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International Conferenceon
Quantum Optics
Book of Abstracts
Obergurgl, Tirol, Austria12th–18th February, 2012
Contents
Talks 3
Posters I (Monday and Tuesday) 29
Posters II (Thursday and Friday) 43
Monday, 13th February 2012 59
Tuesday, 14th February 2012 60
Wednesday, 15th February 2012 61
Thursday, 16th February 2012 62
Friday, 17th February 2012 63
Talks
Talks
A toolbox for quantum optics experiments with nanoparticles
Markus ArndtVienna Center for Quantum Science and Technology (VCQ),
Faculty of Physics, University of ViennaBoltzmanngasse 5, 1090 Vienna, Austria
I will discuss the state of the art in quantum optics with clusters and molecules.New beam preparation, detection and coherent manipulation schemes allowus to study fundamental quantum physics in a high mass regime and toexploit de Broglie coherence to quantify internal electronic and magneticproperties of highly complex compounds.
Quantum optomechanics: exploring the interface betweenquantum physics and gravity?
Markus AspelmeyerVienna Center for Quantum Science and Technology (VCQ),
Faculty of Physics, University of ViennaBoltzmanngasse 5, 1090 Vienna, Austria
Quantum optics provides a high-precision toolbox to enter and to controlthe quantum regime of the motion of massive mechanical objects. This opensthe door to a hitherto untested parameter regime of macroscopic quantumphysics. Due to the large available mass range – from picograms in nanome-chanical waveguides to kilograms in mirrors for gravitational wave detection– it becomes possible to explore the fascinating interface between quantumphysics and (quantum) gravity in table-top quantum optics experiments. Iwill discuss a few examples.
3
Talks
Engineering and detecting Majorana fermions with cold atoms
Mikhail BaranovInstitut für Theoretische Physik, Universität Innsbruck & IQOQI
Technikerstraße 25, 6020 Innsbruck, [email protected]
We introduce a one-dimensional system of fermionic atoms in an optical lat-tice, whose phase diagram includes topological states of different symmetryclasses. These states can be identified by their zero-energy edge modes whichare Majorana fermions. We propose several universal methods of detectingthe Majorana edge states, based on their genuine features: zero-energy, lo-calized character of the wave functions, and induced non-local fermionic cor-relations.
Quantum Information Processing with Trapped Ca+ Ions
Rainer BlattInstitut für Experimentalphysik, Universität Innsbruck & IQOQI
Technikerstraße 25, 6020 Innsbruck, [email protected]
Trapped strings of cold ions provide an ideal system for quantum informationprocessing. We will report on our recent progress, in particular, the genera-tion of GHZ states of up to 14 ion qubits, the realization of an open-systemquantum simulator, digital quantum simulations of interacting spin-1/2 sys-tems, and the quantum error correction of a measurement projection.
4
Talks
Quantum computation and simulation in non-equilibrium systems
Hans BriegelInstitut für Theoretische Physik, Universität Innsbruck & IQOQI
Technikerstraße 25, 6020 Innsbruck, [email protected]
Rare earth spin ensemble to interface microwave and optical
Pavel BushevKarlsruher Institut für Technologie
Wolfgang-Gaede-Straße 1, 76131 Karlsruhe, [email protected]
Interfacing superconducting quantum processors, working in the GHz fre-quency range, with optical quantum networks and atomic qubits is a chal-lenging task for the implementation of distributed quantum information pro-cessing as well as for quantum communication. Using spin ensembles of rareearth ions provides an excellent opportunity to bridge microwave and opticaldomains at the quantum level.
5
Talks
Ultrastrong coupling cavity and circuit QED
Cristiano CiutiUniversité Paris Diderot
10, rue Alice Domon et Léonie Duquet, 75013 Paris, [email protected]
I will review recent advances in the field of ultrastrong coupling cavity andcircuit QED with a particular emphasis on collective excitation properties,vacuum (ground state) degeneracies and symmetries, as well as their impacton quantum decoherence. The ultrastrong coupling regime, now accessible instate-of-the-art semiconductor microcavities and superconducting quantumcircuits, is achieved when the vacuum Rabi coupling becomes comparableor larger than the photon and electronic transition frequencies, allowing toexplore a rich variety of spin-boson systems.
The two-dimensional Bose gas: thermodynamics and beyond
Jean DalibardLaboratoire Kastler Brossel,
Département de physique de l’Ecole normale supérieure24, rue Lhomond, 75005 Paris, France
A two-dimensional Bose fluid is a remarkably rich many-body system, whichallows one to revisit several features of quantum statistical physics. Firstly,the role of thermal fluctuations is enhanced compared to the 3D case, whichdestroys the ordered state associated with Bose-Einstein condensation. How-ever interactions between particles can still cause a superfluid transition,thanks to the Berezinskii-Kosterlitz-Thouless mechanism. Secondly, a weaklyinteracting Bose fluid in 2D must be scale-invariant, a remarkable featurethat manifests itself in the very simple form taken by the equation of stateof the fluid. In this talk I will present recent experimental progress in the in-vestigation of 2D atomic gases, which provide a nice illustration of the mainfeatures of low dimensional many-body physics.
6
Talks
Topology by Dissipation: Majorana Fermions in One and TwoDimensions
Sebastian DiehlInstitut für Theoretische Physik, Universität Innsbruck & IQOQI
Technikerstraße 25, 6020 Innsbruck, [email protected]
We discuss the emergence of topological phases in stationary states of engi-neered driven-dissipative dynamics for fermions. The key feature for a dissi-pative quantum wire is the existence of Majorana edge modes, representing anon-local decoherence free subspace. The dissipative Majorana modes shownon-abelian exchange statistics, and their topological origin is granted by anontrivial winding number of the system density matrix. In two dimensions, adissipation specific violation of bulk-edge correspondence allows for the exis-tence of single isolated Majorana modes despite a vanishing bulk topologicalinvariant.
Critical exponent of a quantum-noise-driven phase transition:The open-system Dicke model
Peter DomokosResearch Institute for Solid State Physics and Optics
Konkoly-Thege Miklós út 29-33, 1121 Budapest, [email protected]
The quantum phase transition of the Dicke model has been observed recentlyin a system formed by motional excitations of a laser-driven BEC coupledto an optical cavity [Baumann et al., Nature 464, 1301 (2010)]. The cavity-based system is intrinsically open: photons leak out of the cavity where theyare detected. Even at zero temperature, the continuous weak measurementof the photon number leads to an irreversible dynamics toward a steadystate. In the framework of a generalized Bogoliubov theory, we show that thesteady state exhibits a dynamical quantum phase transition. We find thatthe critical point and the mean field are only slightly modified with respect tothe phase transition in the ground state. However, the critical exponents ofthe singular quantum correlations are significantly different in the two cases.There is also a drastic modification of the atom-field entanglement, since thedivergence of the logarithmic negativity of the ground state at the criticalpoint is suppressed and a finite entanglement is found in the steady state.
7
Talks
New Directions in Matterwave Interferometry
Wolfgang ErtmerInstitute for Quantum Optics, Leibniz Universität Hannover
Welfengarten 1, 30167 Hannover, [email protected]
The rapid progress in the generation and manipulation of ultracold atoms hasopened new perspectives for interferometry with atomic matter waves. Onthe verge from proof-of-principle experiments to leading-edge precision sen-sors, atom interfero-meters offer exciting possibilities for future gyroscopes,accelerometers, gravity sensors, atomic clocks and even gravitational wavedetectors. We will present our re-cent advances to increase the sensitivity ofsuch devices.
In general, atom interferometers profit from long interrogation times. Suchlong interrogation times can be reached by expanding the free fall of theatomic sample. Within the QUANTUS collaboration, we are able to pro-duce atomic Bose-Einstein condensates in the microgravity environment ofthe Bremen drop tower. In this apparatus, the implementation of a three-dimensional atom-optical lens has recently allowed for interferometric se-quences of 700 ms during free fall. For compact sensors, long interrogationtimes have to be reached in trapped ensembles. We have employed a methodcalled Spin Self-Rephasing to demonstrate coherence times of up to 20 s inan optically trapped Rubidium sample. At constant interrogation time, atominterferometers are restricted by the shot noise limit if operated with unen-tangled atomic samples. We will summarize our recent progress towards thegeneration of useful entanglement for interferometry beyond the shot noiselimit.
8
Talks
Towards the production of a dipolar RbCs quantum gas
Francesca FerlainoInstitut für Experimentalphysik, Universität Innsbruck
Technikerstraße 25, 6020 Innsbruck, [email protected]
Ultracold atomic quantum gases have exceptional properties and offer anideal test-bed to elucidate intriguing phenomena of modern quantum physics.The great appeal of such systems stems from the possibility to control almoston demand the interaction between the particles. A very appealing researchline is provided by ultracold dipolar quantum gases, which are expected toexhibit novel many-body quantum phases as a result of the long-range andanisotropic dipole-dipole interaction. For our Rb-Cs mixture experiment thefocus is on the creation of a bosonic quantum gas of polar ground-state RbCsmolecules from double Bose-Einstein condensate (BEC) of Rb and Cs. Inpreliminary experiments, we produce rovibrational ground-state moleculeswith a transfer efficiencies up to 50% by first associating RbCs Feshbachmolecules and subsequently performing stimulated adiabatic Raman trans-fer (STIRAP). For the STIRAP transfer it is crucial to have knowledge ofboth the intermediate electronically excited levels and the ground-state bind-ing energy, which we have carefully measured by performing high-resolutionmolecular spectroscopy. Finally, we create a double Mott-insulator state hav-ing precisely one atom of each species at each site of the optical lattice. Adouble Mott insulator will provide us with optimal stating conditions forhighly efficient STIRAP transfer and for accessing the regime of stronglycorrelated dipoles.
