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Operational Work Fluctuation Theorem for Open Quantum Systems.

Konstantin Beyer^1,2, Walter T Strunz²

¹Stevens Institute of Technology, Department of Physics, Hoboken, New Jersey 07030, USA.

Physical Review Letters

|April 25, 2025

Summary

This summary is machine-generated.

This study introduces a new quantum fluctuation theorem for measuring work in quantum systems. It provides bounds for free energy differences, unlike previous methods, and works for open systems without needing the Hamiltonian.

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Area of Science:

Quantum Thermodynamics
Statistical Mechanics
Non-equilibrium Physics

Background:

The classical Jarzynski equality relates work done on systems out of equilibrium to free energy differences.
This equality is experimentally valuable for determining free energy via nonequilibrium work measurements.
Quantum versions of the Jarzynski equality require complex two-point measurements, limiting predictive power.

Purpose of the Study:

To propose a novel quantum fluctuation theorem for externally measurable quantum work.
To enable free energy determination in quantum systems without prior knowledge of the Hamiltonian.
To extend fluctuation theorems to open quantum systems.

Main Methods:

Developed a quantum fluctuation theorem applicable to work measured during a driving protocol.
The theorem is valid for open quantum systems and does not require knowledge of the system's Hamiltonian.
The proposed theorem is formulated as an inequality providing bounds on the free energy difference.

Main Results:

The proposed quantum fluctuation theorem allows for the determination of bounds on free energy differences.
The inequality is saturated in the quasiclassical limit, where energy coherences are minimal.
This work highlights a quantum disadvantage compared to classical systems in this context.

Conclusions:

The new quantum fluctuation theorem offers a practical approach to studying nonequilibrium quantum thermodynamics.
It overcomes limitations of previous quantum Jarzynski equality formulations by using externally measurable work.
The findings underscore the unique challenges and characteristics of quantum systems in thermodynamic processes.