An optical fiber-based source of polarization-entangled photon pairs

We describe the preparation of a high spectral brightness, broad wavelength coverage, single-spatial mode source of polarization-entangled photon pairs operated at room temperature. The source takes advantage of single-mode fiber optics, highly nonlinear microstructure fiber, judicious phase-matching, and the inherent stability provided by a Sagnac interferometer. With a modest average pump power (300 mu W), we create all four Bell states with a detected two-photon coincidence rate of 7 kHz per bandwidth of 0.9 nm, in a spectral range of more than 20 nm.