Separable Multipartite Mixed States - Operational Asymptotically   Necessary and Sufficient Conditions
  We introduce an operational procedure to determine, with arbitrary probability and accuracy, optimal entanglement witness for every multipartite entangled state. This method provides an operational criterion for separability which is asymptotically necessary and sufficient. Our results are also generalized to detect all different types of multipartite entanglement. 
Fernando G. S. L. Brandao and Reinaldo O. Vianna