# Chiral quantum optics using a topological resonator

## TL;DR

This paper demonstrates chiral light-matter interactions in a topological resonator using valley-Hall edge states, achieving directional emission and Purcell enhancement, advancing nanophotonic quantum devices.

## Contribution

It introduces a topological helical resonator with counter-propagating modes for enhanced chiral light-matter coupling, a novel extension of topological photonics.

## Key findings

- Achieved Purcell enhancement of 3.4 in the topological resonator.
- Demonstrated chiral coupling of quantum emitters to the resonator.
- Realized a helical resonator with opposite polarization modes.

## Abstract

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.