Fluctuation Theorems for Continuous Quantum Measurement and Absolute Irreversibility

TL;DR

This paper extends fluctuation theorems to continuous quantum measurements without thermal baths, revealing absolute irreversibility and violations of Jarzynski and Crooks equalities in quantum measurement processes.

Contribution

It introduces a fluctuation theorem for continuous quantum measurements, linking irreversibility to measurement-induced wave-function collapse without thermal baths.

Findings

Measurement-induced collapse exhibits absolute irreversibility.

Fluctuation theorem applies to various continuous measurement schemes.

Jarzynski and Crooks equalities are violated in this context.

Abstract

Fluctuation theorems are relations constraining the out-of-equilibrium fluctuations of thermodynamic quantities like the entropy production that were initially introduced for classical or quantum systems in contact with a thermal bath. Here we show, in the absence of thermal bath, the dynamics of continuously measured quantum systems can also be described by a fluctuation theorem, expressed in terms of a recently introduced arrow of time measure. This theorem captures the emergence of irreversible behavior from microscopic reversibility in continuous quantum measurements. From this relation, we demonstrate that measurement-induced wave-function collapse exhibits absolute irreversibility, such that Jarzynski and Crooks-like equalities are violated. We apply our results to different continuous measurement schemes on a qubit: dispersive measurement, homodyne and heterodyne detection of a qubit's fluorescence.