Phase diffusion and locking in single-qubit lasers

TL;DR

This paper investigates phase coherence, diffusion, and synchronization in a single-qubit laser system, emphasizing the effects of strong coupling and low-frequency noise, with implications for experimental realizations.

Contribution

It extends previous models to include strong qubit-resonator coupling and low-frequency noise effects, providing new insights into spectral features and phase dynamics.

Findings

Strong coupling can cause a double peak in the spectrum.

Low-frequency noise influences the shape and width of the spectral features.

Phase locking and synchronization are achievable with ac driving.

Abstract

Motivated by recent experiments, which demonstrated lasing and cooling of the electromagnetic field in an electrical resonator coupled to a superconducting qubit, we study the phase coherence and diffusion of the system in the lasing state. We also discuss phase locking and synchronization induced by an additional {\sl ac} driving of the resonator. We extend earlier work to account for the strong qubit-resonator coupling and to include the effects of low-frequency qubit's noise. We show that the strong coupling may lead to a double peak structure of the spectrum, while the shape and width are determined to the low-frequency noise.