Revivals in One-dimensional Quantum Walks with a Time and Spin-dependent Phase Shift

TL;DR

This paper explores how time and spin-dependent phase shifts influence one-dimensional quantum walks, revealing conditions for revivals, localization, and robustness against noise, with implications for quantum control and computation.

Contribution

It demonstrates the occurrence of revivals in quantum walks with phase shifts, analyzing their dependence on phase rationality and noise, and compares standard and split-step protocols.

Findings

Complete revivals occur at rational phase values in standard quantum walks.

Partial revivals and localization occur at irrational phase values.

Revivals persist under small noise but vanish with larger phase noise.

Abstract

We investigate the role of a time and spin-dependent phase shift on the evolution of one-dimensional discrete-time quantum walks. By employing Floquet engineering, a time and spin-dependent phase shift ($\phi$) is imprinted onto the walker's wave function while it shifts from one lattice site to another. For a quantum walk driven by the standard protocol we show with our numerical simulations that complete revivals with equal periods occur in the probability distribution of the walk for rational values of the phase factor, i.e., $\phi/2\pi = p/q$. For an irrational value of $\phi/2\pi$ our results show partial revivals in the probability distribution with unpredictable periods, and the walker remains localized in a small region of the lattice. We further investigate revivals in a split-step quantum walk with a time and spin-dependent phase shift for rational values of $\phi/2\pi$. In contrast to the case of standard protocol, the split-step quantum walk shows partial revivals in the probability distribution. Furthermore, in view of an experimental realization we investigate the robustness of revivals against noise in the phase shift. Our results show that signatures of revivals persist for smaller values of the noise parameter, while revivals vanish for larger values. Our work is important in the context of quantum computation where quantum walks with a time and spin-dependent phase shift can be used to control and manipulate a desired quantum state on demand.