Patent ID: 7289738

Claim:
An apparatus comprising: a pulse source including, a pulse generator for generating a pulse of photons; a parametric down-converter for receiving said pulse of photons, wherein photons that make up a portion of said pulse of photons are each parametrically down-converted into first and second photons, in which said first and second photons being such that alteration of a characteristic of one of said first and second photons alters a corresponding characteristic in the other of said first and second photons; a transmitter for receiving said first photons from said pulse source, said transmitter including a collapse event device for selectably altering said characteristic of said first photon; and a receiver for receiving said second photons from said pulse source, said receiver having a detector to detect alteration of said characteristic of said second photon wherein said receiver includes a nonlinear element for enhancing said detection, wherein said parametric down-converter further provides photons, that make up another portion of said pulse of photons, that are non down-converted; and wherein said receiver receives said non down-converted photons to correspond said second photons received by said receiver with said pulse of photons.