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 X09: Open Quantum SystemsLive
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Chair: Jason Kestner, UMBC |
Friday, June 4, 2021 8:00AM - 8:12AM Live |
X09.00001: Non-Hermitian spin-orbit coupled quantum gases Zejian Ren, Chengdong HE, Elnur Hajiyev, Entong ZHAO, Ka Kwan Pak, Gyu-boong Jo The recent developments in non-Hermitian physics, open new possibilities for utilizing dissipation processes but have raised numerous open questions including the classification of topological states. In this talk, we report our experimental demonstration of non-Hermitian spin-orbit coupled quantum system with ultracold fermions. The dissipation is introduced by engineering spin-selective light scattering enabling us to engineer the energy gap and close it at the critical value of the dissipation, so-called exceptional point. We measure the energy spectrum of the system via quasimomentum-resolved Rabi spectroscopy, and identify an exceptional point where the PT symmetry transition occurs. We explore the topological feature around the exceptional point by dynamically encircling the exceptional point in the parameter space. Our work highlights the full controllability of non-Hermitian quantum system, and will set the stage for the realization of the non-Hermitian topological states and (unconventional) topological superfluid with spin-orbit coupling. |
Friday, June 4, 2021 8:12AM - 8:24AM Live |
X09.00002: Non-Markovian dissipative dynamics of neutral impurities in a BEC Rosaria G Lena, Andrew Daley The system of impurities immersed in a BEC reservoir provides an excellent platform for studies of both coherent and dissipative dynamics to probe the BEC. Thanks to the high degree of control over the parameters of the system and the environment, such as spatial confinement and interactions, this system allows us to access non-Markovian dynamics via reservoir engineering. |
Friday, June 4, 2021 8:24AM - 8:36AM Live |
X09.00003: Using N-point-function space-time mappings to exactly relate pairs of experiments with Markovian open quantum gases Etienne Wamba, Axel Pelster We present an exact space-time mapping between the N-point correlation functions of two different quantum gas experiments to extend a quantum-field mapping result for closed systems[1] to the general case of open quantum systems with the Markovian property[2]. For this, we consider an open many-body system consisting of a D-dimensional quantum gas of bosons or fermions that interacts with a bath under Born-Markov approximation and evolves according to a Lindblad master equation in a regime of loss or gain. We derive the Heisenberg evolution of any arbitrary N-point function of the system in such a regime. Our quantum field mapping for closed quantum systems is rewritten in the Schrödinger picture and then extended to open quantum systems by relating onto each other two different evolutions of the N-point functions of the open quantum system. As a concrete example of the mapping, we consider the mean-field dynamics of a one-dimensional Bose-Einstein condensate being locally bombarded by a dissipating beam of electrons in both cases when the beam amplitude or the waist is steady and modulated. |
Friday, June 4, 2021 8:36AM - 8:48AM Live |
X09.00004: Non-thermal energy fluctuations of a qutrit under feedback-controlled dissipative dynamics Santiago Hernández Gómez, Stefano Gherardini, Francesco Poggiali, Nicolas Staudenmaier, Michele Campisi, Andrea Trombettoni, Francesco Cataliotti, Paola Cappellaro, Nicole Fabbri Diamond spins disclose new possibilities for exploring how thermodynamic processes take place in open systems at the nanoscales, where fluctuations play a paramount role, and quantum features show up. |
Friday, June 4, 2021 8:48AM - 9:00AM Live |
X09.00005: Quantum thermodynamically consistent local master equations Gabriele De Chiara Local master equations are a widespread tool to model open quantum systems, especially in the context of many-body systems. These equations, however, are believed to lead to thermodynamic anomalies and violation of the laws of thermodynamics. In contrast, here we rigorously prove that local master equations are consistent with thermodynamics and its laws without resorting to a microscopic model, as done in previous works. In particular, we consider a quantum system in contact with multiple baths and identify the relevant contributions to the total energy, heat currents, and entropy production rate. We show that the second law of thermodynamics holds when one considers the proper expression we derive for the heat currents. We confirm the results for the quantum heat currents by using a heuristic argument that connects the quantum probability currents with the energy currents, using an analogous approach as in classical stochastic thermodynamics. We finally use our results to investigate the thermodynamic properties of a set of quantum rotors operating as thermal devices and show that a suitable design of three rotors can work as an absorption refrigerator or a thermal rectifier. For the machines considered here, we also perform an optimization of the system parameters using an algorithm of reinforcement learning. |
