Long-distance genuine multipartite Entanglement between Magnetic Defects in Spin Chains

TL;DR

This paper demonstrates that three magnetic defects in a spin chain can induce long-distance genuine multipartite entanglement, even when two-qubit entanglement is absent, using analytical and numerical methods.

Contribution

It reveals conditions for long-distance GME in spin chains with magnetic defects and provides methods to quantify this entanglement.

Findings

GME exists across the entire parameter space, including regions with zero two-qubit concurrence.

Bound states localized at defects are analytically and numerically characterized.

Analytical GME concurrence is derived for rank-two reduced density matrices.

Abstract

We investigate the emergence and properties of long-distance genuine multipartite entanglement, induced via three localized magnetic defects, in a one-dimensional transverse-field XX spin-$1/2$ chain. Using both analytical and numerical techniques, we determine the conditions for the existence of bound states localized at the defects. We find that the reduced density matrix (RDM) of the defects exhibits long-distance genuine multipartite entanglement (GME) across the whole range of the Hamiltonian parameter space, including regions where the two-qubit concurrence is zero. We quantify the entanglement by using numerical lower bounds for the GME concurrence, as well as by analytically deriving the GME concurrence in regions where the RDM is of rank two. Our work provides insights into generating multipartite entanglement in many-body quantum systems via local control techniques.