Thermodynamics of a Quantum Subsystem

TL;DR

This paper develops a dynamic framework for quantum thermodynamics of a subsystem, revealing nonlocal work effects and a quantum lever that can amplify local work up to 100%.

Contribution

It introduces a method to define thermodynamic functions of a quantum subsystem via its local spectrum, addressing previous inconsistencies.

Findings

Thermodynamic functions can be defined dynamically using local spectra.

Quantum work is inherently nonlocal due to quantum state properties.

A quantum lever can amplify local work by up to 100%.

Abstract

Several prior attempts to formulate the Laws of Thermodynamics for a small region within a larger quantum system have led to inconsistencies and unexplained infinities. The entropy and external work, in particular, require careful analysis when partitioning over the various subsystems. In this work, we analyze the thermodynamics of a quantum subsystem driven quasi-statically by external forces. We show that the thermodynamic functions of a quantum subsystem can be defined dynamically in terms of its local spectrum. The external work is found to be intrinsically nonlocal due to the nonlocal character of the underlying quantum states. This nonlocal quantum work can be harnessed in a "quantum lever" to provide up to 100% amplification of the local work done on a quantum subsystem.