The Bell inequality will decide

John Bell proved a theorem in 1964 that pertains to the results of measurements carried out on particles and some of the inequalities they have to fulfil. The theorem pertains to the basic logic of the measurements and is valid independent of the kind of particles and of the nature of their interaction. The theorem soon became very famous, because it turned out to be a useful tool allowing us to verily some fundamental features of our knowledge about the world. 

John Stuart Bell (1928-1990), Irish malhemalician at Centre Europeen de la Recherche Nucleaire (CERN) in Geneva. In the 1960s Bell reconsidered an old controversy of locality versus non-locality, hidden variables, etc., a subject apparently exhausted after exchange of ideas between Einstein and Bohr. 

fcss-Andreae, C. Keller, G. van der Zouw, A. Zeilinger, Nature -101 (1999) 

we repeat Experiment I, but this time slit A will be rotated by a small angle a (Experiment II). At the slit B nothing has changed, and therefore we must obtain there exactly the same sequence of zeros and ones as in Experiment 1. At slit A, however, the results may be different. Since the rotation angle is small, the difference list will be short. We might get the following result 

There are two differences (highlighted in bold) between the lists for the two detectors. 

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