  Topological photonic structures exhibit chiral edge states that are robust to
disorder and sharp bends. When coupled to quantum emitters, these edge states
generate directional light emission that enables unprecedented control of
interactions between light and matter in a nanophotonic device. While
directional light emission in one-dimensional topological, as well as
conventional, waveguides has been previously demonstrated, the extension of
these concepts to resonator structures that enhance light-matter coupling
remains challenging. Here we demonstrate chiral lightmatter interactions in a
topological resonator. We employ valley-Hall topological edge states to realize
a helical resonator at the interface of two topologically distinct regions.
Such a helical resonator has two counter-propagating modes with opposite
polarizations. We show chiral coupling of the resonator to a quantum emitter
resulting in a Purcell enhancement of 3.4 due to resonant coupling. Such chiral
resonators could enable designing complex nanophotonic circuits for quantum
information processing, and studying novel quantum many-body dynamics.
