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International Workshop on Analog Quantum Simulators for many-body dynamics AQuS 2016 Internationales Wissenschaftsforum Universität Heidelberg September 05-08, 2016 Programme & Abstracts Topics Quantum simulaton, certfcaton, robustness, and complexity Quantum simulaton of contnuous and latce atomic gases Exciton-Polariton condensates and their dynamics Quantum fuids of light Universality out of equilibrium Analog gravity Informaton htps://www.kip.uni-heidelberg.de/aqus/aqus2016/ Horizon 2020 FET-Proactve Consortum AQuS – Partners: Universität Heidelberg (Coordinator), LPN-CNRS Marcoussis, FU Berlin, INO-CNR Trento, LMU München, U Cambridge & TU Wien Scientfc Board Alberto Amo (Marcoussis) Jürgen Berges (Heidelberg) Jacqueline Bloch (Marcoussis) Iacopo Carusoto (Trento) Jens Eisert (Berlin) Thomas Gasenzer (Heidelberg) Markus Oberthaler (Heidelberg) Jörg Schmiedmayer (Wien) Ulrich Schneider (Cambridge/LMU) Coordinaton Thomas Gasenzer Funded by the Horizon 2020 Framework Programme of the European Union text Programme Monday, 5 September 2016 11:10 Opening Chair: Markus Oberthaler Bose-Einstein Condensation of Photons and Periodic Potentials for Light Quantum Fisher information as efficient entanglement witness in many-body systems 11:30 Martin Weitz (Bonn) 12:10 Philipp Hauke (Innsbruck) 12:50 Lunch Chair: Tomaž Prosen 14:30 Fabian Essler (Oxford) Thermalization and light cones in a model with weak integrability breaking 15:10 Jean-Sébastien Caux (Amsterdam) Dynamics and relaxation in integrable quantum systems 15:50 Coffee/Tea Chair: Martin Weitz Quantum simulations with trapped ions 16:30 Petar Jurcevic (Innsbruck) 17:10 Evening at free disposition 3 Tuesday, 6 September Chair: Alberto Amo Dissipative dynamics and quantum state engineering with ultracold atoms Thermal quenches in the stochastic Gross-Pitaevskii equation: morphology of the vortex network 09:00 Andrew Daley (Strathclyde) 09:40 Leticia Cugliandolo (Paris) 10:20 Coffee/Tea Chair: Leticia Cugliandolo Quantum critical phenomena in open lattice systems Correlations in nonequilibrium polariton quantum fluids 11:10 Cristiano Ciuti (Paris) 11:50 Michiel Wouters (Antwerpen) 12:30 Lunch Chair: Fabian Essler Exactly solvable open many-body systems Synthetic dimensions in ultracold atoms and photonics 14:30 Tomaž Prosen (Ljubljana) 15:10 Tomoki Ozawa (Trento) 15:50 Coffee/Tea Chair: Michiel Wouters Out of equilibrium condensation in polariton lattices 16:30 Alberto Amo (Marcoussis) 18:00 Dinner buffet and Posters 4 Wednesday, 7 September Chair: Andrew Daley Ultracold Dysprosium gases: a complex system from radiative trapping to many-body physics Out of equilibrium dynamics of ergodic and disordered systems and the quest for quantum supremacy for quantum simulators 09:00 Silvain Nascimbène (Paris) 09:40 Jens Eisert (Berlin) 10:20 Coffee/Tea 11:10 Austen Lamacraft (Cambridge) 11:50 Henrik Lüschen (Cambridge) Chair: Jens Eisert Weak Many Body Localization in the Quantum Random Energy Model Experimental Results on Many-Body Localization 12:30 Lunch Chair: Silvain Nascimbène From collectives excitations to turbulence in a uniform Bose gas From Quenches to Critical Dynamics and Non-Thermal Fixed Points in Ultracold Bose Gases 14:30 Nir Navon (Cambridge) 15:10 Markus Karl (Heidelberg) 15:50 Coffee/Tea Chair: Ulrich Schneider Investigating ultracold atom systems with higher order correlation functions in and out of equilibrium Non-equilibrium dynamics of long-range interacting Rydberg systems 16:30 Thomas Schweigler (Wien) 17:10 Adrien Signoles (Heidelberg) 17:50 Evening at free disposition 5 Thursday, 8 September Chair: Jörg Schmiedmayer Bose and Fermi polarons in ultracold atoms Simulating quantum fields 09:00 Eugene Demler (Harvard) 09:40 Tobias Osborne (Hannover) 10:20 Coffee/Tea Chair: Eugene Demler Analog Hawking physics in atomic and optical systems 11:10 Iacopo Carusotto (Trento) 12:30 Closing and Departure 6 Practical Information The local participants will wear a green sticker on their name tag. They will answer any practical questions you may have. Location The conference hall is in the Internationales Wissenschaftsforum Heidelberg (IWH), situated in the old town of Heidelberg at the foot of the castle hill. The address is the following: Internationales Wissenschaftsforum Heidelberg Hauptstrasse 242 D-69117 Heidelberg The public transport station that is closest is “S-Bahnhof Altstadt”. It can be reached with the S-Bahn (lines S1 and S2) or the bus (line 33). Then it’s a 3 minutes walk in direction of the city centre to reach the IWH. The nearest parking opportunities are "Parkhaus 13" at the "Karlsplatz" (17.50 € per day) and "Parkhaus 12" at the "Kornmarkt" (13.50 € per day). It is a 3-minute walk from there to the IWH. For more information, please look up the local public transportation and German railway Internet pages: http://www.vrn.de http://www.bahn.com Transportation to and from Frankfurt airport can be found at: http://frankfurt-airport-shuttles.de/en/home-2/ https://www.tls-heidelberg.de/en/ There is also map with many useful annotations at: http://g.co/maps/jt46s A small map can be found at the end of this booklet. Internet There is a wifi Internet access in the conference hall. Connect to WLAN ’UNIWEBACCESS’ and open your browser. It will automatically redirect to the login page. login and password: see note on whiteboard in the lecture room The web-page of the conference is: https://www.kip.uni-heidelberg.de/aqus/aqus2016/ 7 8 Talks Bose-Einstein Condensation of Photons and Periodic Potentials for Light Martin Weitz Institut für Angewandte Physik, Universität Bonn, D-53115 Bonn Bose-Einstein condensation has been observed with cold atomic gases, quasiparticles in solid state systems as polaritons, and more recently also with photons in a dye-filled optical microcavity. I will here describe measurements of our Bonn group determining the coherence of a photon Bose-Einstein condensate and realizing periodic potentials for the optical quantum gas. The optical condensate is generated in a wavelength-sized optical cavity, where the small mirror spacing imprints a low-frequency cutoff with a spectrum of photon energies restricted to well above the thermal energy. The cavity mirrors provide a trapping potential and a non-vanishing effective photon mass, making the system formally equivalent to a two-dimensional gas of trapped massive bosons. Thermalization of the photon gas is reached in a number conserving way by repeated absorption re-emission cycles in the dye molecules. Recent experiments realizing periodic lattice potentials for the photon gas will be reported, as well as measurements investigating the competition of tunneling and effective photon interactions in doublewell potentials. 