptik, Leibniz Universität Hannover,<br />
Welfengarten 1, D-30167 Hannover, Germany<br />
Within the past decade, quantum degenerate bosonic and fermionic<br />
ensembles were investigated in detail. The use of Feshbach resonances<br />
now allows for precise control of the interactions in heteronuclear mixtures<br />
of two atomic species. Within our experiments, bosonic 87 Rb<br />
atoms are used to cool an ensemble of fermionic 40 K atoms to joint<br />
quantum degeneracy. This mixture provides the starting point for the<br />
detailed analysis and manipulation of the interactions.<br />
Applying a homogeneous magnetic field up to 700G allows for the investigation<br />
of heteronuclear Feshbach resonances in this mixture. The<br />
measurement of these resonances is of great interest for the precise<br />
investigation of the molecular potential. We have been able to observe<br />
28 resonances in ten different spin combinations. Together with results<br />
from molecular spectroscopy, this allowed for a large improvement of<br />
the interaction model. One of the observed resonances is used for the<br />
production of weakly bound heteronuclear Feshbach molecules. The<br />
collisional stability of these molecules can be enhanced significantly by<br />
removing residual Rb atoms.<br />
We report on the production of ultracold Feshbach molecules and<br />
the ongoing steps towards a deexcitation of such molecules into deeply<br />
bound molecular states via a Stimulated Raman Adiabatic Passage.<br />
Q 60.7 Fr 12:30 3G/H<br />
Correlated Tunneling of Few Bosons in a 1-D Double<br />
Well — •Sascha Zöllner 1 , Hans-Dieter Meyer 1 , and Peter<br />
Schmelcher 1,2 — 1 Universitaet Heidelberg, Theoretische Chemie, Im<br />
Neuenheimer Feld 229, 69120 Heidelberg — 2 Universitaet Heidelberg,<br />
Physikalisches Institut, Philosophenweg 12, 69120 Heidelberg<br />
This talk is about few-boson tunneling in a one-dimensional doublewell<br />
trap, covering the full crossover from weak interactions to the<br />
fermionization limit of strong correlations. After reviewing the underlying<br />
mechanism of ground-state fermionization of trapped bosons, it<br />
will be shown how the tunneling of two atoms evolves from Rabi oscillations<br />
to correlated pair tunneling as we increase the interaction<br />
strength. The physics behind it will be analyzed, rounded off by an
Fachverband Quantenoptik und Photonik (Q) Freitag<br />
outlook on how many-body effects modify the picture and how the<br />
tunneling can be controlled via tilting the wells.<br />
Q 60.8 Fr 12:45 3G/H<br />
A coherent single atom shuttle between two Bose-Einstein<br />
condensates — •Uwe R. Fischer 1 , Christian Iniotakis 2 , and<br />
Anna Posazhennikova 3 — 1 Institut für Theoretische Physik, Universität<br />
Tübingen, Auf der Morgenstelle 14, D-72076 Tübingen, Germany<br />
— 2 ETH Zürich, Institut für Theoretische Physik, CH-8093 Zürich,<br />
Switzerland — 3 Physikalisches Institut, Universität Bonn, D-53115<br />
Bonn, Germany<br />
We study an atomic quantum dot representing a single hyperfine “impurity”<br />
atom which is coherently coupled to two well-separated Bose-<br />
Einstein condensates, in the limit when the coupling between the dot<br />
and the condensates dominates the inter-condensate tunneling coupling.<br />
It is demonstrated that the quantum dot by itself can induce coherent<br />
oscillations of the particle imbalance between the condensates,<br />
which display a two-frequency behavior. For noninteracting condensates,<br />
we provide an approximate solution to the coupled nonlinear<br />
equations of motion which allows us to obtain these two frequencies<br />
analytically.<br />
Q 61: Quanteninformation (Photonen und nichtklassisches Licht II)<br />
Zeit: Freitag 14:00–15:30 Raum: 1A<br />
Q 61.1 Fr 14:00 1A<br />
Spectral decomposition of quantum light — •Wolfgang<br />
Mauerer and Christine Silberhorn — University Erlangen-<br />
Nuremberg, Max-Planck Research Group IOIP, Integrated Quantum<br />
Optics Group<br />
A growing number of applications for quantum mechanics in both computation<br />
and communication has been devised during the last years.<br />
The experimental realisation is usually performed with optical technologies.<br />
Most concepts are well understood theoretically, but they are<br />
usually based on a single-mode description. This is not the case in reality,<br />
especially when fast pulsed sources are employed. Contributions<br />
from many spectral modes are unavoidable in such regimes and need<br />
to be accounted for by the models.<br />
Following initial work presented in Ref. [1], we develop various techniques<br />
for the analysis of multi-mode states. Special emphasis is put on<br />
how to find simple and effective multi-mode descriptions for a number<br />
of recent experiments. We demonstrate that noise which has previously<br />
been accounted to experimental imperfections can emerge from<br />
spectral effects.<br />
We also show how to derive the Bogoliubov transformations for<br />
quadratic nonlinear interactions (e.g., parametric downconversion)<br />
from a fully quantum mechanical spatio-spectral model. This is used<br />
as a basis for further structural analysis of multi-mode quantum states<br />
with various techniques, for instance Bloch-Messiah decomposition.<br />
[1] P. P. Rohde, W. Mauerer, and Ch. Silberhorn, New Journal of<br />
Physics 9, 91(2007)<br />
Q 61.2 Fr 14:15 1A<br />
Improved methods for Polarization squeezing with photonic<br />
crystal fibers — •Josip Milanovic 1 , Alexander Huck 2 ,<br />
Joel Heersink 1 , Christoph Marquardt 1 , Ulrik L. Andersen 2 ,<br />
and Gerd Leuchs 1 — 1 Institute of Optics, Information and<br />
Photonics, Max-Planck Research Group, University of Erlangen-<br />
Nuremberg, Guenther-Scharowsky-Straße 1, 91058, Erlangen, Germany<br />
— 2 Department of Physics, Technical University of Denmark,<br />
Fysikvej, 2800, Kgs. Lyngby, Denmark<br />
Squeezing or quantum noise reduction of optical states in glass fibers<br />
has been chronically afflicted by the large phase noise from Guided<br />
Acoustic Wave Brillouin Scattering (GAWBS). This excess noise is<br />
one of the main effects that decrease the purity of the quantum states.<br />
In previous experiments we have already shown that Photonic Crystal<br />
Fibers (PCFs) represent a promising new approach to reduce this<br />
noise.<br />
At a squeezing level of −3.3 ± 0.3 dB at 810 nm the purity of the<br />
squeezed state was three times higher than in experiments with standard<br />
telecom fibers. A major problem is that the dispersion properties<br />
for different axes are not identical. Due to the different spectral evolution<br />
of the pulses in the PCFs the interference of squeezed pulses<br />
is very low which implies a large loss in the detectable squeezing. We<br />
present improved methods which can be used to increase and detect<br />
higher levels of polarization squeezing.<br />
Q 61.3 Fr 14:30 1A<br />
Modal Properties of Parametric Down-conversion in the High<br />
Gain Regime — •Kaisa Laiho, Malte Avenhaus, and Christine<br />
Silberhorn — Max Planck Junior Research Group, Günther-<br />
Scharowsky-Str. 1 / Bau 24, D-91058 Erlangen<br />
Parametric down-conversion (PDC) is widely used in the low gain<br />
regime as a source of photon pairs. It is also a promising candidate<br />
for Non-Gaussian state engineering [1]. Recently, bright waveguided<br />
PDC sources have become available. In this high gain regime it is possible<br />
to generate pairs of pairs, which can be understood as quadrature<br />
squeezing in the continuous variable picture.<br />
The photon pairs generated in the PDC process are spectrally correlated.<br />
Although we use a broadband, ultrafast pump, the phasematching<br />
is a limiting factor. In order to be able to define the state<br />
as a broadband single mode squeezer, it needs to be decorrelated [2].<br />
We have studied the spectral correlations in the ultrafast regime for<br />
a 10mm long type II PP-KTP waveguide and spectrally resolved the<br />
tilted correlation function. Our measured photon statistics indicate<br />
strong multimodal behaviour. To modify the spectral correlations we<br />
have cut down the waveguide to 2.5mm length and study the modal<br />
properties by spectral filtering. Ultimately, we aim at Non-Gaussian<br />
state preparation where it is crucial to drive the state towards single<br />
mode characteristics to ensure the purity.<br />
[1] A. I. Lvovsky et al., Phys. Rev. Lett. 87, 050402 (2001)<br />
