Fluctuation theorem in cavity quantum electrodynamics systems.

Area of Science:

• Quantum thermodynamics
• Cavity quantum electrodynamics
• Statistical mechanics

Background:

• Fluctuation theorems (FTs) are crucial for understanding non-equilibrium thermodynamics.
• Cavity quantum electrodynamics (CQED) systems involve interactions between light and matter confined in a cavity.
• Describing cavity loss often requires considering zero-temperature baths, leading to mathematical challenges like entropy divergence.

Purpose of the Study:

• To derive a generalized integral fluctuation theorem (FT) for cavity quantum electrodynamics (CQED) systems.
• To address and resolve the mathematical difficulty of diverging entropy change in the zero-temperature limit.
• To establish relationships between the FT and observable quantities in CQED systems.

Main Methods:

• Derivation of an integral fluctuation theorem using principles of absolute irreversibility.
• Analysis of entropy change behavior in the zero-temperature limit of external baths.
• Numerical simulations applied to a quantum heat engine model.

Main Results:

• Successfully derived an integral fluctuation theorem applicable to general CQED systems.
• Identified two types of absolute irreversibility contributing to the integral FT.
• Established simple relationships between FT contributions and average photon emission under stationary, small cavity-loss conditions.
• Obtained an approximate FT form independent of specific system details.

Conclusions:

• The derived integral FT offers a robust theoretical framework for non-equilibrium processes in CQED.
• Absolute irreversibility provides a key to resolving divergences in thermodynamic calculations for open quantum systems.
• The findings have implications for the design and analysis of quantum heat engines and other quantum devices.