Efficient, Tunable Single Photon Source Based on Integrated Diamond Nanophotonic System*

An efficient source of single photons that can be interfaced with a long-lived quantum memory is a central element for many protocols in quantum information science. We demonstrate an on-demand source of arbitrarily temporally shaped single photon pulses with high purity (detection efficiency = 14.9\%, g$^2$(0) = 0.017). Our approach is based on  a silicon-vacancy center in a highly directional fiber-integrated diamond nanophotonic cavity designed using a new approach to photonic crystal cavity design. We use this sysment for conincidne measurement with  up to 11 consecutively detected single photons. Combined with previously demonstrated spin-photon gates, this system enables on-demand generation of streams of correlated photons such as cluster states, which could be used as a resource for fault tolerant transmission of quantum information and one-way quantum computation.