6 Atomic Physics and Quantum Optics

6 Atomic Physics and Quantum Optics
Wednesday, 15.06.2011, CE 101
Time ID I: Fundamental PhysIcs / matter Waves
Chair: Antoine Weis, Uni Fribourg
14:00 601 Listening to the Quantum Drum: Mechanics in its Ground State
Tobias Donner 1, 2, 3 , John Teufel 3 , Konrad Lehnert 2, 3 , Ray Simmonds 3
1 ETH Zürich, CH-8093 Zürich
2 JILA, University of Colorado 80309 Boulder, CO, USAs
3 National Institute of Standards and Technology, Boulder, 80305 CO, USA
A mechanical resonator is a physicist’s most tangible example of a harmonic oscillator. If cooled to
sufficiently low temperatures a mechanical oscillator is expected to behave differently to our classical
perception of reality. Observing the quantum behavior of a mechanical oscillator is challenging
because it is difficult both to prepare the oscillator in a pure quantum state of motion and to detect
those states. I will present experiments in which we couple the motion of a micro-fabricated oscillator
to the microwave field in a superconducting high-Q resonant circuit. The displacement of the oscillator
imprints a phase modulation on the microwave field which we detect with a nearly shot-noise
limited interferometer. We employ the radiation pressure force of the microwave photons to cool the
mechanical oscillator to its motional ground state. Finally, we increase the parametric coupling and
the system enters the strong coupling regime.
14:30 602 Entanglement in Neutron Polarimetric Experiments
Stephan Sponar 1 , Jürgen Klepp 2 , Claus Schmitzer 3 , Hannes Bartosik 3 ,
Katharina Durstberger-Rennhofer 1 , Gerald Badurek 1 , Yuji Hasegawa 1
1 Atominstitut, Vienna University of Technology, Stadionallee 2, AT-1020 Vienna
2 Faculty of Physics, University of Vienna, Boltzmanngasse 5, AT-1090 Vienna
3 CERN, CH-1211 Genève 23
Entanglement is a remarkable peculiarity in quantum mechanics. Not only space-like separated particles,
but also systems whose observables belong to disjoint Hilbert spaces, are known for occurrence
of entanglement. This is likewise the case in single-neutron systems, where entanglement is
achieved between different degrees of freedom. Due to its high contrast and insensitivity to ambient
disturbances, the neutron polarimeter is suitable for studying non-contextual hidden-variable
theories. Two experiments, violation of a Bell-like inequality and of an inequality for a triply entangled
Greenberger-Horne-Zeilinger-like state derived by Mermin, are presented. The former yields a
spin-energy correlation function S=2.333(2)>2, which violates the Clauser–Horne–Shimony–Holt Bell
inequality by more than 166 standard deviations. The latter results in a final value M = 3.936(2)>2, for
an entanglement of spin, total energy and momentum degree of freedom, exhibiting a clear violation
of the classical limit. Both experiments verify the predictions of quantum mechanics which are at
variance with non-contextual hidden variable theories.
15:00 603 Leggett's noncontextual model studied with neutrons
Katharina Durstberger-Rennhofer 1 , Claus Schmitzer 2 , Hannes Bartosik 2 , Jürgen Klepp 3 ,
Stephan Sponar 1 , Gerald Badurek 1 , Yuji Hasegawa 1
1 Atominstitut, TU Wien, Stadionallee 2, AT-1020 Wien ; 2 CERN, CH-1211 Genève 23
3 Fakultät für Physik, Universität Wien, Boltzmanngasse 5, AT-1090 Wien
It is a long-lasting debate whether nature can be described by deterministic hidden variable theories
(HVT) underlying quantum mechanics (QM). Bell inequalities for local HVT as well as the Kochen-
Specker theorem for non-contextual models stress the conflict between these alternative theories
and QM. Leggett showed that even nonlocal hidden variable models are incompatible with quantum
predictions.
Neutron interferometry and polarimetry are very proper tools to analyse the behaviour of singleneutron
systems, where entanglement is created between different degrees of freedom (e.g., spin/
path, spin/energy) and thus quantum contextuality can be studied.
We report the first experimental test of a contextual model of quantum mechanics a la Leggett,
which deals with definiteness of measurement results before the measurements. The results show
a discrepancy between our model and quantum mechanics of more than 7 standard deviations and
confirm quantum indefiniteness under the contextual condition.
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15:15 604 Matter wave interferometry with cool metal clusters
Philipp Geyer 1 , Philipp Haslinger 1 , Jonas Rodewald 1 , Stefan Nimmrichter 1 , Bernd v. Issendorff 2 ,
Markus Arndt 1
1 Faculty of Physics, University of Vienna, Boltzmanngasse 5, AT-1090 Vienna
2 Faculty of Physics, University of Freiburg, Stefan-Meier-Str. 21, DE-79104 Freiburg
Matter wave interferometry with clusters and molecules is a versatile tool for testing the foundations
of quantum physics and for establishing new precision measurements on clusters.
We describe a new instrument to explore de Broglie physics of large clusters. Our all-optical ionizing
Talbot-Lau interferometer in the time domain [1,2] consists of three pulsed UV/VUV lasers which are
all retro-reflected by one and the same single mirror to generate three standing light waves. The
expected advantages of interferometry with optical gratings in the time-domain are the complete
elimination of dispersive effects, the compactness and ruggedness as well the absence of clusterwall
interaction that one would find in the presence of material gratings.
[1] Reiger, E., et al., Exploration of gold nanoparticle beams for matter wave interferometry. OpticsCommunications,
2006. 264(2): p. 326-332.
