An efficient quantum spin-photon interface in diamond for a quantum network~

In a future quantum network distant nodes will be connected via entanglement. Nitrogen-vacancy (NV) centers in diamond have developed into a building block for such a network. The current success probability of heralded entanglement generation is limited by the probability that the NV center emits a photon in the zero-phonon line, as well as by the photon collection efficiency from the diamond. We can address both by embedding the NV in a Fabry-Perot cavity at cryogenic temperatures, benefitting from Purcell enhancement and an improved collection efficiency. Here we report the latest results on such a system with a thin diamond membrane in a tunable fiber-based microcavity at cryogenic temperatures. This new quantum interface should enable significant speed-up in the remote entangling rate, and allow us to extend a quantum network over multiple nodes and longer distance.