Topological phases and delocalization of quantum walks in random environments

TL;DR

This paper explores how one-dimensional quantum walks with topological properties behave in random environments, revealing coexistence of edge states and delocalization phenomena that challenge previous localization assumptions.

Contribution

It demonstrates that spatial disorder does not necessarily lead to localization in topological quantum walks, highlighting the robustness of edge states against certain types of randomness.

Findings

Spatial disorder allows coexistence of edge states and delocalization.

Temporal disorder destroys topological edge states.

Quantum walks can avoid complete Anderson localization in certain conditions.

Abstract

We investigate one-dimensional (1D) discrete time quantum walks (QWs) with spatially or temporally random defects as a consequence of interactions with random environments. We focus on the QWs with chiral symmetry in a topological phase, and reveal that chiral symmetry together with bipartite nature of the QWs brings about intriguing behaviors such as coexistence of topologically protected edge states at zero energy and Anderson transitions in the 1D chiral class at non-zero energy in their dynamics. Contrary to the previous studies, therefore, the spatially disordered QWs can avoid complete localization due to the Anderson transition. It is further confirmed that the edge states are robust for spatial disorder but not for temporal disorder.