Bulletin of the American Physical Society
APS March Meeting 2018
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session V15: NonEquilibrium Quantum Thermodynamics 
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Sponsoring Units: DQI GSNP Chair: Jens Eisert, Dahlem Center for Complex Quantum Systems, Freie Universität Berlin Room: LACC 304C 
Thursday, March 8, 2018 2:30PM  2:42PM 
V15.00001: Observing a Quantum Maxwell Demon at Work Sébastien Jezouin , Nathanaël Cottet , Landry Bretheau , Philippe CampagneIbarcq , Quentin Ficheux , Janet Anders , Alexia Auffeves , Benjamin Huard Since the introduction of Maxwell's demon in 1867, many physicists like Szilard, Landauer, Bennett and Feynman have questioned the thermodynamics of systems with an internal memory, which has lead to the advent of thermodynamics of information. Recent experiments have enabled to test some of its fundamental predictions in the classical domain. Here, we present an experimental realization of a quantum version of the Maxwell's demon using superconducting circuits. The thermal energy of a system (superconducting qubit) is used to extract energy towards a detector thanks to the knowledge acquired by a demon (a superconducting cavity) on the system. Thanks to the high level of controllability of superconducting circuits, we have experimental access to the flows of entropy, heat and work in all parts of the experiment. Moreover the transition between accurate or inaccurate information extracted by the demon and the role of quantum coherence on this particular implementation are investigated. 
Thursday, March 8, 2018 2:42PM  2:54PM 
V15.00002: Extracting work from quantum measurement Cyril Elouard , David HerreraMartí , Benjamin Huard , Alexia Auffeves , Andrew Jordan In classical heat engines, a thermal bath provides heat to the working agent. This uncontroled form of energy exchange is associated with entropy production as the reservoir acts randomly on the working agent. 
Thursday, March 8, 2018 2:54PM  3:06PM 
V15.00003: CorrelationEnhanced Algorithmic Cooling Nayeli Azucena RodríguezBriones , Raymond Laflamme , Eduardo MartinMartinez , Achim Kempf

Thursday, March 8, 2018 3:06PM  3:18PM 
V15.00004: Quantum Nonequilibrium Statistical Mechanics Meets the Measurement Problem David Rogers We present a complete theory of experimental measurement for heat and work on small nonequilibrium quantum systems under strong environmental coupling. It is consistent with the usual laws of thermodynamics at all temperatures, while only operating on ancilla that interacted with the system at some time. We show that the backaction of measurement must be counted as work rather than heat to satisfy the second law, and that this backaction strictly prevents reversible conversion of heat and entropy in the quantum setting. Our total entropy production is a lower bound on weak coupling, quantum jump / unravelling, and transitionprobability based definitions, which appear as particular limits of the present model. Two interesting consequences of the theory are that systems actively interacting with a real environment have a minimum achievable temperature irrespective of the environmental temperature, and that it is impossible to apply traditional fluctuation relations in the presence of backaction. The phenomenon of minimum temperature offers a novel explanation of recent experiments aimed at testing fluctuation theorems in the quantum realm and places a fundamental purity limit on quantum computers. 
Thursday, March 8, 2018 3:18PM  3:30PM 
V15.00005: Information Gain and Loss in Quantum Feedback Protocols Mahdi Naghiloo , Jose Alonso , Alessandro Romito , Eric Lutz , Kater Murch Recent advances in fabrication and control of small systems where quantum fluctuations are dominant over thermal fluctuations allow for novel studies of thermodynamics in the quantum regime. As seen in stochastic thermodynamics, one may extract work from a system by using the information acquired from measurements. In the quantum world, measurement inevitably induces backaction on the state of the system and the amount of information gained evolves stochastically. In particular, information can be ‘lost’ due to measurement backaction, which, owing to superposition and entanglement, has no classical counterpart. Here, we use a superconducting qubit to study “information dynamics” of a quantum system subject to continuous weak measurement. With different state preparations and varying drive protocols, we experimentally investigate the transition between regimes of information loss and gain. 
Thursday, March 8, 2018 3:30PM  3:42PM 
V15.00006: Repeated Interaction Approach to Dissipationdriven Nonequilibrium Open Quantum Systems: Open Quantum Walks and Open Quantum Brownian Motion Francesco Petruccione , Ilya Sinayskiy Microscopic modelbased approaches play a crucial role in nonequilibrium statistical mechanics. Traditionally, in quantum statistical mechanics one starts from the microscopic Hamiltonian of the system, bath, and systembath interaction. After performing typical approximations, such as Born, Markov, and rotating wave, one obtains a quantum master equation for the reduced density matrix of the open system. Repeated interaction is a systematic and mathematically rigorous approach to the description of the dynamics and thermodynamics of nonequilibrium quantum systems. In the continuous time limit, together with the weakcoupling assumption, this approach naturally leads to a quantum master equation in GoriniKosakowskiSudarshanLindblad form. Here, we extend the repeated interaction formalism to the description of open quantum walks and open quantum Brownian motion, which are examples of quantum stochastic dynamical systems purely driven by the dissipative interaction with an environment. We show that the repeated interaction approach provides a natural tool for the investigation and simulation of dynamical and thermodynamical properties of these nonequilibrium dissipation driven systems. 
