On the relationship between local friendliness and Bell locality

Abstract

Bell’s locality theorem is a fundamental theorem about quantum theory, which states that quantum theory is incompatible with local hidden variable theories. Wigner’s friend is a thought experiment that questions the consistency of the applicability of quantum theory. This thought experiment can be extended, and the correlations between observables that it permits are studied under some reasonable assumptions of physical theories called local friendliness. This thesis addresses general Wigner’s friend scenarios where the assumptions of local friendliness and Bell locality are equivalent. The results are extended to an arbitrary number of observers and measurements. We also give a general recipe for connecting a Wigner’s friend setup with a contextual scenario. A natural extension of this work would be to identify necessary conditions for the equivalence of local friendliness and Bell locality assumptions.