Patent ID: 8433070

Claim:
A quantum cryptographic key distribution system comprising: a pulsed laser source arranged to transmit a pulse; and an interferometer including: a non-polarizing beam splitter configured to split the pulse into a clockwise pulse and a counterclockwise pulse; a polarization rotator configured to rotate a polarization of the counterclockwise pulse to produce a polarized counterclockwise pulse; a polarization-maintaining photonic crystal fiber configured to delay one of the clockwise pulse and the polarized counterclockwise pulse relative to the other one of the clockwise pulse and the polarized counterclockwise pulse; and an active birefringence modulator to phase encode a symbol on one of the clockwise pulse and the polarized counterclockwise pulse; wherein each of the clockwise and counterclockwise pulses are output as one of a phase-encoded pulse and reference pulse.