Observation of novel robust edge states without bulk-boundary correspondence in non-Hermitian quantum walks

TL;DR

This paper reports the experimental discovery of unconventional, robust edge states in non-Hermitian quantum walks that defy the traditional bulk-boundary correspondence, especially in broken PT-symmetric phases, with implications for robust transport in complex systems.

Contribution

It presents the first experimental observation of such edge states in non-Hermitian periodically driven systems, challenging existing topological understanding.

Findings

Unconventional edge states observed outside bulk-boundary rules

Edge states are robust against perturbations and disorder

Demonstrated in a non-Hermitian light quantum walk platform

Abstract

Recently, the study of non-Hermitian physics has attracted considerable attention. The modified bulk-boundary correspondence has been proposed to understand topological edge states in non-Hermitian static systems. Here we report a new experimental observation of edge states in non-Hermitian periodically driven systems. Some unconventional edge states are found not to be satisfied with the bulk-boundary correspondence when the system belongs to the broken parity-time (PT) symmetric phase. The experiments are performed in our constructed non-Hermitian light quantum walk platform with left and right boundaries, where the beams outside system boundary are blocked subtly at the end of each step. The robust properties of these edge states against to static perturbations and disorder have also been demonstrated experimentally. The finding of robust edge states in broken PT-symmetric phase inspires us to explore a robust transport channel in ubiquitously complex systems with strong dissipation.