9 Quantum Fisher information as efficient entanglement witness in many-body systems Philipp Hauke Institute for Theoretical Physics, University of Innsbruck, Austria Entanglement is considered a resource for quantum simulation, but it is difficult to quantify experimentally in a many-body setting. Here, we discuss scenarios where many-body entanglement becomes accessible via the quantum Fisher information, a known witness for genuinely multipartite entanglement. First, we introduce a direct relation of the QFI in thermal states with linear response functions, which makes the QFI measurable with standard methods. Using this relationship, we show that close to continuous quantum phase transitions the QFI, and thus multipartite entanglement, is strongly divergent. Second, we demonstrate that the quantum Fisher information can witness many-body localized phases, showing a characteristic growth of entanglement at long times after a quantum quench. These results illustrate that the quantum Fisher information represents a useful and efficiently measurable witness for entanglement in quantum many-body settings. Thermalization and light cones in a model with weak integrability breaking Fabian Essler The Rudolf Peierls Centre for Theoretical Physics, University of Oxford, United Kingdom I discuss the application of equation of motion techniques to study the non-equilibrium dynamics in a class of lattice models of weakly interacting spinless fermions. Our model provides a simple setting for analyzing the effects of weak integrability breaking perturbations on the time evolution after a quantum quench. 10 Dynamics and relaxation in integrable quantum systems Jean-Sébastien Caux Institute of Physics, University of Amsterdam, The Netherlands This talk will outline integrability-based results on the out-of-equilibrium dynamics of low-dimensional systems such as interacting atomic gases and quantum spin chains. A number of recent developments will be explained, including a new method for explicitly calculating the relaxation of observables after a quantum quench. Exact solutions to the interaction turn-on quench in the Lieb-Liniger model and to the Néel-to-XXZ quench in spin chains will be presented. Particular emphasis will be given to interesting open issues, including the failure of the (local) Generalized Gibbs Ensemble to properly describe post-quench steady-state properties and the necessity to include quasilocal conserved charges to obtain correct answers. Quantum simulations with trapped ions Petar Jurcevic Institut für Experimentalphysik, Universtität Innsbruck, Austria 11 Dissipative dynamics and quantum state engineering with ultracold atoms Andrew Daley Department of Physics, University of Strathclyde, Glasgow, United Kingdom The time-dependent microscopic control available over systems of ultracold atoms has opened new opportunities to explore many-body dynamics, addressing fundamental questions both in and out of equilibrium. As always in such systems, a key experimental challenge is found in the need to cool systems to lower temperatures. However, the time-dependent control available over these dynamics can provide a new tools for realising low-entropy many-body states, and this is further enhanced by the possibility to generate dissipative dynamics that are also well understood on a microscopic level. I will discuss recent developments in this area, illustrated with our recent theoretical work in two directions: (i) the generation of spin-entangled states of fermionic atoms in an optical lattice by combining Fermi statistics with dissipation induced by a reservoir gas not trapped by a lattice, and (ii) the application of bilayer lattice systems, together with dynamical control of atoms in optical lattices, to dynamically disentangle two subsystems and achieve sensitive many-body states via adiabatic cooling. 12 Thermal quenches in the stochastic Gross-Pitaevskii equation: morphology of the vortex network Leticia Cugliandolo Laboratoire de Physique Théorique et Hautes Energies, Sorbonne Universités Université Pierre et Marie Curie A system taken across a second order phase transition from its disordered into its symmetry-broken phase undergoes a phase ordering process. Topological defects are left in the system at finite times after the quench and, in open systems, they are gradually eliminated in the course of evolution towards equilibrium. I will discuss a recent detailed study of the evolution of 3d weakly interacting bosons at finite chemical potential, taken across their phase transition, using the stochastic GrossPitaevskii equation. In short, I will explain the full characterisation of the vortex network in and out of equilibrium. This is work in collaboration with Michikazu Kobayashi (Kyoto University). Quantum critical phenomena in open lattice systems Cristiano Ciuti Univ. Paris Diderot, Paris, France In this invited talk, I will present recent theoretical results of my group about nonequilibrium critical phenomena in open quantum systems. In particular, I will show predictions for driven-dissipative photonic systems and also dissipative spin lattices. 