Bulletin of the American Physical Society
50th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics APS Meeting
Volume 64, Number 4
Monday–Friday, May 27–31, 2019; Milwaukee, Wisconsin
Session Q08: Quantum Simulation II |
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Sponsoring Units: DQI Chair: Kaden Hazzard, Rice University Room: Wisconsin Center 103C |
Thursday, May 30, 2019 2:00PM - 2:30PM |
Q08.00001: Observation of a Dynamical Phase Transition in a Quantum Degenerate Fermi Gas Invited Speaker: Ana Maria Rey Out-of-equilibrium quantum systems can display fascinating phenomena that cannot exist in equilibrium and that fall outside the typical framework of statistical mechanics. Testing conjectured universal behaviors and new organizing principles of dynamical quantum matter is therefore in high demand. One emerging new paradigm is the dynamical phase transition (DPT) characterized by the existence of a long-time-average order parameter that distinguishes two non-equilibrium phases. In this talk we report the observation of a DPT in a trapped quantum degenerate Fermi gas[1]. Above a critical interaction strength, a non-equilibrium magnetization is long lived, and protected by an energy gap against inhomogeneous field-induced dephasing. Through detailed comparisons to theory and by testing the reversibility of the collective many-body dynamics, we identify a regime in which the complex far-from-equilibrium dynamics of interacting fermions is quantitatively described by a collective Heisenberg model with an inhomogeneous axial field, a canonical model for magnetism recently used to describe quenched superconductors. Our quantum simulation of this model reveals the ``phase-I'' to ``phase-II'' transition predicted to exist but not yet directly observed in $s$-wave superconductors. [1] Observation of a Dynamical Phase Transition in the Collective Heisenberg Model,S.Smale, P. He, B. A. Olsen, K. G. Jackson, H. Sharum, S. Trotzky, J. Marino, A. M. Rey and J.H. Thywissen, arXiv:1806.11044 [Preview Abstract] |
Thursday, May 30, 2019 2:30PM - 3:00PM |
Q08.00002: Self-Verifying Variational Quantum Simulation of Lattice Models Invited Speaker: Rick van Bijnen Hybrid classical-quantum algorithms aim at variationally solving optimization problems, using a feedback loop between a classical computer and a quantum co-processor, while benefitting from quantum resources. Here we present experiments demonstrating self-verifying, hybrid, variational quantum simulation of lattice models in condensed matter and high-energy physics. Contrary to analog quantum simulation, this approach forgoes the requirement of realising the targeted Hamiltonian directly in the laboratory, thus allowing the study of a wide variety of previously intractable target models. Our quantum co-processor is a programmable, trapped-ion analog quantum simulator with up to 20 qubits, capable of generating families of entangled trial states respecting symmetries of the target Hamiltonian. We determine ground states, energy gaps and, by measuring variances of the Schwinger Hamiltonian, we provide algorithmic error bars for energies, thus addressing the long-standing challenge of verifying quantum simulation. [Preview Abstract] |
Thursday, May 30, 2019 3:00PM - 3:30PM |
Q08.00003: Exploring spontaneous-emission phenomena with matter waves Invited Speaker: Dominik Schneble The quantitative understanding of spontaneous emission harks back to the early days of QED, when in 1930 Weisskopf and Wigner, using Dirac’s radiation theory, calculated the transition rate of an excited atom undergoing radiative decay. Their model, which describes the emission of a photon through coherent coupling of the atom’s dipole moment to the continuum of vacuum modes, reflects the view that spontaneous emission into free space, driven by vacuum fluctuations, is inherently irreversible. -- We have recently studied [1] spontaneous emission in a novel context that allowed us to go beyond the model's usual assumptions. For this purpose, we created an array of microscopic atom traps in an optical lattice that emit single atoms, rather than single photons, into the surrounding vacuum. Our ultracold-atom system, which provides a tunable matter-wave analog of photon emission in photonic-bandgap materials, revealed behavior beyond standard exponential decay with its associated Lamb shift. It includes non-Markovian backflow of radiation into the emitter, and the formation of a long-predicted bound state in which the emitted particle hovers around the emitter in an evanescent wave. -- My talk will conclude with an outlook on using our new platform for studies of dissipative many-body physics and matter-wave quantum optics in optical lattices. \newline [1] L. Krinner et al., Nature {\bf 559}, 589 (2018); M. Stewart et al., Phys.Rev.A {\bf 95}, 013626 (2017) [Preview Abstract] |
Thursday, May 30, 2019 3:30PM - 4:00PM |
Q08.00004: Band Engineering for Quantum Simulation in Circuit QED Invited Speaker: Alicia Kollar The field of circuit QED has emerged as a rich platform for both quantum computation and quantum simulation. Lattices of coplanar waveguide (CPW) resonators realize artificial photonic materials in the tight-binding limit. In combination with qubit-mediated photon-photon interactions, these systems can be used to study dynamical phase transitions and many-body phenomena in driven-dissipative systems. In this talk, we will show how graph-theory and graph-level operations can be used to tailor the single-particle band structures of such systems. In particular, we will show that the process of taking a line graph produces controllably gapped flat bands at $-2$ and that subdividing all graph edges produces Dirac cones from formerly quadratic band edges and chiral flat bands at zero energy. [Preview Abstract] |
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