Quantum and classical correlations and Werner states in finite spin linear arrays

TL;DR

This paper explores how quantum and classical correlations in a finite spin chain can be controlled by tuning interactions, demonstrating the formation of Werner states and their potential for practical entanglement manipulation.

Contribution

It shows how to reversibly switch between entangled and disentangled states in a spin chain, identifying Werner states through correlation functions in a condensed matter system.

Findings

Correlation functions exhibit universal behavior with respect to the spin-spin correlation parameter.

Werner states can be realized and controlled in antiferromagnetic spin chains.

Practical methods for entanglement control in condensed matter systems are feasible.

Abstract

Pairwise quantum correlations in the ground state of a N-spins antiferromagnetic chain described by the Heisenberg model with nearest neighbor exchange coupling are investigated. By varying a single coupling between two neighboring sites it is possible to drive spins from entangled to disentangled states, reversibly. For even N the two-spin density matrix is written in the form of a Werner state, allowing identification of the weight parameter with the usual spin-spin correlation function $\langle S_i^z \, S_j^z \rangle = \Gamma_{ij}$. The correlation functions show universal behavior in the $\Gamma$-dependence. This study presents a concrete possibility for the practical demonstration of entanglement control, opening alternatives for probing non-classical correlations and the realization of Werner states in familiar condensed matter systems. All required fabrication and measurement ingredients are currently available.