On-chip quantum interference between silicon photon-pair sources

Large-scale integrated quantum photonic technologies(1,2) will require on-chip integration of identical photon sources with reconfigurable waveguide circuits. Relatively complex quantum circuits have been demonstrated already(1-7), but few studies acknowledge the pressing need to integrate photon sources and waveguide circuits together on-chip(8,9). A key step towards such large-scale quantum technologies is the integration of just two individual photon sources within a wave-guide circuit, and the demonstration of high-visibility quantum interference between them. Here, we report a silicon-on-insulator device that combines two four-wave mixing sources in an interferometer with a reconfigurable phase shifter. We configured the device to create and manipulate two-colour (non-degenerate) or same-colour (degenerate) path-entangled or path-unentangled photon pairs. We observed up to 100.0 +/- 0.4% visibility quantum interference on-chip, and up to 95 +/- 4% off-chip. Our device removes the need for external photon sources, provides a path to increasing the complexity of quantum photonic circuits and is a first step towards fully integrated quantum technologies.