Efficient and spectrally bright source of polarization-entangled photons
  We demonstrate an efficient fiber-coupled source of nondegenerate polarization entangled photons at 795 and 1609 nm using bidirectionally pumped parametric down-conversion in bulk periodically poled lithium niobate. The single-mode source has an inferred bandwidth of 50 GHz and a spectral brightness of 300 pairs/s/GHz/mW of pump power that is suitable for narrowband applications such as entanglement transfer from photonic to atomic qubits. 
Friedrich K\"onig, Elliott J. Mason, Franco N. C. Wong, and Marius A.   Albota