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Two-particle localization and antiresonance in disordered spin and qubit chains

L. F. Santos·M. I. Dykman
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Abstract

We show that, in a system with defects, two-particle states may experience destructive quantum interference, or antiresonance. It prevents an excitation localized on a defect from decaying even where the decay is allowed by energy conservation. The system studied is a qubit chain or an equivalent spin chain with an anisotropic ($XXZ$) exchange coupling in a magnetic field. The chain has a defect with an excess on-site energy. It corresponds to a qubit with the level spacing different from other qubits. We show that, because of the interaction between excitations, a single defect may lead to multiple localized states. The energy spectra and localization lengths are found for two-excitation states. The localization of excitations facilitates the operation of a quantum computer. Analytical results for strongly anisotropic coupling are confirmed by numerical studies.

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L. F. Santos, M. I. Dykman. 2003-11-13. Two-particle localization and antiresonance in disordered spin and qubit chains. https://doi.org/10.1103/physrevb.68.214410

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