A scheme for a bidirectionally pumped quantum light source on a silicon chip

Large-scale quantum photonic circuits require integrating multiple single-photon sources, which are typically based on spontaneous four-wave mixing (SFWM) in spiral waveguides or microring resonators (MRRs). Photons can be generated in both clockwise (CW) and counterclockwise (CCW) orientations from a single source within a Sagnac loop, which shows promise for improving scalability. In this work, we propose a fully integrable scheme for bidirectional creation and usage of single photons. This concept is based on two asymmetric Mach-Zehnder interferometers (AMZIs) integrated within the Sagnac loop. As a proof of concept, we fabricated a device with a spiral waveguide on a silicon photonic chip and demonstrated its application as a quantum splitter and two multi-wavelength quantum light sources.