Pairwise entanglement in symmetric multi-qubit systems
Wang, X, Mølmer, K · CERN Document Server (European Organization for Nuclear Research) · 2001
The concurrence, a quantitative measure of the entanglement between a pair of particles, is determined for the case where the pair is extracted from a symmetric state of N two-level systems. Examples are given for both pure and mixed states of the N-particle system, and for a pair extracted from two ensembles with correlated collective spins.