Antiresonance and interaction-induced localization in spin and qubit chains with defects

TL;DR

This paper investigates how quantum interference can suppress decay in a spin chain with a defect, revealing localization phenomena relevant for quantum computing models.

Contribution

It demonstrates that destructive interference prevents decay of localized excitations in a spin chain with a defect, combining analytical and numerical methods.

Findings

Localized two-excitation states form near the defect.

Quantum interference suppresses excitation decay.

Numerical results confirm analytical predictions.

Abstract

We study a spin chain with an anisotropic XXZ coupling in an external field. Such a chain models several proposed types of a quantum computer. The chain contains a defect with a different on-site energy. The interaction between excitations is shown to lead to two-excitation states localized next to the defect. In a resonant situation scattering of excitations on each other might cause decay of an excitation localized on the defect. We find that destructive quantum interference suppresses this decay. Numerical results confirm the analytical predictions.