Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session A29: Driven, Dissipative Manybody Systems 
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Sponsoring Units: DAMOP Chair: Daniel Grief, ETH Zurich Room: 603 
Monday, March 3, 2014 8:00AM  8:12AM 
A29.00001: Extrapolation of the long time behavior of a quasithermal field driven quantum system Herbert Fotso, Jim Freericks We study the relaxation of an isolated interacting heavylight FermiFermi mixture after it is placed under the influence of an artificial constant electric field. In the regime where the dynamics of the system are characterized by a monotonic evolution through quasithermal states and respects the fluctuation dissipation theorem throughout its relaxation, we use the monotonic increase of the effective temperature to infer the twotime selfenergy and extrapolate it at long times. This allows us to calculate, in the Dynamical Mean Field Theory framework, momentum dependent quantities at longer times than would otherwise be accessible. Such an approach makes it possible to observe the realtime approach to the steady state with a very low computational cost. [Preview Abstract] 
Monday, March 3, 2014 8:12AM  8:24AM 
A29.00002: Beyond PlanckEinstein quanta: Crossover from frequency driven to amplitude driven excitation in a nonequilibrium manybody system James Freericks, Wen Shen, Tom Devereaux Planck introduced the idea of light quanta to calculate the spectrum for black body radiation, which was employed by Einstein to explain the photoelectric effect. Later, Kubo and Greenwood derived the linear response of a quantum system to an applied external field, and found that the energy available for excitation was determined by the frequency of the driving field as given by the PlanckEinstein relation. As the magnitude of the driving field is further increased into the nonlinear regime, one expects to see multiphoton processes and then for there to be a crossover from frequencydriven excitation of the quantum system to amplitudedriven excitation. Here we use the exact quantum solution of ultracold spinless fermions in a doublewell optical lattice driven by an artificial pulsed electric field to show generically how such a crossover occurs. We find that the behavior is quite complex due to excitation and deexcitation processes, so that it is no longer true that tunneling is optimized when the field amplitude is the highest. When the field amplitude becomes very large, there is a novel quantum oscillatory behavior in the excitation spectroscopy that appears to describe a new regime for quantum phenomena. [Preview Abstract] 
Monday, March 3, 2014 8:24AM  8:36AM 
A29.00003: Dissipation as a resource for atomic binding and crystallization Mikhail Lemeshko, Johannes Otterbach, Hendrik Weimer The formation of molecules and supramolecular structures results from bonding by conservative forces acting among electrons and nuclei and giving rise to equilibrium configurations defined by minima of the interaction potential. Here we show that bonding can also occur by the nonconservative forces responsible for interactioninduced coherent population trapping. The bound state arises in a dissipative process and manifests itself as a stationary state at a preordained interatomic distance. Remarkably, such a dissipative bonding is present even when the interactions among the atoms are purely repulsive. The dissipative bound states can be created and studied spectroscopically in presentday experiments with ultracold atoms or molecules and can potentially serve for cooling strongly interacting quantum gases [1]. An extension of this technique to a manyparticle system (BoseEinstein Condensate of Rydbergdressed atoms) allows to observe longrange ordered crystalline structures emerging due to dissipation [2]. \\[4pt] [1] M. Lemeshko, H. Weimer, ``Dissipative binding of atoms by nonconservative forces'' Nature Communications 4, 2230 (2013)\\[0pt] [2] Johannes Otterbach, Mikhail Lemeshko, ``LongRange Order Induced by Dissipation,'' arXiv:1308.5905 [Preview Abstract] 
Monday, March 3, 2014 8:36AM  8:48AM 
A29.00004: Quantum quench dynamics in the presence of a thermal bath Smitha Vishveshwara, Aashish Clerk, Peter Nalbach We explore the dynamics of a system driven through a quantum critical point by quenching its associated Hamiltonian at a specific rate in the presence of dissipation due to a thermal bath. In contrast to the quantum version of the wellknown KibbleZurek mechanism in the absence of the bath, we discuss the enhancement of postquench defect production due to thermal excitations. We argue that the degree of enhancement depends on an interplay between the outofequilibrium dynamics determined by the quench rate and finite temperature, and that it respects a scaling form related to these two quantities. We demonstrate our arguments within the specific context of the transverse Ising system in the presence of a global bath. Our approach is based on the physics of a LandauZener system coupled to a dissipative bath and it allows us to extend our analyses to a broad class of systems of differing dimensions and universality classes. [Preview Abstract] 
Monday, March 3, 2014 8:48AM  9:00AM 
