Archak Purkayastha

Out-of-equilibrium open quantum systems: A comparison of approximate quantum master equation approaches with exact results

We present the Born-Markov approximated Redfield quantum master equation (RQME) description for an open system of noninteracting particles (bosons or fermions) on an arbitrary lattice of

Block entanglement and fluctuations in finite-size correlated electron systems

N

Nonlinear transport in an out-of-equilibrium single-site Bose-Hubbard model: Scaling, rectification, and time dynamics

sites in any dimension and weakly connected to multiple reservoirs at different temperatures and chemical potentials. The RQME can be reduced to the Lindblad equation, of various forms, by making further approximations. By studying the

Quantum transport under ac drive from the leads: A Redfield quantum master equation approach

N=2

Nonequilibrium phase diagram of a one-dimensional quasiperiodic system with a single-particle mobility edge

case, we show that RQME gives results which agree with exact analytical results for steady-state properties and with exact numerics for time-dependent properties over a wide range of parameters. In comparison, the Lindblad equations have a limited domain of validity in nonequilibrium. We conclude that it is indeed justified to use microscopically derived full RQME to go beyond the limitations of Lindblad equations in out-of-equilibrium systems. We also derive closed-form analytical results for out-of-equilibrium time dynamics of two-point correlation functions. These results explicitly show the approach to steady state and thermalization. These results are experimentally relevant for cold atoms, cavity QED, and far-from-equilibrium quantum dot experiments.

Sub-diffusion and non-equilibrium probes of phases in Aubry-Andre-Harper Model

The block entanglement entropy and fluctuations are investigated in one dimension in finite-size correlated electron systems using the Gutzwiller wave function as a prototype correlated electron state. Entanglement entropy shows logarithmic divergence for all values of the correlation projection parameter

Classifying transport behavior via current fluctuations in open quantum systems.

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Anomalous transport in the Aubry-André-Harper model in isolated and open systems

, as predicted by conformal field theories for critical systems, but the central charge requires finite-size corrections. There is an infinite correlation length corresponding to correlation between the same kinds of spins, for all values of

Open quantum systems: a comparison of Redfield and Lindblad approaches with exact results

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Exact Redfield description for open non-interacting quantum systems and failure of the Lindblad approach

. A scaling form for the block entropy, as a function of