Intrinsic Hamiltonian of Mean Force and Strong-Coupling Quantum Thermodynamics

TL;DR

This paper introduces a universal quantum thermodynamic framework for strongly coupled systems, enabling clear definitions of thermodynamic properties and laws that are experimentally accessible.

Contribution

It provides a novel approach that maintains gauge freedoms and entropy definitions, applicable to strongly coupled quantum systems with experimental relevance.

Findings

Framework validated on a strong-coupling bosonic reservoir model

Enables thermodynamic analysis using only accessible microscopic variables

Preserves von Neumann entropy and gauge freedoms in strong coupling

Abstract

We present a universal thermodynamic framework for quantum systems that may be strongly coupled to thermal environments. Unlike previous approaches, our method enables a clear definition of thermostatic properties while preserving the same gauge freedoms as in the standard weak-coupling regime and retaining the von Neumann expression for thermodynamic entropy. Furthermore, it provides a formulation of general first and second laws using only variables accessible through microscopic control of the system, thereby enhancing experimental feasibility. We validate the framework by applying it to a paradigmatic model of strong coupling with a structured bosonic reservoir.