Experimental realization of qubit-state-controlled directional edge states in waveguide QED

TL;DR

This paper demonstrates the experimental creation of tunable, directional photonic edge states in a waveguide QED system, enabling controlled qubit interactions with minimal crosstalk.

Contribution

It provides the first experimental realization of in-situ tunable, directional edge states in a waveguide QED setup using a Rice-Mele configuration.

Findings

Achieved 99.4% directionality fidelity.

Demonstrated active and passive control of edge states.

Enabled potential for long-range, low-crosstalk qubit coupling.

Abstract

We experimentally realise the theoretical proposal for in-situ tunable photonic edge states emerging from qubits coupled to a waveguide with a photonic bandgap. These edge states are directional, exhibiting theoretically zero population in the opposite direction. Our experiment implements a tunable Rice-Mele waveguide configuration, where the directionality of edge states is controlled in-situ by varying the qubit energy. The Rice-Mele waveguide is constructed using lumped resonators coupled to a standard Xmon qubit. We demonstrate the existence of these edge states both actively, via waveguide transmission, and passively, through qubit emission via an edge state. We estimate a 99.4% fidelity in the directionality, constrained by our measurement noise floor. These results hold significant promise for the development of long-range qubit couplers with effectively zero crosstalk.