Quadratic bell inequalities as tests for multipartite entanglement.
This Letter presents quantum mechanical inequalities which distinguish, for systems of n spin- 1 / 2 particles ( n>2), between fully entangled states and states in which at most n-1 particles are entangled. These inequalities are stronger than those obtained by Gisin and Bechmann-Pasquinucci [Phys. Lett. A 246, 1 (1998)] and by Seevinck and Svetlichny [quant-ph/0201046].
Uffink
Jos
J
Institute for History and Foundations of Science, Utrecht University, PO Box 80.000, 3508 TA Utrecht, The Netherlands. uffink@ phys.uu.nl