Atomic excitation delocalization at the clean to disordered interface in a chirally-coupled atomic array

TL;DR

This paper investigates how atomic excitation localization and delocalization occur at the interface between clean and disordered regions in a one-dimensional quantum emitter array, revealing size-dependent effects and implications for quantum information.

Contribution

It introduces a detailed analysis of excitation delocalization at the clean-disordered interface, including measures like participation ratio and gap ratio, and explores size and disorder effects on localization phenomena.

Findings

Localization occurs at lower disorder strength with larger disordered zones.

Delocalization is facilitated when the clean zone significantly exceeds the disordered zone.

Size and ratio of zones influence the crossover between localization and delocalization.

Abstract

In one-dimensional quantum emitter systems, the dynamics of atomic excitations are influenced by the collective coupling between emitters through photon-mediated dipole-dipole interactions. By introducing positional disorders in a portion of the atomic array, we investigate the delocalization phenomena at the interface between disordered zone and clean zone. The excitation is initialized as symmetric Dicke states in the disordered zone, and several measures are used to quantify the excitation localization. We first use population imbalance and half-chain entropy to investigate the excitation dynamics under time evolutions, and further investigate the crossover of excitation localization to delocalization via the gap ratio from the eigenspectrum in the reciprocal coupling case. In particular, we study the participation ratio of the whole chain and the photon loss ratio between both ends of the atomic chain, which can be used to quantify the delocalization crossover in the non-reciprocal coupling cases. Furthermore, by increasing the overall size or the ratio of the disordered zone under a fixed number of the whole chain, we observe that excitation localization occurs at a smaller disorder strength in the former case, while in the latter, a facilitation of the delocalization appears when a significant ratio of clean zone to disordered zone is applied. Our results can reveal the competition between the clean zone and the disordered zone sizes on localization phenomenon, give insights to non-equilibrium dynamics in the emitter-waveguide interface, and provide potential applications in quantum information processing.