ENTANGLEMENT MEASURES FOR INTERMEDIATE SEPARABILITY

We present a set of entanglement measures R-m for n - qubit quantum states. Since the measure R-m vanishes if and only if a state is separable into m subsystems, this measure R-m indicates whether the state can be decomposed into m subsystems. This R-m for m = n is equivalent to Meyer-Wallach measure while R-m for m = 2 is effectively equivalent to the one recently introduced by Love et al. In order to show the utility of our measures for characterising globally entangled states, the measures R-m are evaluated explicitly for the GHZ, W and Dicke states.