  Photon-number resolving (PNR) single-photon detectors are an enabling
technology in many areas such as photonic quantum computing, non-classical
light source characterisation and quantum imaging. Here, we demonstrate
high-efficiency PNR detectors using a parallel superconducting nanowire
single-photon detector (P-SNSPD) architecture that does not suffer from
crosstalk between the pixels and that is free of latching. The behavior of the
detector is modelled and used to predict the possible outcomes given a certain
number of incoming photons. We apply our model to a 4-pixel P-SNSPD with a
system detection efficiency of 92.5%. We also demonstrate how this detector
allows reconstructing the photon-number statistics of a coherent source of
light, which paves the way towards the characterisation of the photon
statistics of other types of light source using a single detector.
