Bulletin of the American Physical Society
52nd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 66, Number 6
Monday–Friday, May 31–June 4 2021; Virtual; Time Zone: Central Daylight Time, USA
Session X06: Generation and Detection of Novel Quantum PhasesLive
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Chair: Ana Maria Rey, JILA |
Friday, June 4, 2021 8:00AM - 8:12AM Live |
X06.00001: Cavity-Enhanced Microscope for Cold Atoms : towards Resolved-Sideband Cavity-Cooling of Neutral Atoms. Tigrane Cantat-Moltrecht, Jean-Philippe Brantut, Nick Sauerwein, Nicola Reiter We have set up a novel type of atom microscope, consisting of ultra-cold Lithium 6 atoms in a high-finesse cavity, combined with high-numerical-aperture optics (0.37). This combined system allows to trap the atoms in a micro-tweezer at 780nm and an intra-cavity optical dipole-trap at 1342nm, inside the near-concentric cavity mode at 671nm addressing the D2 transition of Li6. A beam at 460nm addressing the 2P → 4D transition of Li6, tightly-focused through the high-NA optics, will allow to tune the atom-cavity coupling, temporally and spatially. The dependance of the atom-cavity coupling with detuning will provide a super-resolution effect to this "microscope". |
Friday, June 4, 2021 8:12AM - 8:24AM Live |
X06.00002: A cavity-QED quantum simulator of dynamical phases of a BCS superconductor Robert J Lewis-Swan, Diego E Barberena, Julia R Cline, Dylan Young, James K Thompson, Ana Maria Rey We propose to simulate dynamical phases of a BCS superconductor using atom-light interactions in an optical cavity. The absence or presence of Cooper pairs is encoded in the internal electronic states of atoms confined within the cavity, while collective atom-atom interactions mediated by the cavity photons provide the analogue of the electron-electron attraction. Further, tunable inhomogeneous Stark and magnetic Zeeman shifts can be used to modify the dispersion relation of the effective Cooper pairs. These features allow us to controllably probe in real time, and without the need of ultrafast probes, the dynamical phase diagram of the BCS model as a function of the system parameters and/or the initial non-equilibrium state. We demonstrate the robustness of our predictions to typical experimental sources of noise, including the realization of a dynamical phase featuring persistent and robust coherent oscillations of the superconducting order parameter. Given the level of control available in state-of-the-art cavities, our work paves the way for the study of non-equilibrium features of quantum magnetism and superconductivity by harnessing atom-light interactions in cold atomic gases. |
Friday, June 4, 2021 8:24AM - 8:36AM Live |
X06.00003: Building a Shaken Lattice of Ultracold Lithium Atoms Kaiyue Wang, Colin V Parker, Feng Xiong, Yun Long The shaken lattice technique has provided new ways of controlling tunneling coefficients, manipulating band structures, enhancing interactions, exhibiting non-trivial topology, and to the discovery of interesting symmetry breaking phases. For ultracold fermions in particular, this offers the possibility of quantum simulation for a wide range of Hamiltonians relevant to solid state and materials physics. We are currently building an optical lattice that can be shaken by acousto-optical modulation and loaded with ultracold lithium gas. We shall introduce lattice setup and initial tests, as well as the efforts on acquiring a precise control on its modulation. We will also discuss planned experiments involving tunable Fermi surface shape. |
Friday, June 4, 2021 8:36AM - 8:48AM Live |
X06.00004: Cavity quantum electrodynamics with pairs in a strongly interacting Fermi gas Hideki Konishi, Kevin Roux, Victor Helson, Jean-Philippe Brantut The last decade has seen a convergence of concepts and methods between many-body physics, in particular condensed matter, and quantum optics, exemplified by the use of quantum gases as simulators for many-body phenomena. The use of quantized light fields with ultracold atoms permitted in the settings of cavity QED, however, has been restricted to thermal or bosonic atoms, without the ability to control independently the atom-atom and light-matter interactions. |
Friday, June 4, 2021 8:48AM - 9:00AM Live |
X06.00005: First order structural phase transition between two configurations of a superradiant crystal Xiangliang Li, Davide Dreon, Alexander Baumgaertner, Simon Hertlein, Philip Zupancic, Andrea Morales, Wei Zheng, Nigel R Cooper, Tobias Donner, Tilman Esslinger We experimentally Synthesize self-organized crystals in an Atomic Bose-Einstein condensate (BEC) of a Rubidium gas by inducing cavity mediated long range interactions. The BEC is placed inside an optical cavity mode and transversely illuminated by a blue detuned pump lattice beam combining a standing wave and a running wave component. Two crystalline phases arise from the couplings to different quadrature of the cavity mode, induced by mode softening in the P-band and S-band of the pump lattice, respectively. The two phases have different non-polar and centrosymmetric structures, connected by a first order phase transition. The transition is thus related to a change of crystal polarization. Thanks to our cavity QED setup, we measure in real-time the transient dynamics of the order parameter across the phase transition by recording the quadrature components of the cavity photon field, where the relaxation frequencies reveal the excitation spectrum of the self-organized crystal. |
Friday, June 4, 2021 9:00AM - 9:12AM Live |
