Enhancement of quantum synchronization via continuous measurement and feedback control

TL;DR

This paper demonstrates that quantum synchronization of a quantum van der Pol oscillator can be significantly improved through continuous measurement and feedback control, balancing measurement backaction with phase coherence enhancement.

Contribution

The study introduces a feedback strategy based on continuous homodyne measurement to enhance quantum synchronization, optimizing measurement quadratures for maximum phase coherence.

Findings

Quantum measurement reduces phase fluctuations and enhances synchronization.

Feedback control suppresses measurement-induced fluctuations.

Maximum synchronization enhancement occurs at optimal measurement quadrature.

Abstract

We study synchronization of a quantum van der Pol oscillator with a harmonic drive and demonstrate that quantum synchronization can be enhanced by performing continuous homodyne measurement on an additional bath linearly coupled to the oscillator and applying feedback control to the oscillator. The phase coherence of the oscillator is increased by reducing quantum fluctuations via the continuous measurement, whereas the measurement backaction inevitably induces fluctuations around the phase-locking point. We propose a simple feedback policy for suppressing measurement-induced fluctuations by adjusting the frequency of the harmonic drive, which results in enhancement of quantum synchronization. We further demonstrate that the maximum enhancement of quantum synchronization is achieved by performing quantum measurement on the quadrature angle at which the phase diffusion of the oscillator is the largest and the maximal information of the oscillator phase is extracted.