Department of Mathematics, Capital Normal University, Beijing 100037, China
;Institut für Angewandte Mathematik, Universität
Bonn, D-53115, Germany
Abstract:
We study the normal form of multipartite density matrices. It is shown that
the correlation matrix (CM) separability criterion can be improved
from the normal form we obtained under filtering transformations.
Based on CM criterion the entanglement witness is further
constructed in terms of local orthogonal observables for both
bipartite and multipartite systems.