Highly Squeezed Mechanical State Generation in an Optomechanical System Assisted by Nitrogen‐Vacancy Ensembles

Narrow linewidth and macroscopically accessible mechanical microstructures make mechanical squeezing a promising platform for ultra‐high‐sensitivity detection and fundamental investigations of classical‐to‐quantum quantum effects. The conventional approaches to utilizing optomechanical interactions for generating mechanical squeezing are restricted to the resolved‐sideband regime, limiting their practical applicability. In this paper, we propose a scheme to generate a highly squeezed mechanical state in both resolved‐ and unresolved‐sideband optomechanical systems assisted by nitrogen‐vacancy ensembles (NVEs). By coupling two NVEs to the optical cavity, the detrimental counter‐rotating terms that degrade mechanical squeezing are efficiently suppressed via destructive quantum interference originating from the NVEs‐cavity coupling channels. Numerical results reveal that mechanical squeezing exhibits non‐monotonic behavior with respect to both the optomechanical coupling ratio and the cavity‐spin coupling strength. Moreover, the achievable degree of mechanical squeezing degrades as the initial thermal‐phonon occupation of the mechanical resonator and the dissipation rates of the NVEs increase. This work offers an alternative feasible pathway toward strong mechanical squeezing beyond the 3‐dB limit and broadens the application scope of hybrid solid‐state‐optomechanical quantum systems.