Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session K52: Thermodynamics and Thermalization in Quantum Information TheoryFocus

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Sponsoring Units: GQI GSNP Chair: Dibyendu Mandal, University of California, Berkeley Room: 399 
Wednesday, March 15, 2017 8:00AM  8:36AM 
K52.00001: A single atom heat engine Invited Speaker: Eric Lutz We review the miniaturization of heat engines towards the nanoscale. We discuss in detail the recent experimental realization of a single atom engine using an ultracold trapped ion coupled to engineered reservoirs. We further address the question of how to enter the quantum regime and exploit quantum effects to enhance the performance of the machine. [Preview Abstract] 
Wednesday, March 15, 2017 8:36AM  8:48AM 
K52.00002: Quantum Heat Engines using Superconducting Circuits A. M. Vadiraj, C. W. S. Chang, Pol FornDiaz, I. Nsanzineza, H. Percival, C. Warren, C. M. Wilson Quantum heat engines are prototypical systems for studying the interplay between classical thermodynamics and quantum mechanics. Extensive theoretical investigations of these engines have predicted novel effects absent from classical enginges, but no experiment has confirmed these predictions. We propose to build a quantum heat engine from a system of nonlinearly coupled superconducting microwave resonators. The working substance of the engine is photons in one of the resonators. The resonators are coupled via a superconducting quantum interference device (SQUID) leading to an optomechanical interaction where the photon number in one resonator couples to the coherent current in the other. Our ``photonic pisto'' is an all electrical system which makes use of this interaction in order to perform useful work. We will present preliminary results which characterize our engine. [Preview Abstract] 
Wednesday, March 15, 2017 8:48AM  9:00AM 
K52.00003: Tackling Quantum Thermodynamics via Quantum Collision Models Francesco Ciccarello, Salvatore Lorenzo, G. Massimo Palma Quantum collision models embody an advantageous tool for studying openquantumsystem dynamics within a microscopic and physically welldefined framework, which allows to address some problems intractable with other approaches. In this talk, we will show the potential of collision models to shed light on nonequilibrium quantum thermodynamics issues, such as the Landauer’s principle and quantum fluctuation theorems. [Preview Abstract] 
Wednesday, March 15, 2017 9:00AM  9:12AM 
K52.00004: Quantum Thermalization between a Superconducting Qubit and Resonator Ibrahim Nsanzineza, Helen Percival, A. M. Vadiraj, C.W.S. Chang, Chris Warren, Pol FornDíaz, C. M. Wilson Superconducting quantum circuits have emerged as the leading candidate technology for scalable quantum computing. More recently, they have been proposed as a testbed for quantum thermodynamics, for instance, as a way to explore practical aspects of the design, control and optimization of quantum heat engines. Along these lines, we have designed and fabricated circuits with a transmon qubit coupled to a tunable superconducting coplanar waveguide resonator. The circuit is designed so that we can study “quantum thermalization” of the qubit, prepared in a mixed state, coupled to the resonator. We will present our preliminary measurements characterizing this process. [Preview Abstract] 
Wednesday, March 15, 2017 9:12AM  9:24AM 
K52.00005: Timereversibility in quantum measurement Patrick Harrington, Andrew Jordan, Kater Murch In quantum mechanics, the stochastic backaction of quantum measurement disrupts unitary Schr\"odinger dynamicscanonically referred to as wavefunction collapsecausing irreversible quantum evolution by virtue of the manytoone property of projective measurements. However, weak measurements cause minimal perturbations to the quantum state and therefore can be reversible. We develop statistical measures to characterize the arrow of time from individual quantum trajectories. These measures involve a comparison of path probabilities for both forward and timereversed trajectories. We apply this analysis to different measurement schemes for superconducting qubits ranging from dispersive quantum nondemolition measurement to fluorescence detection. [Preview Abstract] 
Wednesday, March 15, 2017 9:24AM  9:36AM 
K52.00006: Experimental Study of Quantum Graphs With and Without TimeReversal Invariance Steven Mark Anlage, Ziyuan Fu, Trystan Koch, Thomas Antonsen, Edward Ott An experimental setup consisting of a microwave network is used to simulate quantum graphs. The random coupling model (RCM) is applied to describe the universal statistical properties of the system with and without timereversal invariance. The networks which are large compared to the wavelength, are constructed from coaxial cables connected by T junctions, and by making nodes with circulators timereversal invariance for microwave propagation in the networks can be broken. The results of experimental study of microwave networks with and without timereversal invariance are presented both in frequency domain and time domain. With the measured Sparameter data of twoport networks, the impedance statistics and the nearestneighbor spacing statistics are examined. Moreover, the experiments of time reversal mirrors for networks demonstrate that the reconstruction quality can be used to quantify the degree of the timereversal invariance for wave propagation. Numerical models of networks are also presented to verify the time domain experiments. [Preview Abstract] 
Wednesday, March 15, 2017 9:36AM  9:48AM 
K52.00007: Nonequilibrium dynamics of the BoseHubbard model and the discrete nonlinear Schrödinger equation in one dimension Christian B. Mendl, Johannes M. Oberreuter, Michael Knap, Herbert Spohn We study finite temperature time correlations of the BoseHubbard model and its classical analogue, the discrete nonlinear Schrödinger (DNLS) equation, on a onedimensional lattice. In the high temperature regime the DNLS exhibits diffusive spreading of the density and energy correlations. With lowering temperature, Umklapp processes become rare, such that phase differences appear as an additional (almost) conserved field. Using nonlinear fluctuating hydrodynamics as theoretical framework, we establish that the DNLS time correlations have the same signature as a generic anharmonic chain, in particular KardarParisiZhang (KPZ) broadening for the sound peaks and Lévy 5/3 broadening for the heat peak. These theoretical predictions agree well with numerical simulations of the DNLS. In the, so far not sharply defined, ultralow temperature regime the integrability of the dynamics becomes visible. Finally, we investigate how these results can be transcribed to quantum systems by comparing with numerical simulations of the BoseHubbard model, using timedependent density matrix renormalization group schemes at finite temperature. [Preview Abstract] 
