Entanglement Measures for Intermediate Separability of Quantum States
Abstract
We present a family of entanglement measures Rm which act as indicators for separability of n-qubit quantum states into m subsystems for arbitrary 2 ≤ m ≤ n. The measure Rm vanishes if the state is separable into m subsystems, and for m = n it gives the Meyer-Wallach measure while for m = 2 it reduces, in effect, to the one introduced recently by Love et al. The measures Rm are evaluated explicitly for the GHZ state and the W state (and its modifications, the Wk states) to show that these globally entangled states exhibit rather distinct behaviors under the measures, indicating the utility of the measures Rm for characterizing globally entangled states as well.
0