Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session X01: Dissipative and Far-From-Equilibrium Quantum Dynamics in AMO Systems |
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Sponsoring Units: DAMOP Room: 103 |
Friday, March 6, 2020 11:15AM - 11:27AM |
X01.00001: Theory of non-Hermitian fermionic superfluidity subject to inelastic collisions in ultracold atoms Kazuki Yamamoto, Masaya Nakagawa, Kyosuke Adachi, Kazuaki Takasan, Masahito Ueda, Norio Kawakami In recent years, non-Hermitian (NH) quantum systems have been actively studied [1,2]. However, since most of the previous studies dealt with single-particle physics, understanding of many-body physics in NH systems is yet in its infancy. |
Friday, March 6, 2020 11:27AM - 11:39AM |
X01.00002: The Threefold Way in Non-Hermitian Random Matrices Ryusuke Hamazaki, Kohei Kawabata, Naoto Kura, Masahito Ueda Non-Hermitian random matrices have been utilized in diverse scientific fields such as dissipative and stochastic processes, nuclear physics, and neural networks. However, the only known universal level-spacing statistics are those of the Ginibre ensemble characterized by complex-conjugation symmetry. In this talk, we report our discovery of two distinct universality classes characterized by transposition symmetry [1]. We find that transposition symmetry alters repulsive interactions between two neighboring eigenvalues and deforms their spacing distribution, which is not possible with other symmetries including Ginibre's complex-conjugation symmetry which can affect only nonlocal correlations. Our results complete the non-Hermitian counterpart of Dyson's threefold classification of Hermitian random matrices and serve as a basis for characterizing nonintegrability and delocalization in open quantum systems with symmetry [1,2]. |
Friday, March 6, 2020 11:39AM - 11:51AM |
X01.00003: The property of open quantum system and nonhermiticity in strongly-correlated electron system Yoshihiro Michishita, Robert PETERS The effective non-hermitian Hamiltonian(ENH) in strongly-correlated electron systems(SCES), which introduced by H.Shen and L.Fu{PhysRevLett.120.146402}, is derived by the spectral function, and the non-hermitian physics is now studied eagerly. |
Friday, March 6, 2020 11:51AM - 12:03PM |
X01.00004: Dissipative quantum Ising chain as a non-Hermitian Ashkin-Teller model Naoyuki Shibata, Hosho Katsura The Lindblad equation is a well-known quantum master equation that describes the evolution of open quantum systems. In general, the Lindblad equation is more challenging to analyze than the Schrödinger equation for closed systems, as one has to deal with the space of operators rather than the Hilbert space. One approach to this difficulty is to construct exactly solvable models. However, very few exact results are available for open many-body systems, although many such examples are known in closed many-body systems. |
Friday, March 6, 2020 12:03PM - 12:15PM |
X01.00005: Effects of dipole-dipole interaction in atomic vapors probed by two-dimensional coherent spectroscopy Danfu Liang, Shaogang Yu, Yifu Zhu, Xiaojun Liu, Hebin Li Neutral atoms without permanent dipole moments can interact due to transition-induced dipole moments. Dipole-dipole interactions (DDIs) can lead to an energy shift of the atomic energy level and a change in the dephasing rate. The DDIs are usually detected by measuring the energy shift which might be difficult for weak DDIs, while the dephasing rate change has been largely overlooked. Optical two-dimensional coherent spectroscopy (2DCS) is extremely sensitive to DDIs and able to reveal the dephasing rate change due to DDIs. We implemented photon-echo, 1Q-2Q and double-quantum optical 2DCS to probe the effect of DDIs in the rubidium atomic vapor. From these spectra, we retrieved the decay rate change due to DDIs for the hyperfine levels of ^{87}Rb or ^{85}Rb’s D2 lines. The results show that the change in dephasing rate is the primary effect, compared to the energy shift, of DDIs in dilute atomic vapors. This technique allows us to detect weak DDIs and measure the effects in both energy shift and dephasing rate due to DDIs. |
Friday, March 6, 2020 12:15PM - 12:27PM |
