

Preprint 31/2006
Two-Setting Bell Inequalities for Many Qubits
Kai Chen, Sergio Albeverio, and Shao-Ming Fei
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Submission date: 22. Mar. 2006 (revised version: October 2006)
Pages: 12
published in: Physical review / A, 74 (2006) 5, art-no. 050101
DOI number (of the published article): 10.1103/PhysRevA.74.050101
Bibtex
PACS-Numbers: 03.65.Ud, 03.67.Mn, 42.50.-p
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Abstract:
We present a family of tight Bell inequalities involving only two
measurement settings of each party for N>2 qubits. All the
Greenberger-Horne-Zeilinger states of N qubits (up to local unitary
transformations) are shown to violate the inequalities maximally, by an amount
that grows exponentially with N. Remarkably our new inequalities are violated
by some states which do satisfy all the standard Bell inequalities.
Furthermore the inequalities automatically recover all the standard ones for
systems less than N qubits. Their implementations are not only favorably
within the reach of well-established technology of linear optics, but also can
provide stronger nonlocality tests and contribute significantly to the
reduction of experimental efforts.