High-efficiency WSi superconducting nanowire single-photon detectors for   quantum state engineering in the near infrared
  We report on high-efficiency superconducting nanowire single-photon detectors based on amorphous WSi and optimized at 1064 nm. At an operating temperature of 1.8 K, we demonstrated a 93% system detection efficiency at this wavelength with a dark noise of a few counts per second. Combined with cavity-enhanced spontaneous parametric down-conversion, this fiber-coupled detector enabled us to generate narrowband single photons with a heralding efficiency greater than 90% and a high spectral brightness of $0.6\times10^4$ photons/(s$\cdot$mW$\cdot$MHz). Beyond single-photon generation at large rate, such high-efficiency detectors open the path to efficient multiple-photon heralding and complex quantum state engineering. 
H. Le Jeannic, V.B. Verma, A. Cavaill\`es, F. Marsili, M.D. Shaw, K.   Huang, O. Morin, S.W. Nam, J. Laurat
quant-ph physics.ins-det physics.optics