Chiral quantum optics in broken-symmetry and topological photonic crystal waveguides

TL;DR

This paper compares conventional and topological photonic crystal waveguides for chiral quantum light-matter interfaces, showing topological waveguides achieve higher Purcell enhancement and lower backscattering losses, aiding quantum device design.

Contribution

It provides full-wave 3D calculations demonstrating the performance differences of topological versus non-topological waveguides as chiral interfaces, highlighting advantages of topological structures.

Findings

Topological waveguides support higher Purcell factors.

Backscattering losses are smaller in topological waveguides at high enhancement.

Loss reduction is due to mode positioning, not topological protection.

Abstract

On-chip chiral quantum light-matter interfaces, which support directional interactions, provide a promising platform for efficient spin-photon coupling, non-reciprocal photonic elements, and quantum logic architectures. We present full-wave three-dimensional calculations to quantify the performance of conventional and topological photonic crystal waveguides as chiral emitter-photon interfaces. Specifically, the ability of these structures to support and enhance directional interactions while suppressing subsequent backscattering losses is quantified. Broken symmetry waveguides, such as the non-topological glide-plane waveguide and topological bearded interface waveguide are found to act as efficient chiral interfaces, with the topological waveguide modes allowing for operation at significantly higher Purcell enhancement factors. Finally, although all structures suffer from backscattering losses due to fabrication imperfections, these are found to be smaller at high enhancement factors for the topological waveguide. These reduced losses occur because the optical mode is pushed away from the air-dielectric interfaces where scattering occurs, and not because of any topological protection. These results are important to the understanding of light-matter interactions in topological photonic crystals and to the design of efficient, on-chip chiral quantum devices.