Characterization of entanglement of more than two qubits with Bell inequalities and global entanglement

Abstract
It is shown that the entanglement-structure of 3- and 4qubit states can be characterized by optimized operators of the Mermin-Klyshko type. It is possible to discriminate between pure 2qubit entanglements and higher entanglements. A comparison with a global entanglement measure is made.