CONSTRUCTING MULTIPARTITE ENTANGLEMENT WITNESSES

The method of transforming a hamiltonian of a composite quantum system into an entanglement witness, explored in an earlier papers, is extended to the multipartite case. The witness can be made not only to detect general entanglement but also to discriminate among its various multipartite types. Partial knowledge of the lowest part of energy spectrum is sufficient for approximate witness construction. As an example, we carry out analytic calculations with the hamiltonian of a 1-dimensional Heisenberg XXZ model.