Thermodynamics of a quantum subsystem
Phys. Rev. B 111, 245412 – Published 10 June, 2025
DOI: https://doi.org/10.1103/4lw8-x1vr
Abstract
Several prior attempts to formulate the laws of thermodynamics for a small region within a larger quantum system 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 quasistatically 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.