P. R. Wells Jr., C. M. Chaves, J. A. e. Castro, Belita Koiller
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.
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http://arxiv.org/abs/1305.5818
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