A29.00005: Coherence and a quench dynamics of a dissipative quantum system: renormalization group and dynamical phases Oleksiy Kashuba We study dissipation in a small quantum system coupled to an environment held in thermodynamic equilibrium. The relaxation dynamics of a system subjected to an abrupt quench in the parameters of the underlying Hamiltonian was investigated using two complementary renormalization group approaches. The methods were applied to the Ohmic spinboson model close to the coherenttoincoherent transition. In particular, the role of nonMarkovian memory and the spinboson coupling strength in the pre and postquench behavior is investigated. Additionally, we revealed several ``phases'' of the relaxation dynamics distinguished by the discrimination of the damping at long and intermediate time scale. Surprisingly, elevated temperature can render the system ``more coherent'' by inducing a transition from the partially coherent to the coherent regime. [Preview Abstract] 
Monday, March 3, 2014 9:00AM  9:12AM 
A29.00006: Fluorescence spectrum of thermally driven array of QED cavities Mykola Bordyuh, Marco Schiro, Camille Aron, Baris Oztop, Hakan Tureci Developments in cavity QED technology allow us to engineer strong interactions between photons and atoms and therefore create possibilities to use lightmatter systems as quantum simulators of manybody quantum systems. Quantum Phase Transition (QPT) of photons in arrays of coupled cavities described by models of closed systems such as the JaynesCummingsHubbard and the RabiHubbard models (RHM) [18] have been studied extensively during last few years [18]. Our aim is to describe more realistic situations in which the system is open to an environment. We consider the RHM in which photons can leak out of the cavities. Based on the generalized inputoutput formalism, we show that measuring the fluorescence spectrum of the leaked photons gives us information about the system and the nature of the QPT.\\[4pt] [1] A. D. Greentree et al., Nature Phys. {\bf 466}, 856 (2006)\\[0pt] [2] M. J. Hartmann, F. G. S. L. Brandao, and M. B. Plenio, Nature Phys. {\bf 462}, 849 (2006).\\[0pt] [3] A. Tomadin, V. Giovannetti, R. Fazio, D. Gerace, I. Carusotto, Hakan E. T\"ureci, A. Imamoglu Phys. Rev. A {\bf 81}, 061801(R) (2010).\\[0pt] [4] S. Schmidt and G. Blatter Phys. Rev. Lett. {\bf 103}, 086493 (2009). [Preview Abstract] 
Monday, March 3, 2014 9:12AM  9:24AM 
A29.00007: Quantum phases of the Rabi lattice in the dispersive regime Guanyu Zhu, Sebastian Schmidt, Jens Koch Photonbased strongly correlated lattice models like the JaynesCummings and Rabi lattices differ from their more conventional relatives like the BoseHubbard model by the presence of an additional tunable parameter: the frequency detuning between the pseudospin degree of freedom and the harmonic mode frequency on each site. Whenever this detuning is large compared to relevant coupling strengths, the system is said to be in the dispersive regime. The physics of this regime is wellunderstood at the level of a single JaynesCummings or Rabi site, and can be realized in circuitQED architecture. Here, we extend the theoretical description of the dispersive regime to lattices with many sites, for both strong and ultrastrong coupling. We discuss the nature and spatial range of the resulting qubitqubit and photonphoton coupling. In the ultrastrong coupling regime, we demonstrate the emergence of the paramagnetictoferromagnetic phase transition of photondressed qubits in the negative detuning regime, and the photonpairing and vacuum squeezing in the positive detuning regime. We illustrate our results by exact diagonalization of the Rabi dimer. [Preview Abstract] 
Monday, March 3, 2014 9:24AM  9:36AM 
A29.00008: Pattern Formation and Strong Nonlinear Interactions in ExcitonPolariton Condensates Li Ge, Ani Nersisyan, Baris Oztop, Hakan Tureci Excitonpolaritons generated by lightinduced potentials can spontaneously condense into macroscopic quantum states that display nontrivial spatial and temporal density modulation. While these patterns and their dynamics can be reproduced through the solution of the generalized GrossPitaevskii equation, a predictive theory of their thresholds, oscillation frequencies, and multipattern interactions has so far been lacking. Here we represent such an approach based on currentcarrying quasimodes of the nonHermitian potential induced by the pump. The presented theory allows us to capture the patterns formed in the steadystate directly and account for nonlinearities exactly. We find a simple but powerful expression for thresholds of condensation and the associated frequencies of oscillations, quantifying the contribution of particle formation, leakage, and interactions. We also show that the evolution of the condensate with increasing pump strength is strongly geometry dependent and can display contrasting features such as enhancement or reduction of the spatial localization of the condensate. [Preview Abstract] 
Monday, March 3, 2014 9:36AM  9:48AM 
A29.00009: Timereversal symmetric expansion of the time evolution operator of open quantum systems Naomichi Hatano, Gonzalo Ordonez We here consider open quantum systems of the tightbinding model, specifically a tightbinding chain with a scatter in the center. We succeeded in deriving a new expansion of the time evolution operator only with respect to the states of point spectra (bound, antibound, resonant and antiresonant states), without the background integral over the continuum spectrum of scattering states. Since the expansion has no arbitrariness of the integration contour upon including decaying states, the expansion is perfectly symmetric under the time reversal. Among the expansion terms, the decaying resonant states naturally survive when we consider the time evolution from an initial condition, while the growing antiresonant states naturally survive when we consider the time evolution to a terminal condition. This clearly shows that the emergence of the arrow of time is due to the choice of initial or terminal conditions, that it is not embedded in the time evolution itself. [Preview Abstract] 
