Using quantum entangled photons to measure the absolute photon detection efficiency of a multi-pixel SiPM array

Spontaneous parametric down-conversion (SPDC)of a visible pump photon is the generation of two less energetic, quantum entangled photons (QEPs), often in the near infrared (NIR), using a non-linear crystal e.g. beta barium borate. Since the detection of one QEP predicates the existence of its entangled twin, QEPs have previously been used to measure the absolute photon detection efficiency (PDE), η(λ), of a detector under test by measuring time-coincident events with an additional trigger detector, allowing evaluation of η DUT (λ)without recourse to a calibrated reference detector. In this paper, the QEP absolute PDE measurement technique is outlined, and an extension of this technique is proposed to measure η(λ)for pixels on a multi-pixel array where each pixel provides an individual signal output. By treating all pixels in a multi-pixel array as indistinguishable, Monte Carlo simulations show that the symmetry of the measurement allows η(λ)to be determined for each pixel. A route towards experimental measurements using this technique with a 64-pixel SiPM array combined with a 64-channel waveform digitiser module is outlined.