Decoherence and disorder in quantum walks: From ballistic spread to localization

TL;DR

This paper explores how decoherence and disorder affect quantum walks, demonstrating transitions from ballistic spread to localization in a photonic system through controlled environmental simulations.

Contribution

It presents the first experimental observation of Anderson localization in a discrete quantum walk using photonic implementation with controlled decoherence and disorder.

Findings

Ballistic spread observed in pure quantum evolution.

Transition to diffusive classical walk under certain conditions.

First experimental demonstration of Anderson localization in discrete quantum walks.

Abstract

We investigate the impact of decoherence and static disorder on the dynamics of quantum particles moving in a periodic lattice. Our experiment relies on the photonic implementation of a one-dimensional quantum walk. The pure quantum evolution is characterized by a ballistic spread of a photon's wave packet along 28 steps. By applying controlled time-dependent operations we simulate three different environmental influences on the system, resulting in a fast ballistic spread, a diffusive classical walk and the first Anderson localization in a discrete quantum walk architecture.