Quantum walk on a random comb

TL;DR

This paper investigates how continuous time quantum walks behave on a random comb graph, revealing localization effects that trap the walk and prevent it from spreading infinitely along the spine.

Contribution

It provides a novel analysis of quantum walk localization on a random comb graph using spectral theory and Anderson localization techniques.

Findings

Quantum walk exhibits localization along the spine of the comb.

Walk can escape to infinity along the teeth but not along the spine.

Initial position influences the probability of remaining trapped.

Abstract

We study continuous time quantum walk on a random comb graph with infinite teeth. Due to localization effects along the spine, the walk cannot go to infinity in the spine direction, while it can escape to infinity along the teeth of the comb. Starting from an initial vertex the walk has a nonzero probability to stay trapped in a finite region. These results are obtained by studying the spectrum and eigenstates of the random Hamiltonian for the graph and analysing its properties. We use both analytic and numerical methods many of which come from the theory of Anderson localization in one dimension.