Thermodynamics of Quantum-Jump-Conditioned Feedback Control

TL;DR

This paper develops a thermodynamic framework for open quantum systems under quantum feedback control, analyzing how feedback influences thermodynamic laws and system efficiency, with applications to heat pumps and state stabilization.

Contribution

It introduces a thermodynamic description of quantum feedback control, revealing modifications to thermodynamic laws and demonstrating feedback's role in stabilizing quantum states.

Findings

Quantum feedback modifies the first and second laws of thermodynamics.

Feedback can enhance the efficiency of quantum heat pumps.

Quantum feedback stabilizes coherences, sometimes leading to pure states.

Abstract

We consider open quantum systems weakly coupled to thermal reservoirs and subjected to quantum feedback operations triggered with or without delay by monitored quantum jumps. We establish a thermodynamic description of such system and analyze how the first and second law of thermodynamics are modified by the feedback. We apply our formalism to study the efficiency of a qubit subjected to a quantum feedback control and operating as a heat pump between two reservoirs. We also demonstrate that quantum feedbacks can be used to stabilize coherences in nonequilibrium stationary states which in some cases may even become pure quantum states.