[2] Nimmrichter, S., et al., Concept of a time-domain ionizing matter wave interferometer. arXiv:1102.3644v1 2011.
15:30
16:00 Coffee Break
II: cold atoms / molecules
Chair: Jean-Luc Robyr, Uni Fribourg
16:30 611 Optomechanical Coupling of Ultracold Atoms and a Membrane Oscillator
Andreas Jöckel 1 , Maria Korppi 1 , Stephan Camerer 2 , David Hunger 2 , Theodor W. Hänsch 2 ,
Philipp Treutlein 1
1 Departement Physik, Universität Basel, Klingelbergstrasse 82, CH-4056 Basel
2 LMU München, Schellingstrasse 4, DE-80799 München
We report the recent results of our experiment, where we couple a single mode of a high-Q membrane-oscillator
to the motion of laser-cooled atoms in an optical lattice. The optical lattice is formed
by retroreflection of a laserbeam from the membrane surface. The coupling is mediated by power
modulation of the lattice beam due to the vibrations of the atoms in the lattice. If the trap frequency
of the atoms in the lattice is matched to the eigenfrequency of the membrane, we observe resonant
energy transfer between the two systems.
In the long term, such coupling mechanism could be exploited to develop hybrid quantum systems
between atoms and solid-state devices. As another intriguing perspective, a new generation of optical
lattice experiment is in sight, where the mirrors creating the laser standing waves are micromechanical
oscillators interacting with the atoms on a quantum level.
17:00 612 Spin-Squeezing a Bose-Einstein Condensate on an Atom Chip
Roman Schmied, Max Riedel, Pascal Böhi, Caspar Ockeloen, Philipp Treutlein
Departement Physik, Universität Basel, Klingelbergstrasse 82, CH-4056 Basel
Quantum information technology will one day tear down the speed barriers that limit our understanding
of complex quantum systems. At its core lies the deterministic and robust generation of entanglement.
Our group has succeeded in generating multiparticle entangled states of trapped atoms for
the first time, by spin-squeezing a two-component Bose-Einstein condensate of 87 Rb atoms [1]. We
have developed a novel tomographic method for analyzing and visualizing these experimental states
through the spherical Wigner function [2].
[1] M. Riedel, P. Böhi, Y. Li, T. W. Hänsch, A. Sinatra, and P. Treutlein, Atom-chip-based generation of entanglement for
quantum metrology, Nature 464, 1170 (2010)
[2] R. Schmied and P. Treutlein, Tomographic reconstruction of the Wigner function on the Bloch sphere, arXiv:1101.4131
(2011)
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17:30 613 BCS-BEC crossover in a two-dimensional Fermi gas
Gianluca Bertaina 1 , Stefano Giorgini 2
1 Institut de Théorie des Phénomènes Physiques, EPFL, Station 3, CH-1015 Lausanne
2 INO-CNR BEC Center and Physics Dep., Univ. of Trento, Via Sommarive 14, IT-38123 Povo, Trento
We investigate the crossover from Bardeen-Cooper-Schrieffer (BCS) superfluidity to Bose-Einstein
condensation (BEC) in a two-dimensional Fermi gas at T=0 using the fixed-node diffusion Monte
Carlo method. We calculate the equation of state and the gap parameter as a function of the interaction
strength, observing large deviations compared to mean-field predictions. In the BEC regime our
results show the important role of dimer-dimer and atom-dimer interaction effects that are completely
neglected in the mean-field picture. Results on Tan’s contact parameter associated with short-range
physics are also reported along the BCS-BEC crossover.
17:45 614 Towards an ion-photon quantum interface
Andreas Stute, Bernardo Casabone, Birgit Brandstätter, Diana Habicher, Andrew McClung,
Johannes Ghetta, Tracy Northup, Rainer Blatt
Inst. für Experimentalphysik, Uni Innsbruck, Technikerstr. 25, AT-6020 Innsbruck
In one promising scheme for an ion-based quantum network, photons transfer quantum information
as flying qubits between stationary ions. For this transfer to be reversible, the quantum interface is
realized via the coherent coupling of the ion to the field of an optical resonator. Here, we discuss our
experimental progress towards the realization of such an ion-photon quantum interface.
In our system, a single trapped 40 Ca + ion is coupled to the mode of a high-finesse optical resonator.
Single photons are generated in a vacuum-stimulated Raman process between two atomic states
driven by a laser and the vacuum field of the resonator. In this Raman process, all Zeeman substates
of the atom are resolved. Both the polarization state of the photon as well as the state of the atom
are detected. These prerequisites enable schemes including ion-photon entanglement as well as ionphoton
state mapping, both of which will be discussed.
18:00 615 Towards the creation of a quantum gas of polar ground state molecules
Markus Debatin, Lukas Reichsöllner, Tetsu Takekoshi, Raffael Rameshan, Almar Lercher,
Fransesca Ferlaino, Rudolf Grimm, Hanns-Christoph Nägerl
Inst. für Experimentalphysik, Universität Innsbruck, Technikerstr 25, AT-6020 Innsbruck
Dipolar quantum gases promise the realization of novel many-body quantum phases as a result of
the long-range and anisotropic interaction, c.f. Ref[1]. For our Rb-Cs mixture experiment the focus
is on the creation of a bosonic quantum gas of polar ground-state RbCs molecules using Feshbach
association and subsequent stimulated adiabatic Raman transfer (STIRAP). Our approach is similar
to the one used in Ref’s. [2,3]. We create a high phase-space density sample of ultracold Feshbach
molecules. Prior to that, we produce a double Bose-Einstein condensate (BEC) of Rb and Cs atoms
[4]. We perform high-resolution molecular spectroscopy on the Feshbach molecules and find intermediate
electronically excited levels suitable for RbCs ground-state transfer. We have measured the
binding energy of the RbCs rovibrational ground state in two-photon spectroscopy. We are currently
implementing an optical lattice to create a Mott-insulator state having precisely one atom of each
species at each lattice site with the aim to improve the creation efficiency for the Feshbach molecules
and to shield the particles from collisional loss during state transfer.
