Experimental demonstration of generalized quantum fluctuation theorems in the presence of coherence

TL;DR

This paper experimentally validates a quantum fluctuation theorem in a photonic system, revealing how quantum coherence influences entropy production and time-reversal symmetry in nonclassical quantum processes.

Contribution

It provides the first experimental demonstration of a generalized quantum fluctuation theorem accounting for coherence and multiple time-reversal processes.

Findings

Confirmed the ratio of quasi-probabilities obeys a generalized Crooks QFT

Quantum coherence induces imaginary components in entropy production

Established fundamental symmetry between quantum processes and their time reversals

Abstract

Fluctuation theorems have elevated the second law of thermodynamics to a statistical realm by establishing a connection between time-forward and time-reversal probabilities, providing invaluable insight into nonequilibrium dynamics. While well established in classical systems, their quantum generalization, incorporating coherence and the diversity of quantum noise, remains open. We report the experimental validation of a quantum fluctuation theorem (QFT) in a photonic system, applicable to general quantum processes with nonclassical characteristics, including quasi-probabilistic descriptions of entropy production and multiple time-reversal processes. Our experiment confirms that the ratio between the quasi-probabilities of the time-forward and any multiple time-reversal processes obeys a generalized Crooks QFT. Moreover, coherence induced by a quantum process leads to the imaginary components of quantum entropy production, governing the phase factor in the QFT. These findings underscore the fundamental symmetry between a general quantum process and its time reversal, providing an elementary toolkit to explore noisy quantum information processing.