Bright phase-stable broadband fiber-based source of polarization-entangled photon pairs

We describe an achromatic, phase-stable, broadband source of polarization-entangled photon pairs with high spectral brightness that uses four-wave mixing in a fiber Sagnac interferometer. We achieved a polarizationentangled two-photon coincidence rate of 7 kHz per 0.5 THz 0.9 nm of bandwidth per 300 W of average pump power. At this rate, we observed two-photon fringe interference visibilities greater than 97%, over a 10 THz 21 nm spectral range. We measured violations of Bell’s inequality by more than 22 standard deviations for each of the four Bell states in less than 3 minutes per state. The high spectral brightness 26 kHz nm−1 mW−1 , large tunable wavelength range, single spatial mode, and phase stability make this source a promising candidate for a wide range of quantum-information applications.