Quantum coherence of a single NV center in a spin-cavity hybrid system

Hybrid interfaces between photonic cavities and quantum emitters are promising physical platforms in the fields of quantum sensing, quantum metrology and quantum information processing. Light-matter interaction in these systems can be engineered into the regime of strong coupling and ultrastrong coupling. In this work we experimentally explore the coherent properties of a single solid spin in a hybrid system consisting of a nitrogen-vacancy center in nanodiamond and a metal-dielectric cavity. We statistically characterize the cavity enhancement factor of fluorescence intensity for a group of single nitrogen-vacancy centers. The fluorescence intensity of a single nitrogen-vacancy center can be enhanced in a metal-dielectric cavity with a factor about 3. We measure the relaxation time T_1 and decoherence time T_2 of nitrogen-vacancy centers and show the robustness of spin coherent properties in a cavity. This work shows the possibility of selectively controlling on the optical and spin coherence of a single nitrogen-vacancy center in a nanocavity. The spin-cavity hybrid system can be further used in applications such as quantum sensing and quantum engineering with nitrogen-vacancy centers. Graphic abstract