Strongly interacting Fermi gases
Rudolf GrimmInstitut für Experimentalphysik, Universität Innsbruck & IQOQI
Technikerstraße 25, 6020 Innsbruck, [email protected]
9
Talks
Non-Classical States of Nano-Mechanical Oscillators
Michael HartmannTechnische Universität München
James-Franck-Straße, 85748 Garching, [email protected]
I will discuss optomechanical schemes to drive nanomechanical resonatorsinto stationary states that are entangled or have negative Wigner functions.The latter is achieved by electrostatically enhancing the resonator’s intrinsicnonlinearity until it exceeds the cavity line-width. This approach offers newpossibilities for manipulating nanomechanical resonators.
Topological optical lattice & sub-recoil cavity cooling
Andreas HemmerichUniversität Hamburg, Institut für Laser-Physik
Luruper Chaussee 149, 22761 Hamburg, [email protected]
I will discuss the observations of topological features in the band structureof an optical square lattice and sub-recoil cavity cooling at particle densitiesincompatible with conventional laser cooling.
10
Talks
Is the electron round?
Ed HindsCentre for Cold Matter, The Blackett Laboratory, Imperial College London
Prince Consort Rd, SW7 2BW London, United [email protected]
We have made a new measurement of the electron’s electric dipole moment(EDM) using a beam of YbF molecules [1]. By measuring atto-eV energyshifts in a molecule, this experiment probes new physics at the tera-eV en-ergy scale. According to the standard model, this EDM is de ≈ 10−38e cm– some eleven orders of magnitude below the current experimental limit.However, most extensions to the standard model predict much larger values,potentially accessible to measurement [2]. Hence, the search for the electronEDM is a search for physics beyond the standard model. I will describe ourexperimental method, our current results and their implications for particlephysics. I will also note the prospects for further major improvement in sen-sitivity.[1] J. J. Hudson, D. M. Kara, I. J. Smallman, B. E. Sauer, M. R. Tarbutt,E. A. Hinds, “Improved measurement of the shape of the electron”, Nature473, 493 (2011). doi:10.1038/nature10104[2] E. D. Commins, “Electric dipole moments of leptons”, in Advances inAtomic, Molecular, and Optical Physics, Vol. 40, B. Bederson and H. Walther(Eds.), Academic Press, New York, pp. 1-56 (1999).
Deterministic few-fermion systems
Selim JochimPhysikalisches Institut, Universität Heidelberg
Philosophenweg 12, 69117 Heidelberg, [email protected]
We have prepared samples of 1-10 fermionic atoms in a tightly confining trap.In first experiments we have studied a repulsively interacting two-particlesystem and observed fermionization of two distinguishable fermions. Fur-thermore we have studied pair tunneling out of an attractively interactingsystem, revealing a strong odd-even effect.
11
Talks
Compressed quantum simulation of the Ising model
Barbara KrausInstitut für Theoretische Physik, Universität Innsbruck
Technikerstraße 25, 6020 Innsbruck, [email protected]
Recently it has been shown that a match gate circuit running onn qubits canbe compressed to a universal quantum computation on log(n)+3 qubits. Here,we show how this compression can be employed to simulate the Ising interac-tion of a 1D–chain consisting of n qubits using a universal quantum computerrunning on log(n) qubits. We demonstrate how the adiabatic evolution canbe realized on this exponentially smaller system and how the magnetization,which displays a quantum phase transition, can be measured. This showsthat the quantum phase transition of very large systems can be observedexperimentally with current technology.
The Casimir Effect: Quantum Optics in Vacuum
Astrid LambrechtLaboratoire Kastler Brossel, ENS, UPMC and CNRS
4, place Jussieu, 75252 Paris, [email protected]
The Casimir effect is a jewel with many facets: It is an observable mechan-ical effect of vacuum fluctuations and has strong relations with atomic andmolecular physics, condensed matter and surface physics, chemical and bi-ological physics, micro- and nano-technology. Precise experiments are per-formed between flat or nano-structured plates and a sphere. The talk willsummarize recent developments in the field of Casimir physics and give thecurrent status in the comparison between theory and experiment after yearsof improvements in both measurements as well as theoretical evaluations.
12
Talks
SU(N) Quantum Magnetism
Andreas LäuchliInstitut für Theoretische Physik, Universität Innsbruck
Technikerstraße 25, 6020 Innsbruck, [email protected]
Using infinite projected entangled-pair states (iPEPS), exact diagonalization,and flavor-wave theory, we investigate SU(N) Heisenberg models on variouslattices and uncover SU(N) symmetry breaking magnetic phases with pecu-liar spatial structures, SU(N) generalizations of valence bond singlet statesand possibly novel spin liquid states at larger N .
From coherent many-body dynamics to a Fokker-Planck equation
Igor LesanovskyUniversity of Nottingham
University Park, NG7 2RD Nottingham, United [email protected]
The description of the thermalization dynamics of closed quantum systemsis prohibitively complex. Here, we present a spin model - in one and twodimensions - for which we can analytically show that the evolution into ther-mal equilibrium is governed by a Fokker-Planck equation derived from theunderlying quantum dynamics. We do not rely on a formal distinction ofbath and system DOFs.
13
Talks
Cavity QED with Magnetically Coupled Collective Spin States
Johannes MajerTU Wien
Stadionallee 2, 1020 Wien, [email protected]
We present measurements of the strong coupling between an ensemble ofnitrogen-vacancy center electron spins in diamond and a superconductingmicrowave coplanar waveguide resonator. We observe hyperfine coupling to13C nuclear spins and make use of the dispersive shift of the cavity resonancefrequency to measure the relaxation time of the NV centers.
Quantum Networks of Trapped Atomic Ions
Christopher MonroeJoint Quantum Institute and University of Maryland
College Park, MD 20742-4111, [email protected]
Trapped atomic ions are standards for quantum information processing, andcan be networked through phonon or photon quantum buses. I present re-cent work on both fronts, including the quantum simulation of magnetismwith up to 16 trapped ion qubits and the progress toward multiplexing withprobabilistic photonic interfaces.
14
Talks
Realization of a long-range interacting quantum gas
Rafael MottlQuantum Optics Group, ETH Zürich
Schafmattstrasse 16, 8093 Zurich, [email protected]
We realize the Dicke quantum phase transition in a BEC-cavity system. Theopen cavity allows time-resolved information about fluctuations in this long-range interacting quantum gas. We measure increased density fluctuationsand mode softening in the excitation spectrum. Quantum fluctuations dom-inate a wide region below the phase transition. We reveal the role of atomicand photonic dissipation.
Ion-photon entanglement and state mapping in an optical cavity
Tracy NorthupInstitut für Experimentalphysik, Universität Innsbruck
Technikerstraße 25, 6020 Innsbruck, [email protected]
Quantum networks require an interface between light and matter; here, wepresent two recent steps toward a cavity-based interface for trapped ions.First, fully tunable entanglement is generated between a single ion and thepolarization state of a cavity photon. Second, a quantum superposition ismapped from ion to photon and characterized via process tomography. Ad-ditionally, prospects for single-ion strong coupling are discussed.
15
Talks
Multi-qubit microwave quantum logic and precisionmeasurements with trapped ions
Christian OspelkausInstitute of Quantum Optics, Leibniz Universität Hannover
Welfengarten 1, 30167 Hannover, [email protected]
Most current schemes for Quantum Information Processing (QIP) with trapped ions im-plement quantum logic gates through a laser-induced state-dependent interaction betweenions held in the same trap. We describe experiments in surface-electrode traps performed atNIST that explore alternative ideas to these well-established techniques. In particular, wedemonstrate Coulomb coupling between two ions held in individual traps separated by 40µm [Nature 471, 196 (2011)]. The interaction between the ions is seen as an avoided cross-ing in the motional frequencies of the system. We observe oscillations of energy between thetwo mechanical oscillators at the single quantum level by measuring the time-dependentmotional state populations of one of the ions. Beyond the fundamental analog of this quan-tum system to the classical system of two pendulums coupled via a spring, these resultsopen up new experimental perspectives for quantum simulation, novel entangling schemesfor QIP and for precision spectroscopy.
Furthermore, we experimentally demonstrate a microwave near-field approach to quan-tum logic gates with trapped ions, where oscillating magnetic fields and field gradients frommicrowave currents propagating in the electrodes of a surface-electrode trap are used toimplement single- and multi-qubit quantum logic gates. This approach has several im-portant potential advantages with respect to operation fidelity and reduced complexity.With randomized benchmarking, we experimentally demonstrate that this technique en-ables single-qubit gates with an infidelity of 2.0(2) · 10−5, below some estimates for fault-tolerant quantum information processing. In a different apparatus, to demonstrate thespeed of single-qubit operations, we show that it is possible to implement pi pulses withdurations less than 20 ns. We show how gradients of the microwave field enable couplingbetween motional and internal states of the ions and implement motional sideband tran-sitions and microwave sideband cooling for a two-ion rocking mode. We demonstrate therealization of an entangling two-qubit quantum logic gate using a bichromatic microwavemagnetic gradient field [Nature 476, 181 (2011)]. All operations are implemented on amagnetic-field insensitive qubit transition.