[1] M.A. Baranov, Physics Reports 464 (2008)
[2] J.G. Danzl et al., Science 321 (2008), J.G. Danzl et al, Nature Physics 6 (2010)
[3] K.-K. Ni et al., Science 322, 231 (2008)
[4] A. Lercher et al. arXiv:1101.1409v1 (2011)
18:15 616 Probing Spin-fluctuations in an ultracold Fermi gas
David Stadler, Institute for Quantum Electronics, ETH Zürich, Schafmattstrasse 16, 8093 Zürich
Current theoretical and experimental efforts in the field of ultra cold atoms are directed towards the
preparation and detection of magnetically ordered systems, in the context of which the observation
of spin-fluctuations has been proposed as a promising tool.
We present in-situ observations of spin fluctuations in a two-component Fermi gas of Lithium atoms.
Therefore we use a quantum-limited interferometer with a spatial resolution of 1.8 µm to directly
probe the correlations in our atomic gas by measuring the probability distribution of the local spinpolarization.
We observe a temperature-dependent reduction of spin-fluctuations up to 4.5 dB below
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shot-noise in weakly interacting Fermi gases and a even stronger reduction by 9.2 dB in a strongly
interacting gas of molecules. From these measurements we determine the macroscopic magnetic
susceptibility of our Fermi gas.
18:30 Postersession and Apéro
Thursday, 16.06.2011, CE 101
Time ID III: Quantum oPtIcs
Chair: Victor Lebedev, Uni Fribourg
14:00 621 Hybrid Quantum System:Coupling Color Centers to Superconducting Cavities
Johannes Majer 1 , Robert Amsüss 1 , Christian Koller 1 , Tobias Nöbauer 1 , Stefan Putz 1 ,
Matthias Schramböck 1 , Stefan Rotter 2 , Jörg Schmiedmayer 1
1 Atominstitut, TU Wien, Stadionallee 2, AT-1020 Wien
2 Institute for Theoretical Physics, TU Wien, Stadionallee 2, AT-1020 Wien
Reversible transfer of quantum information between long-lived memories and quantum processors
is a favorable building block of scalable quantum information devices. We present recent experimental
results of strong coupling between an ensemble of nitrogen-vacancy center electron spins in
diamond and a superconducting microwave coplanar waveguide resonator. Although the coupling
between a single spin and the electromagnetic field is typically rather weak, collective enhancement
allows entering the strong coupling regime. With our experimental set-up we are able to directly observe
this characteristic scaling of the collective coupling strength with the square root of the number
of emitters. Additionally, we measure hyperfine coupling to 13 C nuclear spins, which is a first step
towards a nuclear ensemble quantum memory. Using the dispersive shift of the cavity resonance
frequency, we measure the relaxation time T 1 of the NV center at millikelvin temperatures in a nondestructive
way.
14:30 622 Generation of Orbital Angular Momentum Carrying Beams
in Semiconductor Microcavities
Francesco Manni 1 , Konstantinos G. Lagoudakis 1 , Taofiq Paraiso 1 , Roland Cerna 1 ,
Yoan Leger 1 , Tim C. H. Liew 2 , I. A. Shelykh 3 , A. V. Kavokin 4 , François Morier-Genoud 1 ,
Benoit Deveaud-Plédran 1
1 EPFL-ICMP-LOEQ, Station 3, Boite C, CH-1015 Lausanne
2 EPFL-ITP, Station 3, Boite C, CH-1015 Lausanne
3 Science Institute, University of Iceland, Dunhagi-3, IS-107 Reykjavik
4 Physics & Astronomy School, University of Southampton, Highfield, Southampton, SO171BJ, UK
It is notable that all techniques for the creation of beams with orbital angular momentum, to the best
of our knowledge, require an optically inhomogeneous and/or anisotropic material or strong focusing.
In this work, we demonstrate that the spin-to-orbital angular momentum (SOAM) conversion
can also be achieved in a planar semiconductor microcavity. Despite being an isotropic system, microcavities
exhibit a polarization splitting between transverse electric - transverse magnetic (TE-TM)
modes, which induces the appearance of an L = +2 orbital angular momentum in one of the circular
polarizations, under excitation in the cross-circular polarization [1]. The vortical entities resulting from
this conversion process can be regarded as the optical equivalent of a pair of half-quantum vortices.
We provide a theoretical model which rigorously derives the principle of the SOAM conversion and
quantitatively reproduces the experimental observations.
