  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, we
report single-photon sources using single quantum dots (QDs) embedded in
topological slow light waveguides based on valley photonic crystals. We observe
Purcell-enhanced single-photon emission 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.