We discuss experiments which are currently being set up at Leibniz Universität Han-
nover and at PTB, Braunschweig, to apply these ideas to quantum simulation and to tests
of discrete symmetries, in particular to quantum logic spectroscopy of single (anti-)protons
[Heinzen and Wineland, PRA 42, 2977 (1990) and Wineland et al., J. Res. NIST 103, 259
(1998)].
Work at NIST has been supported by IARPA, DARPA, NSA, ONR, and the NIST Quan-
tum Information Program. Work at Hannover is supported by the cluster of excellence
QUEST, Leibniz Universität Hannover and PTB, Braunschweig.
16
Talks
Towards strong coupling between light and electronics
Eugene PolzikNiels Bohr Institutet, Københavns UniversitetBlegdamsvej 17, 2100 København Ø, Denmark
Mechanical oscillators can couple disparate quantum systems. A dielectricmembrane couples to photons via radiation pressure, and at the same timecan couple capacitively to excitations in an LC circuit. A semiconductormembrane can be coupled to light via electron-hole mediated stress. Per-spectives of such systems for quantum limited sensing and state transfer willbe reviewed.
Optomechanical systems in the single photon strong coupling
Peter RablIQOQI Austrian Academy of Sciences
Technikerstraße 21a, 6020 Innsbruck, [email protected]
In this talk I discuss the implementation of single photon nonlinearities instrongly coupled optomechanical (OM) systems. I first describe the basicphysical processes, which lead to photon blockade effects in single and multi-mode OM systems and show then, how such interactions could serve as a basicbuilding block for various optical quantum communication and informationprocessing applications.
17
Talks
Coherent Photon Conversion (CPC) for Scalable Non-LinearOptical Quantum Computing
Sven RamelowVienna Center for Quantum Science and Technology (VCQ),
Faculty of Physics, University of Vienna & IQOQIBoltzmanngasse 5, 1090 Vienna, Austria
Single photons make excellent qubits, but current schemes for photonic quan-tum information processing are inefficient. Our new scheme CPC offers a newway for efficient generation and processing of complex multi-photon statesenabling scalable optical quantum computing (Nature 478, 360, 2011). Ourfirst experiments study how to reach the deterministic regime with currenttechnology. Interestingly, the scheme could be applied to optomechanical orsuperconducting systems.
Trapping and Interfacing Cold Neutral Atoms Using OpticalNanofibers
Arno RauschenbeutelTechnische Universität Wien - Atominstitut
Stadionallee 2, 1020 Vienna, [email protected]
We trap and optically interface cold cesium atoms in the evanescent fieldaround an optical nanofiber. This technique enables the integration of laser-cooled atomic ensembles into fiber networks. Moreover, it is ideally suitedto the realization of hybrid quantum systems. And finally, it allows one torealize exotic trapping geometries.
18
Talks
Quantum Optical Quantum Networks
Gerhard RempeMax-Planck-Institut für Quantenoptik
Hans-Kopfermann-Straße 1, 85748 Garching, [email protected]
A single atom strongly coupled to an optical resonator is an ideal test bedfor both, the investigation of fundamental quantum nonlinear effects of light-matter interaction [1] as well as the implementation of a promising quantumtechnology [2,3]. The talk highlights two recent cavity QED experiments: Oneaddresses the hitherto unexplored regime of strong cavity driving, where aphoton stream with a pronounced time asymmetry can be generated evenunder continuous-wave excitation [4]. This asymmetry occurs on the timescale of the coherent energy exchange between the drive laser and the cavityQED system. The other experiment drives the atom and generates a pulsedstream of single photons which are employed to excite a second cavity QEDsystem [5]. This allows us to transfer the quantum state of a local atomto a remote atom, or vice versa, and entangle two distant atoms on thepush of a button, with high fidelity and unprecedented efficiency. The twoconnected cavity QED systems constitute a macroscopic quantum object withall properties of a scalable quantum network.[1] A. Ourjoumtsev et al., Nature 474, 623 (2011)[2] M. Mücke et al., Nature 465, 755 (2010)[3] H.P. Specht et al., Nature 473, 190 (2011)[4] M. Koch et al., Phys. Rev. Lett. 107, 023601 (2011)[5] S. Ritter et al., in preparation
Mesoscopic many-body systems on atoms chips
Jörg SchmiedmayerTU Wien, Atominstitut
Stadionallee 2, 1020 Vienna, [email protected]
19
Talks
Nuclear Physics in a solid-state system
Thorsten SchummTU Wien, Atominstitut
Stadionallee 2, 1020 Vienna, [email protected]
Th-229 has a very low-energy excited nuclear state at 7.6eV. The narrowtransition line width qualifies it for a new solid state nuclear atomic clock. Iwill review the quest for the nuclear transition and discuss experimental ap-proaches. Electronic structure calculations allow to estimate transition shifts,experimental progress towards sample crystals and first characterizations arepresented.
Quantum Simulation of Frustrated Classical Magnetism inTriangular Optical Lattices
Klaus SengstockInstitut für Laserphysik und
Zentrum für Optische Quantentechnologien, Universität HamburgLuruper Chaussee 149, 22167 Hamburg, Germany
Magnetism plays a key role in modern technology and stimulates researchin several branches of condensed matter physics. Although the theory ofclassical magnetism is well developed, the demonstration of a widely tunableexperimental system has remained an elusive goal. We present the realizationof a large-scale simulator for classical magnetism on a triangular lattice byexploiting the particular properties of a quantum system [1]. We use the mo-tional degrees of freedom of atoms trapped in an optical lattice to simulate alarge variety of magnetic phases: ferromagnetic, antiferromagnetic, and evenfrustrated spin configurations. A rich phase diagram is revealed with differ-ent types of phase transitions. Our results provide a route to study highlydebated phases like spin-liquids as well as the dynamics of quantum phasetransitions. [1] Struck et al., Science, 21 July 2011 (10.1126/science.1207239)
20
Talks
Time multiplexed photonic quantum walks
Christine SilberhornUniversität Paderborn, Fakultät für Naturwissenschaften, Department Physik
Warburger Straße 100, 33098 Paderborn, [email protected]
Linear optical networks, which comprise a large number of optical modes havebeen investigated intensively over the last two decades in various theoreticalproposals. Most recently their relevance for studies of photonic quantumwalk systems has attracted attention, because they can be considered as astandard model to describe the dynamics of quantum particles in a discretizedenvironment and serve as a test bed for quantum algorithms. However theirexperimental realization requires setups with increasing complexity in termsof number of modes and control of the system parameters.
We employ time-multiplexing using pulsed light in combination with aspecific fiber loop geometry to demonstrate a fully coherent photonic quan-tum walk over 28 steps, corresponding to a network of over four hundred beamsplitters. By introducing a fast optical modulator we can precisely control thedynamics of the photonic walk. In particular we studied experimentally thepropagation of a quantum particle in the presence of different types of en-gineered noise. By artificially introducing random fluctuations with differentcharacteristics we could suppress the interference resulting in a classical ran-dom walk, simulate static disorder, observe Anderson localization, and studythe controlled transition between both scenarios.
Fast CNT memory, and Rabi splitting for surface plasmons
Päivi TörmäAalto University
P.O.Box 15100, 76 Aalto, [email protected]
We demonstrate 100 ns write/erase speed of single-walled carbon nanotubefield-effect transistor memory elements (Nano Lett. 9, 643 (2009)), exceedingthe previous 10 ms speeds. We use atomic layer deposited hafnium oxideas a gate dielectric. We report on strong coupling between surface-plasmonpolaritons and Rhodamine 6G molecules with tunable Rabi splitting (Phys.Rev. Lett. 103, 053602 (2009))
21
Talks
Ab-initio simulation of ultracold atomic gases
Matthias TroyerInstitut für Theoretische Physik, ETH Zürich
Wolfgang-Pauli-Strasse 16, 8093 Zurich, [email protected]
The successful validation of experiments on bosons in optical lattices hasbeen followed by similar efforts for fermions. While for bosons direct numer-ically exact ab-initio simulations of quantum gases with millions of particlesare easily possible, fermions pose a bigger challenge. Supercomputer simula-tions using cluster extensions of dynamical mean field theory for the Hubbardmodel can accurately calculate properties of fermions in deep optical latticesat temperatures down to the Néel temperature. To simulate shallow opticallattices and non-equilibrium dynamics we have generalized Kohn-Sham den-sity functional theory (the workhorse for materials simulations) to ultracoldquantum gases and I will present first results for ground states and dynamicsof repulsively interacting fermions.