13 Correlations in nonequilibrium polariton quantum fluids Michiel Wouters Universiteit Antwerpen, Antwerpen (Wilrijk), Belgium Microcavity polaritons interact much stronger than photons, but can still be safely described by the Bogoliubov approximation. I will discuss the coherence properties of both resonant and nonresonantly excited polariton condensates. For the case of pulsed resonant excitation, connections to the dynamical Casimir effect and quenches in many-body systems can be made. Exactly solvable open many-body systems Tomaž Prosen Faculty of Mathematics and Physics, University of Ljubljana, Slovenia I will discuss several examples of one-dimensional interacting open quantum many-body systems for which one can write exact solution for the steady state, or even compute the full Liouvillian spectrum of decay modes. Among the most prominent ones are the boundary driven XXZ and fermi Hubbard chains, the former displaying a non-equilibrium quantum phase transition in the steady state, while the full spectrum of the XX chain with de-phasing bulk noise and possible boundary driving can be shown to be equivalent to Bethe-ansatz spectrum of the Hubbard model with imaginary interaction U. 14 Synthetic dimensions in ultracold atoms and photonics Tomoki Ozawa Dipartimento di Fisica, INO-CNR BEC Center and University of Trento, Povo (TN), Italy I discuss recent developments of the study of “synthetic dimensions” in ultracold gases and photonics. The idea of synthetic dimensions is to identify internal states of an atom or a photonic cavity as extra dimensions, and to simulate higher dimensional lattice models using physically lower dimensional systems. The concept was originally proposed and experimentally realized in ultracold gases. I first review the existing theoretical and experimental studies of synthetic dimensions. After discussing some challenges and limitations of the existing methods of synthetic dimensions, I explain our proposals of realizing synthetic dimensions both in ultracold gases and in photonic cavities, which overcome some of these limitations. Finally I discuss how the four dimensional quantum Hall effect can be observed in ultracold gases and photonics using the synthetic dimensions. 15 Out of equilibrium condensation in polariton lattices F. Baboux1 , D. De Bernardis2 , C. Gomez1 , E. Galopin1 , A. Lemaître1 , L. Le Gratiet1 , I. Sagnes1 , A. Amo1 , M. Wouters1 , J. Bloch1,3 1 2 Centre de Nanosciences et de Nanotechnologies, CNRS, Univ. Paris-Sud, Université Paris-Saclay, C2N Marcoussis, 91460 Marcoussis, France Theory of Quantum and Complex Systems, Universiteit Antwerpen, Universiteitsplein 1, B-2610 Antwerpen, Belgium 3 Physics Department, École Polytechnique, F-91128 Palaiseau Cedex, France Exciton polaritons in semiconductor microcavities provide an excellent platform to study the out-of-equilibrium properties of interacting quantum fluids. An important characteristic of polariton condensates is that they coexist with a bath of reservoir particles at high energies in a far-from-thermal state [1]. The combination of bosonic stimulation with the interactions between condensed and non-condensed polaritons results in an effective attractive interaction [2]. This gives rise to strong instabilities that destroy the polariton condensate when using large excitation spots []. Here we will show evidence of this instability and how polariton condensates can become stable in a periodic lattice. The stabilisation of polariton condensates demonstrated in this work, opens a new paradigm in polariton physics, allowing the exploration of the Kardar–Parisi–Zhang physics, and provide a route for the spatial engineering of the sign of the interactions. [1] F. Baboux et al., Bosonic Condensation and Disorder-Induced Localization in a Flat Band. Phys. Rev. Lett. 116, 066402(2016). [2] N. Bobrovska, E. A. Ostrovskaya, and M. Matuszewski, Stability and spatial coherence of nonresonantly pumped exciton-polariton condensates. Phys. Rev. B 90, 205304 (2014). [3] K. S. Daskalakis, S. A. Maier, and S. Kéna-Cohen, Spatial Coherence and Stability in a Disordered Organic Polariton Condensate. Phys. Rev. Lett. 115, 035301 (2015). 16 Ultracold Dysprosium gases: a complex system from radiative trapping to many-body physics Sylvain Nascimbène LKB ENS Paris, Laboratoire Kastler Brossel, Collège de France, Paris, France Atomic Dysprosium features a complex electronic structure, which leads to several interesting properties in the context of atomic physics: a large electronic angular momentum, a large magnetic moment, many narrow optical transitions. Those characteristics imply specific physical behaviors, from the radiative cooling and trapping to the design of novel schemes for quantum many-body physics. We will first present a detailed study of the magneto-optical trapping (MOT) of ultracold Dysprosium. We will show that the MOT can be operated in several regimes, with either all or a single Zeeman components involved. Due to the weak radiative forces obtained with a narrow optical transition, gravity plays an major role, and tends to polarize the atomic sample. We will also discuss light-induced inelastic collisions. The second part of the talk will address the prospects of our experiment, which aims at realizing topological superfluids with ultracold Dysprosium. We will show that the structure of optical transitions is well suited for realizing light-induced gauge fields, the basic ingredient for realizing a topological superfluid. We will also present several schemes to reveal the presence of Majorana fermions at the edges of the topological superfluid. 