Reformulating Bell's theorem: The search for a truly local quantum theory

• Published in: Studies in History and Philosophy of Modern Physics 2020-05, Vol.70, p.39-50
• Main Authors: Waegell, Mordecai, McQueen, Kelvin J.
• Format: Article
• Language: English
• ISSN: 1355-2198; 1879-2502
• DOI: 10.1016/j.shpsb.2020.02.006

The apparent nonlocality of quantum theory has been a persistent concern. Einstein et al. (1935) and Bell (1964) emphasized the apparent nonlocality arising from entanglement correlations. While some interpretations embrace this nonlocality, modern variations of the Everett-inspired many worlds interpretation try to circumvent it. In this paper, we review Bell's “no-go” theorem and explain how it rests on three axioms, local causality, no superdeterminism, and one world. Although Bell is often taken to have shown that local causality is ruled out by the experimentally confirmed entanglement correlations, we make clear that it is the conjunction of the three axioms that is ruled out by these correlations. We then show that by assuming local causality and no superdeterminism, we can give a direct proof of many worlds. The remainder of the paper searches for a consistent, local, formulation of many worlds. We show that prominent formulations whose ontology is given by the wave function violate local causality, and we critically evaluate claims in the literature to the contrary. We ultimately identify a local many worlds interpretation that replaces the wave function with a separable Lorentz-invariant wave-field. We conclude with discussions of the Born rule, and other interpretations of quantum mechanics. •Implicit axioms of Bell's theorem are made explicit resulting in a reformulation of the theorem.•A direct proof of many worlds is provided following the axioms of local causality and no superdeterminism.•Prominent many worlds models are examined and are found to be not truly local.•A truly local many worlds model based on a separable Lorentz invariant wavefield in spacetime is described.•Implications for the Born rule and other interpretations are discussed.