Simulation of Strongly Correlated Quantum Systems
Frank VerstraeteFakultät für Physik, Universität Wien
Boltzmanngasse 5, 1090 Vienna, [email protected]
22
Talks
Ultrafast all-optical switching by single photons
Thomas VolzETH Zürich
Wolfgang-Pauli-Strasse 16, 8093 Zurich, [email protected]
We present results on the observation of strong single-photon non-linearitiesin a strongly coupled quantum-dot cavity device on a chip. Strong quantumcorrelations between photons are observed and all-optical switching by sin-gle photons on picosecond timescales is demonstrated. The device presentedhere could form a building block of future high-bandwidth quantum-photonicnetworks.
23
Talks
Quantum Optics with Superconducting Circuits: ExploringPropagating Microwave Photons
Andreas WallraffETH Zürich
Schafmattstrasse 16, 8093 Zurich, [email protected]
Using modern micro and nano-fabrication techniques combined with super-conducting materials we realize quantum electronic circuits. We create, store,and manipulate individual microwave photons on a chip. The strong inter-action of photons with superconducting quantum two-level systems allowsus to probe fundamental quantum effects of light and also to develop com-ponents for applications in quantum information technology. In particular, Iwill discuss experiments in which we demonstrate first and second-order cor-relation function measurements of microwave frequency single photon sourcesintegrated on the same chip with 50/50 beam splitters. In the absence of ef-ficient single photon counters at microwave frequencies, linear amplifiers andquadrature amplitude detectors are used for correlation measurements [1].Our data clearly displays single photon coherence in first-order and photonantibunching in second-order correlation function measurements of the prop-agating fields [2]. We have also used these techniques to investigate photonblockade in the context of cavity QED [3] and to reconstruct the Wignerfunction of itinerant single photon Fock states and their superposition withthe vacuum [4]. To perform these measurements we have developed efficientmethods to separate the detected single photon signal from the noise addedby the amplifier by analyzing the moments of the measured amplitude distri-bution up to 4th order. Current experiments aim at using parametric ampli-fiers, for which we have observed two-mode squeezing [5], to perform nearlyquantum limited simultaneous detection of both quadrature amplitudes ofelectromagnetic fields. The techniques and methods demonstrated in thiswork may find application in future linear quantum optics and quantum in-formation processing experiments.[1] M. P. da Silva et al., Phys. Rev. A 82, 043804 (2010)[2] D. Bozyigit et al., Nat. Phys. 7, 154 (2011)[3] C. Lang et al., Phys. Rev Lett. 106, 243601 (2011)[4] C. Eichler et al., Phys. Rev Lett. 106, 220503 (2011)[5] C. Eichler et al., Phys. Rev. Lett. 107, 113601 (2011)
24
Talks
Photonic Quantum Computations, Simulations and Networks
Philip WaltherFaculty of Physics, University of ViennaBoltzmanngasse 5, 1090 Vienna, Austria
During the last few years the degree of control over photonic multi-particleentanglement has improved substantially and allows for not only overcomingthe random nature of spontaneous emission sources, but also for the quantumsimulation of other quantum systems. Here, I will also present the simulationof four spin-1/2 particles interacting via any Heisenberg-type Hamiltonian.Moreover, recent experimental and theoretical progress, using the concepts ofmeasurement-based quantum computation, indicates that photons are bestsuited for quantum networks. I will also present results for the realizationfor such a client-server environment, where quantum information is securelycommunicated and computed such that the privacy of the client is preserved.
Advanced entangled photon pair sources
Gregor WeihsInstitut für Experimentalphysik, Universität Innsbruck
Technikerstraße 25d, 6020 Innsbruck, [email protected]
Entangled photon pairs are the work horses of optical quantum informationprocessing. For various tasks we require specific properties of our sources. Iwill report on the first realization of an ultrafast pulsed parametric down-conversion source with superior properties and on the successful coherentexcitation of single InAs quantum dots for time-bin entanglement generation.
25
Talks
Multiphoton entanglement analysis
Harald WeinfurterFaculty of Physics, LMU München
Schellingstraße 4/III, 80799 München, [email protected]
We describe several tools to observe and to efficiently analyse multipartiteentanglement for SPDC-photons and to how to use it for quantum metrology.
Quantum gates and dressed states with spin-spin coupled ions
Christof WunderlichUniversität Siegen
Department Physik, 57068 Siegen, [email protected]
We report on two-qubit quantum gates using magnetic gradient-induced spin-spin coupling between thermally excited trapped ions. Single spins are ad-dressed and coherently manipulated using microwave radiation. Further ex-periments show that microwave-dressed states enhance the coherence time ofspin states and allow for fast quantum gates [N. Timoney et al., Nature 476,185 (2011)].
26
Talks
Photon Entanglement Experiments in Larger Real and HilbertSpaces
Anton ZeilingerVienna Center for Quantum Science and Technology (VCQ),
Faculty of Physics, University of Vienna & IQOQIBoltzmanngasse 5, 1090 Vienna, Austria
27
Posters I (Monday and Tuesday)
Posters I (Monday and Tuesday)
Entanglement spectra in quantum systems
Vincenzo AlbaMax-Planck-Institut für Physik komplexer Systeme
Nöthnitzer Straße 38, 1187 Dresden, [email protected]
We study the entanglement spectrum of several two dimensional systems (2DBose-Hubbard, XXZ, tight binding systems). We found a physical descriptionof the low part of the ES in terms of effective hamiltonians (entanglementhamiltonians). For the 2D Bose Hubbard we also characterized the behaviorof the ES in the superfluid phase, where we found clear signature of thecondensate wavefunction.
The Oxford planar ion trap project
David AllcockClarendon Laboratory, University of Oxford
Parks Road, OX1 3PU Oxford, [email protected]
Testing of microfabricated ion traps in collaboration with Sandia NationalLaboratories [1]. Reduction of anomalous ion heating by pulsed laser clean-ing of the trap structure [2]. 43Ca+ hyperfine clock qubits in the intermedi-ate field regime. Development of a trap for two-qubit entanglement drivenby microwave near-fields. [1] Allcock et al arXiv:1105.4864 [2] Allcock et alarXiv:1110.1486
29
Posters I (Monday and Tuesday)
Qubits in Fluctuating Fields
Yehuda BandBen-Gurion University
Depts. of Chemistry & Physics, 84105 Beer-Sheva, [email protected]
The temporal evolution of two-level systems in the presence of noise is afundamental process that occurs in a wide range of phenomena. We developthe calculus to treat such processes for white noise and colored noise anduse it to calculate the temporal behavior of expectation value of the spindescribing one such particle and the correlation of two such spins.
Dephasing of Rydberg excitations for entanglement generation
Francesco BarianiGeorgia Institute of Technology
837 State Street, 30332 - 0430 Atlanta, [email protected]
We propose an approach to fast entanglement generation based on Ryd-berg dephasing of collective excitations (spin waves) in large, optically thickatomic ensembles. Long range resonant atomic interactions are induced bymicrowave mixing of opposite-parity Rydberg states. The dephasing mech-anism is shown to have favorable, approximately exponential, scaling forentanglement generation.
30
Posters I (Monday and Tuesday)
Experimental Demonstration of Blind Quantum Computing
Stefanie BarzUniversity of Vienna
Boltzmanngasse 5, 1090 Vienna, [email protected]
Quantum computers are expected to preserve the privacy of a computation.Here we show the first experimental demonstration of blind quantum com-puting where the input, computation, and output all remain unknown tothe computer. Our demonstration is crucial for future unconditionally securequantum cloud computing and might become a key ingredient for real-lifeapplications.
Study of a 1D bosonic Josephson junction
Tarik BerradaVCQ, Atominstitut
Stadionallee 2, 1020 Vienna, [email protected]
We realize a bosonic Josephson junction with coupled 1D quasi-condensates.Itsphysics is driven by the interplay between 1D fluctuations,interactions andtunnel coupling.We use RF dressing to shape elongated double-wells on anatom chip,and matter-wave interference experiments to probe the system.After having characterized its thermal equilibrium,we are now studying itsrich tunnelling dynamics.
31
Posters I (Monday and Tuesday)
AF correlations and entropy in ultracold lattice fermions
Nils BlümerInstitut für Physik
Staudingerweg 7, 55128 Mainz, [email protected]
Cooling below the critical entropy s = log(2)/2 appears as the main obstaclefor verifying antiferromagnetic (AF) signatures in ultracold fermions on op-tical lattices. Our calculations using DMFT, determinantal QMC, and Betheansatz reveal AF signatures in the double occupancy, spin correlations, andkinetic energy already at s ≤ log(2), with surprisingly universality regardingdimensionality.
Pair Superfluids in Constrained Bose Systems
Lars BonnesInstitut für Theoretische Physik, Universität Innsbruck
Technikerstraße 25, 6020 Innsbruck, [email protected]
We examine the equilibrium properties of lattice bosons with attractive on-site interactions in the presence of a three-body hard-core constraint thatstabilizes the system against collapse and gives rise to a dimer superfluidphase formed by virtual hopping processes of boson pairs. Employing quan-tum Monte Carlo simulations, the ground state phase diagram of this systemon the square lattice is analyzed. In particular, we study the quantum phasetransition between the atomic and dimer superfluid regime and analyze thenature of the superfluid-insulator transitions. Evidence is provided for theexistence of a tricritical point along the saturation transition line, where thetransition changes from being first-order to a continuous transition of thedilute bose gas of holes. The Berzinskii-Kosterlitz-Thouless transition fromthe dimer superfluid to the normal fluid is found to be consistent with ananomalous stiffness jump, as expected from the unbinding of half-vortices.
32
Posters I (Monday and Tuesday)
A Collective Ion-Photon Interface
Marko CetinaIQOQI
Technikerstraße 21a, 6020 Innsbruck, [email protected]
We trap linear chains of Yb ions in a microfabricated surface-electrode RFtrap inside the mode of a medium-finesse optical cavity. The cavity is used toanalyze the spectrum of the ions’ near-resonance fluorescence, demonstrat-ing ion-cavity coupling. Our system could be used to store photons in thecollective states of individually-addressable ions (Lamata et al., Phys. Rev.Lett. 107, 030501).
Linear-zigzag transition in a quantum potential
Cecilia CormickSaarland University
University Campus Gebäude E2.6, 66041 Saarbrücken, [email protected]
We study the dynamics of a chain of ultracold ions in a pumped standing-wave optical cavity, focusing on the case when the chain is close to the linear-zigzag structural transition. We analyze how to obtain information about theion chain through the light at the cavity output, and show that the back-action of the cavity field on the ions can qualitatively modify the characterof the transition.
33
Posters I (Monday and Tuesday)
Complete set of operational measures for the characterization of3-qubit entanglement
Julio De VicenteInstitut für Theoretische Physik, Universität Innsbruck
Technikerstraße 25, 6020 Innsbruck, [email protected]
We characterize the entanglement contained in a pure three–qubit state viaoperational entanglement measures. To this end we derive a new decomposi-tion for arbitrary 3–qubit states which is characterized by five parameters (upto local unitary operations). We show that these parameters are uniquely de-termined by bipartite entanglement measures. These quantities measure onthe one hand the entanglement required to generate the state and on theother hand the entanglement contained in the state and have a clear physicalmeaning.
Quantum interference of clusters in the OTIMA Interferometer
Nadine DörreUniversity of Vienna
Boltzmanngasse 5, 1090 Vienna, [email protected]
We discuss the principle of the recently established OTIMA interferometerwhich uses three pulsed laser ionization gratings to the show the quantumbehavior of clusters of atoms and molecules. We will show the first resultsand give an overview on future prospects of this experiment.
34
Posters I (Monday and Tuesday)
Coherent all-optical cooling schemes for atoms and molecules
Alexander DunningUniversity of Southampton
Building 46, Highfield, SO17 1BJ Southampton, United [email protected]
We describe an experimental setup for the coherent manipulation of hyperfinestates in ultracold Rubidium-85 using tailored coherent Raman pulses, anddiscuss its application in proposed schemes for the interferometric cooling ofatoms and the coherent amplification of the optical scattering force, with aview to extending such schemes to the cooling of molecular beams.
Ultracold ytterbium for state-dependent optical lattices
Simon FöllingLMU München
Schellingstraße 4, 80799 Muenchen, [email protected]
The metastable excited states of alkaline earth-like metals enables new ap-proaches for the design of state-dependent optical lattices with low photonscattering rates. We present the state of our new setup for the realization ofdegenerate Yb ensembles in state-dependent optical potentials.
35
Posters I (Monday and Tuesday)
Creation of optical flux lattices using Raman transitions
Juzeliunas GediminasVilnius University
A. Gostauto 12, 1108 Vilnius, [email protected]
Recently N. R. Cooper showed that an artificial magnetic flux over for ultra-cold atoms can be increased using the optical flux lattices. Here we considera realistic scheme of creating a square optical flux lattice using Raman tran-sitions induced by a set of properly chosen polarization-dependent opticalstanding waves with a time-phase difference (G. Juzeliunas and I.B. Spiel-man, in preparation).
Atomic Rydberg Reservoirs for Polar Molecules
Alexander GlätzleInstitut für Theoretische Physik, Universität Innsbruck
Technikerstraße 25, 6020 Innsbruck, [email protected]
We engineer interaction potentials between Rydberg atoms and polar molecules,to achieve direct cooling of generic polar molecules. The designed reservoirof atoms has potentially useful properties: (i) strong repulsive shields protectfrom inelastic collisions and (ii) large elastic scattering cross sections leadto rapid thermalization. Moreover, (iii) we discuss a dissipative (inelastic)collision where a spontaneously emitted photon carries away energy similarto a “collisional Sisyphus” effect, thus providing a significant energy loss ina single collision.
36
Posters I (Monday and Tuesday)
Coherent amplification of the optical scattering force
Rachel GregoryUniversity of Southampton
44, Shakespeare Avenue, SO17 2GY Southampton, United [email protected]
Coherent amplification of the optical scattering force can be achieved bythe application of alternately-propagating pi pulses; a greater momentumdifference can be introduced before spontaneous decay.A tailored series ofpulses improves the speed of cooling and the number of spontaneous decaysincurred.We describe an experimental setup for the implementation of thisscheme in Rubidium-85.
Quantum Kinetic Theory of Polarizable Particles in a Cavity
Tobias GrießerInstitut für Theoretische Physik, Universität Innsbruck
Technikerstraße 25, 6020 Innsbruck, [email protected]
A recently derived master equation for the reduced one-body density matrixof polarizable bosons in a cavity, valid both above and below the selforgani-sation threshold, is presented and discussed.
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Posters I (Monday and Tuesday)
Entanglement generation of ions by single-photon detection
Markus HennrichInstitut für Experimentalphysik, Universität Innsbruck
Technikerstraße 25, 6020 Innsbruck, [email protected]
The generation of distant entanglement of single atoms is an essential prim-itive for quantum networks. Experimental realizations generally rely on twophoton detection. Cabrillo’s protocol based on single photon detection couldsignificantly improve the entanglement rate. We report on the experimentalrealization of Cabrillo’s scheme generating local entanglement of two Ba ionswithin one trap.
A nonlinear Interferometer by four wave mixing
Florian HudelistEast China Normal University
zhongshanbeilu 3671/626/601, 200062 Shanghai, [email protected]
I introduce a nonlinear MZ interferometer formed by two four wave mixingprocesses in rubidium vapour instead of beam splitters. The beams of the twoarms are the signal and idler of the FWM process. In the interferometer thetwo beams are entangled by quadrature squeezing and can give accuraciesbetter than the shot noise limit. This is the first experimental realisation ofsuch an interferometer.
38
Posters I (Monday and Tuesday)
Universal Dynamical Decoupling of Qubits from Environment
Adilet ImambekovRice University
6100 Main street, MS 61, 77005 Houston, [email protected]
We will discuss the dynamical decoupling of multi-qubit states from envi-ronment. For a system of M qubits, the nested Uhrig dynamical decouplingsequence can suppress arbitrary decoherence to order N using (N + 1)2M
pulses. We will prove that this sequence is universal, i.e., it can restore thecoherence of M-qubit quantum system independent of the details of system-environment interaction.
Non-Linear Dynamics of Measured Bose-Einstein Condensates
Denis IvanovSt. Petersburg State University
Petrodvoretz, Ul’yanovskaya 5, 198504 Saint-Petersburg, [email protected]
Center-of-mass measurement of trapped interacting BEC is considered. It isshown that the atomic delocalization due to the measurement back actionis smaller for a strongly interacting gas. Atomic bunching as a result of themeasurement is predicted. It is also shown that for rather strong interactionsthe width of an instant density profile can become smaller than the ground-state cloud size.
39
Posters I (Monday and Tuesday)
Dynamics of a Repulsive Fermi-Fermi Mixture
Michael JagInstitut für Experimentalphysik, Universität Innsbruck & IQOQI
Technikerstraße 25, 6020 Innsbruck, [email protected]
There is a growing interest in repulsively interacting Fermi gas mixtures,which could enable investigations of correlated quantum systems. As repul-sive interactions in Fermi gases near a Feshbach resonance arise from thepresence of a loosely bound molecular state, they are always associated withdecay into bosonic molecules [1]. The interplay between repulsion and decayhas made the realization and understanding of repulsive Fermi systems chal-lenging [2, 3]. We investigate the dynamics of a strongly interacting 40K-6LiFermi-Fermi mixture on the repulsive side of an interspecies Feshbach reso-nance. For this purpose, we employ magnetic field ramps, RF spectroscopy,in-situ and time-of-flight imaging. Close to the resonance, we observe a staticbehavior of the K atomic population, redistribution of the Li density awayfrom the K cloud and an absence of the interaction-induced shifts in the dis-sociation RF spectra in the strongly interacting repulsive regime. In spite ofa strong initial atom loss, our results suggest that repulsive interactions arecrucial for the dynamics of our system.[1] D. Pekker, et al., Phys. Rev. Lett. 106, 050402 (2011).[2] G. Jo, et al., Science 325, 5947 (2009).[3] C. Sanner et al., arXiv:1108.2017
Two-photon excitation of biexciton in an InAs quantum dot
Harishankar JayakumarInstitut für Experimentalphysik, Universität Innsbruck
Technikerstraße 25d, 6020 Innsbruck, [email protected]
Semiconductor quantum information demands for use of systems which arecoherently excited. Here, we demonstrate resonant two photon excitation of abiexciton in a single InAs/GaAs self-assembled quantum dot in a microcavity.Results of coherence control measurements will also be presented.