[2] P. P. Rohde et al., New J. Phys. 9, 91 (2007)<br />
Q 61.4 Fr 14:45 1A<br />
Linear optics unleashed — •Konrad Kieling 1,2 and Jens<br />
Eisert 1,2 — 1 QOLS, Blackett Laboratory, Imperial College London,<br />
Prince Consort Road, London SW7 2BW, UK — 2 Institute for Mathematical<br />
Sciences, Imperial College London, Prince’s Gate, London<br />
SW7 2PE, UK<br />
Linear optical architectures for quantum information processing are<br />
based on single-photon sources, photon-number preserving optical elements,<br />
and photon (number resolving) detectors. Due to the allowed set<br />
of tools being narrowed down, specific problems can often be cast into<br />
a mathematical framework that allows for the assessment of possible<br />
state manipulation, measurement and preparation. The measurement<br />
based nature of optical gates and the issue of encoding qubits in a way<br />
to easily access them experimentally leads to a rich structure of problems.<br />
In this talk, we will discuss issues of resource consumption in<br />
optical state preparation, optimal success probabilities, and prescriptions<br />
of how to build linear optical quantum gates and measurement<br />
devices.<br />
Q 61.5 Fr 15:00 1A<br />
Is the role of beam-splitters in quantum optics any different<br />
from that in classical optics? — •Daniela Denot, Lev Plimak,<br />
and Wolfgang P. Schleich — Institute of Quantum Physics, Ulm<br />
University, 89069 Ulm, Germany<br />
A statement is often made that the role of beam-splitters in quantum<br />
optics is fundamentally different from that in classical optics [1]. This<br />
statement is based on the paper by Mandel et al [2] showing that the<br />
action of a beam-splitter on a single-photon state is turning it into an<br />
entangled state of two modes. The question we ask if there exists an<br />
experimental proof of this statement. We show that the answer is negative<br />
for all photodetection measurements with two beams involving<br />
local oscillators. To prove this we devise a Gedanken-experiment where<br />
the joint photocurrent statistics of the two detectors is fully imitated<br />
in a measurement where the incident beam is detected directly. This<br />
statement is easily proven for arbitrary classical states of the incident<br />
beam while its validity for quantum states follows from the optical<br />
equivalence theorem by Sudarshan [3].<br />
[1] G. S. Agarwal, a talk given at the Institute of Quantum Physics,<br />
Ulm, Sept. 2007, unpublished.
Fachverband Quantenoptik und Photonik (Q) Freitag<br />
[2] C. K. Hong, Z. Y. Ou, and L. Mandel, Phys. Rev. Lett., 59(18),<br />
2044, 1987.<br />
[3] E. C. G. Sudarshan. Phys. Rev. Lett., 10(7), 277, 1963.<br />
Q 61.6 Fr 15:15 1A<br />
Experimental demonstration of anyonic statistics with<br />
multiphoton entanglement — •Witlef Wieczorek 1,2 , Jiannis<br />
Pachos 3 , Christian Schmid 1,2 , Nikolai Kiesel 1,2 , Reinhold<br />
Pohlner 1,2 , and Harald Weinfurter 1,2 — 1 Max-Planck-<br />
Institut für Quantenoptik, D-85748 Garching — 2 Department für<br />
Physik, Ludwig-Maximilians-Universität München, D-80799 München<br />
— 3 School of Physics & Astronomy, University of Leeds, Leeds LS2<br />
9JT, UK<br />
Q 62: Ultrakalte Atome (Fallen und Kühlung)<br />
Particles in nature appear as two distinct types according to their<br />
statistics: bosons and fermions. However, if one considers only two spatial<br />
dimensions statistical behaviour ranging from bosonic to fermionic<br />
is found. Particles exhibiting such a behaviour are called anyons. Our<br />
experimental demonstration of their statistics is based on a particular<br />
two-dimensional model: the toric code proposed by Kitaev [1]. There,<br />
anyons arise as excitations that are generated by local operations. We<br />
show that for this model anyonic behaviour is revealed for as little as<br />
four qubits. This allowed us to experimentally demonstrate anyonic<br />
statistics in a quantum simulation using four-photon entanglement [2].<br />
[1] A.Y. Kitaev, Ann. Phys. (N.Y.) 303, 2-30 (2003).<br />
[2] J.K. Pachos et al., e-print arXiv: 0710.0895 (2007).<br />
Zeit: Freitag 14:00–15:45 Raum: 3B<br />
Q 62.1 Fr 14:00 3B<br />
An intense clean source for cold Lithium — Tobias Tiecke,<br />
