Spectrally engineered broadband photon source for two-photon quantum   interferometry
  We present a new approach to engineering broadband sources of entangled photon pairs for quantum interferometry. The source is based on quasi-phase-matched spontaneous parametric down conversion in a titanium diffused periodically poled lithium niobate waveguide with a strongly-chirped poling period. The proposed non-standard asymmetric poling mitigates phase distortions associated with the process of chirping. Asymmetric poling significantly broadens the entangled source bandwidth while preserving high visibility quantum interferometric sensing. 
Abu Thomas, Mackenzie Van Camp, Olga Minaeva, David Simon and   Alexander V. Sergienko
quant-ph physics.optics