X01.00006: Effects of a dissipative coupling to the momentum of a particle in a double well potential Dominik Maile, Sabine Andergassen, Gianluca Rastelli Double well potentials offer the possibility of coherent state preparation and therefore constitute important building blocks in the analysis of quantum information and quantum engineering devices. Here we present a study of the coherent tunneling in a parabolic double well potential in presence of different dissipative interactions. Specifically, we investigate the effects of an environmental coupling to the momentum and/or to the position of a particle in the potential. Using the semiclassical approximation to calculate instanton paths in Euclidean time, we find that momentum dissipation greatly enhances the coherent tunnel splitting. In presence of both types of dissipation, the momentum dissipation shifts the critical coupling strength of the dissipative phase transition induced by the position dissipation. |
Friday, March 6, 2020 12:27PM - 12:39PM |
X01.00007: Symmetry Breaking and Phase Transition in a Driven-Dissipative Kerr Oscillator X. H. H. Zhang, Harold U Baranger We show that quantum many-body effects can appear in a single non-linear oscillator that is driven by an external field in the presence of dissipation. This simple system is a paradigmatic example of open quantum many-body systems in which there has been great interest recently due to recent experimental advances such as quantum simulation. Here, weak non-linearity plays the role of the thermodynamic limit. Using both analytical and numerical methods, we demonstrate Z_{2} symmetry breaking and the corresponding phase transition. |
Friday, March 6, 2020 12:39PM - 12:51PM |
X01.00008: Open quantum systems approach to Bose polaron problems with applications Miguel Garcia-March, Mohammad Mehboudi, Christos Charalambous, Aniello Lampo, Luis A. Correa, Maciej A Lewenstein We discuss the dynamics of one and two quantum impurities immersed in a homogeneous or trapped Bose-Einstein condensate (BEC) in the framework of the quantum Brownian motion model [1-4]. When the impurities are untrapped, we show that the long-time behavior is superdiffusive. For the trapped impurities, we discuss the realistic conditions for the final state to be squeezed or to present entanglement in the two impurities case. We discuss two applications: i) for quantum non-demolition thermometry in a BEC [5]; and ii) to construct a system that permits a heat current between two BECs, and evaluate this system as a thermal diode [6]. |
Friday, March 6, 2020 12:51PM - 1:03PM |
X01.00009: Universality in the decay and evival of Loschmidt Echoes Myung-Joong Hwang, Bo-Bo Wei, Susana Huelga, Martin Plenio Understanding non-equilbrium quench dynamics through a quantum phase transition is an important theoretical task. It has long been obsereved that a sudden quench dynamics near a quantum phase transition characterised by the Loschmidt echo exhibits a critically enhanced decay. In this contribution, we present the dynamical scaling laws that govern the decay and revival of the Loschmidt echo completely characgterised by equilibrium critical exponents of a critical point. We reveal such dynamical scaling laws by analyzing relevant perturbations to the Loschmidt echo cast in a scaling invariant form. We will show the validity and the generality of the predicted dynamical scaling laws using numerical calculation of a diverse range of critical models such as Ising spin models with a short and long range interaction, a finite-component system phase transition, and a topological phase transition. Our finding promotes the Loschmidt echo to a quantitative non-equilibrium probe of criticality and allows for quantitative predictions on the role of criticality on various physical scenarios where the Loschmidt echo is central to describing non-equilibrium dynamics. |
Friday, March 6, 2020 1:03PM - 1:15PM |
X01.00010: Analytical Study of Decoherence in Rydberg Atom Qubits Anant Kale, Manuel Endres Individually trapped neutral atoms are a promising candidate for use in quantum computing and simulation applications. Entanglement can be generated between these atoms via strong dipole-dipole interactions by driving them to highly excited Rydberg states (n>20). However, the fidelity of single qubit operations as well as 2 qubit entangling gates is limited by several decoherence channels of which the dominant ones are finite temperature effects, laser frequency noise and intensity noise. Here we present an analytical (perturbative) expression for the effect of these noise sources on the rabi oscillations of a single atom and a pair of atoms in the Rydberg blockade regime. We derive this result in terms of the power spectral density (PSD) of the noise sources and use it to predict the maximum achievable single qubit and 2-qubit gate fidelities. Using this analytical result, we can appropriately adjust the driving laser’s locking parameters in experiments to modify its PSD and increase coherence time as well as gate fidelities. This work provides crucial insight for upcoming experiments aiming to entangle two alkaline-earth atoms for the first time. |
