Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session X25: Driven and Dissipative AMO Systems |
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Sponsoring Units: DAMOP Chair: Christine Muschik Room: BCEC 160A |
Friday, March 8, 2019 8:00AM - 8:12AM |
X25.00001: Observation of classical dynamical isolation in nonadiabatically modulated photonic cavities Avik Dutt, Momchil Minkov, Qian Lin, Luqi Yuan, David A. B. Miller, Shanhui Fan We experimentally demonstrate the phenomenon of dynamical isolation in harmonically modulated photonic cavities. We achieve this by strongly modulating a fiber ring cavity at a rate much faster than its linewidth. Such a nonadiabatically modulated cavity can show complete suppression of intracavity power even for an on-resonance input, resulting in dynamical isolation of the cavity field from the input light, as predicted in a recent theoretical study by Minkov et al. [APL Photonics 2, 076101 (2017)]. This counterintuitive behavior is strikingly different from the adiabatic regime typically studied in modulated photonic cavities, where the intracavity field is enhanced when the cavity’s instantaneous resonance frequency matches the input light’s frequency. Our work shows that periodically driven photonic systems can exhibit classical versions of quantum effects such as dynamical decoupling, which rely on modulating an open system at a rate faster than the system-reservoir interaction. Such effects have applications in signal optimization and frequency conversion in integrated photonics. |
Friday, March 8, 2019 8:12AM - 8:24AM |
X25.00002: Floquet quantum critical points in (1+1) dimensions Xueda Wen, Jie-Qiang Wu Given a generic (1+1) dimensional quantum critical points which can be described by conformal field theory (CFT), we propose an analytically solvable setup to study the Floquet dynamics of the CFT, i.e., the dynamics of a CFT subject to a periodic driving. A complete phase diagram in the parameter space can be analytically obtained within our setup. We find two phases: the heating phase and the non-heating phase. In the heating phase, the entanglement entropy keeps growing linearly in time, indicating that the system keeps absorbing energy; in the non-heating phase, the entanglement entropy oscillates periodically in time, i.e., the system is not heated. At the phase transition, the entanglement entropy grows logarithmically in time in a universal way. Furthermore, we can obtain the critical exponent by studying the entanglement evolution near the phase transition. Mathematically, different phases (and phase transition) in a Floquet quantum critical point correspond to different types of Mobius transformations. |
Friday, March 8, 2019 8:24AM - 8:36AM |
X25.00003: Entanglement features of Floquet random and fully random unitary quantum circuits Wei-Ting Kuo, Daniel Arovas, Yizhuang You We study the entanglement dynamics for Floquet random and fully random unitary circuits. The Floquet circuit consists of an on-site Haar random layer alternating with a nearest neighbor interaction layer. In the limit where the local Hilbert space dimension q is large, we show an emergent Ising symmetry and obtain an analytical expression for short time periods via the transfer matrix method. Based on our short time result, we promote the "entanglement feature" to an operator formalism and derive a diffusion equation for the entanglement dynamics at long times. The similar functional form of the corresponding diffusion operators implies a universal thermalization behavior in Floquet random and fully random unitary circuits. |
Friday, March 8, 2019 8:36AM - 8:48AM |
X25.00004: Single-photon bound states in atomic ensembles Yidan Wang, Michael Gullans, Antoine Browaeys, James V Porto, Darrick Chang, Alexey V Gorshkov
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Friday, March 8, 2019 8:48AM - 9:00AM |
X25.00005: Semiclassical Phase Redcution Theory for Quantum Dissipative Nonlinear Oscillators Yuzuru Kato, Hiroya Nakao The phase reduction theory is a framework for analyzing rhythmic dynamics of weakly perturbed classical limit-cycle oscillators. It has been widely used for analyzing synchronization properties of classical dissipative nonlinear oscillators, but it has not been formulated for quantum dissipative nonlinear oscillators in a general way. Thus, we formulate a phase reduction theory for quantum dissipatve oscillators. More specifically, we derive a semiclassical multi-dimensional Langevin equation from a general master equation for quantum dissipative systems exhibiting limit-cycle oscillations, and reduce it to an approximate one-dimensional classical stochastic differential equation describing phase dynamics of the oscillator. The density matrix and power spectrum of the oscillator can be explicitly reconstructed from the reduced phase equation. As an example, we analyze synchronization properties of a quantum van der Pol oscillator with harmonic driving and squeezing. The proposed framework allows us to analyze the dynamics of quantum dissipative nonlinear oscillators by using a simple classical stochastic differential equation under semiclassical approximation. |
