Realization of quantum walks with negligible decoherence in waveguide lattices

TL;DR

This paper demonstrates that waveguide lattices can effectively implement large-scale quantum walks with minimal decoherence, enabling advanced studies of quantum algorithms and phenomena.

Contribution

It shows that waveguide lattices serve as a scalable, low-decoherence platform for realizing and studying quantum walks experimentally.

Findings

Observation of quantum walks in systems with ~100 sites

Confirmation of ballistic propagation and disorder effects

Experimental validation of theoretical quantum walk phenomena

Abstract

Quantum random walks are the quantum counterpart of classical random walks, and were recently studied in the context of quantum computation. A quantum random walker is subject to self interference, leading to a remarkably different behavior than that of classical random walks such as ballistic propagation or localization due to disorder. Physical implementations of quantum walks have only been made in very small scale systems severely limited by decoherence. Here we show that the propagation of photons in waveguide lattices, which have been studied extensively in recent years, are essentially an implementation of quantum walks. Since waveguide lattices are easily constructed at large scales and display negligible decoherence, they can serve as an ideal and versatile experimental playground for the study of quantum walks and quantum algorithms. We experimentally observe quantum walks in large systems (~100 sites) and confirm quantum walks effects which were studied theoretically, including ballistic propagation, disorder and boundary related effects.