Patent ID: 7489436

Claim:
A polarization-entangled photon source comprising: a down conversion crystal including a periodically poled region and an unpoled region and having a first waveguide and a second waveguide traversing the poled and unpoled regions, wherein within the unpoled region, the first waveguide and the second waveguide are configured to form a beamsplitter that splits a coherent beam of electromagnetic radiation in a first polarization state into a first beam carried by the first waveguide and a second beam carried by the second waveguide, and within the periodically poled region, the first beam is converted into a first pair of signal and idler photons carried by the first waveguide and the second beam is converted into a second pair of signal and idler photons carried by the second waveguide; a dielectric spacer positioned adjacent to the down conversion crystal and configured to receive the first pair of signal and idler photons emitted from the first waveguide in the first polarization state; a half-wave plate positioned adjacent to the down conversion crystal and configured to receive the second pair of signal and idler photons emitted from the second waveguide and rotate the second pair of signal and idler photons into a second polarization state orthogonal to the first polarization state; and a beam displacer positioned adjacent to the dielectric spacer and the half-wave plate and configured to combine the first and second pair of signal and idler photons output from the dielectric spacer and the half-wave plate into a single beam of polarization-entangled signal and idler photons.