Page "EPR paradox" Paragraph 40

In 1964, John Bell showed that the predictions of quantum mechanics in the EPR thought experiment are significantly different from the predictions of a particular class of hidden variable theories ( the local hidden variable theories ).

Roughly speaking, quantum mechanics has a much stronger statistical correlation with measurement results performed on different axes than do these hidden variable theories.

These differences, expressed using inequality relations known as " Bell's inequalities ", are in principle experimentally detectable.

Later work by Eberhard showed that the key properties of local hidden variable theories which lead to Bell's inequalities are locality and counter-factual definiteness.

Any theory in which these principles apply produces the inequalities.

Arthur Fine subsequently showed that any theory satisfying the inequalities can be modeled by a local hidden variable theory.