  Superconducting single photon detectors (SSPD) based on nanopatterned niobium
nitride wires offer single photon counting at fast rates, low jitter, and low
dark counts, from visible wavelengths well into the infrared. We demonstrate
the first use of an SSPD, packaged in a commercial cryocooler, for single
photon source characterization. The source is an optically pumped,
microcavity-coupled InGaAs quantum dot, emitting single photons on demand at
902 nm. The SSPD replaces the second silicon Avalanche Photodiode (APD) in a
Hanbury-Brown Twiss interferometer measurement of the source second-order
correlation function, g (2) (tau). The detection efficiency of the
superconducting detector system is >2 % (coupling losses included). The SSPD
system electronics jitter is 170 ps, versus 550 ps for the APD unit, allowing
the source spontaneous emission lifetime to be measured with improved
resolution.