[1] T. C. H. Liew, et al., PRB, 75, 241301 (2007)
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14:45 623 Phonon-tunneling dissipation in mechanical resonators
Garrett Cole 1 , Ignacio Wilson-Rae 2 , Katharina Werbach 1 , Michael Vanner 1 , Markus Aspelmeyer 1
1 Vienna Center for Quantum Science and Technology, Faculty of Physics, University of Vienna,
Boltzmanngasse 5, AT-1090 Vienna
2 Physik Department, James-Franck-Straße, DE-85748 Garching
Micro- and nanoscale mechanical resonators have emerged as ubiquitous devices for application in
a wide range of technical disciplines including communications, sensing, metrology, and fundamental
scientific endeavors. In many instances, the performance of these devices is limited by the deleterious
effects of mechanical damping. To further compound this limitation, the quantitative understanding
of many damping mechanisms remains elusive. Here, we report a significant advancement
towards predicting and controlling support-induced losses, a key dissipation mechanism in highquality-factor
mechanical resonators. We have developed an efficient finite-element-enabled numerical
solver, employing the recently introduced “phonon tunneling” approach. Exploiting this solver
we demonstrate the ability to predict the design-limited damping of generic mechanical resonators,
yielding excellent agreement with experimental measurements on custom-fabricated monocrystalline
resonators [1]. Thus, our phonon-tunneling solver represents a major step towards accurate prediction
of the mechanical quality factor in micro- and nanomechanical resonators.
[1] G. D. Cole, I. Wilson-Rae, K. Werbach, M. R. Vanner, and M. Aspelmeyer, “Phonon-tunnelling dissipation in mechanical
resonators,” Nature Communications 2, 231, 8 March (2011)
15:00 624 Towards Time-Bin Entangled Photons from Quantum Dots
Harishankar Jayakumar 1 , Gregor Weihs 1 , Ana Predojevic 1 , Glenn Solomon 2
1 Institute for Experimental Physics, Universität Innsbruck, Technikerstrasse 25d, AT-6020 Innsbruck
2 JQI, NIST, University of Maryland, Maryland, 20899 Gaithersburg, USA
Entangled photon pairs are essential for the implementation of quantum communication protocols.
The most common is the polarization entangled photons produced from a parametric down conversion
(PDC) source. J.D Franson proposed an experiment for the test of Bell´s inequality with energytime
entangled photons, experimentally realized by P. G. Kwiat et al using photon pairs from a PDC
source. J. Brendel et al , realized a discrete version of energy-time entanglement, the time-bin entanglement
by pumping PDC crystal at two well defined times set by a pump interferometer. Based on
this discrete version C. Simon and J-P Poizat PRL 94, 110501 (2005) proposed a scheme for generating
time-bin entangled photon pairs from quantum dots. Here we will be presenting our experimental
setup and the progress towards the generation of time-bin entangled photons from quantum dots.
This research was supported in part by the European Research Council (ERC) and by the Canadian Institute for Advanced
Research (CIFAR).
15:15 625 Optically driven electron pump using In(Ga)As quantum dots
Laurent Nevou 1 , Valeria Liverini 1 , Arun Mohan 2 , Giancarlo Cerulo 1 , Fabrizio Castellano 1 ,
Alfredo Bismuto 1 , Peter Friedli 3 , Hans Sigg 3 , Eli Kapon 2 , Jerome Faist 1
1 Institute for Quantum Electronics, ETH Zürich, Wolfgang-Pauli-Strasse 16, CH-8093 Zürich
2 EPFL, CH-1015 Lausanne
3 Laboratory for Micro- and Nanotechnology, PSI, CH-5232 Villigen PSI
The discoveries of the Josephson and the quantum Hall effects have revolutionized the metrology of
electrical quantities. As a result, there is an increased interest in closing the metrological triangle [1]
by the construction of an electron pump in which N electrons of charge q are pumped individually at
a frequency f.
Here, we propose an electron pump based on In(Ga)As/GaAs quantum dots (QDs) optically pumped
by a pulsed laser. It consists of one plane of QDs coupled to an InGaAs quantum well (QW) reservoir
via an AlGaAs barrier. A pulsed laser periodically ionizes the QDs. As a result, if the laser pulse
duration is shorter than the time required for the electrons in the QW to refill the QDs, the number of
electrons generated can be counted [2].
[1] J. Flowers, Science,306, 1324(2004).
[2] L. Nevou, et al., Nature Physics (in print),Published online: 20 February 2011
123

15:30 626 Strong coupling between the cyclotron resonance
of a high mobility 2D electron gas and a LC metamaterial
Giacomo Scalari 1 , Dana Turcinkova 1 , Christian Reichl 2 , Dieter Schuh 3 , Werner Wegscheider 2 ,
Mattias Beck 1 , Jérôme Faist 1
1 Institute of Quantum Electronics, ETH Zürich, Wolfgang Pauli Strasse 16, CH-8093 Zürich
2 Laboratory for Solid State physics, ETH Zürich, Schafmattstr. 16, CH-8093 Zürich
3 Universität Regensburg, Universitätsstraße 31, DE-8093 Regensburg
We report about observation of strong light-matter coupling between the cyclotron resonance of an
high-mobility two dimensional electron gas (2DEG) and the resonances of a planar THz metamaterial
composed by LC split-ring resonators. A THz-TDS system coupled to superconducting magnet
probes the THz transmission of the sample in the banwidth 0-3.5THz. The LC resonances observed
with no applied magnetic field are at 1 THz and 2.3 THz. Once the magnetic field value is increased,
we observe a strong modification of the transmission spectra with some clear anticrossings between
the different branches. Uncoupled cyclotron signal is also observed because the 2DEG in between
the resonators is still present. We observe the disappearing of both cavity modes as the system enters
the strong coupling regime and the evolution of the magnetopolaritonic branches as the value of
the field is swept through the resonances.
