Spin-phase-space-entropy production

TL;DR

This paper introduces a phase-space-entropy production framework using Wehrl entropy to quantify irreversibility in spin systems, applicable at any temperature and for nonequilibrium baths, addressing limitations of traditional methods.

Contribution

The authors develop a novel Wehrl entropy-based approach for measuring irreversibility in spin systems, extending analysis to nonequilibrium environments and zero-temperature limits.

Findings

Wehrl entropy production rate remains valid at all temperatures.

Framework extends to arbitrary nonequilibrium baths.

Application to spin-photon interactions demonstrates the method's effectiveness.

Abstract

Quantifying the degree of irreversibility of an open system dynamics represents a problem of both fundamental and applied relevance. Even though a well-known framework exists for thermal baths, the results give diverging results in the limit of zero temperature and are also not readily extended to nonequilibrium reservoirs, such as dephasing baths. Aimed at filling this gap, in this paper we introduce a phase-space-entropy production framework for quantifying the irreversibility of spin systems undergoing Lindblad dynamics. The theory is based on the spin Husimi-Q function and its corresponding phase-space entropy, known as Wehrl entropy. Unlike the von Neumann entropy production rate, we show that in our framework, the Wehrl entropy roduction rate remains valid at any temperature and is also readily extended to arbitrary nonequilibrium baths. As an application, we discuss the irreversibility associated with the interaction of a two-level system with a single-photon pulse, a problem which cannot be treated using the conventional approach.