On-chip, photon-number-resolving, telecom-band detectors for scalable   photonic information processing
  Integration is currently the only feasible route towards scalable photonic quantum processing devices that are sufficiently complex to be genuinely useful in computing, metrology, and simulation. Embedded on-chip detection will be critical to such devices. We demonstrate an integrated photon-number resolving detector, operating in the telecom band at 1550 nm, employing an evanescently coupled design that allows it to be placed at arbitrary locations within a planar circuit. Up to 5 photons are resolved in the guided optical mode via absorption from the evanescent field into a tungsten transition-edge sensor. The detection efficiency is 7.2 \pm 0.5 %. The polarization sensitivity of the detector is also demonstrated. Detailed modeling of device designs shows a clear and feasible route to reaching high detection efficiencies. 
Thomas Gerrits, Nicholas Thomas-Peter, James C. Gates, Adriana E.   Lita, Benjamin J. Metcalf, Brice Calkins, Nathan A. Toml...
quant-ph physics.optics