Bell-type inequalities à la Schrödinger

Already in 1935, Schrödinger assembled all prerequisites for a proof of Bell-type inequalities, namely: (i) a suitable two-particle state; (ii) a sufficient number of observables which are correlated in that state; and (iii) a tentative interpretation of these correlations in the spirit of local hidden-variables theories. The inequalities derived here from these assumptions are violated in quantum mechanics, which shows once more that quantum correlations cannot be understood in terms of local hidden-variables theories. This was realized before Bell (1964), since all previous authors — including Schrödinger — focused their attention to perfect correlations and underestimated the importance of the imperfect ones.