Single-Photon Switching and Entanglement of Solid-State Qubits in an   Integrated Nanophotonic System
  Efficient interfaces between photons and quantum emitters form the basis for quantum networks and enable nonlinear optical devices operating at the single-photon level. We demonstrate an integrated platform for scalable quantum nanophotonics based on silicon-vacancy (SiV) color centers coupled to nanoscale diamond devices. By placing SiV centers inside diamond photonic crystal cavities, we realize a quantum-optical switch controlled by a single color center. We control the switch using SiV metastable orbital states and verify optical switching at the single-photon level by using photon correlation measurements. We use Raman transitions to realize a single-photon source with a tunable frequency and bandwidth in a diamond waveguide. Finally, we create entanglement between two SiV centers by detecting indistinguishable Raman photons emitted into a single waveguide. Entanglement is verified using a novel superradiant feature observed in photon correlation measurements, paving the way for the realization of quantum networks. 
Alp Sipahigil, Ruffin E. Evans, Denis D. Sukachev, Michael J. Burek,   Johannes Borregaard, Mihir K. Bhaskar, Christian T. N...
quant-ph cond-mat.mes-hall physics.optics