40
Posters I (Monday and Tuesday)
Multi-dimensional optimization of an atom optics experiment
Stefan JöllenbeckIQ-Leibniz Universität Hanvoer
Welfengarten 1, 30167 Hannover, [email protected]
We present a Differential Evolution algorithm that automatically optimizeshighly correlated parameters of an experimental setup. This algorithm isshown to find a global optimum for up to 12 correlated parameters. It isrobust against local maxima and experimental noise. We demonstrate thealgorithm for the optimization of the parameters of a cold atom experimentbased on a mesoscopic atom chip.
Dipolar BEC in optical lattices
Mattia Jona-LasinioITP - Leibniz University Hannover
Appelstraße 2, 30167 Hannover, [email protected]
I will present recent theoretical and experimental results on the stability ofa dipolar BEC in a 1D optical lattice. The presence of the lattice highlightsthe long range character of the dipole-dipole potential. I will also discuss thepossible observation of roton instabilities in this system.
41
Posters I (Monday and Tuesday)
Entanglement creation in ultracold gases
Carsten KlemptLeibniz Universität Hannover
Welfengarten 1, 30159 Hannover, [email protected]
Two processes for the creation of entanglement in ultracold gases are demon-strated: Spin dynamics in Bose Einstein condensates is similar to the entan-glement creation in optics with parametric down conversion. Spatially inho-mogeneous Raman coupling allows for coupling atoms by the excitation ofcoupled trap modes, similar to the generation of entanglement with trappedions.
42
Posters II (Thursday and Friday)
Posters II (Thursday and Friday)
Relaxation Dynamics in 1d Bose Gases
Tim LangenTU Wien
Stadionallee 2, 1020 Vienna, [email protected]
We study the dynamics in a coherently split 1d Bose gas through measure-ments of full probability distributions, which provides us with unprecedentedinformation about the dynamical states of the system. Following an initialrapid evolution, the distributions approach a thermal-like steady state. Thisphenomenon is the first demonstration of the existence of prethermalization.
Mechanical motion of a microspherical pendulum
Sile Nic ChormaicUniversity College Cork
Physics Department, UCC, N/A Cork, [email protected]
Silica microspherical pendulums are fabricated and their mechanical reso-nances are detected as variations in the transmitted laser power from a ta-pered fiber. The thermal damping and amplification of the taper/pendulumcoupling noise is observed.
43
Posters II (Thursday and Friday)
Entanglement and momentum correlations in a ring resonator
Wolfgang NiedenzuInstitut für Theoretische Physik, Universität Innsbruck
Technikerstraße 25, 6020 Innsbruck, [email protected]
We study (conditional) entanglement properties and momentum correlationsof cold particles confined in one mode of a ring resonator. An analytical toymodel describing the microscopic system behaviour is derived and its resultscompared to the numerical predictions.
Undoing a measurement projection by quantum error correction
Daniel NiggInstitut für Experimentalphysik, Universität Innsbruck
Technikerstraße 25, 6020 Innsbruck, [email protected]
The projective measurement of a single qubit onto the two qubit states canbe interpreted as a complete phase damping process. The projection can bereversed using a three qubit error correction algorithm protecting againstphase flip errors. We report on the experimental realization of such quantummeasurement reversal in a system of trapped Calcium ions.
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Posters II (Thursday and Friday)
A single-atom quantum memory
Christian NöllekeMax-Planck-Institut für Quantenoptik
Hans-Kopfermann-Straße 1, 85748 Garching, [email protected]
A prerequisite for quantum networks are optical quantum memories. Wereport on the most fundamental implementation based on a single atomtrapped inside an optical cavity. We map the polarization of single photonsinto and out of the atom with high fidelity. This experiment is a major stepin the development of a universal quantum node that can send, receive, storeand process quantum information.
Quantum degenerate strontium
Benjamin PasquiouIQOQI
Technikerstraße 21a, 6020 Innsbruck, [email protected]
The properties of the alkaline-earth element strontium open exciting possibil-ities for quantum simulation. A necessary requirement for these applicationsis the availability of quantum degenerate gases. Here, we report our latestresults, as the improved production of quantum degenerate samples of allstrontium isotopes and the creation of a strontium Mott insulator.
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Posters II (Thursday and Friday)
Toward degenerate Bose gases on an atom chip in Villetaneuse
Aurélien PerrinUniversité Paris 13
99, Avenue J.-B. Clément, 93430 Villetaneuse, [email protected]
In this poster I will describe a novel atom chip setup, currently being devel-oped in Villetaneuse. This new experiment is aiming for the investigation ofnon-equilibrium dynamics of Bose gases in exotic geometries. Sodium atomswill be brought to degeneracy in rf-dressed states potentials realized on topof an atom chip.
Non-equilibrium dynamics of bosonic atoms in optical lattice
Hannes PichlerInstitut für Theoretische Physik, Universität Innsbruck
Technikerstraße 25, 6020 Innsbruck, [email protected]
We focus on heating of bosonic atoms arising due to classical fluctuationsof the intensity of the lasers that generate the optical lattice. To this endwe derive a stochastic model describing this problem and calculate heatingrates and effects on state-characteristics in the different regimes of the Bose-Hubbard model. Finally, we propose a setup that is immune against this kindof noise.
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Posters II (Thursday and Friday)
Measurement of the Gouy Shift in a Down-Conversion Processvia Phase of a Quantum State
Ana PredojevicInstitut für Experimentalphysik, Universität Innsbruck
Technikerstraße 25d, 6020 Innsbruck, [email protected]
We demonstrate a picosecond-pulsed system for generation of entangled pho-ton pairs. This source is built embedded in a Sagnac-type interferometer.Here, we theoretically and experimentally show the influence of Gouy phaseshift onto the phase of the output state created in this system. The presentedsource is a promising candidate for a compact, semiconductor laser drivensource of entangled photon pairs.
Probing Dicke-Hubbard matter states via photon statistics
Sara RajaramThe Ohio State University
2873 Neil Ave, Apt 451B, 43202 Columbus, United [email protected]
The DHL model describes a Bose-Hubbard like system coupled to light. For aregion of parameter space, the light is superradiant and the matter is eithera Mott-insulator or superfluid. Through mean field, exact diagonalization,and qmc calculations I examine photon statistics across the matter phasetransition in order to elucidate how the photon statistics reflect the mattercorrelations.
47
Posters II (Thursday and Friday)
Measurements on the simultaneous Superfluid (SF) toMott-Insulator (MI) Transition for Rb and Cs
Lukas ReichsöllnerInstitut für Experimentalphysik, Universität Innsbruck
Technikerstraße 25, 6020 Innsbruck, [email protected]
Ultracold dipolar systems promise various applications in the fields of e.g.ultracold chemistry, quantum simulation, and quantum many-body physics[1]. In our experimental work we focus on the creation of ultracold samplesof ground-state RbCs molecules. We adapt the coherent production schemedescribed in Ref. [2]. Two spatially separated Bose-Einstein condensates ofRb and Cs are to be merged in the presence of an optical lattice. We produceweakly bound RbCs molecules with the Feshbach-association technique andtransfer the molecules into the rovibrational ground state by applying theSTIRAP method. At present, the ground-state transfer efficiency is 50% forultracold thermal samples.
We have implemented an optical lattice and simultaneously produce MIstates of both species in the same lattice while the samples are separated bytypically 200 micrometers. The presence of an optical lattice should allowus to improve the overall molecule creation efficiency by first creating a MIstate for Cs with an optimized number of singly occupied sites in a regimewhere Rb is still superfluid and merging the two samples. We present ourapproach to move the superfluid Rb sample onto the „frozen“ Cs samplewhile tuning the interspecies scattering length to a value where exactly oneRb atom attaches to one Cs atom with the aim to prevent interspecies threebody loss.[1] M.A. Baranov, Physics Reports 464, 71 (2008)[2] J.G. Danzl et al., Nature Physics 6, 265 (2010)
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Posters II (Thursday and Friday)
Remote Entanglement between a Single Atom and a BEC
Stephan RitterMax-Planck-Institut für Quantenoptik
Hans-Kopfermann-Straße 1, 85748 Garching, [email protected]
We create remote entanglement between a single atom inside an optical cav-ity and a Bose-Einstein condensate (BEC) - a key resource for quantumnetworks. A single photon generated from and entangled with the atom isstored as a collective excitation in the BEC. Readout via photon-photonentanglement proves that the entanglement survives all described mappingprocedures with negligible degradation.
Towards Integrated Atom Chips
Joseph RushtonUniversity of Southampton
University Road, SO17 1BJ Southampton, United [email protected]
We describe our progress in producing integrated atom chips, microfabricateddevices used to confine and manipulate cold atoms within cavities of hermet-ically sealed Si-Pyrex wafers. We show how UHV conditions are maintainedwith Non Evaporable Getters while embedded LIAD films serve as atomicsources. Finally a new MOT geometry is presented, designed to have goodoptical access when on atom chip.
