Manipulating Excitation Dynamics in Structured Waveguide Quantum Electrodynamics

TL;DR

This paper introduces a structured waveguide quantum electrodynamics framework that allows local engineering of emitter coupling directionality to control excitation transport, localization, and coherence in quantum photonic systems.

Contribution

It proposes a novel structured wQED approach with programmable directional couplings, enabling new control over excitation dynamics and transport in atom-nanophotonic interfaces.

Findings

Identifies four distinct excitation dynamical configurations: centering, wave-like, leap-frog, and dispersion.

Spectral analysis links dynamics to interference among subradiant eigenmodes.

Transport remains robust with high coupling efficiencies (beta >= 0.99).

Abstract

Waveguide quantum electrodynamics (wQED) has become a central platform for studying collective light-matter interactions in low-dimensional photonic environments. While conventional wQED systems rely on uniform chirality or reciprocal emitter-waveguide coupling, we propose a structured wQED framework, where the coupling directionality of each emitter can be engineered locally to control excitation transport in an atom-nanophotonic interface. For different combinations of patterned coupling directionalities of the emitters, we identify four representative configurations that exhibit distinct dynamical behaviors: centering, wave-like, leap-frog, and dispersion excitations. Spectral analysis of the effective non-Hermitian Hamiltonian reveals that these dynamics originate from interferences among subradiant eigenmodes. Variance analysis further quantifies the spreading of excitation as functions of interatomic spacing and global chirality, showing tunable localization-delocalization transitions. Including nonguided losses, we find that the transport characteristics remain robust for realistic coupling efficiencies (beta >= 0.99). These results establish structured wQED as a practical route to manipulate excitation localization, coherence, and transport through programmable directionality patterns, paving the way for controllable subradiant transport and chiral quantum information routing.