Cavity quantum electrodynamic sensors with steady state mode cooling in the strong coupling regime*

Nitrogen-vacancy (NV) centers in diamonds have been successfully used as quantum sensors to accurately measure, e.g., magnetic fields. However, the performance of NV-based sensors is limited by the absence of a high-fidelity readout technique. In this talk, we employ spin refrigeration - reduction in Johnson noise below ambient temperature - in a highly cooperative NV-cavity system for sensing applications. We present a model that effectively describes the optically polarized spin system with inhomogeneous broadening in the nonlinear regime relevant to sensing. We demonstrate through experiments that our magnetometer achieves competitive broadband sensitivity. We will also highlight wider applications of our findings, including their impact on gyroscope and clock technologies, and discuss performance constrained by sensor dimensions and energy usage.