A Robust Semidefinite Programming Approach to the Separability Problem
  We express the optimization of entanglement witnesses for arbitrary bipartite states in terms of a class of convex optimization problems known as Robust Semidefinite Programs (RSDP). We propose, using well known properties of RSDP, several new sufficient tests for the separability of mixed states. Our results are then generalized to multipartite density operators. 
Fernando. G. S. L. Brandao and Reinaldo O. Vianna