Noise Reduction in Photon Counting by Exploiting Spatial Correlations

Sometimes you need a steady drip, not a torrent---as in certain optics experiments, where the precise number of photons in each ``drip'' of a faint beam is important. The authors use an intensified charge-coupled device as a photon-number-resolving detector with spatial resolution, to study at once the joint photocount distributions and spatial correlations of weak twin beams of light. Compared to the usual analysis of photocount distributions, their spatially resolved analysis provides additional information about the statistical properties of the beams, and allows noise reduction.