A characterization of global entanglement
Abstract
We define a set of entanglement monotones for qubits and give a single measure of entanglement in terms of these. This measure is zero except on globally entangled (fully inseparable) states. This measure is compared to the Meyer-Wallach measure for two, three, and four qubits. We determine the four-qubit state, symmetric under exchange of qubit labels, which maximizes this measure. It is also shown how the elementary monotones may be computed as a function of observable quantities. We compute the magnitude of our measure for the ground state of the four-qubit superconducting experimental system investigated in [M. Grajcar et al., Phys. Rev. Lett._96_, 047006 (2006)], and thus confirm the presence of global entanglement in the ground state.
Cite
@article{arxiv.quant-ph/0602143,
title = {A characterization of global entanglement},
author = {Peter J. Love and Alec Maassen van den Brink and A. Yu. Smirnov and M. H. S. Amin and M. Grajcar and E. Il'ichev and A. Izmalkov and A. M. Zagoskin},
journal= {arXiv preprint arXiv:quant-ph/0602143},
year = {2007}
}
Comments
4 pages, 1 figure, REVTeX 4, v2 Minor errors corrected, three new references, expanded discussion of extension to mixed states