A system and method of detecting entangled photon pairs, each pair
including a signal photon and an idler photon, is disclosed. Entangled
photon pairs are provided having an entanglement time and an entanglement
area selected to substantially increase an associated entangled
two-photon cross-section of an associated target medium. The entangled
photon pairs are also selected to have an energy distribution between the
signal photon and the idler photon to substantially decrease an
associated random two-photon absorption cross section of the target
medium. The entangled photon pairs are directed to the target medium, and
at least one entangled-photon pair being absorbed by the target medium is
detected. The techniques for detecting entangled photons may be adapted
to accommodate hiding information in entangled photons. That is, these
techniques may be used for quantum steganography.