Entropy and information flow in quantum systems strongly coupled to baths

TL;DR

This paper develops a NEGF-based framework to analyze entropy and information flow in strongly coupled quantum systems, bridging thermodynamics and quantum transport with applications to open nonequilibrium systems.

Contribution

It introduces a consistent NEGF approach to quantify entropy and information flows in strongly coupled quantum systems, including interacting cases, with practical simulation methods.

Findings

Derived bath and energy resolved entropy expressions

Validated the approach with numerical simulations on junction models

Unified thermodynamic and quantum transport descriptions

Abstract

Considering von Neumann expression for reduced density matrix as thermodynamic entropy of a system strongly coupled to baths, we use nonequilibrium Green's function (NEGF) techniques to derive bath and energy resolved expressions for entropy, entropy production, and information flows. The consideration is consistent with dynamic (quantum transport) description and expressions reduce to expected forms in limiting cases of weak coupling or steady-state. Formulation of the flows in terms of only system degrees freedom is convenient for simulation of thermodynamic characteristics of open nonequilibrium quantum systems. We utilize standard NEGF for derivations in noninteracting systems, Hubbard NEGF is used for interacting systems. Theoretical derivations are illustrated with numerical simulations within generic junction models.