Microwave mode cooling and cavity quantum electrodynamics effects at room temperature with optically cooled nitrogen-vacancy center spins

Recent experimental and theoretical studies demonstrated microwave mode cooling and cavity quantum electrodynamics (C-QED) effects at room temperature using optically cooled nitrogen-vacancy (NV) spins. This article explores improved performance by adopting parameters from diamond maser experiments with a high-frequency (9.22 GHz) microwave resonator. Incorporating the full NV electronic and spin-level structure, the study models optical pumping and dissipation and analyzes laser-power dependence. It predicts a reduction of the resonator’s mean microwave photon number to 261 (effective temperature 116 K), about five times lower than previously reported. It further predicts laser-power-controlled C-QED effects across weak-to-strong coupling regimes and observes saturation under strong optical pumping. The framework can be readily adapted to other solid-state spins and to investigate C-QED effects relevant to maser operation.

Yuan Zhang, Qilong Wu, Hao Wu, Xun Yang, Shi-Lei Su, Chongxin Shan, Klaus Mølmer