Context and non-locality

S.M. Rijken

In this thesis, I analyze the concepts of spacelike and timelike non-locality in the context of Bell’s conceptual framework and the EPR-type thought experiment. After defining locality in this context, I argue in favor of a Shimonian subdivision of independence assumptions about parameters of an EPR-type thought experiment\nand I argue against alternative subdivisions. I then discuss direct timelike analogues of spacelike locality that have recently been introduced in the literature on quantum foundations. I argue that there are indeed good reasons for considering the possibilities for timelike non-locality, but that the formal similarity between spacelike and timelike locality in the context of Bell’s conceptual framework is misleading. I conclude that spacelike and timelike non-locality are strongly disanalogous.

Philippe Grangier

In this article we argue that what is usually called non locality, leading to the violation of Bell's inequality and more generally of classical local realism, can be explained by considering contextual inferences, that are both possible and necessary in quantum physics. They do not show up in classical physics, where contexts may be discarded because physical properties are non-contextual. This analysis allows us to explain why non locality does not contradict relativistic causality. Our argument is general from a probabilistic point of view, and it strongly suggests that the usual quantum formalism must be completed, by specifying the measurement context.

Demetrios A. Kalamidas

We present, at the gedanken level, a possibly novel non-statistical demonstration of nonlocality for two maximally entangled particles. The argument requires only two alternative experimental contexts, only one and the same single-particle observable, and leads to a contradiction with a constrained form of local realism in 50% of experimental runs. However, the argument is based on a 'plausible' but not definitive notion of locality.