Locality and Reality Revisited

  • Adrian Kent
Part of the NATO Science Series book series (NAII, volume 64)


Bell gave the now standard definition of a local hidden variable theory and showed that such theories cannot reproduce the predictions of quantum mechanics without violating his “free will” criterion: experimenters’ measurement choices can be assumed to be uncorrected with properties of the measured system prior to measurement.

An alternative is considered here: a probabilistictheory of hidden variablesunderlyingquantum mechanics could be statistically local, in the sense that it supplies global configuration probabilities which are defined by expressions involving only local terms. This allows Bell correlations without relying on either a conspiracy theory in which prior common causes correlate the system state with experimenters’ choices or a reverse causation principle in which experimenters' choices affect the earlier system states. In particular, there is no violation of the free will criterion. It gives a different perspectiveon Bell correlations, in which the puzzle is not that apparently non-local correlations should emerge from rules involvinglocal quantities, but rather that we do not see more general non-local correlations that allow paradox-immune forms of superluminal signalling.


Ising Model Hide Variable Probability Weight Entangle Photon Pair Annihilation 
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    Bell, J. S. (1985) The theory of local beables, Epistemological Letters, March 1976, reprinted in Dialectica 39, 85–96.Google Scholar
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    Shimony, A. (1985) Reply to Bell, Dialectica 39, 107–110.MathSciNetCrossRefGoogle Scholar
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    Bell, J. S. (1985) Free variables and local causality, Epistemological Letters, February 1977; reprinted in Dialectica 39, 103-106.Google Scholar
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    Price, H. (1996) Time’s Arrow and Archimedes’ Point: New Directions for the Physics of Time, Oxford University Press, Oxford.Google Scholar
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    See e.g. Kent, A. (1998) Causality in time-neutral cosmologies, Physical Review D 59, 043505 1–5.MathSciNetCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media Dordrecht 2002

Authors and Affiliations

  • Adrian Kent
    • 1
    • 2
  1. 1.University of CambridgeCambridgeUK
  2. 2.Hewlett-Packard LaboratoriesBristolUK

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