17 Out of equilibrium dynamics of ergodic and disordered systems and the quest for quantum supremacy for quantum simulators Jens Eisert Dahlem Center for Complex Quantum Systems, Freie Universität Berlin, Berlin-Dahlem, Germany Dynamical analogue quantum simulators allow to probe a plethora of physical phenomena related to the physics of quantum systems out of equilibrium. In this talk, we will consider questions of equilibration, Gaussification, the dynamics of quantum phase transitions and the absence of thermalisation - present in disordered interacting models that show features of the multi-faceted phenomenon of many-body localisation. We discuss both new theoretical results, as well as tools employed in collaborations with experimentalists working with cold atoms in optical lattices and on atom chips. In the last part of the talk, we will have a look at work in progress on conceptual questions that seem to be key to the idea of a quantum simulator: This in on the one hand one of how to devise quantum simulators that have the potential of computationally outperforming classical devices, discussing variants of IQP circuits. On the other hand, it the question of the certification of quantum simulators for which no classical simulation algorithm is known. Weak Many Body Localization in the Quantum Random Energy Model Austen Lamacraft Cavendish Laboratories, University of Cambridge, United Kingdom 18 Experimental Results on Many-Body Localization Henrik Lüschen Fakultät für Physik, Max Planck Institute of Quantum Optics, München, Germany The phenomenon of many-body localization (MBL) describes a generic nonthermalizing phase in which quantum information can persist locally up to infinite times. MBL is separated from a phase obeying the eigenstate-thermalization hypothesis via a disorder driven dynamical phase transition, which happens not only in the ground state but over an extended range of energy densities. An effect similar to finite temperatures smearing out ground state phase transitions into universal crossovers is expected in the presence of a small coupling to an external heat bath. I will present recent experimental results on the MBL phase transition, as well as MBL in the presence of a weak photon bath, based on the relaxation of fast local observables in a quasi-random optical lattice. We find slow powerlaw dynamics close to the MBL critical point, which is potentially connected to Griffith type effects. Also, in the presence of controllable weak photon scattering, we observe restoration of ergodicity on a timescale dependent on the microscopic parameters of the Hamiltonian. 19 From collectives excitations to turbulence in a uniform Bose gas. Nir Navon University of Cambridge, United Kingdom The recent realisation of Bose-Einstein condensates in uniform traps has opened interesting possibilities to study far-from-equilibrium phenomena with textbook systems. In this talk, we will present a study where we drive a homogeneous Bose-Einstein condensate (BEC) out of equilibrium with an oscillating force that pumps energy into the system at the largest lengthscale. In the limit of weak drives, the BEC’s response is linear, well captured by its lowest-lying excitations. For stronger drives, a nonlinear response is apparent and we observe a gradual development of a cascade characterised by an isotropic power-law distribution in momentum space. We will report on our latest progress on the detailed characterisation of the steady-state turbulent state, as well as a joint experimental/theoretical investigation into the finite-temperature behaviour of the BEC lowest-lying mode. 20 From Quenches to Critical Dynamics and Non-Thermal Fixed Points in Ultracold Bose Gases Markus Karl Kirchhoff Institut für Physik, Universität Heidelberg, Deutschland Ultracold quantum gases provide a vast playground for exploring dynamical critical phenomena, such as phase transitions and universal scaling far from equilibrium. Here, we consider one- and multi-component (spin) systems of ultracold Bose gases, inducing highly non-linear dynamical evolution via sudden parameter quenches and instabilities. We identify critical scaling and universal scaling forms in the post-quench time evolution of the respective systems. For quenches within the symmetric phase of a two-component Bose gas, we show that shorttime quench dynamics can be described by a universal crossover function, where the quench-induced energy appears as the relevant energy scale. Scaling properties have been found which indicate the importance of pre-thermalisation temperatures long before dephasing has occurred in the nearly gapless system. We discuss the theoretical results in the light of and illustrated by recent experimental measurements. For the single-component gas, we find a new universal phase of time evolution, characterised by an anomalously slow, glass-like, phase ordering process of vortex defects in the symmetry-broken phase. We discuss our results, in particular, for dynamical universal scaling forms in the light of the concept of non-thermal fixed points. 21 Investigating ultracold atom systems with higher order correlation functions in and out of equilibrium Thomas Schweigler Vienna Center for Quantum Science and Technology, Atominstitut, TU Wien, Austria We experimentally study a pair of tunnel-coupled one-dimensional atomic superfluids, which realize the quantum sine-Gordon model relevant for a wide variety of disciplines from particle to condensed-matter physics. From measured interference patterns we extract phase correlation functions and analyze if, and under which conditions, the higher-order correlation functions factorize into lower ones. This allows us to characterize some essential features of the model solely from our experimental measurements. The method is also used to investigate the non-equilibrium dynamics following a quench in the tunnel-coupling strength between the superfluids. Non-equilibrium dynamics of long-range interacting Rydberg systems Adrien Signoles Physical Institute, Heidelberg University, Germany Rydberg atoms in ultracold gases constitute controllable systems to experimentally study non-equilibrium phenomena. Of specific interest is the possibility to introduce resonant dipolar exchange interactions. This provides new opportunities for investigating the dynamics of strongly correlated many-body quantum systems with beyondnearest neighbour coupling. Here we present an experimental realization of such a system, by exciting nS and nP Rydberg states and coupling them with microwave fields, which allow for studying