High-dimensional entanglement and topological protection in nonlinear waveguide arrays

We demonstrate a nonlinear AlGaAs photonic chip generating biphotons with high-dimensional spatial correlations. Photon pairs are generated by parametric down conversion in a waveguide array and simultaneously spread through quantum walks along the various waveguides, allowing to generate various types of high-dimensional entangled states of light. We further implement the Su-Schriefer-Heeger model and demonstrate the topological protection of the SPDC process against disorder. These results highlight nonlinear waveguide arrays as a promising platform for exploring the interplay between nonlinearity, disorder and topology in quantum photonic circuits.