Fiber-Optic Sources of Quantum Entanglement

Abstract

We present a fiber-based source of polarization-entangled photon pairs that is well suited for quantum communication applications in the 1.5$μ$m band of standard telecommunication fiber. Quantum-correlated signal and idler photon pairs are produced when a nonlinear-fiber Sagnac interferometer is pumped in the anomalous-dispersion region of the fiber. Recently, we have demonstrated nonclassical properties of such photon pairs by using Geiger-mode InGaAs/InP avalanche photodiodes. Polarization entanglement in the photon pairs can be created by pumping the Sagnac interferometer with two orthogonally polarized pulses. In this case the parametrically scattered signal-idler photons yield biphoton interference with $>$90% visibility in coincidence detection, while no interference is observed in direct detection of either the signal or the idler photons.

6 pages, 4 figures; to appear in the Proceedings of QCMC'02: Quantum Communication, Measurement, and Computing (QCMC'02), J. H. Shapiro and O. Hirota, Eds., (Rinton Press, New Jersey, 2002)