15:45 627 Highly efficient lasers and amplifiers in double tungstates
Markus Pollnau, Dimitri Geskus, Koop van Dalfsen, Sonia M. García-Blanco, Shanmugam Aravazhi,
MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, NL-7500 AE Enschede
The double tungstates KY(WO ) , KGd(WO ) , and KLu(WO ) are excellent candidates for solid-state
4 2 4 2 4 2
lasers because of the large transition cross-sections of optically active rare-earth ions doped into
these hosts. We grow actively doped KY Gd Lu (WO ) layers onto KY(WO ) substrates by liquid-
1-x-y x y 4 2 4 2
phase epitaxy. Co-doping the layers with optically inert Gd3+ and Lu3+ ions simultaneously allows for
lattice matching and enhanced refractive index contrast with respect to the substrate. Low-loss channel
waveguides are microstructured into the layers by Ar + 16:00
-beam etching, resulting in strong pumpand
signal-mode confinement. Yb-doped channel waveguide lasers deliver 650 mW output power at
1 µm. Record-high slope efficiency (85%) and record-low quantum defect (0.7%) for dielectric lasers
are achieved. In pump-signal experiments, exploiting highly doped KGd Lu Yb (WO ) chan-
0.447 0.078 0.475 4 2
nel waveguides, we demonstrate a giant optical gain of 950 dB/cm, exceeding the gain previously
reported in rare-earth-ion-doped materials by two orders of magnitude and comparable to the gain
obtained in semiconductor optical amplifiers.
Coffee Break
Time ID Iv: codensed helIum / atomIc clocks
Chair: Antoine Weis, Uni Fribourg
16:30 631 Electron Spin Resonance of 87Rb Monomers on Superfluid Helium Nanodroplets
and Introduction of a Simple Model for Optical Pumping
Alexander Volk, Johannes Poms, Markus Koch, Wolfgang E. Ernst
Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, AT-8010 Graz
Electron spin resonance (ESR) spectroscopy on superfluid helium nanodroplets (HeN) has recently
been performed for 85 Rb [1]. Electronic perturbation of the alkali-metal atom induced by the HeN
leads to a droplet size dependent change of the hyperfine constant aHFS. The investigation of ESR
silent species inside HeN, by measuring their interaction with an alkali-metal atom situated on the
droplet surface, is expected to be more sensitive for 87 Rb because of its larger hyperfine coupling
(aHFS = 3417 MHz). We present new ESR spectra of single 87 Rb atoms on HeN [2]. The amplitude of
ESR transitions measured by means of optically detected magnetic resonance, turned out to strongly
depend on the laser polarization and power. A simple model for optical pumping on HeN has been
established. Modelling of changes in the observed line shapes is expected to reveal new information
concerning the droplet size dependence of aHFS and is object of current work.
[1] M. Koch, G. Auböck, C. Callegari, and W. E. Ernst, Phys. Rev. Lett. 103, 035302 (2009)
[2] A. Volk, J. Poms, M. Koch, and W. E. Ernst, J. Phys. Chem. A, in press 2011
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17:00 632 High-Spin States of Heavy Alkali Trimers
Gerald Auböck 1 , Andreas W. Hauser 2 , Wolfgang E. Ernst 2
1 Laboratory of Ultrafast Spectroscopy, EPFL, Station 6 , CH-1015 Lausanne
2 Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, AT-8010 Graz
Triatomic alkali-metal molecules in their high-spin manifolds of electronic states are of fundamental
interest for different reasons: On one hand, they represent a class of highly magnetic metal clusters
whose electronic level structure obeys a simple shell model [1]. On the other hand, three parallel spin
alkali atoms may form a weakly bound molecule in low-temperature collisions in a magneto-optic
trap. From a theoretical point of view, they provide the chance to investigate the spectroscopic consequences
of the combination of Jahn-Teller effect and spin-orbit coupling with powerful methods
of quantum chemistry such as open-shell coupled cluster approaches and multireference Rayleigh-
Schroedinger perturbation theory. With respect to available experimental data the 2 4 E1 4 A2 transitions
are selected to document the quenching of the paradigmatic Exe Jahn-Teller distortion with
increasing spin-orbit coupling. Simulated spectra for potassium, rubidium and cesium trimers are
provided together with all relevant parameters such as harmonic frequencies, Jahn-Teller parameters
and spin-orbit splittings obtained from the ab initio approach [2].
[1] A. W. Hauser, C. Callegari and W. E. Ernst, in: Advances in the Theory of Atomic and Molecular Systems (eds. P.
Piecuch et al.), (Springer Series Progress in Theoretical Chemistry and Physics 20) DOI 10.1007/978-90-481-2985-
0_10, Springer Science+Business Media B.V. 2009, p. 199-214.
[2] A. W. Hauser, G. Auböck and W. E. Ernst, in: Vibronic Interactions and the Jahn-Teller Effect II: Applications (ed.
Claude Daul), (Springer Series Progress in Theoretical Chemistry and Physics) Springer Science+Business Media
2011, in press.
17:15 633 Spectroscopy of Cs and Rb perturbed by He in gas and condensed phase
Victor Lebedev, Peter Moroshkin, Antoine Weis
Department of Physics, University of Fribourg, Chemin du Musee 3, CH-1700 Fribourg
Electronic transitions of alkali-metal atoms interacting with rare-gas atoms are well-known model
systems for the study of line broadening due to atomic collisions in the gas phase, and of atomic
bubbles formed by foreign atoms embedded in condensed helium cryomatrices. In the gas phase
the motion of rare gas atoms is totally uncorrelated, even at high densities, and their interactions with
the alkali atom can be treated independently. In contrast, in the atomic bubble model the motion of
the He atoms surrounding the impurity is strongly correlated and is described in terms of collective
modes, such as phonons or bubble interface oscillations. Here we present an experimental and
theoretical study of the crossover between these two regimes, which occurs in supercritical fluid
helium doped with Cs or Rb atoms and locally heated by strong laser pulses, conditions which have
not been addressed to date.
