Various embodiments of the present invention are directed to compact
systems for generating polarization-entangled photons. In one embodiment
of the present invention, a non-degenerate, polarization-entangled photon
source comprises a half-wave plate that outputs both a first pump beam
and a second pump beam, and a first beam displacer that directs the first
pump beam into a first transmission channel and the second pump beam into
a second transmission channel. A down-conversion device converts the
first pump beam into first signal and idler photons and converts the
second pump beam into second signal and idler photons. A second beam
displacer directs both the first signal and idler photons and the second
signal and idler photons into a single transmission channel. A dichroic
mirror directs the first and second signal photons to a first fiber optic
coupler and the first and second idler photons to a second fiber optic
coupler.