An integrated diamond nanophotonics platform for quantum optics

Solid-state quantum-emitters with long spin coherence times and strong interactions with single-photons could form the building blocks of a quantum network. Unique among solid-state systems, silicon-vacancy (SiV) color centers in diamond can address both of these challenges. First, we place single SiV centers in diamond nanophotonic crystal cavities and demonstrate a single-atom cooperativity greater than 10, realizing strong atom-photon interactions that are nonlinear at the single-photon level. Using this platform, we demonstrate entanglement generation and two-SiV interactions mediated by the cavity mode. Finally, we improve the spin coherence time to greater than 13 milliseconds by cooling the system to below 100 mK. These results enable the realization of gates between multiple atoms and optical photons in solid-state devices.