Work funded by SNF, #200020-129831
17:30 634 Measurement of the DC Stark shift of the Cs clock transition frequency
Jean-Luc Robyr, Paul Knowles, Antoine Weis
Department of physics, University of Fribourg, 3 rue du Musée, CH-1700 Fribourg
The Stark effect describes the shift of atomic energy levels induced by an external electric field. In
Cs atomic clocks, the AC Stark shift arising from the blackbody radiation is an important source of
systematic frequency shifts. We are performing an optical Raman-Ramsey pump-probe experiment
on a thermal Cs atomic beam to make a precise measurement of the Cs ground states third-order
electric polarizabilities parameterizing the Stark shift. The experimental scheme is similar to that of Cs
atomic beam clocks except that the microwave cavities are replaced by coherent population trapping
(CPT) interactions and that a static electric field is applied to the atoms during their free evolution.
The electric field calibration by numerical simulation as well as direct field measurements using the
(3) Aharonov-Casher phase shift will be discussed and an absolute value for a will be presented.
0
Work funded by SNF #200020-126499
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18:00 635 Laser-microwave double-resonance spectroscopy
in mm-scale Rb vapour cells for atomic clocks
Christoph Affolderbach 1 , Matthieu Pellaton 1 , Gaetano Mileti 1 , Yves Pétremand 2 , Nico de Rooij 2
1 Laboratoire Temps-Fréquence, Université de Neuchâtel, Bellevaux 51, CH-2000 Neuchâtel
2 SAMLAB, EPFL, Jaquet-Droz 1, CP 526, CH-2002 Neuchâtel
We report on double-resonance spectroscopy of the 87Rb ground-state hyperfine “clock” transition in
mm-scale micro-fabricated vapour cells, in view of novel miniature atomic clocks for low-power and
mobile applications. Compared to clocks based on coherent population trapping developed during
the past decade, the double-resonance scheme has the advantage of reduced signal background
and avoids the issue of high-frequency modulation of the laser source.
The micro-fabricated cells are produced from Si pre-form wafers and glass plates sealed by anodic
bonding, and filled with Rb and a buffer gas. Double-resonance clock signals are obtained by optical
pumping with a 795 nm DFB laser and applying microwave radiation at 6.8 GHz via a compact
microwave resonator. Analysis of the clock signals in view of the main parameters relevant for an
atomic clock is presented. Preliminary clock stabilities are < 3·10-11 at 1 second and < 4·10-12 at 100
seconds of integration time.
18:15 END
19:30 Conference Dinner
ID atomIc PhysIcs and Quantum oPtIcs Poster
641 Energy harvesting in doped helium nano-droplets
Matthias Daxner 1 , Harald Schoebel 1 , Peter Bartl 1 , Christian Leidlmair 1 , Samuel Zoettl 1 , Stephan Denifl 1 ,
Tilmann D. Märk 1 , Paul Scheier 1 , Daniel Spånberg 2 , Andreas Mauracher 2 , Diethard K. Bohme 3
1 Institute for Ion Physics and Applied Physics, University of Innsbruck, Technikerstraße 25, AT-6020 Innsbruck
2 Department of Materials Chemistry, Uppsala University, Box 538, SE-75121 Uppsala
3 Department of Chemistry, York University, 4700 Keele Street, CA-Toronto, M3J 1P3
We report the observation of a novel ionization mechanism in which doubly charged ions are produced inside a
helium droplet by sequential Penning Ionization. Doping superfluid 4He-clusters with methyl iodide or mercury
and exposing them to electrons enhances the formation of doubly charged atomic ions (I ++ or Hg ++ ) at the energy
threshold for the production of two metastable He-atoms.
These observation points toward a novel ionization process in which doubly-charged ions are produced by sequential
PI. We observed also changes in the distribution of argon clusters within He-clusters, due to Coulomb
explosion, at the energy threshold for the production of two or three metastable He-atoms, again indicating the
occurrence of this novel ionization process. Our experimental results clearly demonstrate the possibility of sequential
PI and energy harvesting in He nano-droplets. This universal process may well contribute substantially
to radiation damage in biological systems exposed to ionizing radiation.
642 Time and frequency metrology with laser cooled atoms:
Evaluation of the Swiss continuous atomic fountain clock
Laurent Devenoges 1 , Gianni Di Domenico 1 , André Stefanov 2 , Alain Joyet 1 , Pierre Thomann 1
1 Laboratoire Temps-Fréquence, Université de Neuchâtel, Av. de Bellevaux 51, CH-2000 Neuchâtel
2 Office fédéral de métrologie (METAS), Lindenweg 50, CH-3003 Bern-Wabern
Atomic fountain clocks presently contributing to the international atomic time (TAI) are operating in a pulsedmode.
They provide the best realization of the SI second with relative uncertainties of a few parts in 10 16 . Our
alternative approach consists in using a continuous beam of laser-cooled cesium atoms. Besides circumventing
the Dick effect, a continuous fountain is interesting from the metrological point of view because the relative
importance of the error budget contributors is quite different compared to a pulsed one. Evaluation of the frequency
shifts specific to the continuous approach is currently underway in our laboratory. In particular, we can
mention the light shift, which has been measured below 1.5·10 -16 , the second order Zeeman shift, with its error
budget contribution below 5·10 -16 , the collisional shift and the end-to-end cavity phase shift. The latest results
will be presented at the conference.