dynamics of correlated spin systems. We report the observation of interaction-induced effects in the dynamics of this ensemble of atoms and show that the system can be understood in terms of a dipolar XX model, providing a benchmark for spin systems. I will review recent theoretical and experimental progress in the study of Bose and Fermi polarons in ultracold atoms. The emphasis will be on understanding non-equilbrium aspects such as dynamics of polaron formation probed by Ramsey interferometry 22 Bose and Fermi polarons in ultracold atoms Eugene Demler Harvard University, Cambridge, MA 02138, USA I will review recent theoretical and experimental progress in the study of Bose and Fermi polarons in ultracold atoms. The emphasis will be on understanding non-equilbrium aspects such as dynamics of polaron formation probed by Ramsey interferometry Simulating quantum fields Tobias Osborne Institut für Theoretische Physik, Leibniz Universität Hannover, Germany During the past decades we have seen important hints coming from string theory and holography – particularly in the study of 4D SUSY gauge theories – that the parametrisation of QFTs in terms of lagrangians via the path integral is not always the most efficient representation. Thus, given the success of tensor networks in condensed matter theory, it seems worthwhile to contemplate how to formulate QFT directly in terms of a state represented as a TNS. Doing this directly suggests new quantum simulation algorithms for interacting quantum fields. In this talk I will describe the modern Wilsonian approach to defining QFT and explain how to implement this approach directly in terms of TNS and describe how to take the continuum limit of tensor networks ranging from matrix product states, projected entangled pair states, tree tensor networks, and the multiscale entanglement renormalisation ansatz. These continuum limits then form the basis for quantum simulation algorithms, both analog and discrete, which allow for a direct comparison between the simulation results coming from discretisations and the desired continuum theory. 23 Analog Hawking physics in atomic and optical systems Iacopo Carusotto BEC Trento, INO-CNR BEC Center, 38123 Povo (Trento), Italy In this talk I will present the latest advances of the AQuS project in the study of analog models of black holes using condensed matter and optical systems. In the first part of the talk, I will focus on the stimulated and spontaneous Hawking emission of phonons in a flowing fluid of polaritons in a semiconductor microcavity and I will outline the perspectives in view of an experimental observation. I will then review on-going theoretical studies of the consequences of the non-equilibrium condition on the quantum properties of the Hawking emission polariton fluids, and of Hawking emission in atomic gases with spin degrees of freedom or trapped in a elongated twowell potential. I will conclude with an outline of more speculative investigations in the direction of highlighting the back-reaction effect of Hawking emission onto the condensate motion. 24 Posters Exploring few-fermion systems in single- and multi-well potentials A. Bergschneider , V. M. Klinkhamer, J. H. W. Becher, M. Dehabe, G. Zürn, P. M. Preiss and S. Jochim Physikalisches Institut der Universität Heidelberg, 69120 Heidelberg, Germany We present several measurements that use ultracold fermionic atoms to investigate the crossover from few to many-body physics in different kinds of quantum systems. The measurements follow a bottom-up approach: We first generate and control the smallest realization that contains the relevant physics and then gradually increase the size of the system. With our setup, we can generate one or several cigar-shaped potentials to trap ultracold atoms. We deterministically prepare few fermions in these potential wells with full control over the particle number and the quantum state of the system. Furthermore, we can tune the interparticle interactions between the fermions over a large range. In a first set of experiments we studied the transition from few- to many-body physics in a one-dimensional system. We prepared a single impurity and an increasing number of majority particles in a single well and studied the interaction energy as a function of the number of majority atoms [1]. We also realized few-particle antiferromagnetic spin chains by starting with noninteracting two-component systems in one well and ramping to strong repulsion [2]. Recently, we prepared two fermions in the ground state of a double-well potential and demonstrated full control and tunability of this system without increasing its entropy. This system can be considered as the fundamental building block of the Fermi-Hubbard model. Combining several double wells can allow to prepare low-entropy states in a few-site lattice [3]. [1] A. N. Wenz et al., Science 342, 457(2013). [2] S. Murmann et al., in preparation. [3] S. Murmann et al., PRL 114, 080402 (2015). 25 Black-Hole lasing in spinorial condensates Salvatore Butera Heriot-Watt University, Edinburgh, United Kingdom We study the analogue of the Hawking radiation physics in a coherently coupled two component Bose-Einstein condensate. In practice, we consider a gas of two level atoms, whose internal states are coupled by an external laser field. Both for the homogeneous and the harmonically trapped (quasi-) one-dimensional system we show, by properly tuning the mean-field coupling constants and the Rabi frequency of the light-atoms interaction, the occurrence of the black-hole lasing effect respectively in the density and in the spin-density branches of the fluctuation field. The advantage of considering this set-up relies on the high controllability of the parameters of the light-atoms interaction in state-of-the-art cold-atom experiments and on the fact that, coupling the internal states by a two-photons Raman interaction, the inhomogeneity of the laser-atom interaction do not locally modify the chemical potential of the system, which remain homogeneous