LOCAL INVARIANTS AND PAIRWISE ENTANGLEMENT IN SYMMETRIC MULTIQUBIT SYSTEM
A. R. Usha Devi, M. S. Uma, R. Prabhu, SUDHA · International Journal of Modern Physics B · 2006
Pairwise entanglement properties of a symmetric multi-qubit system are analyzed through a complete set of two-qubit local invariants. Collective features of entanglement, such as spin squeezing, are expressed in terms of invariants and a classification scheme for pairwise entanglement is proposed. The invariant criteria given here are shown to be related to the recently proposed (Phys. Rev. Lett.95, 120502 (2005)) generalized spin squeezing inequalities for pairwise entanglement in symmetric multi-qubit states.