Room-Temperature Picosecond Single-Photon Emission from a Silicon Vacancy Center in Diamond

Artificially tailoring quantum emitters by coupling them to optical cavities is critical for applications such as all-photonic quantum computing and quantum key distribution. Among quantum emitters, diamond defect centers, with their atomic-like characteristics, have drawn intense interest for quantum applications. However, the spontaneous emission lifetime of single photons from diamond defects has been limited to several hundred picoseconds, partly due to challenges in realizing cavities in diamond with sufficiently small mode volumes. Here, we sandwich an only 10 nm diamond membrane with implanted negatively charged silicon vacancy centers (SiV^-) between a gold mirror and arrays of nanodisks, resulting in ultrafast single-photon sources with lifetimes as short as 5.5 ps. This corresponds to an improvement in the radiative spontaneous emission rate of over 700-fold, also termed the Purcell factor, and is the result of a greatly enhanced local density of states in the ultrasmall mode-volume cavities. Furthermore, the cavity-coupled single SiV^- centers exhibit a 4800-fold photoluminescence enhancement with a single-photon generation rate of up to 361 Mcps at room temperature. These results could refine the engineering of diamond defect centers and position other solid-state platforms as strong quantum-information contenders when coupled to ultrasmall mode-volume cavities, thus illustrating the potential for large-scale, artificially tailored single-photon sources.