Two-photon ghost image and quantum cropto-fax

Abstract

The reported experiment is a two-photon optical imaging experiment¹ in which a spontaneous-parametric-downconversion light beam, which consists of pairs of orthogonally polarized signal and idler photons, is split into two diverging beams by a polarization beam splitter, so that co- incidence detections may be performed between two distant photon-counting detectors. An aperture (mask) placed in front of one of the detectors is illuminated by the signal beam through a convex lens. Surprisingly, an image of this aperture is observed in the coincidence counting rate when the other detector is scanned in the transverse plane of the idler beam, even though both detectors’ single counting rates remain constant.