Demonstration of Jarzynski's Equality in Open Quantum Systems Using a Step-Wise Pulling Protocol

TL;DR

This paper generalizes Jarzynski's Equality for quantum systems using a step-wise pulling protocol, enabling the calculation of free-energy changes from work fluctuations, and demonstrates its application on a quantum harmonic oscillator.

Contribution

It introduces a quantum generalization of Jarzynski's Equality with a step-wise pulling protocol and proposes methods to identify optimal pathways contributing to free-energy changes.

Findings

Work distribution functions can be constructed from reaction coordinate fluctuations.

Optimal pathways follow the principle of detailed balance.

The theory is validated on a quantum harmonic oscillator.

Abstract

We present a generalization of Jarzynski's Equality, applicable to quantum systems, relating discretized mechanical work and free-energy changes. The theory is based on a step-wise pulling protocol. We find that work distribution functions can be constructed from fluctuations of a reaction coordinate along a reaction pathway in the step-wise pulling protocol. We also propose two sets of equations to determine the two possible optimal pathways that provide the most significant contributions to free-energy changes. We find that the transitions along these most optimal pathways, satisfying both sets of equations, follow the principle of detailed balance. We then test the theory by explicitly computing the free-energy changes for a one-dimensional quantum harmonic oscillator. This approach suggests a feasible way of measuring the fluctuations to experimentally test Jarzynski's Equality in many-body systems, such as Bose-Einstein condensates.