High visibility time-energy entangled photons from a silicon   nanophotonic chip
  Advances in quantum photonics have shown that chip-scale quantum devices are translating from the realm of basic research to applied technologies. Recent developments in integrated photonic circuits and single photon detectors indicate that the bottleneck for fidelity in quantum photonic processes will ultimately lie with the photon sources. We present and demonstrate a silicon nanophotonic chip capable of emitting telecommunication band photon pairs that exhibit the highest raw degree of time-energy entanglement from a micro/nanoscale source, to date. Biphotons are generated through cavity-enhanced spontaneous four-wave mixing (SFWM) in a high-Q silicon microdisk resonator, wherein the nature of the triply-resonant generation process leads to a dramatic Purcell enhancement, resulting in highly efficient pair creation rates as well as extreme suppression of the photon noise background. The combination of the excellent photon source and a new phase locking technique, allow for the observation of a nearly perfect coincidence visibility of (96.6 $\pm$ 1.1)$\%$, without any background subtraction, at a large pair generation rate of (4.40 $\pm$ 0.07) $\times$ 10$^5$ pairs/s. 
Steven Rogers, Daniel Mulkey, Xiyuan Lu, Wei C. Jiang, and Qiang Lin
quant-ph physics.optics