%0 Journal Article
%T Separability and entanglement in 2x2xN composite quantum systems
%A S. Karnas
%A M. Lewenstein
%J Physics
%D 2001
%I arXiv
%R 10.1103/PhysRevA.64.042313
%X We investigate separability and entanglement of mixed states in ${\cal C}^2\otimes{\cal C}^2\otimes{\cal C}^N$ three party quantum systems. We show that all states with positive partial transposes that have rank $\le N$ are separable. For the 3 qubit case (N=2) we prove that all states $\rho$ that have positive partial transposes and rank 3 are separable. We provide also constructive separability checks for the states $\rho$ that have the sum of the rank of $\rho$ and the ranks of partial transposes with respect to all subsystems smaller than 15N-1.
%U http://arxiv.org/abs/quant-ph/0102115v4