# Frankfurt 2006 – wissenschaftliches Programm

## Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

# Q: Quantenoptik und Photonik

## Q 9: Quanteninformation I

### Q 9.5: Vortrag

### Montag, 13. März 2006, 15:00–15:15, HI

**Two-setting Bell Inequalities for Graph States** — •Geza Toth^{1,2}, Otfried Gühne^{3}, and Hans J. Briegel^{3,4} — ^{1}Research Institute of Solid State Physics and Optics, Hungarian Academy of Sciences, H-1525 Budapest P.O. Box 49, Hungary — ^{2}Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, D-85748 Garching, Germany — ^{3}Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, A-6020 Innsbruck, Austria — ^{4}Institut für Theoretische Physik, Universität Innsbruck, Technikerstraße 25, A-6020 Innsbruck, Austria

We present Bell inequalities for graph states with high violation of local realism. In particular, we show that there is a basic Bell inequality for every nontrivial graph state which is violated by the state at least by a factor of two. This inequality needs the measurement of at most two operators for each qubit and involves only some of the qubits. We also show that for some families of graph states composite Bell inequalities can be constructed such that the violation of local realism increases exponentially with the number of qubits. We prove that some of our inequalities are facets of the convex polytope containing the many-body correlations consistent with local hidden variable models. Our Bell inequalities are built from stabilizing operators of graph states. For further details, please see quant-ph/0510007.