Strongly trapped space-inhomogeneous quantum walks in one dimension

TL;DR

This paper develops an analytical method to calculate eigenvectors of space-inhomogeneous quantum walks, extending previous work to more general models and quantitatively analyzing localization and trapping effects.

Contribution

The authors introduce a transfer matrix-based analytical method to compute eigenvectors and extend eigenvalue characterization to broader quantum walk models.

Findings

Eigenvectors can be calculated analytically using the transfer matrix.

Localization and trapping properties are quantitatively characterized.

Time-averaged limit distributions are derived for multiple models.

Abstract

Localization is a characteristic phenomenon of space-inhomogeneous quantum walks in one dimension, where particles remain localized around their initial position. The existence of eigenvalues of time evolution operators is a necessary and sufficient condition for the occurrence of localization, and their associated eigenvectors are deeply related to the amount of localization, i.e., the probability that the walker stays around the starting position in the long-time limit. In a previous study by authors, the eigenvalues of two-phase quantum walks with one defect were studied using a transfer matrix, which focused on the occurrence of localization (Quantum Inf. Process 20(5), 2021). In this paper, we introduce the analytical method to calculate eigenvectors using the transfer matrix and also extend our results to characterize eigenvalues not only for two-phase quantum walks with one defect but also for a more general space-inhomogeneous model. With these results, we quantitatively evaluate localization and study the strong trapping property by deriving the time-averaged limit distributions of five models studied previously.