Friday, March 8, 2019 9:00AM - 9:12AM |
X25.00006: Achieving transitionless quantum driving in a many-particle system via coupling to an auxiliary many-particle system of opposing statistics Rafael Hipolito, Paul M. Goldbart Transitionless quantum driving (TQD) in a quantum system driven by a time dependent Hamiltonian, $H_0(t)$, is in principle always possible via the addition of a counterdiabatic term, $H_1(t)$, as shown by Berry, and where $H_1(t)$ is in general nonlocal. Time dependence of $H_0$ gives rise to a curvature term in the comoving frame, which can be described via a gauge field, that induces transitions between different states, and whose influence is exactly nullified by $H_1(t)$. We explore an alternative way of achieving TQD in a many-particle quantum system (composed of either bosons or fermions), where all fields are coupled locally. In lieu of $H_1(t)$, we locally couple the original system A to a second system B (whose particles carry statistics opposite to A's) via a gaugino field. We explore the relationships between the A and B systems and the gauge and gaugino fields necessary to achieve TQD, and show that these relationships have a SUSY-like character. To illustrate, we explore the suppression of the Schwinger effect in a 1+1 D gas of Dirac electrons coupled to a time-dependent electric field that results from the suitable coupling (via gauginos) to its SUSY like partner. |
Friday, March 8, 2019 9:12AM - 9:24AM |
X25.00007: A flow equation approach to periodically driven quantum systems Michael Vogl, Pontus Laurell, Aaron Barr, Gregory Fiete We present a theoretical method to generate a highly accurate time-independent Hamiltonian governing the finite-time behavior of a time-periodic system. The method exploits infinitesimal unitary transformation steps, from which renormalization group-like flow equations are derived to produce the effective Hamiltonian. The method has a range of validity reaching into frequency regimes that are usually inaccessible via high frequency expansions. Our approach is demonstrated for many-body Hamiltonians where it offers an improvement over the more well-known Magnus expansion. We show how the method relates to the rotating frame approximation and how it can be used to approximately transform to a rotating frame where the exact transformation isn't tractable because infinitely many couplings are generated in an exact treatment. We compare our approximate results to those found via exact diagonalization. |
Friday, March 8, 2019 9:24AM - 9:36AM |
X25.00008: Driven-dissipative coupled Ising models: a new non-equilibrium universality class Jeremy Young, Michael Foss-Feig, Alexey V Gorshkov, Mohammad Maghrebi Driven-dissipative systems can potentially exhibit non-equilibrium phenomena that are absent in their equilibrium counterparts. However, phase transitions present in these systems generically exhibit an effectively classical, equilibrium behavior in spite of their non-equilibrium origin. In this talk, I investigate an experimentally motivated model where two Ising-like order parameters interact and form a multicritical point. Using perturbative renormalization group techniques, I show that a pair of inherently non-equilibrium multicritical points emerge. These non-equilibrium multicritical points exhibit a variety of exotic phenomena with no counterpart in equilibrium, including spiraling phase boundaries, the emergence of discrete scale invariance rather than the more familiar continuous scale invariance, and the violation of the fluctuation-dissipation theorem at all length scales, resulting in a system which becomes hotter and hotter at longer and longer wavelengths. |
Friday, March 8, 2019 9:36AM - 9:48AM |
X25.00009: Driven-Dissipative Quantum Phase Transitions Oscar Viyuela Garcia, Jiasen Jin, Alberto Biella, Cristiano Ciuti, Rosario Fazio, Davide Rossini In this talk, I will explain how quantum simulators can produce novel phases of matter known as driven-dissipative quantum phases. Just like equilibrium phases of matter, systems out-of-equilibrium display critical behavior when transitioning from an ordered to a disordered phase. However, the appearance of different steady-state ordering is of purely dynamical origin and cannot be reduced to the usual equilibrium results. Within this framework, I will show how a combination of powerful numerical and analytical tools beyond mean-field theory unveils novel phases of matter and quantum many-body physics not present under purely equilibrium conditions. I will also discuss how these effects and phases can be found using state-of-the-art quantum simulators. |