Monday, March 3, 2014 9:48AM  10:00AM 
A29.00010: Perturbative approach to open circuit QED systems Andy C.Y. Li, Francesco Petruccione, Jens Koch Perturbation theory (PT) is a powerful and commonly used tool in the investigation of closed quantum systems. In the context of open quantum systems, PT based on the Markovian quantum master equation is much less developed. The investigation of open systems mostly relies on exact diagonalization of the Liouville superoperator or quantum trajectories. In this approach, the system size is rather limited by current computational capabilities. Analogous to closedsystem PT, we develop a PT suitable for open quantum systems. The proposed method is useful in the analytical understanding of open systems as well as in the numerical calculation of system observables, which would otherwise be impractical. This enables us to investigate a variety of open circuit QED systems, including the open JaynesCummings lattice model. [Preview Abstract] 
Monday, March 3, 2014 10:00AM  10:12AM 
A29.00011: Splitting time dependence in Lindblad master equation Gehad Sadiek, E.I. Lashin We consider the Markovian master equation in the Lindblad form. We assume an ansatz for the solution of the equation in the form of a timedependent density matrix of the same form as the solution of the Hamiltonian but with timedependent coefficients. We show that applying this ansatz one can find the solution of the master equation by solving a system of coupled differential equations of the coefficients utilizing the known timeevolved wave function driven by the Hamiltonian only. This approach splits the time dependence problem in the master equation into two parts, one carried by the wave function of the Hamiltonian and the other by the coefficients of the density matrix, which significantly simplifies the evaluation process. As an example we apply this approach to the problem of a system of qubits coupled to a Lindblad environment and demonstrate how powerful it is treating the problem. [Preview Abstract] 
Monday, March 3, 2014 10:12AM  10:24AM 
A29.00012: Quantum Interference between independent environments in open quantum systems ChingKit Chan, GuinDar Lin, Susanne Yelin, Mikhail Lukin When a general quantum system interacts with multiple environments, the environmental effects are usually treated in an additive manner in the master equation. This assumption becomes questionable for nonMarkovian environments that have finite memory times. Here, we show that quantum interferences between independent environments exist and can qualitatively modify the dynamics of the reduced physical system. We illustrate this effect with examples of atomic systems coupled to structured reservoirs, and discuss its origin in general using a nonequilibrium diagrammatic technique. The consequential decoherence dynamics cannot be captured by an additive master equation. [Preview Abstract] 
Monday, March 3, 2014 10:24AM  10:36AM 
A29.00013: Observation of a DissipationInduced Classical to Quantum Transition James Raftery, Darius Sadri, Sebastian Schmidt, Hakan T\"ureci, Andrew Houck The emergence of nontrivial structure in manybody physics has been a central topic of research bearing on many branches of science. Important recent work has explored the nonequilibrium quantum dynamics of closed manybody systems. With the rapid technological advances in solid state quantum optics, it is now possible to experimentally study strongly correlated photons, and to build model systems whose open nature gives rise to rich emergent behavior. We report the experimental observation of a novel dissipation driven dynamical localization transition of strongly correlated photons in an extended superconducting circuit. Interaction with an environment has been argued to provide a mechanism for the emergence of classical behavior from a quantum system. Surprisingly, homodyne measurements reveal the observed localization transition to be from a regime of classical oscillations into a macroscopically selftrapped state manifesting revivals, a fundamentally quantum phenomenon. This experiment also demonstrates a new class of scalable quantum simulators with well controlled coherent and dissipative dynamics suited to the study of quantum manybody phenomena out of equilibrium. [Preview Abstract] 

A29.00014: ABSTRACT WITHDRAWN 
Monday, March 3, 2014 10:48AM  11:00AM 
A29.00015: Symmetries and conserved quantities in open quantum systems Victor V. Albert, Zaki Leghtas, Robert Schoelkopf, Michel Devoret, Mazyar Mirrahimi, Liang Jiang Recent developments in quantum engineering and quantum information highlight the need to better understand the steadystate behavior of open systems whose steady state is dependent on initial conditions. This work analyzes the structure and response to perturbations of the steadystate subspace of timeindependent Lindblad master equations. We discuss the role of symmetries and conserved quantities in Lindblad systems and show that the effect of the environment in the infinitetime limit can be tracked exactly for arbitrary initial state and without knowledge of dynamics at intermediate time [1]. Applying this approach, we analytically determine the steady state for driven singlemode twophoton absorption and calculate that dephasing is exponentially suppressed to first order in such a system [2]. \newline [1] V.V. Albert and Liang Jiang, arXiv:1310.1523 \newline [2] M. Mirrahimi {\it et al.} (in preparation) [Preview Abstract] 
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