Qubit-photon bound states in topological waveguides with long-range hoppings

TL;DR

This paper explores how qubit-photon bound states behave in topological waveguides with long-range hoppings, revealing new topological phases and how giant atoms can be used to distinguish them, with potential circuit QED implementations.

Contribution

It extends the study of topological photonic models by analyzing extended SSH models with long-range hoppings and introduces giant atoms as a tool to probe different topological phases.

Findings

Bound states' features depend on topological phase and can be tuned via giant atoms.

Giant atoms can distinguish all topological phases through their dynamics.

Experimental implementation feasible with circuit QED systems.

Abstract

Quantum emitters interacting with photonic band-gap materials lead to the appearance of qubit-photon bound states that mediate decoherence-free, tunable emitter-emitter interactions. Recently, it has been shown that when these band-gaps have a topological origin, like in the photonic SSH model, these qubit-photon bound states feature chiral shapes and certain robustness to disorder. In this work, we consider a more general situation where the emitters interact with an extended SSH photonic model with longer range hoppings that displays a richer phase diagram than its nearest-neighbour counterpart, e.g., phases with larger winding numbers. In particular, we first study the features of the qubit-photon bound states when the emitters couple to the bulk modes in the different phases, discern its connection with the topological invariant, and show how to further tune their shape through the use of giant atoms, i.e., non-local couplings. Then, we consider the coupling of emitters to the edge modes appearing in the different topological phases. Here, we show that giant atoms dynamics can distinguish between all different topological phases, as compared to the case with local couplings. Finally, we provide a possible experimental implementation of the model based on periodic modulations of circuit QED systems. Our work enriches the understanding of the interplay between topological photonics and quantum optics.