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Posters II (Thursday and Friday)
Integration of optical nanofibres with cold atoms
Laura RussellUniversity College Cork/OIST
Castle Farm, 0 Monkstown, [email protected]
The optical nanofibre has already been used as a tool in cold atom tech-nologies. As a dark probe, the nanofibre collects fluorescent photons fromsurrounding cold atoms. Our recent work has shown how the nanofibre canbe be used to measure cloud temperature in a forced oscillation method.Here, we will also discuss 1 and 2 photon absorption measurements in a Rbsystem.
Quantum simulation of driven dissipative dynamics with trappedions
Philipp SchindlerInstitut für Experimentalphysik, Universität Innsbruck
Technikerstraße 25, 6020 Innsbruck, [email protected]
The use of controlled dissipation in many-body quantum systems has at-tracted great interest as a resource for quantum simulation. Its combinationwith coherent Hamiltonian dynamics leads to interesting non-equilibriumdynamics such as phase transitions resulting from the competition betweendissipative and coherent processes. We present first experimental results of aspin model with trapped ions.
50
Posters II (Thursday and Friday)
Source design for quantum experiments with nanoparticles
Philipp SchmidVCQ - University of Vienna
Boltzmanngasse 5, 1090 Vienna, [email protected]
Quantum experiments with nanoparticles require cold and slow samples ofneutral massive molecules in the gas phase. We discuss our approach towardssamples in the mass range up to 1 MDa. A laser desorption source fills neg-atively charged ions into a cryogenic buffer gas loaded ion trap to provideinternally and externally cold particles. Neutral particles can be derived bylaser-postneutralization.
A novel nanofiber based trapping scheme
Philipp SchneeweissAtominstitut TU Wien
Stadionallee 2, 1020 Vienna, [email protected]
Advancing the established nanofiber-based two-color trap for cold atoms, wediscuss potential geometries based on a fiberguided red-detuned optical fieldand the centrifugal barrier. Stable orbits form for atoms with 600 quantaof angular momentum. The wave-packet dynamics in this new trap shouldshow collaps and revival, proofing angular momentum quantization for atomsspinning around the fiber.
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Posters II (Thursday and Friday)
Quantum degenerate Strontium
Florian SchreckIQOQI, OEAW
Technikerstraße 21a, 6020 Innsbruck, [email protected]
The properties of the alkaline-earth element strontium open exciting possibil-ities for quantum simulation. A necessary requirement for these applicationsis the availability of quantum degenerate gases. Here, we report our latestresults, as the improved production of quantum degenerate samples of allstrontium isotopes and the creation of a strontium Mott insulator.
Collective modes and quantum phases of a quasi-two-dimensionaldipolar Fermi gas
Lukas SiebererInstitut für Theoretische Physik, Universität Innsbruck
Technikerstraße 25, 6020 Innsbruck, [email protected]
We examine collective modes (zero sound), stability, and BCS pairing in aquasi-two-dimensional gas of dipolar fermions aligned by an external field. Atintermediate coupling we find unstable modes that can lead either to collapseof the system or the formation of a density wave. The BCS transition to asuperfluid phase occurs at arbitrarily weak strengths of the dipole-dipoleinteraction, provided the tilting angle exceeds a critical value. We determinethe critical temperature of this transition.
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Posters II (Thursday and Friday)
Lightforces and deformation in an elastic object
Matthias SonnleitnerInstitut für Theoretische Physik, Universität Innsbruck
Technikerstraße 25, 6020 Innsbruck, [email protected]
Scattering and absorption of laser light in initially homogeneous elastic me-dia induces local optical forces, which lead to local density modulations anddeformations. We show how trap position, force distribution and final lengthof an object depend nonlinearly and nontrivally on the injected laser inten-sities. The results should lead to interesting applications in microfluidics oroptoacustics.
Dark Entangled States in Cascaded Quantum Networks
Kai StannigelInstitut für Theoretische Physik, Universität Innsbruck
Technikerstraße 25, 6020 Innsbruck, [email protected]
We study the dissipative dynamics of driven, cascaded quantum networks,where individual two-level systems interact via a unidirectional bath. Weshow that these systems exhibit a class of pure steady states, which arise dueto radiation emitted by one part of the system being coherently reabsorbedby another part.
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Posters II (Thursday and Friday)
Optical Tweezers for Neutral Atoms
Dustin StuartUniversity of Oxford
Merton College, Merton Street, OX1 4JD Oxford, United [email protected]
Neutral atoms are promising candidates as the building blocks of a scal-able quantum network. We propose coupling the atoms to single photons viafibre-tip cavities. To hold the atoms in the cavity mode, we have developed areconfigurable dipole trap using a spatial light modulator (SLM). We demon-strate the storage of atoms in arbitrary shaped potentials, and the ability toswitch their positions.
Tunable ion-photon entanglement
Andreas StuteInstitut für Experimentalphysik, Universität Innsbruck
Technikerstraße 25, 6020 Innsbruck, [email protected]
In order to realize a coherent interface between a single ion and a singlephoton, we couple a single calcium ion to two orthogonal polarization modesof a high-finesse optical resonator. Applying bichromatic Raman transitions,we are able to generate an arbitrary entangled state of ion and photon.
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Posters II (Thursday and Friday)
Dicke-model quantum phase transition in a cavity
Gergely SzirmaiResearch Institute for Solid State Phyis
Konkoly-Thege Miklos ut 29-33, 1121 Budapest, [email protected]
Feshbach resonances, weakly bound states, and coupled-channelmodel of the 87Rb-Cs system
Tetsu TakekoshiIQOQI Innsbruck
Technikerstraße 25, 6020 Innsbruck, [email protected]
We have studied interspecies scattering in an ultracold mixture of 87Rb and133Cs atoms, both in their lowest-energy spin states, cataloguing three-bodyloss signatures for 30 incoming s- and p-wave magnetic Feshbach resonancesover the range 0 to 667 G. RbCs Feshbach molecules were created at three ofthe resonances. Magnetic field modulation spectroscopy was used to observemolecular states bound by up to 2.5 MHz×h. We have set up a coupled-channel model of the interaction and have used direct least-squares fittingto refine its parameters to fit the experimental results from the Feshbachmolecules, in addition to the Feshbach resonance positions and previous spec-troscopic results for deeply bound levels. The final model gives a good de-scription of all the experimental results and predicts a large resonance near790 G, which may be useful for tuning the interspecies scattering properties.Quantum numbers and vibrational wavefunctions from the model can also beused to choose optimal initial states of Feshbach molecules for their transferto the rovibronic ground state using stimulated Raman adiabatic passage(STIRAP).
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Posters II (Thursday and Friday)
Photosynthesis: Entanglement, Transport & Fourier’s law
Markus TierschInstitut für Theoretische Physik, Universität Innsbruck & IQOQI
Technikerstraße 25, 6020 Innsbruck, [email protected]
In the primary step of photosynthesis light is absorbed by pigment moleculecomplexes and transported to a reaction center where charge separation oc-curs. We critically revisit recent claims of the existence of entanglement dur-ing this energy transfer step in model systems of photosynthesis. The energytransport efficiency is discussed within a steady-state scenario, and validityof Fourier’s law.
Observation of strong coupling between single rubidium atoms
Jürgen VolzTU Wien - Atominstitut
Stadionallee 2, 1020 Vienna, [email protected]
We report on the observation of strong coupling between single atoms and ahigh-Q whispering-gallery-mode of a bottle microresonator. We observe clearsignals of individual atoms passing through the resonator mode within severalmicroseconds. Implementing a real-time atom detection/probing scheme wecan perform experiments on this timescale which allows us to characterizethe atom-cavity system.
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Posters II (Thursday and Friday)
Metastability and coherence of repulsive polarons in a stronglyinteracting Fermi mixture
Matteo ZaccantiIQOQI Innsbruck
Technikerstraße 21a, 6020 Innsbruck, [email protected]
Ultracold Fermi gases with tuneable interactions represent a unique test bedto explore the many-body physics of strongly interacting quantum systems[1, 2]. In the past decade, experiments have investigated a wealth of intrigu-ing phenomena, and precise measurements of ground-state properties haveprovided exquisite benchmarks for the development of elaborate theoreticaldescriptions. Metastable states in Fermi gases with strong repulsive inter-actions [3–7] represent an exciting new frontier in the field. The realizationof such systems constitutes a major challenge since a strong repulsive inter-action in an atomic quantum gas implies the existence of a weakly boundmolecular state, which makes the system intrinsically unstable against de-cay. Here, we exploit radio-frequency spectroscopy to measure the completeexcitation spectrum of fermionic 40K impurities resonantly interacting witha Fermi sea of 6Li atoms. In particular, we show that a well-defined quasi-particle exists for strongly repulsive interactions. For this “repulsive polaron”[5, 8, 9] we measure its energy and its lifetime against decay. We also probeits coherence properties by measuring the quasiparticle residue. The resultsare well described by a theoretical approach that takes into account the fi-nite effective range of the interaction in our system. We find that a non-zerorange of the order of the interparticle spacing results in a substantial lifetimeincrease. This major benefit for the stability of the repulsive branch opensup new perspectives for investigating novel phenomena in metastable, repul-sively interacting fermion systems.1. Giorgini, S., Pitaevskii, L. P. & Stringari, S. Rev.Mod. Phys. 80, 1215(2008).2. Chevy, F. & Mora, C. Rep. Prog. Phys. 73, 112401 (2010).3. Duine, R. A. & MacDonald, A. H. Phys. Rev. Lett. 95, 230403 (2005).4. Jo, G.-B. et al. Science 325, 1521 (2009).5. Pilati, S., Bertaina, G., Giorgini, S. & Troyer, M. Phys. Rev. Lett. 105,030405 (2010).6. Chang, S.-Y., Randeria, M. & Trivedi, N. PNAS 108, 51–54 (2011).7. Sanner, C. et al. arXiv:1108.2017.8. Massignan, P. & Bruun, G. M. Eur. Phys. J D 65, 83–89 (2011).9. Schmidt, R. & Enss, T. Phys. Rev. A 83, 063620 (2011).
