Measuring photon correlation using imperfect detectors

Single-photon detectors are “blind” after the detection of a photon, and thereafter display a characteristic recovery in efficiency, during which the number of undetected photons depends on the statistics of the incident light. We show how the efficiency recovery, photon statistics, and intensity have an interdependent relationship which suppresses a detector’s ability to count photons and measure correlations. We also demonstrate this effect with an experiment using 𝑛 such detectors to determine the 𝑛⁢th-order correlation function with pseudothermal light.