Wednesday, March 15, 2017 9:48AM  10:00AM 
K52.00008: Local entropy of a nonequilibrium fermion system Charles Stafford, Abhay Shastry The local entropy of a nonequilibrium quantum system of independent fermions is investigated, and analyzed in the context of the laws of thermodynamics. The concept of ``parentropy'' is introduced, which is a state function related to the local nonequilibrium entropy by a variational principle: the parentropy is the entropy of a distribution maximizing the local entropy subject to the same constraints as the actual nonequilibrium distribution. It is shown that the local temperature and chemical potential measured by a floating thermoelectric probe can be expressed in terms of derivatives of the parentropy. The first law of thermodynamics can also be expressed in differential form in terms of the parentropy. However, the actual nonequilibrium entropy is related to the parentropy only via an inequality. It is not a state function, and its differential can not be expressed in terms of the first law of thermodynamics. [Preview Abstract] 
Wednesday, March 15, 2017 10:00AM  10:12AM 
K52.00009: Nonequilibrium dynamics of a driven Ising model coupled to a dissipative bath Anzi Hu, Mohammad Maghrebi We discuss numerical studies on the dynamics and steady state properties of a driven transversefield Ising model coupled to a dissipative bath. We consider various parameter regions, and identify regimes where the nonequilibrium quantum system can be mapped to a classical Ising model at an effective temperature determined by the transverse field and the dissipation. [Preview Abstract] 
Wednesday, March 15, 2017 10:12AM  10:24AM 
K52.00010: Renormalization group, normal form theory and the Ising model Archishman Raju, Lorien Hayden, Colin Clement, Danilo Liarte, James Sethna The results of the renormalization group are commonly advertised as the existence of power law singularities at critical points. Logarithmic and exponential corrections are seen as special cases and dealt with on a casebycase basis. We propose to systematize computing the singularities in the renormalization group using perturbative normal form theory. This gives us a way to classify all such singularities in a unified framework and to generate a systematic machinery to do scaling collapses. We show that this procedure leads to some new results even in classic cases like the Ising model and has general applicability. [Preview Abstract] 
Wednesday, March 15, 2017 10:24AM  10:36AM 
K52.00011: What Can Reinforcement Learning Teach Us About NonEquilibrium Quantum Dynamics Marin Bukov, Alexandre Day, Dries Sels, Phillip Weinberg, Anatoli Polkovnikov, Pankaj Mehta Equilibrium thermodynamics and statistical physics are the building blocks of modern science and technology. Yet, our understanding of thermodynamic processes away from equilibrium is largely missing. In this talk, I will reveal the potential of what artificial intelligence can teach us about the complex behaviour of nonequilibrium systems. Specifically, I will discuss the problem of finding optimal drive protocols to prepare a desired target state in quantum mechanical systems by applying ideas from Reinforcement Learning [one can think of Reinforcement Learning as the study of how an agent (e.g. a robot) can learn and perfect a given policy through interactions with an environment.]. The driving protocols learnt by our agent suggest that the nonequilibrium world features possibilities easily defying intuition based on equilibrium physics. [Preview Abstract] 
Wednesday, March 15, 2017 10:36AM  10:48AM 
K52.00012: Bridging global and local quantum quenches in conformal field theories Xueda Wen Entanglement evolutions after a global quantum quench and a local quantum quench in 1+1 dimensional conformal field theories (CFTs) show qualitatively different behaviors, and are studied within two different setups. In this work, we bridge global and local quantum quenches in (1+1)d CFTs in the same setup, by studying the entanglement evolution from a specific inhomogeneous initial state. By utilizing conformal mappings, this inhomogeneous quantum quench is analytically solvable. It is found that the entanglement evolution shows a global quantum quench feature in the short time limit, and a local quantum quench feature in the long time limit. The same features are observed in singlepoint correlation functions of primary fields. We provide a clear physical picture for the underlying reason. [Preview Abstract] 
Wednesday, March 15, 2017 10:48AM  11:00AM 
K52.00013: Phase Space Approach to Dynamics of Interacting Fermions Shainen Davidson, Dries Sels, Valentin Kasper, Anatoli Polkovnikov Understanding the behavior of interacting fermions is of fundamental interest in many fields ranging from condensed matter to high energy physics. Developing numerically efficient and accurate simulation methods is an indispensable part of this. Already in equilibrium, fermions are notoriously hard to handle due to the sign problem. Out of equilibrium, an important outstanding problem is the efficient numerical simulation of the dynamics of these systems. In this work we develop a new semiclassical phasespace approach (a.k.a. the truncated Wigner approximation) for simulating the dynamics of interacting lattice fermions in arbitrary dimensions. We demonstrate the strength of the method by comparing the results to exact diagonalization (ED) on small 1D and 2D systems. We furthermore present results on ManyBody Localized (MBL) systems in 1D and 2D, and demonstrate how the method can be used to determine the MBL transition. [Preview Abstract] 
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