The existence of hidden variables was postulated by Einstein as an explanation of the thought experiment described in his paper with Podolski and Rosen. Prof Ross will review the arguments that led John Bell to formulate inequalities, which had to be satisfied in any theory of (local) hidden variables, as well as the modifications of these inequalities which enabled them to be tested experimentally. He will then describe some of the experiments which were carried out in order to test these inequalities, with particular emphasis on the Nobel-prize-winning experiments of Aspect, Clauser and Zeilinger.

This colloquium should be accessible to anybody who has attended a course of Quantum Mechanics.