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643 Controlling the coherent atom-light interaction in free space
Lukas Slodicka, Gabriel Hetet, Nadia Röck, Markus Hennrich, Rainer Blatt
Institut für Experimentalphysik, Universität Innsbruck, Technikerstrasse 25/4, AT-6020 Innsbruck
Understanding single atom-light interaction is essential for fundamental studies of quantum mechanics and for
efficient realization of many quantum information protocols. We report on extinction experiments with a single
atom in free space. By focusing a weak and narrowband Gaussian laser beam onto trapped single Barium ion
using a high numerical aperture lens, we observe light extinction of up to 1.35%. We also demonstrate electromagnetically
induced transparency of the ion by tuning a strong control beam over a two-photon resonance in
a three-level lambda-type system. Furthermore, we investigate the properties of a single atom as a coherent
reflector. We use a novel cavity setup where one of the mirrors is replaced by a single trapped ion. We observe
quantum-electro-dynamics effects in a regime, where the laser intensity is already changed by the atom alone.
644 On Relativistic Photoexcitation and Decay Rates in Hydrogenic Atoms
Gerhard Adam 1 , A. V. Soldatov 2 , Josip Seke 1 , Martin Polak 1
1 Institut für Theoretische Physik, Technische Universität Wien, Wiedner Hauptstrasse 8-10/136, AT-1040 Wien
2 V. A. Steklov Mathematical Institute, Dept. of Mechanics, 8, Gubkina str., RU-119991 Moscow
By using the plane-wave expansion for the electromagnetic-field vector potential, relativistic bound-bound and
bound-unbound transition matrix elements for hydrogenic atoms are expressed universally in terms of hypergeometric
functions of the type F in such a way that these functions only depend on the absolute value of
2 1
the wave vector |k| and the dependence on angular variables of the wave vector is totally factored out and only
comes through functional multipliers built of spherical harmonics. The newfound representation for the matrix
elements in question is very convenient for exact analytical and precise numerical evaluation of the relativistic
photoexcitation and decay rates in hydrogenic atoms, thus providing precise analytical expressions in terms of
hypergeometric functions for the relativistic rates of bound-bound absorption-emission and bound-unbound
absorption processes.
645 Spatially resolved magneto-relaxation of magnetic nanoparticles detected by cesium
atomic magnetometers
Natascia Castagna 1 , Paul Knowles 1 , Antoine Weis 1 , Alke Fink 2 , Isabelle Geissbühler 2 , Georg Bison 3
1 Department of Physics, University of Fribourg, Chenin du Musée 3, CH-1700 Fribourg
2 Department of Chemistry, University of Fribourg, Chenin du Musée 9, CH-1700 Fribourg
3 Department of Neurology, Friedrich-Schiller University, Erlanger Alee 101, DE-07747 Jena
Biocompatible superparamagnetic iron oxide nanoparticles (SPIONs) are finding many diagnostic and therapeutic
applications in medical healthcare. In an external magnetic field, SPION samples align their magnetic
moments by physical rotation, and a bulk magnetization is created. Once the magnetic field is switched off, the
magnetization relaxes on characteristic time scales that range from nanoseconds to seconds. The relaxation parameters
can be inferred from the time evolution of the magnetization measured via the decay of the associated
field (magneto-relaxometry). When functionalized, the SPIONs can be made to bind to specific morphological
structures. The relaxation signals will thus carry information on the specific particles’ position and environment.
We will report on first magneto-relaxometry measurements made by a Cs atomic magnetometer array operated
in a second order gradiometer configuration used to construct two-dimensional relaxation maps.
We acknowledge financial support by the SNF (Sinergia grant No. CRSII2-130414-1).
646 Hybrid Quantum Systems: Integrating Atomic and Solid-State Qubits
Stefan Minniberger, Robert Amsüss, Stephan Schneider, Fritz Diorico, Christian Koller, Stefan Haslinger,
Christoph Hufnagel, Christian Novotny, Matthias Schramböck, Johannes Majer, Jörg Schmiedmayer,
Atominstitut, TU Wien, Stadionallee 2, AT-1020 Wien
The goal of our project is to couple superconducting qubits to an ultracold cloud of Rubidium atoms. This combination
of two physical systems will allow us to make use of the long coherence times in atomic ensembles and
of the fast processing of solid-state qubits.
A prerequisite is to transport the atom cloud into a cryostat, which we implemented by using a mangetic conveyor
belt. In the cryostat, the atoms are cooled down further and the resulting BEC is transferred to a magnetic wire
trap, which allows precise contol of the location of the atomic cloud with respect to the microwave resonator.
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647 Diploar quantum gases of heteronuclear molecules in optical lattices
Lukas Reichsöllner, Markus Debatin, Tetsu Takekoshi, Raffael Rameshan, Almar Lercher, Francesca Ferlaino,
Rudolf Grimm, Hanns-Christoph Nägerl
Inst. f. Experimentalphysik, Universität Innsbruck, Technikerstraße 25/4, AT-6020 Innsbruck
Dipolar quantum gases promise the realization of novel many-body quantum phases as a result of the longrange
and anisotropic interaction, c.f. Ref [1]. For our Rb-Cs mixture experiment the focus is on the creation
of a bosonic quantum gas of polar ground-state RbCs molecules using Feshbach association and subsequent
stimulated adiabatic Raman transfer (STIRAP). Our approach is similar to the one used in Ref’s. [2,3]. Prior to
that, we produce a double Bose-Einstein condensate (BEC) of Rb and Cs atoms [4].