Friday, June 4, 2021 9:00AM - 9:12AM Live |
X09.00006: Superradiance of few driven two-level quantum dot emitters in the bad cavity limit Joe Wiedemann, Seth Rittenhouse, Peter Brereton, Joel Q Grim, Samuel G Carter The pursuit of an integrated quantum optics system requires the ability to determine the effect of design parameters on the quantum electrodynamics regime. We develop a simple master equation for few, driven, two-level emitters in the bad cavity regime. Comparing the resulting photon-photon correlation function in the steady state with experimental data from InGaAs quantum dots coupled to a photonic crystal waveguide, we validate our model parameters for coupling strength, spontaneous decay rate and incoherent driving rate. Building upon this model, we explore the superradiant regime for InGaAs quantum dots coherently driven within a waveguide, creating a model that captures the collective behavior of two-level emitters in the bad cavity limit. |
Friday, June 4, 2021 9:12AM - 9:24AM Live |
X09.00007: Application of resource theory to bound a molecular switch's probability of switching Nicole Yunger Halpern, David Limmer Resource theories have mushroomed across quantum information theory recently. These models capture how constraints limit the operations one can perform and the systems one can access. In a fixed-temperature environment, for instance, the first law of thermodynamics constrains operations to preserve energy. Scores of resource-theory theorems have been proved. Can they inform science beyond quantum information theory? Can resource theories answer pre-existing questions about the real physical world? We argue affirmatively, illustrating with photoisomers, or molecular switches. |
Friday, June 4, 2021 9:24AM - 9:36AM Live |
X09.00008: Weakly measuring the time atoms spend in the excited state due to a photon they don't absorb Josiah J Sinclair, Daniela Angulo Murcillo, Kyle E Thompson, Kent A Bonsma-Fisher, Aharon Brodutch, Aephraim M Steinberg When a resonant photon traverses a sample of absorbing atoms, how much time do atoms spend in the excited state? Does the answer depend on whether the photon is ultimately scattered or transmitted? In particular, if it is not scattered, meaning that it emerges in the direction it entered, does it cause atoms to spend any time in the excited state?, and if so, how much? We report an experimental measurement of the time a transmitted photon causes atoms to spend in the excited state. The experiment is carried out in an ultra-cold gas of Rubidium 85 atoms and involves simultaneously recording changes to the excited state occupation number induced by incident photons and whether those photons are transmitted. For short pulses and an optically thick medium, we find that the average time atoms spend in the excited state due to one transmitted photon is not zero, but rather (77 +/- 16)% of the time the average incident photon causes them to spend in the excited state. This observation of "excitation without loss" is attributed to coherent forward emission, which arises, for instance, due to the sign-flip the instantaneous Rabi frequency (pulse envelope) picks up when a broadband pulse propagates through an optically thick medium with highly frequency-dependent absorption. These results reveal the complex history of photons as they propagate through an absorbing medium and illustrate the power of utilizing post-selection to experimentally investigate the past behaviour of observed quantum systems. |
Friday, June 4, 2021 9:36AM - 9:48AM Live |
X09.00009: Superradiant phases of an atomic beam traversing an optical cavity Simon B Jäger, Haonan Liu, Athreya Shankar, John Cooper, Murray J Holland We investigate the different emission regimes of a pre-excited and collimated atomic beam passing through a single mode of an optical cavity. In the regime where the cavity degrees of freedom can be adiabatically eliminated, we find that the atoms undergo superradiant emission when the collective linewidth exceeds transit-time, homogeneous, and inhomogeneous broadening mechanisms. After the first superradiant emission we find that the system can reach a plethora of different dynamical superradiant phases depending on the detuning of the atomic transition and the cavity mode, the Doppler-width of the atomic beam, and the angle between the cavity and the atomic beam axis. Our findings highlight the ability of driven-dissipative many-body systems to form coherent dynamical structures that are stable on timescales that exceed the lifetime of all their constituents. |
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