Work measurement in an optomechanical quantum heat engine

TL;DR

This paper theoretically examines how continuous intracavity photon number measurements affect the work output and efficiency of an optomechanical quantum heat engine, highlighting differences between dispersive and absorptive measurement back-actions.

Contribution

It provides a comparative analysis of dispersive and absorptive measurement schemes and their distinct back-action effects on the engine's efficiency.

Findings

Both measurement schemes reduce engine efficiency.

Dispersive measurements cause mixing of photonic and phononic excitations.

Absorptive measurements lead to photon losses and efficiency reduction.

Abstract

We analyze theoretically the measurement of the mean output work and its fluctuations in a recently proposed optomechanical quantum heat engine [K. Zhang {\it et al.} Phys. Rev. Lett. {\bf112}, 150602 (2014)]. After showing that this work can be evaluated by a continuous measurements of the intracavity photon number we discuss both dispersive and absorptive measurement schemes and analyze their back-action effects on the efficiency of the engine. Both measurements are found to reduce the efficiency of the engine, but their back-action is both qualitatively and quantitatively different. For dispersive measurements the efficiency decreases as a result of the mixing of photonic and phononic excitations, while for absorptive measurements, its reduction results from photon losses due to the interaction with the quantum probe.