Energy exchange and fluctuations between a dissipative qubit and a monitor under continuous measurement and feedback

TL;DR

This paper investigates how continuous measurement and feedback cause energy exchange and fluctuations in a dissipative qubit, revealing insights into quantum thermodynamics and potential quantum refrigerator applications.

Contribution

It introduces a detailed analysis of energy flow and fluctuations in a qubit under continuous measurement and feedback, highlighting measurement backaction effects.

Findings

Energy flow varies with measurement and feedback states.

Fluctuations are strongly influenced by measurement backaction.

Results suggest potential for quantum refrigerator development.

Abstract

Continuous quantum measurement and feedback induce energy exchange between a dissipative qubit and a monitor even in the steady state, as a measurement backaction. Using the Lindblad equation, we identified the maximum and minimum values of the steady-state energy flow as the measurement and feedback states vary, and we demonstrate the qubit cooling induced by these processes. Turning our attention to quantum trajectories under continuous measurement and feedback, we observe that the energy flow fluctuates around the steady-state values. We reveal that the fluctuations are strongly influenced by the measurement backaction, distinguishing them from the standard Poisson noise typically observed in electronic circuits. Our results offer potential application in the development of quantum refrigerators controlled by continuous measurement and feedback, and provide deep insight into quantum thermodynamics from the perspective of fluctuation.