Photon-number-resolving detection at 1:04 μm via coincidence frequency upconversion

We demonstrate photon-number-resolving detection based on coincidence frequency upconversion. Pumped by synchronized pulses, the photon signal of the coherent state at 1:04 μm was upconverted into visible replicas with preserved photon number distribution. The upconverted photons were then registered by a silicon multipixel photon counter. The photon-number-resolving performance was improved by reducing the background counts with a synchronous pump as the coincidence gate and reducing the intrinsic parametric fluorescence influence with long-wavelength pumping. A total detection efficiency of 3.7% was achieved with a quite low noise probability per pulse of 0.0002.