over all the condensate without the necessity of opportunely tailoring the external confining potential. Topological Varma superfluid in optical lattices Marco Fedele Di Liberto INO-CNR BEC Center Trento, 38123 Povo (Trento), Italy Topological states of matter are peculiar quantum phases showing different edge and bulk transport properties connected by the bulk-boundary correspondence. While noninteracting fermionic topological insulators are well established by now and have been classified according to a ten-fold scheme, the possible realisation of topological states for bosons has not been much explored yet. Furthermore, the role of interactions is far from being understood. Here, we show that a topological state of matter exclusively driven by interactions may occur in the p-band of a Lieb optical lattice filled with ultracold bosons. The single-particle spectrum of the system displays a remarkable parabolic band-touching point, with both bands exhibiting non-negative curvature. Although the system is neither topological at the single-particle level, nor for the interacting ground state, on-site interactions induce an anomalous Hall effect for the excitations, carrying a non-zero Chern number. Our work introduces an experimentally realistic strategy for the formation of interaction-driven topological states of bosons. 26 Far from equilibrium integrable systems Sebastian Erne Institute for theoretical Physics, Heidelberg University, Germany Relaxation of far-from equilibrium integrable systems is to date an open and interesting question. Recent progress in cold atom experiments in low dimensional systems, allow for a detailed study of integrable field theories. Specifically we consider a system of linearly coupled quasi one-dimensional condensates, realizing the quantum sine-Gordon and Lieb-Liniger theories. By studying quenches in the sine-Gordon model, we are able to explore fundamental questions of quantum physics. In particular we investigate prethermalization and the Generalized Gibbs Ensemble, higher order correlations and their factorization properties in and out of equilibrium, dynamics and decay of topological excitations and false vacua, quantum many body revivals, and tomography of quasiparticle. We compare the experiment to analytical and numerical results, for the latter using the (stochastic) Gross-Pitaevskii equations as well as Monte-Carlo simulations. 27 Verify Many-Body Entanglement via Structure Factor Measurements Oliver Marty Institut für Theoretische Physik, Universität Ulm, Germany A fascinating example of a genuine quantum effect is the concept of spin-squeezing that describes a collective property of an aggregation of spins. Since its first consideration in the context of quantum metrology a central application of spin-squeezing parameters became the detection of multipartite quantum correlations, that is, quantitatively the degree of spin-squeezing is a measure of multipartite entanglement. Entanglement criteria based on spin-squeezing parameters benefit from the fact that these parameters usually depend on simple and global observables only, in particular, typically on loworder moments of collective spin operators. As a consequence, the approach provides an experimentally easily accessible and robust way for entanglement detection that is free of any assumptions on the system and may therefore be suitable for many different platforms. Motivated by a criteria of Sorensen and Molmer [PRL 86, 4431 (2001)] for multipartite entanglement, our contribution is a general scheme, that allows for the detection of many-body entanglement via a variety of observables. As an example we present entanglement criteria based on the structure factor, an observable which can be measured in neutron scattering experiments, but may also be accessible on other platforms such as trapped ions. To explicitly obtain the criteria we combine a recently introduced algorithm for eigenvalue optimization [Mengi, 35, 2 (2014)] with matrix-product states and operator based techniques that theoretically allows for the detection of multipartite entanglement of hundreds of spins. To support the practical importance of our scheme, we discuss states which are optimally detected and show how they can be created in experiments with trapped ions. Generally, our approach provides a scalable method to verify multipartite entanglement which may find a variety of applications, e.g., as a benchmark of various experimental situations, ranging from quantum simulators to adiabatic quantum optimization. 28 Exact Bethe ansatz spectrum of a tight-binding chain with dephasing noise Mariya Medvedyeva Faculty of Mathematics and Physics, University of Ljubljana, Slovenia We construct an exact map between a tight-binding model on any bipartite lattice in presence of dephasing noise and a Hubbard model with imaginary interaction strength. In one dimension, the exact many-body Liouvillian spectrum can be obtained by application of the Bethe ansatz method. We find that both the non-equilibrium steady state and the leading decay modes describing the relaxation at late times are related to the eta-pairing symmetry of the Hubbard model. We show that there is a remarkable relation between the time-evolution of an arbitrary k-point correlation function in the dissipative system and k-particle states of the corresponding Hubbard model. Probing the Dynamics of Superradiant Quantum Phase Transition in a Single Trapped-Ion Ricardo Puebla Institute of Theoretical Physics, Ulm University, Germany The Rabi model can undergo a superradiant quantum phase transition (QPT) despite consisting of a single two-level system and a single bosonic mode [1]. Here we demonstrate that the QPT and its critical dynamics near the QPT can be probed in the setup of a single trapped ion, making use of equilibrium and non-equilibrium universal functions of the Rabi model. We propose a scheme that can faithfully realize the Rabi model in the extreme parameter regime to observe critical behavior: large ratio of the effective atomic transition frequency to the oscillator frequency. It is demonstrated that the predicted universal functions can indeed be observed based on our scheme. Finally, the effects of realistic noise sources on probing the universal functions in experiments are examined [2]. [1] M.