Practical method to obtain a lower bound to the three-tangle

摘要

The quantitative assessment of the entanglement in multipartite quantum states is, apart from its fundamental importance, a practical problem. Recently there has been significant progress in developing new methods to determine certain entanglement measures. In particular, there is a method-in principle, analytical-to compute a certified lower bound for the three-tangle. The purpose of thiswork is to provide amanual for the implementation of this approach and to explicitly discuss several analytically solvable cases in order to gauge the numerical tools. Moreover, we derive a simple analytical bound for the mixed-state three-tangle.