Spin squeezing and concurrence

TL;DR

This paper explores the relationship between spin squeezing and concurrence, demonstrating their qualitative equivalence in symmetric spin-1/2 systems and highlighting spin squeezing's connection to pairwise entanglement.

Contribution

It establishes a qualitative equivalence between spin squeezing and concurrence for symmetric spin-1/2 particles using a recent spin squeezing criterion.

Findings

Spin squeezing and concurrence are qualitatively equivalent in certain symmetric systems.

Spin squeezing relates closely to pairwise entanglement.

The results are exemplified with superpositions of Dicke states.

Abstract

We study the relations between spin squeezing and concurrence, and find that they are qualitatively equivalent for an ensemble of spin-1/2 particles with exchange symmetry and parity, if we adopt the spin squeezing criterion given by the recent work (G. Toth et al. Phys. Rev. Lett. 99, 250405 (2007)). This suggests that the spin squeezing has more intimate relations with pairwise entanglement. We exemplify the result by considering a superposition of two Dicke states.