Friday, March 8, 2019 9:48AM - 10:00AM |
X25.00010: Scrambling and Floquet in Conformal Field Theory Ruihua Fan, Xueda Wen, Yingfei Gu, Ashvin Vishwanath Scrambling and Floquet are two important subjects in the study of quantum dynamics but hard to describe in general. Conformal field theory provides an ideal platform to get more analytical understanding. My talk will be divided into two parts. In the first part, I will discuss scrambling in the unitary minimal models, by analytically calculating out-of-time-order-correlation functions. In particular I will focus on the early-time and late-time behaviors and how they are related to each other. In the second part, I will talk about Floquet physics for general 2D CFTs. The Floquet driving is implemented with the sine-squared deformation. I will discuss the heating features and their stability. |
Friday, March 8, 2019 10:00AM - 10:12AM |
X25.00011: Random Lindblad Dynamics Tankut Can, Sarang Gopalakrishnan, Vadim Oganesyan, Dror Orgad The Lindblad superoperator is the generator of time translation for the quantum Markov master equation. We ask the question: what dynamics follow from a random Lindblad generator? To answer this, we define an ensemble of Lindblad superoperators using random matrix theory, and study the statistical properties its eigenvalues. In particular, we characterize the spectral gap (a.k.a. dissipative gap) which determines the asymptotic decay rate of typical operators in the Hilbert space. We find that the spectral gap is finite in the limit of infinite Hilbert space dimension, and described by a universal non-monotonic scaling function of the dissipative coupling constant. |
Friday, March 8, 2019 10:12AM - 10:24AM |
X25.00012: Drive-dependent dissipation in open quantum systems regularized by thermal fluctuations Rangeet Bhattacharyya We report an alternate formulation of the quantum master equation (QME) to describe the dynamics of a quantum system weakly coupled to a heat bath, in the presence of weak external drive. A key feature of this approach is the introduction of an explicit Hamiltonian to model the thermal fluctuations in the heat bath. We show that the resulting time coarse-grained dynamical equation for the quantum system has dissipators with a natural regulator, which emerges from an ensemble average over the fluctuations. Importantly, such regularized dissipators arise from the second-order contributions of both the external drive as well as the system-environment coupling. We show that the second-order drive terms, regularized to time-scales set by the fluctuations, result in dynamic drive-induced frequency shifts (such as Bloch-Siegert shifts) as well as drive-dependent relaxation phenomena (the Kramers-Kronig pair of the shift terms). We also present the experimental verification of the drive-induced dissipation terms using Nuclear Magnetic Resonance techniques. It is contemplated that such drive-induced dissipation will play important roles in quantum information processing. |
(Author Not Attending)
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X25.00013: Dissipation-induced instabilities of two-component Bose-Einstein condensates in optical cavities Ezequiel Rodriguez Chiacchio, Andreas Nunnenkamp We investigate the dynamics of a gas of ultra-cold spin-1 atoms inside an optical cavity, which is driven transversely by an external laser whose polarization is not aligned with that of the cavity field. By considering the atom population to be equally distributed between the +1 and -1 spin states, we obtain a two-component Dicke model with complex light-matter couplings. We study the effects of cavity losses on the system by computing the steady-state phase diagram and observe the emergence of dynamical instabilities in the form of limit cycles, induced by the interplay between coherent and dissipative processes. We characterize the physical mechanisms behind the unstable behavior and study the role of cavity fluctuations in the system. |
Friday, March 8, 2019 10:36AM - 10:48AM |
X25.00014: Low-cost ultrafast eigenstate transition without undergoing an adiabatic process Fatemeh Mostafavikhatam, Hamidreza Ramezani We introduce a class of non-Hermitian Hamiltonians that offers a dynamical approach to have complete population transfer from the ground state of a system to the ground state of a new system in no time. In particular, in our proposed 2×2 Hamiltonians, one eigenvalue is absolutely real and the other one is complex. This specific form of the eigenvalues helps us to exponentially amplify or decay the population |
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