A note on the supplementary variables in spin-measuring equipments in the EPR-Bell experiment

Abstract

We discuss supplementary (or hidden) variables in spin-measuring equipments in EPR-Bell experiment. This theme was considered in a Bell's later work. We generalize it. First, we show why the original supplementary variable $\lambda$ is not to be regarded to include supplementary variables in spin-measuring equipments (why supplementary variables should be introduced additionally in spin-measuring equipments) Next, we show the followings. When the supplementary variables introduced in spin-measuring equipments have local correlations, the Bell inequality is recovered. On the other hand, when they have nonlocal correlations, the Bell inequality is not recovered. This fact is in accord with the fact that the Bell inequality is derived for local realistic models.