Chiral topological photonics with an embedded quantum emitter

Topological photonic interfaces support topologically non-trivial optical modes with helical character. When combined with an embedded quantum emitter that has a circularly polarised transition dipole moment, a chiral quantum optical interface is formed due to spin-momentum locking. Here, we experimentally realise such an interface by integrating semiconductor quantum dots into a valley-Hall topological photonic crystal waveguide. We harness the robust waveguide transport to create a ring resonator which supports helical modes. Chiral coupling of quantum dot transitions, with directional contrast as high as $75\%$, is demonstrated. The interface also supports a topologically trivial mode, comparison with which allows us to clearly demonstrate the protection afforded by topology to the non-trivial mode.