The propagation of correlated photon pairs in a lattice of coupled waveguides is studied. We calculate the evolution of quantum correlations along the lattice, and experimentally demonstrate a classical analogue using two incoherent sources.
We study quantum and classical Hanbury Brown-Twiss correlations in waveguide lattices. We develop a theory for the propagation of photon pairs in the lattice, predicting the emergence of nontrivial quantum interferences unique to lattice systems. Experimentally, we observe the classical counterpart of these interferences using intensity-correlation measurements. We discuss the correspondence between the classical and quantum correlations, and consider path-entangled input states which do not have a classical analogue. Our results demonstrate that waveguide lattices can be used as a robust and highly controllable tool for manipulating quantum states, and offer new ways of studying the quantum properties of light.
Interference effects of photon pairs propagating through two-dimensional lattices of evanescently coupled waveguides are theoretically analyzed for input states of independent and path-entangled photons. Their correlation unveils characteristic Hong-Ou-Mandel interferences as well as more complex phenomena unique to these structures. Furthermore, purely classical states of light are used to simulate these quantum interferences in intensity correlation experiments. The results suggest that waveguide arrays can be employed as convenient devices for manipulating quantum states of light.
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.