X06.00006: Emergent atomic pump driven by dissipation Davide Dreon, Alexander Baumgärtner, Xiangliang Li, Simon Hertlein, Tilman Esslinger, Tobias Donner The time evolution of a quantum system can be strongly affected by dissipation. Although this mainly implies that the system relaxes to a steady state, in some cases it can bring to the appearance of new phases and trigger emergent dynamics. In our experiment, we study a Bose-Einstein Condensate dispersively coupled to a high finesse resonator. The cavity mode is populated via the atoms, such that the sum of the coupling beam(s) and the intracavity standing wave gives an optical lattice potential. When the dissipative and the coherent timescales are comparable, we find a regime of persistent oscillations where the cavity field does not reach a steady state. In this regime the atoms experience an optical lattice that periodically deforms itself, even without providing an external time dependent drive. Eventually, the dynamical lattice triggers a pumping mechanism. We will show complementary measurements of the light field and of the atomic transport, proving the connection between the emergent non-stationarity and the pump. |
Friday, June 4, 2021 9:12AM - 9:24AM Live |
X06.00007: Controlling the competition between coherent and dissipative processes in a superradiant quantum gas Francesco Ferri, Rodrigo Rosa-Medina, Fabian Finger, Nishant Dogra, Matteo Soriente, Oded Zilberberg, Tobias Donner, Tilman Esslinger Exposing a many-body system to external drives and losses can deeply modify its phases. Beside their fundamental interest, driven-dissipative systems prompt new paradigms for material engineering. A prime example is given by hybrid systems in which tuning of the elementary excitations is obtained by coupling matter to light. In this perspective, gaining conceptual understanding on how the microscopic properties of such systems can be tuned by the coupling to the environment is of primary interest. However, it is often a challenge to find platforms combining well-defined, tunable coherent and dissipative channels and, at the same time, the access to microscopic observables of the system. We report on a synthetic many-body system offering these possibilities, based on a Bose-Einstein condensate that is strongly coupled to an optical cavity. In our experiment, both spin and momentum of the atoms are coupled to the lossy cavity mode via two independent external Raman drives. Adjusting the imbalance between the drives allows to tune the competition between coherent dynamics and dissipation, with the appearance of a dissipation-stabilized phase and bistability. We characterize the properties of polariton modes and relate the observed phases to the microscopic elementary processes in the open system. Our findings provide prospects for studying squeezing in non-Hermitian systems, quantum jumps in superradiance, and dynamical spin-orbit coupling in a dissipative setting. |
Friday, June 4, 2021 9:24AM - 9:36AM Live |
X06.00008: Superradiant spin dynamics in a Bose-Einstein condensate coupled to an optical cavity Rodrigo Rosa-Medina, Francesco Ferri, Fabian Finger, Tobias Donner, Tilman Esslinger Dynamic transients are a natural ingredient of non-equilibrium quantum systems. One paradigmatic example is Dicke superradiance, describing the collectively enhanced population inversion of an ensemble of two-level atoms coupled to a single mode of the electromagnetic field. Here, we present a new experimental approach, which exploits superradiance to engineer spin currents in a quantum gas via spontaneous Raman scattering in an optical cavity. The readout of the leaking photon field provides real-time access to the system’s self-consistent evolution. |
Friday, June 4, 2021 9:36AM - 9:48AM Live |
X06.00009: Fluctuations and symmetry effects in many body self-organization in a dissipative cavity Catalin-Mihai Halati, Ameneh Sheikhan, Alla Bezvershenko, Achim Rosch, Helmut Ritsch, Corinna Kollath We investigate the full quantum evolution of ultracold interacting bosonic atoms on a chain and coupled to an optical cavity. Extending the time-dependent matrix product state techniques and the many-body adiabatic elimination techniques to capture the global coupling to the cavity mode and the open nature of the cavity, we examine the long time behavior of the system beyond the mean-field elimination of the cavity field. We show that the fluctuations beyond the mean-field state give a mixed state character to the dissipative phase transition and self-organized steady states. In the case of ideal bosons coupled to the cavity, the open system exhibits a strong symmetry which leads to the existence of conservation laws and multiple steady states. We find that the introduction of a weak breaking of the strong symmetry by a small interaction term leads to a direct transition from multiple steady states to a unique steady state. |
Friday, June 4, 2021 9:48AM - 10:00AM On Demand |
X06.00010: Demonstrating the 6 K measurement capability of an improved scanning quantum cryogenic atom microscope Stephen Taylor, Fan Yang, Brandon A Freudenstein, Benjamin L Lev The Scanning Quantum Cryogenic Atom Microscope (SQCRAMscope) is a quantum sensor that utilizes an elongated Bose-Einstein condensate to characterize an electromagnetic potential landscape near a sample. Here, we expand the previously reported capabilities of the microscope, improving its ease of use and lowering the base sample temperature from 35 K to 5.7 K. These upgrades include streamlined methods for BEC generation and sample loading, a closed-cycle pulse tube cryostat, and a radiation shield enclosing the sample mount. We present this improvement with cooldown data alongside sample vibration measurements, to demonstrate that the previously measured imaging resolution and field sensitivity of the microscope can be maintained in this new regime. |
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