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Clauser-Horne Inequality


The Clauser-Horne inequality is a Bell inequality for jointly distributed indicator functions, written in terms of single-event and pair-event probabilities (Clauser and Horne 1974). Let A_0, A_1, B_0, and B_1 take values in {0,1} on one probability space. Writing p_i=<A_i>, q_j=<B_j>, and r_(ij)=<A_iB_j>, where the brackets denote expectation values, put C=r_(00)+r_(01)+r_(10)-r_(11)-p_0-q_0. Then

 -1<=C<=0.

The assumption of a common joint distribution is essential.

For deterministic values a_0, a_1, b_0, and b_1 in {0,1},

 a_0b_0+a_0b_1+a_1b_0-a_1b_1-a_0-b_0 in {-1,0}.

Taking expectation values proves the bound. For X_i=2A_i-1 and Y_j=2B_j-1, the CHSH inequality uses S=<X_0Y_0>+<X_0Y_1>+<X_1Y_0>-<X_1Y_1>. Expanding gives S=4C+2, so -1<=C<=0 is equivalent to |S|<=2. The correlation polytope expresses these consistency constraints geometrically (Filipp and Svozil 2003, Trott 2006).


See also

Bell Inequality, CHSH Inequality, Correlation Polytope, Indicator Function, Joint Distribution

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References

Clauser, J. F. and Horne, M. A. "Experimental Consequences of Objective Local Theories." Phys. Rev. D 10, 526-535, 1974. https://doi.org/10.1103/PhysRevD.10.526.Filipp, S. and Svozil, K. "Boole-Bell-Type Inequalities in Mathematica." In Challenging the Boundaries of Symbolic Computation (Ed. P. Mitic, P. Ramsden, and J. Carne). London: Imperial College Press, pp. 215-222, 2003. https://doi.org/10.1142/9781848161313_0028.Trott, M. "Polynomials in Inequalities." §1.2.3 in The Mathematica GuideBook for Symbolics. New York: Springer-Verlag, 2006. https://doi.org/10.1007/0-387-28815-5. https://www.mathematicaguidebooks.org/.

Cite this as:

Weisstein, Eric W. "Clauser-Horne Inequality." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/Clauser-HorneInequality.html

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