Effect of loss on photon-pair generation in nonlinear waveguides arrays
  We describe theoretically the process of spontaneous parametric down-conversion in quadratic nonlinear waveguide arrays in the presence of linear loss. We derive a set of discrete Schrodinger-type equations for the biphoton wave function, and the wave function of one photon when the other photon in a pair is lost. We demonstrate effects arising from loss-affected interference between the generated photon pairs and show that nonlinear waveguide arrays can serve as a robust loss-tolerant integrated platform for the generation of entangled photon states with non-classical spatial correlations. 
Diana A. Antonosyan, Alexander S. Solntsev, Andrey A. Sukhorukov
physics.optics quant-ph