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Posters II (Thursday and Friday)
Sisyphus Cooling of Polyatomic Molecules
Martin ZeppenfeldMax-Planck-Institut für Quantenoptik
Hans-Kopfermann-Straße 1, 85716 Garching, [email protected]
We present the experimental realization of opto-electrical cooling, a gen-eral Sisyphus-type cooling scheme for polar molecules. Electrically trappedmethyl-fluoride molecules are cooled by a factor 4.6 to 77mK, resulting in anincrease in phase-space density by a factor 7. Trap-design improvements willallow cooling to sub-mK temperatures, opening a viable direct route towardsa molecular BEC.
Measurement-based quantum repeaters
Michael ZwergerInstitut für Theoretische Physik, Universität Innsbruck & IQOQI
Technikerstraße 25, 6020 Innsbruck, [email protected]
We present a measurement-based implementation of the quantum repeater.We envision special purpose processors at each repeater node, which integrateentanglement swapping and purification into a single step. This measurement-based integration leads to significantly improved noise thresholds. It is shownthat one or two purification steps per repeater level are sufficient and thatwith seven levels in total one can reach the international scale.
58
Program
Monday, 13th February 2012
08.30-09.15: Jean Dalibard (Laboratoire Kastler Brossel, Paris)The two-dimensional Bose gas: thermodynamics and be-yond
09.15-09.45: Klaus Sengstock (Universität Hamburg)Quantum Simulation of Frustrated Classical Magnetismin Triangular Optical Lattices
09.45-10.05: Igor Lesanovsky (University of Nottingham)From coherent many-body dynamics to a Fokker-Planckequation
10.30-11.00: Rudolf Grimm (Universität Innsbruck)Strongly interacting Fermi gases
11.00-11.30: Markus Arndt (Universität Wien)A toolbox for quantum optics experiments with nanopar-ticles
16.00-16.45: Wolfgang Ertmer (Leibniz Universität Hannover)New Directions in Matterwave Interferometry
16.45-17.15: Selim Jochim (Universität Heidelberg)Deterministic few-fermion systems
17.15-17.35: Sebastian Diehl (Universität Innsbruck)Topology by Dissipation: Majorana Fermions in One andTwo Dimensions
18.00-18.30: Jörg Schmiedmayer (TU Wien)Mesoscopic many-body systems on atoms chips
18.30-19.00: Francesca Ferlaino (Universität Innsbruck)Towards the production of a dipolar RbCs quantum gas
59
Program
Tuesday, 14th February 2012
08.30-09.15: Eugene Polzik (Niels Bohr Institutet)Towards strong coupling between light and electronics
09.15-09.45: Hans Briegel (Universität Innsbruck)Quantum computation and simulation in non-equilibriumsystems
09.45-10.05: Rafael Mottl (ETH Zürich)Realization of a long-range interacting quantum gas
10.30-11.00: Anton Zeilinger (Universität Wien)Photon Entanglement Experiments in Larger Real andHilbert Spaces
11.00-11.30: Gregor Weihs (Universität Innsbruck)Advanced entangled photon pair sources
16.00-16.45: Andreas Wallraff (ETH Zürich)Quantum Optics with Superconducting Circuits: ExploringPropagating Microwave Photons
16.45-17.15: Cristiano Ciuti (Université Paris Diderot)Ultrastrong coupling cavity and circuit QED
17.15-17.35: Pavel Bushev (KIT, Karlsruhe)Rare earth spin ensemble to interface microwave and op-tical
18.00-18.30: Mikhail Baranov (Universität Innsbruck)Engineering and detecting Majorana fermions with coldatoms
60
Program
Wednesday, 15th February 2012
08.30-09.15: Christopher Monroe (University of Maryland)Quantum Networks of Trapped Atomic Ions
09.15-09.45: Christian Ospelkaus (Leibniz Universität Hannover)Multi-qubit microwave quantum logic and precision mea-surements with trapped ions
09.45-10.05: Christof Wunderlich (Universität Siegen)Quantum gates and dressed states with spin-spin coupledions
10.30-11.00: Rainer Blatt (Universität Innsbruck)Quantum Information Processing with Trapped Ca+ Ions
11.00-11.30: Barbara Kraus (Universität Innsbruck)Compressed quantum simulation of the Ising model
16.00-16.45: Matthias Troyer (ETH Zürich)Ab-initio simulation of ultracold atomic gases
16.45-17.15: Frank Verstraete (Universität Wien)Simulation of Strongly Correlated Quantum Systems
17.15-17.45: Andreas Läuchli (Universität Innsbruck)SU(N) Quantum Magnetism
61
Program
Thursday, 16th February 2012
08.30-09.15: Gerhard Rempe (MPQ, Garching)Quantum Optical Quantum Networks
09.15-09.45: Harald Weinfurter (LMU München)Multiphoton entanglement analysis
09.45-10.05: Thomas Volz (ETH Zürich)Ultrafast all-optical switching by single photons
10.30-11.00: Philip Walther (Universität Wien)Photonic Quantum Computations, Simulations and Net-works
11.00-11.30: Arno Rauschenbeutel (TU Wien)Trapping and Interfacing Cold Neutral Atoms Using Op-tical Nanofibers
16.00-16.45: Andreas Hemmerich (Universität Hamburg)Topological optical lattice & sub-recoil cavity cooling
16.45-17.15: Peter Domokos (SZFKI, Budapest)Critical exponent of a quantum-noise-driven phase tran-sition: The open-system Dicke model
17.15-17.35: Peter Rabl (IQOQI, Innsbruck)Optomechanical systems in the single photon strong cou-pling
18.00-18.30: Markus Aspelmeyer (Universität Wien)Quantum optomechanics: exploring the interface betweenquantum physics and gravity?
18.30-19.00: Sven Ramelow (Universität Wien)Coherent Photon Conversion (CPC) for Scalable Non-Linear Optical Quantum Computing
62
Program
Friday, 17th February 2012
08.30-09.15: Päivi Törmä (Aalto University)Fast CNT memory, and Rabi splitting for surface plas-mons
09.15-09.45: Christine Silberhorn (Universität Paderborn)Time multiplexed photonic quantum walks
09.45-10.05: Johannes Majer (TU Wien)Cavity QED with Magnetically Coupled Collective SpinStates
10.30-11.00: Tracy Northup (Universität Innsbruck)Ion-photon entanglement and state mapping in an opticalcavity
11.00-11.30: Astrid Lambrecht (Laboratoire Kastler Brossel, Paris)The Casimir Effect: Quantum Optics in Vacuum
16.00-16.45: Ed Hinds (Imperial College London)Is the electron round?
16.45-17.15: Thorsten Schumm (TU Wien)Nuclear Physics in a solid-state system
17.15-17.35: Michael Hartmann (TU München)Non-Classical States of Nano-Mechanical Oscillators
63
Preliminary�Program
Sunday�12 Monday�13 Tuesday�14 Wednesday�15 Thursday�16 Friday�17 Saturday�18
Ultracold�
Atoms�+�
Molecules�I
Hybrid�SystemsIon�Traps�+�
Quantum�Info
Photons�+�
Ensembles�
Special�Topics�+�
Foundations
8.30r9.15 Keynote Dalibard Polzik Monroe Rempe Törmä return�bus
9.15r9.45 Lecture Sengstock Briegel Ospelkaus Weinfurter Silberhorn return�bus
9.45r10.05 Hot�Topic Lesanovsky Mottl Wunderlich T.�Volz Majer
10.05r10.30 return�bus
10.30r11.00 SFB Grimm Zeilinger Blatt Walther Northrup return�bus
11.00r11.30 SFB/Assoc Arndt Weihs Kraus Rauschenbeutel Lambrecht return�bus
11.30r12.00 Discussions SFB
12.00r15.30 Lunch�+�Discussions SFB
15.30r16.00 Coffee�+�Cake SFB
Ultracold Atoms +
Quantum +
Molecules IIPrecision
Measurements16.00r16.45 Keynote Ertmer Wallraff Troyer Hemmerich Hinds
16.45r17.15 Lecture Jochim Ciuti Verstraete Domokos Schumm
17.15r17.35 Hot�Topic registration Diehl Bushev Läuchli�(30) Rabl Hartmann
17.35r18.00 Coffee registration
18.00r18.30 SFB registration Schmiedmayer Baranov Aspelmeyer
18.30r19.00 SFB registration Ferlaino Ramelow
19.15r20.30 Dinner Conference
20.00r22.00 Posters Posters Dinner Posters Posters
Circuit QED Optical Lattice
Simulations Cavity QED +
Optomechanics