Antje Ludewig, •Sebastian Kraft, Steve Gensemer, and Jook<br />
Walraven — Van der Waals-Zeeman-Instituut, Universiteit van Amsterdam,<br />
The Netherlands<br />
We experimentally investigate a novel atomic beam source for cold<br />
6 Li. The source operates according to the 2D-MOT principle and is<br />
found to be very monochromatic and intense. Its longitudinal velocity<br />
is centered at 33m/s with a full-width at half maximum (FWHM) of<br />
14 m/s, with no flux observed at higher velocities.<br />
We measured the intensity of the source by loading a 3D MOT from<br />
the cold atomic beam. We report loading rates as high as 10 9 s −1 resulting<br />
in up to a total of 10 10 trapped atoms.<br />
Q 62.2 Fr 14:15 3B<br />
Speichereigenschaften einer planaren Mikrochip-Ionenfalle —<br />
•Christian Greve 1 , Michael Kröner 2 , Markus Debatin 1 , Jochen<br />
Mikosch 1 , Sebastian Trippel 1 , Markus Reetz-Lamour 1 , Peter<br />
Woias 2 , Roland Wester 1 und Matthias Weidemüller 1 —<br />
1 Physikalisches Institut, Universität Freiburg — 2 Institut für Mikrosystemtechnik,<br />
Universität Freiburg<br />
Untersuchungen an hydratisierten Ionen ermöglichen tiefgreifende Einsichten<br />
in den Verlauf chemischer und biologischer Prozesse. Für<br />
derartige Experimente entwickeln wir eine planare transparente RF-<br />
Multipolfalle in Kombination mit einer gepulsten Ionenquelle. Die aus<br />
zwei gegenüberliegenden Chips mit kammartiger Elektrodenstruktur<br />
bestehende Ionenfalle hat bereits Lebensdauern von mehr als 10 s mit<br />
Argonionen ermöglicht. Der simulierte Verlauf des erzeugten effektiven<br />
Potentials stimmt dabei hervorragend mit einem analytischen Modell<br />
überein [1]. Für zeitnahes Testen neuer Fallendesigns lassen sich die<br />
Chips mit Photolithographie oder durch Laserablation strukturieren.<br />
Nach der Extraktion findet eine Analyse mit einem Wiley McLarenartigen<br />
Flugzeitmassenspektrometer statt. Im Vortrag wird der aktuelle<br />
Stand des Experimentes insbesondere die Ionenquelle, ein verbessertes<br />
Fallendesign sowie die in der Extraktion erreichte Massenauflösung<br />
vorgestellt. Für die Zukunft ist unter anderem eine Tomographie der<br />
Ionendichte mittels Photodetachment [2] und die Kombination der Ionenfalle<br />
mit einer MOT geplant.<br />
[1] M. Debatin et al., in prep.<br />
[2] S. Trippel et al., PRL 97, 193003 (2006)<br />
Q 62.3 Fr 14:30 3B<br />
Trapping of rubidium atoms by ac electric fields — •Sophie<br />
Schlunk 1,2 , Adela Marian 1 , Wieland Schöllkopf 1 , and Gerard<br />
Meijer 1 — 1 Fritz-Haber-Institut, Berlin, Germany — 2 FOM Institute<br />
for Plasma Physics Rijnhuizen, Nieuwegein, The Netherlands<br />
We have demonstrated trapping of ultracold ground-state Rb atoms<br />
in a macroscopic ac electric trap [S. Schlunk et al., PRL 98, 223002<br />
(2007)]. AC electric trapping has been previously demonstrated for<br />
polar molecules [H. L. Bethlem et al., PRA 74, 063403 (2006)], as<br />
well as for Sr atoms on a chip [T. Kishimoto et al., PRL 96, 123001<br />
(2006)], and recently for Rb atoms in a three-phase electric trap [T.<br />
Rieger et al., PRL 99, 063001 (2007)]. AC traps for neutral particles<br />
operate analogously to Paul traps for ions. A potential energy surface<br />
is created with a saddle point at the trap center, resulting in attractive<br />
forces (focusing) in one direction and repulsive forces (defocusing)<br />
along the other two directions. Alternating between the two electric<br />
field configurations leads to dynamic confinement of the particles.<br />
In the experiment, the Rb atoms are cooled in a standard MOT<br />
and loaded into a magnetic trap. The magnetically trapped cloud is<br />
then transferred into a second vacuum chamber housing the ac trap.<br />
Stable electric trapping is observed in a narrow range of switching frequencies<br />
around 60 Hz, in agreement with trajectory calculations. We<br />
have trapped about 2 × 10 5 atoms with lifetimes on the order of 9 s.<br />
Absorption images of the atom cloud taken at various phases of the<br />
ac switching cycle show different shapes reflecting the focusing and<br />
defocusing forces acting on the atoms.<br />
Q 62.4 Fr 14:45 3B<br />
