Unfolding Correlation from Open-Quantum-System Master Equations

Abstract

Understanding system-bath correlations in open quantum systems is essential for various quantum information and technology applications. Derivations of most master equations (MEs) for the dynamics of open systems require approximations that mask dependence of the system dynamics on correlations, since the MEs focus on reduced system dynamics. Here we demonstrate that the most common MEs indeed contain hidden information about explicit system-environment correlation. We unfold these correlations by recasting the MEs into a universal form in which the system-bath correlation operator appears. The equations include the Lindblad, Redfield, second-order time-convolutionless, second-order Nakajima-Zwanzig, and second-order universal Lindblad-like cases. We further illustrate our results in an example, which implies that the second-order universal Lindblad-like equation captures correlation more accurately than other standard techniques.

Correlation-enabled energy exchange in quantum systems without external driving

“…A direct approach for explicitly considering correlation has been introduced in Refs. [7,8]. The effect of correlation in the thermodynamic arrow of time has been studied in literature and it has been shown that correlation can lead to reversal of the direction of heat flow from cold to hot [9][10][11].…”

Correlation-Enabled Energy Exchange in Quantum Systems without External Driving

“…A direct approach for explicitly considering correlation has been introduced in Ref. [7,8]. The effect of correlation in the thermodynamic arrow of time has been studied in literature and it has been shown that correlation can lead to reversal of the direction of heat flow from cold to hot [9][10][11].…”