Quantum-correlated twin photons from microstructure fiber.

We present a source of correlated photon pairs that relies on spontaneous parametric scattering in microstructure fiber. Quantum correlations are shown between photon pairs that are generated through four-photon scattering where the pump photons are degenerate at a wavelength of 749 nm and the signal and idler photons are nondegenerate at wavelengths of 761 nm and 737 nm, respectively. Careful adjustment of the pump wavelength and polarization are shown to be critical to observing quantum correlations.