Editing CHSH inequality (section)

=== Derivation from Clauser and Horne's 1974 inequality ===

In their 1974 paper,<ref name="Clauser-1974">{{citation |author1=J.F. Clauser |author2=M.A. Horne |year=1974 |title=Experimental consequences of objective local theories |journal=Phys. Rev. D |volume=10 |issue=2 |pages=526–35 |doi=10.1103/PhysRevD.10.526 |bibcode=1974PhRvD..10..526C}}</ref> Clauser and Horne show that the CHSH inequality can be derived from the CH74 one.  As they tell us, in a two-channel experiment the CH74 single-channel test is still applicable and provides four sets of inequalities governing the probabilities ''p'' of coincidences.

Working from the inhomogeneous version of the inequality, we can write:
<math display="block">- 1 \; \leq \; p_{jk}(a, b) - p_{jk}(a, b') + p_{jk}(a', b) + p_{jk}(a', b') - p_{jk}(a') - p_{jk}(b) \; \leq \; 0</math>
where ''j'' and ''k'' are each '+' or '&minus;', indicating which detectors are being considered.

To obtain the CHSH test statistic ''S'' ({{EquationRef|2}}), all that is needed is to multiply the inequalities for which ''j'' is different from ''k'' by &minus;1 and add these to the inequalities for which ''j'' and ''k'' are the same.