Local and nonlocal properties of Werner states - art. no. 044302

We consider a special kind of mixed states-a Werner derivative, which is th e state transformed by nonlocal unitary-local or nonlocal-operations from a Werner state. We show the following: ii) The amount of entanglement of Wer ner derivatives cannot exceed that of the original Werner stair. (ii) Altho ugh it is generally possible to increase the entanglement of a single copy of a Werner derivative by local quantum operations and classical communicat ion. the maximal possible entanglement cannot exceed the entanglement of th e original Werner state. The extractable entanglement of Werner derivatives is limited by the entanglement of the original Werner state.