Friday, March 6, 2020 1:15PM - 1:27PM |
X01.00011: Non-Hermitian topological light steering Han Zhao, Xingdu Qiao, Tianwei Wu, Bikashkali Midya, Stefano Longhi, Liang Feng Photonic topological insulators provide a route for disorder-immune light transport, which holds promise for practical applications. Flexible reconfiguration of topological light pathways can enable high-density photonics routing, thus sustaining the growing demand for data capacity. By strategically interfacing non-Hermitian and topological physics, we demonstrate arbitrary, robust light steering in reconfigurable non-Hermitian junctions, in which chiral topological states can propagate at an interface of the gain and loss domains. Our non-Hermitian–controlled topological state can enable the dynamic control of robust transmission links of light inside the bulk, fully using the entire footprint of a photonic topological insulator. |
Friday, March 6, 2020 1:27PM - 1:39PM |
X01.00012: Quantum Quenches in Coupled Luttinger Liquids: Truncated Spectrum Approach vs Semi-Classics Robert Konik, Andrew James, Andrew Hallam We consider a quantum quench of multiple Luttinger liquids. Here we initialize the system by supposing the Luttinger liquids are in their ground state. At t=0 we turn on a tunnel coupling between the liquids. We then study the subsequent time evolution of quantities such as the mode occupation numbers. We show that there are discrepancies between the results as determined by the truncated spectrum approach and a semi-classical treatment. We argue that this difference is real through unitary perturbation theory which is exact at short times. We comment on the relevance of these results for experimental quantum quenches on two coupled Luttinger liquids. |
Friday, March 6, 2020 1:39PM - 1:51PM |
X01.00013: Non-equilibrium dynamics of the Pokrovsky-Talapov model Valentin Kasper, Jamir Marino, Sicong Ji, Joerg Schmiedmayer, Eugene Demler The unprecedented control in AMO systems allows us to study paradigmatic models of solid-state and high-energy physics. In particular AMO systems give us the unique opportunity to study the non-equilibrium physics of systems of closed quantum systems which is difficult or impossible in a solid state or high energy context. In this work we study the non-equilibrium physics of the Pokrovsky-Talapov model which is effectively realized by two Raman tunnel-coupled one-dimensional Bose gases. In particular, we study two quench protocols: a quench from the commensurate to incommensurate phase and vice versa. In particular, we compute the short and medium time dynamics of density and phase fluctuations and comment on the dynamics of emergent defects in this system. |
Friday, March 6, 2020 1:51PM - 2:03PM |
X01.00014: New exact eigenstates in the Lesanovsky model, proximity to integrability and the PXP model, and approximate scar states Daniel Mark, Cheng-Ju Lin, Olexei I Motrunich Cold Rydberg atoms have received significant recent attention. We study a model of Rydberg atoms in a nearest-neighbor Rydberg blockaded regime, introduced by Lesanovsky in Phys. Rev. Lett. 108, 105301 (2012). This many-body model (which has one parameter z) has an exactly known gapped, liquid ground state, and two exactly known low-lying excitations. We discover two new exact low-lying eigenstates. We also discuss behavior of the model at small parameter z and its proximity to an integrable model. Lastly, we discuss connections between the PXP and Lesanovsky models at intermediate z. The PXP model describes a recent experiment that observed unusual revivals from a charge density wave initial state, which are attributed to a set of many-body "scar states" which do not obey the eigenstate thermalization hypothesis. We discuss the possibility of scar states in the Lesanovsky model. |
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