Topologically‐Protected Single‐Photon Sources with Topological Slow Light Photonic Crystal Waveguides

Slow light waveguides are advantageous for implementing high‐performance single‐photon sources required for scalable operation of integrated quantum photonic circuits (IQPCs), though such waveguides are known to suffer from propagation loss due to backscattering. A way to overcome the drawback is to use topological photonics, in which robust waveguiding in topologically‐protected optical modes has recently been demonstrated. Here, single‐photon sources are reported using single quantum dots (QDs) embedded in topological slow light waveguides based on valley photonic crystals. Purcell‐enhanced single‐photon emission is demonstrated from a QD into a topological slow light mode with a group index over 20 and its robust propagation even under the presence of sharp bends. These results pave the way for the realization of robust and high‐performance single‐photon sources indispensable for IQPCs.