Photon pair generation in quadratic waveguide arrays: A classical optical simulation

This work reveals that linear propagation of classical light beams can be used to simulate the nonlinear effect of SPDC leading to photon pair generation and quantum random walks of the generated biphotons. In particular, the authors demonstrate that the quantum correlations of biphotons generated in a quadratically nonlinear 1D waveguide array can be mapped onto a linear beam propagation in specially designed 2D array of coupled optical waveguides. This analogy enables us to simulate, with classical light, the quantum coincidence counts for biphotons including the regime of breaking a 1D Bell like inequality as indicated by positve values of the non-classicality.