Thursday, March 8, 2018 3:42PM  3:54PM 
V15.00007: Scaling of quantum work distribution for interacting manybody systems Krissia Zawadzki , Marcela Trujillo , Roberto Serra , Irene D'Amico Understanding the dynamics small quantum systems outofequilibrium is at 
Thursday, March 8, 2018 3:54PM  4:06PM 
V15.00008: Exact local entropy of a nonequilibrium quantum system Charles Stafford , Abhay Shastry The statistical mechanics of a system of independent fermions or bosons in a nonequilibrium steady state is analyzed using the density operator in the scattering basis. An exact result for the local entropy is obtained, and identities and inequalities corresponding to the first, second, and third laws of thermodynamics are derived. The second law takes the form of a hierarchy of inequalities relating the exact scattering entropy to entropy formulas based on local measurements that implicitly involve incomplete information. 
Thursday, March 8, 2018 4:06PM  4:18PM 
V15.00009: Work extraction in an isolated quantum lattice systems: Grand canonical and generalized Gibbs ensemble predictions Ranjan Modak , Lev Vidmar , Marcos Rigol We study work extraction in noninteracting and weakly interacting isolated fermionic quantum lattice systems in one dimension [1,2]. We extract work by quenching onsite potentials in a subsystem, letting the entire system equilibrate to the generalized Gibbs ensemble (GGE, noninteracting case) or to the Gibbs ensemble (GE, weakly interacting case), and returning to the initial parameters in the subsystem using a quasistatic process. We identify a class of quenches in both ensembles that does not produce entropy. Those quenches are proved to ensure maximal work extraction in the thermodynamic limit when thermalization occurs. We show that the same remains true in the presence of integrable dynamics that results in equilibration to the GGE [1]. We explore the use of emergent local Hamiltonians as a way to reduce the time taken by our protocol [2]. 
Thursday, March 8, 2018 4:18PM  4:30PM 
V15.00010: Quantum Thermodynamics of Nanoscale Steady States Far from Equilibrium Nobuhiko Taniguchi We develop a quantum thermodynamic description for nanoscale steady states that are sustained arbitrarily far from equilibrium by connecting with multiple reservoirs of different chemical potentials and temperatures. Our focus is to construct the steadystate thermodynamic function Φ_{ss} that accounts for irreversible processes of quantum kinetics. We identify and evaluate Φ_{ss} for the single bosonic or fermionic resonant level model in the wideband limit, demonstrating that the nonequilibrium thermodynamic relations exactly produces the multiterminal, LandauerBüttiker formula of charge, energy or heat currents beyond the linear response. The entropy production rate is also described accordingly. As the quantity Φ_{ss} is stationary in time, we can interpret it as the free entropy (or information) transferable by the steady state. The same nonequilibrium thermodynamic structure persists for a spindegenerate single level with local interaction. Moreover, we show that the universal heat transport phenomena at lowtemperatures exemplify how the function Φ_{ss} can characterize current fluctuations and the cumulant generating function. 
Thursday, March 8, 2018 4:30PM  4:42PM 
V15.00011: Uncertainty Relations in Implementation of Unitary Control Hiroyasu Tajima , Naoto Shiraithi , Keiji Saito We study the underlying mechanism in the implementation of unitary control on a system with an experimental apparatus. We regard the unitary time evolution in the system as a physical phenomenon that results from the interaction between the system and the external system. We consider the conditions required to approximate the dynamics of the reduced density matrix of the system by the desired unitary time evolution U_{S}. Then, we derive fundamental tradeoff relations to implement the unitary dynamics: δ_{U}δ_{E}≧‖[U_{S},H_{S}]‖/40. Here, H_{S} is the Hamiltonian of the system, δ_{U} is the implementation error of the desired unitary U_{S}, and δ_{E} is the energy fluctuation of the external system. We also show that the energy fluctuation δ_{E} should be caused by a quantum superposition. Namely, precise unitary control in the system requires large quantum fluctuation of energy in the external system. 
Thursday, March 8, 2018 4:42PM  4:54PM 
V15.00012: Topological effects in thermodynamics Yiheng Xu , Ferdinand Evers , Charles Stafford We consider entropy and persistent currents induced by topological phases in multiplyconnected open quantum systems. We prove a strong form of the Nernst theorem (third law of thermodynamics) for "fully open" quantum systems: the entropy goes strictly to zero as temperature approaches absolute zero. The conventional formula for the heat current is shown to be problematic for persistent currents, implying a divergent entropy current as temperature goes to zero, in contradiction to the third law. The apparent paradox is resolved through the inclusion of a topological work term in the first law corresponding to the "persistent work" done in establishing the topological fields. 
Thursday, March 8, 2018 4:54PM  5:06PM 
V15.00013: Solid State Voltage Controlled Entanglement Switch based on Open System Dynamical Phase Transition Bhaskaran Muralidharan , Sattwik Deb Mishra , Vivek Arte , Sai Vinjanampathy We propose a solidstate device that generates steadystate entanglement between its constituent impurity spins and is controlled by voltage. We first study this device with two impurity spins. This voltage controlled entanglement switch is based on an open quantum system dynamical phase transition where the entanglement is the order parameter. We also discuss the generation of steady states with genuine multipartite entanglement when there are more than two impurity spins. Our solution of the device’s physics is based on a density matrix approach [1]. 
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