Observation of a trapped cloud of electrons in a planarcryogenic<br />
Penning trap — •Pavel Bushev 1,2 , Stefan Stahl 2 ,<br />
Michael Hellwig 1,4 , Michael Ferner 1 , Riccardo Natali 3 , Gerrit<br />
Marx 4 , Günther Werth 2 , and F. Schmidt-Kaler 1 — 1 Institut für<br />
Quanteninformationsverarbeitung,Universität Ulm, D-89069 Ulm —<br />
2 Institut fürPhysik, Johannes Gutenberg-Universität Mainz, D-55099<br />
Mainz — 3 Dipartimento di Fisica, Università degli Studidi Camerino,<br />
62032 Camerino, Italy — 4 Institutfür Physik, Ernst Moritz Arndt-<br />
Universität Greifswald,D-17489 Greifswald<br />
We have succeeded in trapping, cooling and detecting clouds of electrons<br />
by using a cryogenic planar Penning trap which is installed in a<br />
dilution refrigerator. The trap consists of concentric rings with a diameter<br />
of a few millimeters [1]. The operating temperature range is<br />
50-100 mK, the magnetic field is about 1 Tesla. We observed a lifetime<br />
of trapped electrons of about 3 hours. In the planar geometry, a<br />
strong anharmonicity of the trapping potential prevents us from observing<br />
single electrons. The ways to diminish such anharmonicity and<br />
the current status of cryogenic electron trapping will be presented. The<br />
single electron will be used for an application in quantum computing<br />
[2]. Here the spin of an individually trapped electron represents a qubit,<br />
which can be coherently manipulated with pulses of a microwave field.<br />
Entanglement between electronic qubits is achieved by an electrical<br />
connection of the electrodes of separate traps.<br />
[1] S. Stahl et. al., Eur. Phys. J. D. 32, 139 (2005).<br />
[2] G. Ciaramicioli et. al, Phys. Rev. Lett. 91, 017901 (2003).<br />
Q 62.5 Fr 15:00 3B<br />
Atom cooling in a ring — •Andreas Ruschhaupt — Institut fuer<br />
Mathematische Physik, TU Braunschweig, Mendelssohnstr. 3, D-38106<br />
Braunschweig<br />
We propose a method to cool atoms in a ring. An atom diode -a laser<br />
device which can by passed by atoms in only one direction- is put in<br />
a ring in such a way that the velocity of the crossing atom is also<br />
decreased. In addition, the atom is trapped if its velocity is below a<br />
threshold velocity. In this manner, the atom or an atom cloud moving<br />
in the ring can be cooled and finally trapped after repeated passages<br />
of the atom diode.<br />
Q 62.6 Fr 15:15 3B<br />
Kompaktes und extrem robustes frequenzstabilisiertes Lasersystem<br />
für Experimente mit atomaren Quantengasen —<br />
•Max Schiemangk, André Wenzlawski, Wojciech Lewoczko-<br />
Adamczyk und Achim Peters — Humboldt-Universität zu Berlin,<br />
Institut für Physik, AG Quantenoptik und Metrologie, Hausvogtei-
Fachverband Quantenoptik und Photonik (Q) Freitag<br />
platz 5-7, 10117 Berlin<br />
Auf dem Weg zur Implementierung eines im Rahmen des DLR-<br />
Projekts QUANTUS geplanten Quantengasexperimentes im Weltraum<br />
haben wir eine miniaturisierte und mechanisch stabile Apparatur für<br />
Vorexperimente im Fallturm des ZARM in Bremen entwickelt. Bei einer<br />
Höhe von 110 m erreicht man dort eine Freifallzeit von ca. 4,5 s<br />
mit Restbeschleunigungen von ca. 10 −6 g. Diese Zeit kann durch den<br />
Einsatz eines neu implementierten Katapults verdoppelt werden, wobei<br />
jedoch die Anfangsbeschleunigung von mehr als 30 g sehr hohe<br />
Ansprüche an den experimentellen Aufbau hinsichtlich mechanischer<br />
Stabilität stellt.<br />
In diesem Vortrag wird ein ultrastabiler Master-Laser vorgestellt, der<br />
als Frequenzreferenz für das gesamte Experiment dient. Dieser basiert<br />
auf einem DFB-Diodenlaser und wird mittels Frequenzmodulationsspektroskopie<br />
auf einen atomaren Übergang in Rubidium stabilisiert.<br />
Das kompakte Design, die schnelle Regelelektronik sowie die<br />
Optimierung der atomaren Antwort auf Frequenzänderungen werden<br />
ausführlich diskutiert.<br />
Q 62.7 Fr 15:30 3B<br />
A high-flux atomic source for transportable experiments —<br />
•Tais Gorkhover, Ulrich Eismann, Alexander Senger, Malte<br />
Schmidt, and Achim Peters — Institut für Physik, Humboldt-<br />
Universität zu Berlin<br />
We present a setup for a compact and robust vapor loaded MOT for<br />
Rubidium atoms suitable as an atomic source for transportable experiments<br />
