CW-laser-pumped telecom-band polarization-entangled photon-pair source with a fidelity of 97.8%

Quantum entanglement is one of the most important resources for quantum communication, information and computing. Since active polarization stabilization methods could alleviate the polarization-drift problem over optical fibre, telecom-band polarization-entangled photon-pairs can be well distributed and shared. Spontaneous four-wave mixing in a dispersion-shifted fibre (DSF) can be used to realize a source of telecom-band polarization-entangled photon pairs, but DSF is often cooled to suppress noise photons generated by spontaneous Raman-scattering. Second-order nonlinear crystals or waveguides such as periodically-poled lithium niobate (PPLN) waveguides are also available and generation has been reported on the conditions of careful selection of two nearly identical nonlinear crystals or accurate temperature-control of waveguides.