Editing Bell's theorem (section)

=== Many-worlds interpretation of quantum mechanics ===

The [[Many-worlds interpretation]], also known as the [[Hugh Everett III|Everett]] interpretation, is dynamically local, meaning that it does not call for [[action at a distance]],<ref name=BrownTimpson/>{{rp|17}} and deterministic, because it consists of the unitary part of quantum mechanics without collapse. It can generate correlations that violate a Bell inequality because it violates an implicit assumption by Bell that measurements have a single outcome. In fact, Bell's theorem can be proven in the Many-Worlds framework from the assumption that a measurement has a single outcome. Therefore, a violation of a Bell inequality can be interpreted as a demonstration that measurements have multiple outcomes.<ref>{{cite journal |first1=David |last1=Deutsch |author-link1=David Deutsch |first2=Patrick |last2=Hayden |author-link2=Patrick Hayden (scientist) |title=Information flow in entangled quantum systems |journal=[[Proceedings of the Royal Society A]] |date=2000 |volume=456 |issue=1999 |pages=1759–1774 |doi=10.1098/rspa.2000.0585|arxiv=quant-ph/9906007|bibcode=2000RSPSA.456.1759D |s2cid=13998168 }}</ref>

The explanation it provides for the Bell correlations is that when Alice and Bob make their measurements, they split into local branches. From the point of view of each copy of Alice, there are multiple copies of Bob experiencing different results, so Bob cannot have a definite result, and the same is true from the point of view of each copy of Bob. They will obtain a mutually well-defined result only when their future light cones overlap. At this point we can say that the Bell correlation starts existing, but it was produced by a purely local mechanism. Therefore, the violation of a Bell inequality cannot be interpreted as a proof of non-locality.<ref name=BrownTimpson>{{Cite book|first1=Harvey R. |last1=Brown |author-link1=Harvey R. Brown |first2 = Christopher G. |last2=Timpson|chapter=Bell on Bell's Theorem: The Changing Face of Nonlocality|title=Quantum Nonlocality and Reality: 50 years of Bell's theorem |editor-first1=Mary |editor-last1=Bell |editor-first2=Shan |editor-last2=Gao |publisher=Cambridge University Press|year=2016|pages = 91–123|arxiv=1501.03521|doi=10.1017/CBO9781316219393.008|isbn = 9781316219393|s2cid = 118686956}}</ref>{{rp|28|q=In our discussion of locality in the Everett interpretation we have sought to provide a constructive example illustrating precisely how a theory can be dynamically local, whilst violating local causality}}