as the FINAQS GAIN (Gravimetry Atom Interferometer)<br />
experiment at the HU-Berlin.<br />
The design is based on a modified 2D-MOT with the two pairs of<br />
opposing trap-beams tilted towards the line of flight of the cold atoms<br />
allowing for longitudinal cooling of the atom beam. Using a moving<br />
molasses scheme the atoms can be launched with a narrow velocity<br />
distribution and low mean velocity. Our setup features large MOTbeam<br />
diameter and the possibility of three adjacent cooling stages<br />
which should allow for high fluxes (> 10 12 atoms/s) and a highly recapturable<br />
beam. We report on technical details of the setup and first<br />
characterisations.<br />
Q 63: Quantengase (Wechselwirkungseffekte II / Spinorgase)<br />
Zeit: Freitag 14:00–16:00 Raum: 3G/H<br />
Q 63.1 Fr 14:00 3G/H<br />
Metastable neon atoms in optical dipole traps: collisional<br />
properties of different internal states — •W.J. van Drunen 1 ,<br />
E.-M. Kriener 1 , J. Schütz 1 , N. Herschbach 1 , W. Ertmer 2 , and<br />
G. Birkl 1 — 1 Institut für Angewandte Physik, Technische Universität<br />
Darmstadt, Schlossgartenstr. 7, 64289 Darmstadt — 2 Institut für<br />
Quantenoptik, Leibniz Universität Hannover, Welfengarten 1, 30167<br />
Hannover<br />
After performing a detailed analysis of the collisional properties of<br />
metastable neon atoms ( 3 P2, m=+2) in a magnetic trap [1], we implemented<br />
an optical trap for metastable neon for further investigations.<br />
This enables us to explore possibilities to manipulate interactions and<br />
extend our studies of interactions to states, which are not magnetically<br />
trappable.<br />
As a result, we could demonstrate the first trapping of metastable<br />
neon ( 3 P0) atoms. Measurements of the number decay of trapped<br />
atoms allows us to determine the rate coefficient for two-body loss<br />
of neon in the 3 P0 metastable state for both bosonic isotopes 20 Ne<br />
and 22 Ne. In addition to the requirements of our previous quantitative<br />
studies [1], a careful characterization of the optical trap is required as<br />
well.<br />
[1] P. Spoden et al., Phys. Rev. Lett. 94, 223201 (2005)<br />
Q 63.2 Fr 14:15 3G/H<br />
Cavity QED with a Bose-Einstein Condensate — •Ferdinand<br />
Brennecke, Tobias Donner, Stephan Ritter, Thomas Bourdel,<br />
Michael Köhl, Christine Guerlin, and Tilman Esslinger — Institute<br />
for Quantum Electronics, ETH Zürich, Switzerland<br />
Cavity quantum electrodynamics (cavity QED) studies the coherent<br />
interaction of light and matter inside a high-finesse resonator. One of<br />
the main challenges in present experiments within the optical regime<br />
of cavity QED is to achieve a deterministic coupling strength between<br />
atoms and light, which in particular requires high control over the<br />
atomic external degrees of freedom. Using a Bose-Einstein condensate<br />
(BEC), we enter a new regime of cavity QED where all atoms couple<br />
identically to the cavity field. Here we present a measurement of the<br />
energy spectrum of this strongly coupled system in the low excitation<br />
limit. Due to a collective coupling of several GHz we observe a significant<br />
coupling of the BEC to higher-order transverse cavity modes. The<br />
strong coupling even of a single atom to the cavity mode offers the possibility<br />
to detect and manipulate a minority component of atoms in a<br />
different hyperfine state embedded within a BEC. Besides its relevance<br />
to the field of quantum information processing, the presented system<br />
offers a variety of interesting phenomena expected in the many-body<br />
physics of quantum gases within a quantum optical lattice. In contrast<br />
to the case of optical lattice potentials provided by strong laser fields,<br />
here the light field itself becomes a dynamical quantity depending on<br />
the atomic distribution, which leads to substantial cavity-mediated<br />
long-range interactions between the atoms.<br />
Q 63.3 Fr 14:30 3G/H<br />
Dipole Oscillations of a Bose-Einstein Condensate in Presence<br />
of Defects and Disorder — •Mathias Albert, Nicolas<br />
Pavloff, Patricio Leboeuf, and Tobias Paul — Laboratoire de<br />
Physique Théorique et Modèles Statistiques, Universite Paris Sud<br />
