Ghost interference with an optical parametric amplifier

The “ghost” interference experiment is analyzed when the source of entangled photons is a multimode optical parametric amplifier (OPA) whose weak limit is the two-photon spontaneous parametric down-conversion beam. The visibility of the double-slit pattern is calculated, taking the finite coincidence time window of the photon counting detectors into account. It is found that the coincidence window and the bandwidth of light reaching the detectors play a crucial role in the loss of visibility on coincidence detection, not only in the ghost interference experiment but in all experiments involving coincidence detection. The differences between the loss of visibility with two-mode and multimode OPA sources are also discussed.