Quantum Thermodynamic Force and Flow

TL;DR

This paper introduces the concept of quantum affinity as a quantum analogue of classical thermodynamic affinity, explaining the direction of quantum processes, deriving a new second law, and linking it to quantum coherence and information flow.

Contribution

It defines quantum affinity, derives a new second law based on it, and connects it to quantum coherence and information dynamics in quantum thermodynamics.

Findings

Quantum affinity predicts process direction in quantum systems.

A new second law of thermodynamics is formulated using quantum affinity.

Quantum coherence rate relates to thermodynamic force and flow.

Abstract

Why do quantum evolutions occur and why do they stop at certain points? In classical thermodynamics affinity was introduced to predict in which direction an irreversible process proceeds. In this paper the quantum mechanical counterpart of classical affinity is found. It is shown that the quantum version of affinity can predict in which direction a process evolves. A new version of the second law of thermodynamics is derived through quantum affinity for energy-incoherent state interconversion under thermal operations. we will also see that the quantum affinity can be a good candidate to be responsible, as a force, for driving the flow and backflow of information in Markovian and non-Markovian evolutions. Finally we show that the rate of quantum coherence can be interpreted as the pure quantum mechanical contribution of the total thermodynamic force and flow. Thus It is seen that, from a thermodynamic point of view, any interaction from the outside with the system or any measurement on the system may be represented by a quantum affinity.