We study the influence of a weak defect or disorder potential on the<br />
dipole modes of a weakly interacting Bose Einstein condensate, confined<br />
in a harmonic cigar-shaped trap with a tight transverse confinement<br />
but a shallow axial trapping frequency in presence of an external<br />
defect or disorder potential. We show that for small-amplitude dipole<br />
oscillations the BEC-flow is superfluid and the dipole oscillations are<br />
almost undamped, but the external defect potential induces a small<br />
shift of the excitation frequency. We compute this frequency shifts by<br />
use of a perturbative approach, both in the low-density regime and in<br />
the Thomas-Fermi large-density regime and apply this approach -as<br />
a first test- to a single Gaussian-shaped barrier potential. Then, we<br />
consider the experimental relevant case of an optical speckle-potential<br />
where we find uncorrelated frequency shifts of the dipole mode with respect<br />
to the pure harmonic case. This behavior is confirmed by numerically<br />
solving the Gross-Pitaevskii equation. Finally, we derive a relation<br />
between the disorder correlation-function and the ensemble-averaged<br />
fluctuations of the frequency shift. This opens the perspective for experiments<br />
to obtain from the dipole-frequency fluctuations characteristic<br />
parameters of the disorder potential (e.g. correlation lengths).<br />
Q 63.4 Fr 14:45 3G/H<br />
Far-from-equilibrium dynamics of ultracold Bose gases —<br />
•Philipp Struck and Thomas Gasenzer — Institute for Theoretical<br />
Physics, University of Heidelberg, Philosophenweg 16, 69120 Heidelberg<br />
The dynamical evolution of a Bose-Einstein condensate trapped in<br />
a one-dimensional optical lattice is investigated in the framework of<br />
the Bose-Hubbard model. Of special interest is the far-from equilibrium<br />
evolution of a strongly interacting gas. Using functional integral<br />
techniques, the dynamic equations are derived from the two-particleirreducible<br />
effective action expanded in inverse powers of the field components.<br />
This approach reaches far beyond the Hartree-Bogoliubov<br />
mean-field theory and Quantum Boltzmann approaches. Within this<br />
framework we investigate various configurations of one-dimensional lattices<br />
of particular interest for present experiments. This includes dipole<br />
oscillations of a condensate damped by the thermal cloud and squeezing<br />
of particle number fluctuations below the classical limit.<br />
Q 63.5 Fr 15:00 3G/H<br />
Non-Abelian dynamics of ultracold atoms: From Schrödinger<br />
to Dirac. — •Michael Merkl, Frank Zimmer, and Patrik Öhberg<br />
— Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom<br />
In an atomic system a non-trivial gauge potential is induced with respect<br />
to the external motion of the atoms if two conditions are met.<br />
First, the considered atomic system should, during its time evolution,<br />
remain in space dependent eigenstates, so called dark-states. Secondly,<br />
if there are two degenerated dark-states, the resulting vector poten-
Fachverband Quantenoptik und Photonik (Q) Freitag<br />
tial can be of a non-Abelian nature. These conditions can be fulfilled<br />
if one considers ultra-cold atoms with a tripod-type coupling scheme<br />
in the regime of electromagnetically induced transparency [1]. In the<br />
present talk we consider this tripod system in more detail. Hereby we<br />
distinguish the two limits of weak and strong non-Abelian dynamics.<br />
In the latter the dynamics of the atoms is described by an effective<br />
Dirac equation [2]. For both cases we consider the motion of the atoms<br />
with and without external trapping potentials and show that the corresponding<br />
wave-packet dynamics is highly non-trivial.<br />
[1] J. Ruseckas, G. Juzeliǔnas, P. Öhberg and M. Fleischhauer, Phys.<br />
Rev. Lett. 95, 010404 (2005)<br />
[2] G. Juzeliǔnas, J. Ruseckas, M. Lindberg, L. Santos and P. Öhberg,<br />
preprint<br />
Q 63.6 Fr 15:15 3G/H<br />
Fermi Gases with Arbitrary Spin — •Aristeu Lima 1 and Axel<br />
Pelster 2 — 1 Fachbereich Physik, Freie Universität Berlin, Arnimallee<br />
14, 14195 Berlin, Germany — 2 Fachbereich Physik, Universität<br />
