Non-conjugate quantum subsystems

TL;DR

This paper proposes a new framework for understanding quantum system decomposition, leading to a consistent definition of reduced density operators and a self-consistent quantum thermodynamics formulation with novel physical corrections.

Contribution

It introduces an alternative approach to quantum subsystem decomposition and develops a self-consistent quantum thermodynamics theory incorporating interaction effects.

Findings

New definition of reduced density operator consistent with interaction Hamiltonian

Self-consistent quantum thermodynamics with physical corrections

Application to models with interacting quantum systems

Abstract

We introduce an alternative way to understand the decomposition of a quantum system into interacting parts and show that it is natural in several physical models. This enables us to define a reduced density operator for a working system interacting with a thermal bath that is consistent with the inclusion of the interaction Hamiltonian within the working system's energy. We subsequently provide a self-consistent formulation of quantum thermodynamics that incurs non-trivial physical corrections to thermodynamic relations and quantities previously defined within the literature.