Multiparticle entanglement in graph-diagonal states: Necessary and sufficient conditions for four qubits

Otfried Gühne, Bastian Jungnitsch, Tobias Moroder, Yaakov S. Weinstein

Published 2011-07-25, updated 2011-11-24Version 2

The characterization of genuine multiparticle entanglement is important for entanglement theory as well as experimental studies related to quantum information theory. Here, we completely characterize genuine multiparticle entanglement for four-qubit states diagonal in the cluster-state basis. In addition, we give a complete characterization of multiparticle entanglement for all five-qubit graph states mixed with white noise, for states diagonal in the basis corresponding to the five-qubit Y-shaped graph, and for a family of graph states with an arbitrary number of qubits.