Duisburg-Essen, Lotharstraße 1, 47048 Duisburg, Germany<br />
After the experimental realization of Bose-Einstein condensation in optical<br />
traps, where the spin degree of freedom of the bosonic atoms is no<br />
longer frozen, the question has arisen whether also fermionic atoms can<br />
be optically trapped. In fact, such a system has recently been experimentally<br />
realized with 173 Yb atoms [1]. Other promising examples of<br />
fermionic systems with a total angular moment F in the ground state<br />
which is larger than 1/2 are all alkali fermions (except 6 Li) and 53 Cr.<br />
Thus, now many interesting physical properties of spinor Fermi gases<br />
can be studied. Concerning the contact interaction, many pairing channels<br />
can occur. Furthermore, an additional dipole-dipole interaction,<br />
responsible for anisotropic superfluidity, plays a major role in 53 Cr,<br />
which has six valence electrons. Having these applications in mind, we<br />
calculate the ground-state energy of such systems perturbatively with<br />
respect to the two-particle interaction.<br />
[1] T. Fukuhara et al. Phys. Rev. Lett. 98, 030401 (2007)<br />
Q 63.7 Fr 15:30 3G/H<br />
Exact solution of strongly interacting quasi onedimensional<br />
spinor bose gases — •Frank Deuretzbacher 1 ,<br />
Klaus Fredenhagen 2 , Daniel Becker 1 , Kai Bongs 3,4 , Klaus<br />
Sengstock 3 , and Daniela Pfannkuche 1 — 1 I. Institut für Theoretische<br />
Physik, Universität Hamburg, Germany — 2 II. Institut für<br />
Theoretische Physik, Universität Hamburg, Germany — 3 Institut für<br />
Laserphysik, Universität Hamburg, Germany — 4 School of Physics<br />
and Astronomy, University of Birmingham, United Kingdom<br />
One-dimensional systems of non-interacting fermions can be mapped<br />
to bosons with infinite δ-repulsion. This relationship has been found<br />
by Girardeau already in 1960 for spinless particles. We generalize Girardeau’s<br />
mapping to bosons with spin. The surprising new result<br />
is that hard-core bosons with spin can be mapped to spinless noninteracting<br />
fermions and distinguishable spins.<br />
Our mapping allows for exact calculations of spin densities and the<br />
energy spectrum. Another central result is that the momentum distribution<br />
depends on the symmetry of the spin wave function. States with<br />
completely symmetric spin wave functions have the typical momentum<br />
distribution of spinless bosons, whereas states with very antisymmetric<br />
spin wave functions have much broader and flatter momentum distributions<br />
which resemble the one of non-interacting fermions.<br />
[1] F. Deuretzbacher, et al., arXiv:0708.3039<br />
Q 63.8 Fr 15:45 3G/H<br />
Spontane Musterbildung in antiferromagnetischen Spinor-<br />
Bose-Einstein Kondensaten — •Jochen Kronjäger 1 , Christoph<br />
Becker 1 , Kai Bongs 2 und Klaus Sengstock 1 — 1 Institut für<br />
laser-Physik, Universität Hamburg — 2 Midlands Centre for Ultracold<br />
Atoms, University of Birmingham<br />
Spontane Musterbildung ist ein verbreitetes Phänomen in räumlich<br />
ausgedehnten, nichtlinearen Medien. Die Musterbildung beruht oft<br />
auf der dynamischen Instabilität des homogenen Systems gegenüber<br />
räumlich oszillierenden Störungen, die exponentiell wachsen und<br />
schliesslich zu stabilen raum-zeitlichen Mustern sättigen.<br />
Bose-Einstein Kondensate sind als nichtlineares Medium, in dem<br />
beispielsweise Solitonen auftreten, seit längerem bekannt. Auch neuere<br />
Arbeiten an Spinor-Kondensaten zielen auf räumliche Effekte<br />
ab. Nachgewiesen wurde z.B. bereits die spontane Bildung Spinpolarisierter<br />
Domänen in einem ferromagnetischen Spinor-Kondensat.<br />
Unsere Messungen an elongierten F = 2 87 Rb Spinor-Kondensaten<br />
zeigen erstmals die spontane Bildung von Domänen in einem antiferromagnetisch<br />
wechselwirkenden Spinor-System. Die Domänenbildung<br />
zeigt sich als regelmäßige Modulation des axialen Spins mit charakterischter<br />
Wellenlänge. Induzierte Strukturbildung in einem gezielt angelegten<br />
Magnetfeld-Gradienten wird ebenfalls beobachtet, führt jedoch<br />
entgegen der Erwartung nicht zu regelmäßigen Mustern. Numerische<br />
und analytische Indizien unterstützen die Interpretation unserer Beobachtungen.