Our goal is to improve the production of RbCs molecules by performing the Feshbach association and STI-
RAP transfer in the presence of an optical lattice. We create a Mott-insulator state for the cesium atoms and a
separated superfluid rubidium sample. We attach the rubidium atoms to the cesium atoms to achieve precisely
one atom of each species per lattice site and perform the Feshbach association and the STIRAP transfer. This
scheme prevents three-body loss and thus allows us to maximize the number of RbCs ground-state molecules.
[1] M.A. Baranov, Physics Reports 464 (2008)
[2] J.G. Danzl et al., Science 321 (2008), J.G. Danzl et al, Nature Physics 6 (2010)
[3] K.-K. Ni et al., Science 322, 231 (2008)
[4] A. Lercher et al. arXiv:1101.1409v1 (2011)
648 Loss of hydrogen from amino acids by low energy electron attachment
Benjamin Puschnigg 1 , Violaine Vizcaino 1 , Eugen Illenberger 2 , Paul Scheier 1 , Stephan Denifl 1
1 Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr.25/3, AT-6020 Innsbruck
2 Freie Universität Berlin, Takustrasse 3, DE-14195 Berlin
Theoretical calculations and experiments showed that formic acid loses the hydrogen at the O-H site upon attachment
of electrons with the energy of approximately 1.5 eV. In early studies, it was proposed that electrons
attach initially at the p* (C=O) orbital (at 1.8 eV) and then the hydrogen splits off. Although the s* (O-H) orbital
lies at higher energy (5 eV), we show here that an electron can attach directly at this orbital because of the broad
width of the s* resonance.
In our experiment, we studied a- and b-alanine and found out that the shape of the ion yield was changing
significantly, the same effect was observed with aminobutanoic acid isomers.
We observed sharp structures in the ion yield for the different molecules which can be associated to vibrations
of the molecules (OH stretch overtones). This is confirmed by the measure of deuterated molecules.
649 Towards the generation of entangled microcavity polaritons
Mathias Sassermann 1 , Patrick Mai 1 , Zoltan Vörös 1 , Gregor Weihs 1 , Sven Höfling 2 , Alfred Forchel 2 ,
Andreas Löffler 2
1 University of Innsbruck, Technikerstrasse 25/d, At-6020 Innsbruck
2 University of Würzburg, Am Hubland, DE-97074 Würzburg
Several theoretical studies have recently pointed out that microcavity polaritons can be a viable source of entangled
photon pairs, either in the polarisation, or the frequency degree of freedom.
As a first step towards a successful implementation, one has to have access to the full polariton dispersion. In
order to achieve this, we utilise two spatial light modulators in a non-standard configuration; one for controlling
the polariton momentum, the other for arbitrarily filtering the spectrum of a fs laser pulse, thus controlling the
energy.
In the paper, we will discuss our first results on polariton-polariton scattering in planar GaAs microcavities. We
show that with our experimental configuration, the ingredients of the above-mentioned entanglement schemes
are realised. Evidence for parametric polariton scattering will be presented.
This research was supported in part by the Austrian Science Fund (FWF), the European Research Council (ERC) and the Canadian
Institute for Advanced Research.
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650 Non-equilibrium dynamics in mixtures of Rydberg atoms and polar molecules
Alexander Glätzle, Guido Pupillo, Bo Zhao, Mikhail Baranov, Peter Zoller
Institute for theoretical Physics, University of Innsbruck, Technikerstr. 25, AT-6020 Innsbruck
We study the nonequilibrium dynamics of a many-body classical system of polar molecules and Rydberg atoms,
subject to driving and dissipation. We show that long-range dipole-dipole interactions between hot molecules
and cold atoms separately trapped in quasi two-dimensional geometries can lead to efficient sympathetic cooling
of generic polar molecules to micro-Kelvin temperatures. We propose that direct laser cooling into a strongly
correlated, e.g. crystalline, phase can be performed on a gas of groundstate atoms weakly dressed by laser
light with an excited Rydberg state, in turn allowing for advanced tailoring of the spatial structure of the cold
molecules.
651 Photon-switches in quantum-optical networks
Martin Suda, Christoph Pacher, AIT-Austrian Institute of Technology, Donau-City-Str. 1, AT-1220 Vienna
We investigate quantum-optical networks for several input Fock states of photons and determine the total state
appearing in the output ports. The most simple network is a single-loop Mach-Zehnder interferometer with two
beam splitters and a phase shifter providing two inputs and two outputs. Moreover, we consider a double-loop
interferometer with 3 inputs and 3 outputs. For product Fock states of several input modes the Hong-Ou-Mandel
effect plays an important role. The entangled output states and the mean photon numbers are determined as
a function of various phase shifters. Using computerized simulation different network structures are analyzed.
These investigations can be helpful for optical quantum computing.
652 Light Effects on High Q-Resonators for Hybrid Quantum Systems
Christian Koller, Robert Amsüss, Tobias Nöbauer, Matthias Schramböck, Jörg Schmiedmayer, Johannes Majer,
VCQ, Atominstitut TU Wien, AT-1020 Vienna
Over the last years hybrid quantum systems have drawn attention in the field of quantum information processing,
because of their ability to combine the advantages of different quantum worlds (e.g. cold atoms, NV centers,
superconducting Qubits...). The heart of these hybrid systems are superconducting microwave resonators with
high quality factors (on the order of one million). The response of these resonators under the influence of light
is very crucial, since many of the hybrid applications involve laser light with different intensity. We will present
measurements of the shift of resonator frequency as a function of the applied light power. Furthermore, we show
the effects on the Q value due to the generation of quasiparticles and the saturation of two-level fluctuators in
the superconducting thin films.
We will also put these facts in perspective with resent measurements of resonators strongly coupled to an
ensemble of NV centers.
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