Near perfect two-photon interference out of a down-converter on a silicon photonic chip

Integrated entangled photon-pair sources are key elements for enabling large-scale quantum photonic solutions and address the challenges of both scaling-up and stability. Here we report the first demonstration of an energy-time entangled photon-pair source based on spontaneous parametric down-conversion in silicon-based platform-stoichiometric silicon nitride (Si3N4)-through an optically induced second-order (chi((2))) nonlinearity, ensuring type-0 quasi-phase-matching of fundamental harmonic and its second-harmonic inside the waveguide. The developed source shows a coincidence-to-accidental ratio of 1635 for 8 mu W pump power. We report two-photon interference with remarkable near-perfect visibility of 99.36 +/- 1.94%, showing high-quality photonic entanglement without excess background noise. This opens a new horizon for quantum technologies requiring the integration of a large variety of building functionalities on a single chip. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement