Asymmetries of thermal processes in open quantum systems

TL;DR

This paper explores the asymmetric dynamics of thermal relaxation in open quantum systems, revealing that heating and cooling follow different paths and are characterized by spectral properties, with implications for thermodynamics and quantum computing.

Contribution

It introduces a theoretical framework based on information geometry to analyze the asymmetry in thermal processes, supported by examples involving various quantum systems.

Findings

Faster heating than cooling observed in examples

Thermal relaxation paths depend on temperature change direction

Spectral analysis explains the asymmetry in processes

Abstract

An intriguing phenomenon in non-equilibrium quantum thermodynamics is the asymmetry of thermal processes. Relaxation to thermal equilibrium is the most important dissipative process, being a key concept for the design of heat engines and refrigerators, contributing to the study of foundational questions of thermodynamics, and being relevant for quantum computing through the process of algorithmic cooling. Despite their importance, the dynamics of these processes are far from being understood. We show that the free relaxation to thermal equilibrium follows intrinsically different paths depending on whether it involves the temperature of the system to increase or to decrease. Our theory is exemplified using the recently developed thermal kinematics based on information geometry theory, utilizing three prototypical examples: a two-level system, the quantum harmonic oscillator, and a trapped quantum Brownian particle, in all cases showing faster heating than cooling under the appropriate conditions. A general understanding is obtained based on the spectral decomposition of the Liouvillian and the spectral gap of reciprocal processes.