Thermodynamic processes generated by a class of completely positive quantum operations

TL;DR

This paper explores a class of quantum operations that generate thermodynamic processes, demonstrating how heat and entropy behave, and analyzing state transformations and inequalities in quantum thermodynamics.

Contribution

It introduces a framework using positive operator-valued measures to operationally formulate quantum thermodynamics, revealing state evolution and inequality violations.

Findings

Heat and entropy increase monotonically under the operations

Repeated operations transform pure states into maximally mixed states

Clausius inequality can be violated in these processes

Abstract

An attempt toward the operational formulation of quantum thermodynamics is made by employing the recently proposed operations forming positive operator-valued measures for generating thermodynamic processes. The quantity of heat as well as the von Neumann entropy monotonically increases under the operations. The fixed point analysis shows that repeated applications of these operations to a given system transform from its pure ground state at zero temperature to the completely random state in the high temperature limit with intermediate states being generically out of equilibrium. It is shown that the Clausius inequality can be violated along the processes, in general. A bipartite spin-1/2 system is analyzed as an explicit example.