An on-chip quantum splitter of degenerate photon pairs using a spiral waveguide

Integrated sources of indistinguishable photons have garnered significant attention due to their applications in optical quantum computing, quantum communication and quantum networks. However, photons generated from spontaneous four-wave mixing (SFWM) always occur in pairs, which need to be split into different modes for further applications. Here, we present a quantum splitter for degenerate photon pairs based on a silicon photonic chip. This device incorporates a Sagnac loop, two asymmetrical Mach-Zehnder interferometers (AMZIs), and a spiral waveguide. The spiral waveguide generates pairs of photons, the Sagnac loop facilitates bidirectional pumping of the source, and the two AMZIs enables the extraction of photons from the pump light. The photons generated from two directions interfere at a balanced multi-mode interferemeter (MMI) to enable the reversed Hong-Ou-Mandel (HOM) effect to take place. Our experimental results demonstrated an on-chip interference visibility of 96.63% and an off-chip HOM dip visibility of 90.93%, indicating that the generated photons are well-suited for further integration with other components in quantum applications.