-J. Hwang, R. Puebla, and M. B. Plenio, Phys. Ref. Lett. 115, 180404(2015). [2] R. Puebla, M.-J. Hwang, J. Casanova, and M. B. Plenio, arxiv:1607.03781. 29 Topological Mechanics Grazia Salerno INO-CNR BEC Center, 38123 Povo (TN) Italy We theoretically propose how to observe topological effects in a generic classical system of coupled harmonic oscillators, whose oscillation frequency is modulated fast in time. Making use of Floquet theory in the high-frequency limit, we identify a regime in which the system is accurately described by a Harper-Hofstadter model where the synthetic magnetic field can be externally tuned via the phase of the frequency modulation of the different oscillators. We illustrate how the topologically protected chiral edge states, as well as the Hofstadter butterfly of bulk bands, can be observed in the driven-dissipative steady state under a monochromatic drive. In analogy with the integer quantum Hall effect, we show how the topological Chern numbers of the bands can be extracted from the mean transverse shift of the steady-state oscillation amplitude distribution. Finally, we discuss the regime where the analogy with the Harper-Hofstadter model breaks down. 30 Probing Relaxation at the Many-Body Localization (MBL) Transition with Ultracold Fermions in Optical Lattices Sebastian Scherg Quantum Optics Chair, Ludwig-Maximilians Universität München, Germany The many-body localization transition is a dynamical phase transistion, which happens over an extended range of energy densities. The phase transistion seperates an ergodic, thermal phase, in which the eigenstate thermalization hypothesis (ETH) holds, from a non-thermal, localized phase, which violates the ETH. We study this transistion using interacting Fermions in a one-dimensional quasi-disordered optical lattice by monitoring the decay of an initially imprinted local density pattern. I will show recent experimental results on MBL focusing on the vicinity of the MBL critical point, where we find slow powerlaw dynamics, which might potentially be connected to Griffith type effects. Furthermore, I will present recent experiments on periodical driving of an MBL system, resulting in a localized phase at high drive frequencies and an ergodic phase at low ones. Finally, I will explain recent preliminary data about MBL in a 2D environment. 31 Nonthermal Fixed Points and Superfluid Turbulence in Ultracold Bose Gases Markus Karl, Christian-Marcel Schmied, Stefanie Czischek Kirchhoff-Institute for Physics, Heidelberg University, Germany Ultracold quantum gases provide various means to probe universal many-body dynamics far from equilibrium. Here, we focus on the non-linear dynamical evolution induced in an ultra cold Bose gas by a sudden initial parameter quench. Considering oneor multi-component (spin) systems, various types of spatial and wavenumber- space patterns emerge, being characterized by universal scaling functions associated with non-thermal fixed points. Such fixed points can be observed in existing experiments and are closely related to quantum turbulence usually discussed in systems of more than one spatial dimension. While these situations are associated with quenches to a symmetry-broken state, quenches within the symmetric phase offer a way to probe the properties of universal dynamics similar to those near a quantum critical point in equilibrium. Scaling properties have been found which indicate the importance of prethermalisation temperatures long before dephasing has occurred in the nearly gapless system. We discuss the theoretical results in the light of and illustrated by recent experimental measurements. 32 Heteronuclear Efimov scenario in an ultracold Bose-Fermi mixture with large mass imbalance Juris Ulmanis Physics Institute, Heidelberg University, Germany Universality in few-body systems is a prominent topic in fundamental quantum physics. One of its hallmarks is the Efimov effect, where pairwise resonantly interacting particles can form an infinite geometric series of weakly-bound three-body states, the Efimov states, following a discrete scaling law. Due to the large mass imbalance, an ultracold Bose-Fermi mixture of Cs and Li atoms features a drastically reduced scaling factor, making it a prototypical system for the thorough investigation of the heteronuclear Efimov effect. Here we present our recent measurements and analysis of three-body recombination spectra of Li+Cs+Cs collisions close to two broad Li-Cs Feshbach resonances. We observe how the heteronuclear Efimov scenario is critically modified by the sign of the Cs-Cs intraspecies interaction and compare our results with universal zero-range and van der Waals theories. Our findings show that the three-body parameter and the scaling factor between consecutive resonances are controlled not only by the van der Waals forces, but also by the scattering length between the two bosons, independent of short-range physics. New Geometries for Ultracold Atoms in Optical Lattices Konrad Viebahn Cavendish Laboratory, University of Cambridge, United Kingdom We will present the latest developments on our new apparatus involving ultracold potassium and rubidium atoms in novel optical lattice geometries. 33 Role of geometry in nonlocal superfluids Kali Wilson Institute of Photonics and Quantum Sciences, Heriot-Watt University, Edinburgh, United Kingdom In this work we perform numerical and experimental studies that demonstrate the key role of fluid geometry when the fluid is also nonlocal. We show that the Bogoliubov dispersion relation associated with elementary excitations in a nonlocal quantum fluid may be modified by the system geometry, such that the system can be pushed into a regime where superfluid behavior is observed despite a high degree of nonlocality. This interplay between geometry and nonlocality is a general feature of the nonlocal interaction, with applications to dipolar BECs and nonlocal photon fluids. Tailoring the system geometry thus provides external control of the effective nonlocal length characterizing the fluid, and sets a threshold wavevector below which a linear, sonic dispersion relation consistent with superfluidity may be observed. We discuss this interplay in the context of recent experimental observations of superfluid behavior in a room-temperature, nonlocal photon fluid in a propagating geometry. We have experimentally observed signatures of superfluid behavior in the dispersion relation, and in the nucleation of vortex cores as the photon fluid flows past an extended obstacle, despite working with a highly-nonlocal thermal nonlinearity expected to suppress such superfluid behavior. 34 Participants • L. Angenoorth (Universität Heidelberg, Germany) • K. Geier Germany) • A. Amo (Centre for Nanosciences and Nanotechnologies (C2N), France) • P. Hauke (University of Innsbruck, Austria) • K. Baumann (Goethe Frankfurt, Germany) • M. Holten Germany) Universität (Universität (Universität Heidelberg, Heidelberg, • A. Bergschneider (Universität Heidelberg, Germany) • F. Jendrzejewski (Universität Heidelberg, Germany) • S. Butera (Heriot-Watt University Edinburgh, United Kingdom) • P. Jurcevic (University of Innsbruck, Austria) • I. Carusotto (BEC Trento, Italy) • M. Karl Germany) • J.-S. Caux (University of Amsterdam, The Netherlands) • C. Ciuti (Univ. Paris Diderot, France) • L. Cugliandolo (Université Pierre et Marie Curie, France) • S. Czischek (Universität Heidelberg, Germany) • A. Daley (University of Strathclyde, United Kingdom) • E. Demler (Harvard University, USA) • M. F. Di Liberto (INO-CNR BEC Center Trento, Italy) • J. Eisert Germany) (Freie Universität Berlin, (Universität Heidelberg, • M. Kastner (Stellenbosch University, South Africa) • P. Kunkel Germany) (Universität Heidelberg, • A. Lamacraft (University of Cambridge, United Kingdom) • D. Linnemann (Universität Heidelberg, Germany) • H. Lüschen (MPQ/LMU, Germany) • O. Marty (Universität Ulm, Germany) • M. Medvedyeva (University of Ljubljana, Slovenia) • S. Nascimbène (LKB ENS Paris, France) • T. Enss Germany) (Universität Heidelberg, • N. Navon (University of Cambridge, United Kingdom) • S. Erne Germany) (Heidelberg University, • M. Oberthaler (Universität Heidelberg, Germany) • F. Essler (University of Oxford, United Kingdom) • T. Osborne (Leibniz Hannover, Germany) • T. Gasenzer (Universität Heidelberg, Germany) • T. Ozawa (INO-CNR BEC Center and University of Trento, Italy) 35 Universität • T. Prosen (University of Ljubljana, Slovenia) • M. Prüfer Germany) (Universität Heidelberg, • T. Schweigler (TU Wien, Austria) • A. Signoles (Universität Heidelberg, Germany) • R. Puebla (Ulm University, Germany) • H. Strobel Germany) • M. Rabel Germany) Heidelberg, • A. Tarkhov (Skolkovo Institute of Science and Technology, Russia) • G. Salerno (INO-CNR BEC Center, Italy) • L. Todorov (Durham University, United Kingdom) (Universität • A. Salzinger (Universität Heidelberg, Germany) • S. Scherg (Ludwigs-Maximilians Universität München, Germany) • C.-M. Schmied (Heidelberg University, Germany) • J. Schmiedmayer (TU Wien, Austria) • U. Schneider (University of Cambridge, United Kingdom / Ludwigs-Maximilians Universität München, Germany) 36 • J. Ulmanis Germany) (Universität (Heidelberg Heidelberg, University, • K. Viebahn (University of Cambridge, United Kingdom) • M. Weitz (Universität Bonn, Germany) • K. Wilson (Heriot-Watt United Kingdom) University, • M. Wouters (Universiteit Antwerpen, Belgium) Committees Scientific board • Alberto Amo (Marcoussis) • Jürgen Berges (Heidelberg) • Jacqueline Bloch (Marcoussis) • Iacopo Carusotto (Trento) • Jens Eisert (Berlin) • Thomas Gasenzer (Heidelberg) • Markus Oberthaler (Heidelberg) • Jörg Schmiedmayer (Vienna) • Ulrich Schneider (Cambridge/Munich) Coordinator • Thomas Gasenzer (Kirchhoff-Institut für Physik, Universität Heidelberg) Contact Conference Assistant Christiane Jäger Universität Heidelberg Synthetic Quantum Systems Kirchhoff-Institut für Physik Im Neuenheimer Feld 227 69120 Heidelberg Germany tel: +49 6221 54 5172 fax: +49 6221 54 5179 e-mail: [email protected] www: http://www.kip.uni-heidelberg.de/matterwaveoptics/ 37 Index Programme 3 Practical Information Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Internet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 7 7 Talks Martin Weitz . . . . Philipp Hauke . . . Fabian Essler . . . . Jean-Sébastien Caux Petar Jurcevic . . . Andrew Daley . . . Leticia Cugliandolo . Cristiano Ciuti . . . Michiel Wouters . . Tomaž Prosen . . . Tomoki Ozawa . . . Alberto Amo . . . . Sylvain Nascimbène Jens Eisert . . . . . Austen Lamacraft . Henrik Lüschen . . Nir Navon . . . . . Markus Karl . . . . Thomas Schweigler Adrien Signoles . . . Eugene Demler . . . Tobias Osborne . . Iacopo Carusotto . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Posters Andrea Bergschneider . Salvatore Butera . . . . Marco Fedele Di Liberto Sebastian Erne . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 9 10 10 11 11 12 13 13 14 14 15 16 17 18 18 19 20 21 22 22 23 23 24 . . . . 25 25 26 26 27 Oliver Marty . . . . . . . Ricardo Puebla . . . . . . Grazia Salerno . . . . . . Sebastian Scherg . . . . . Christian-Marcel Schmied Juris Ulmanis . . . . . . . Konrad Viebahn . . . . . Kali Wilson . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 29 29 30 31 32 32 33 Participants 34 Committees 36 39 Internet There is a wifi Internet access in the conference hall. Connect to WLAN ’UNIWEBACCESS’ and open your browser. It will automatically redirect to the login page. login: iq3 password: 8x7du The web-page of the conference is: http://www.thphys.uni-heidelberg.de/ smp/RETUNE2012/index.php It contains additional information about the conference. We will try to assemble the material of the conference and make it available on the web-page as well. 8