How can correlations be explained that have been observed in a quantum mechanical experiment, the EPRB experiment (named after Albert Einstein, Boris Podolsky, Nathan Rosen, and David Bohm)? "Bell’s Theorem“ says that certain assumptions about the experimental arrangement and a causal explanation about the correlations result in “Bell’s inequality.” This inequality has been experimentally refuted, which is why one of the assumptions from which it was deducted must be wrong. The assumptions made about the EPRB experiment and on a causal explanation of the observed correlations are usually considered to be very weak. On the one hand, the diploma thesis by Adrian Wüthrich showed that––in contradiction to these assumptions––at least one of the assumptions, the so-called "Screening-off-condition" is unjustifiably strong. On the other, it is shown that the assumptions can be attenuated in such a way that Bell’s inequality is still deducible.
Finally, the project considers which of these weaker assumptions could be responsible for the contradiction concerning the experiment. In particular, assumptions that presuppose that a causal independence implies a statistical independence are among the possible candidates for solutions. Another part of the thesis investigates the potential consequences of a deviation from Bell’s inequality for a theory of causality as proposed in 2001 by Gerd Graßhoff and Michael May.
Computational model for the EPRB experiment satisfying the criterion of a CFD. Source: