A cavity enhanced spin-photon interface for NV centers in a quantum network*

Fast entanglement generation between remote nodes is the foundation for quantum networks. Experiments with Nitrogen Vacancy (NV) centers in bulk diamond have made promising progress towards such a network, because of their long spin coherence, narrow optical transitions and accessible nuclear spin memories. However, these demonstrations are currently limited by low emission into the zero phonon line and low collection efficiency. To boost emission and collection, we construct a tunable Fabry-Pérot cavity around NV centers in a diamond membrane. We verify the good optical properties of NV centers in membranes and observe the characteristic lifetime reduction from Purcell enhancement of the zero phonon line. These measurements progress towards an NV node for networks with two orders of magnitude faster entanglement rates.