Spontaneous Parametric Down-Conversion and Quantum Walks in Arrays of   Quadratic Nonlinear Waveguides
  We analyze the process of simultaneous photon pair generation and quantum walks realized by spontaneous parametric down conversion of a pump beam in a quadratic nonlinear waveguide array. We demonstrate that this flexible platform allows for creating quantum states with different spatial correlations. In particular, we predict that the output photon correlations can be switched from photon bunching to antibunching controlled entirely classically by varying the temperature of the array or the spatial profile of the pump beam. 
Alexander S. Solntsev, Andrey A. Sukhorukov, Dragomir N. Neshev and   Yuri S. Kivshar
physics.optics quant-ph