A reasonable thing that just might work

Daniel Rohrlich

Submitted to “Quantum Nonlocality and Reality – 50 Years of Bell’s theorem”

In 1964, John Bell proved that quantum mechanics is “unreasonable” (to use Einstein’s term):  there are nonlocal bipartite quantum correlations.  But they are not the most nonlocal bipartite correlations consistent with relativistic causality (“no superluminal signalling”):  also maximally nonlocal “superquantum” (or “PR-box”) correlations are consistent with relativistic causality.  I show that – unlike quantum correlations – these correlations do not have a classical limit consistent with relativistic causality.  The generalization of this result to all stronger-than-quantum nonlocal correlations is a derivation of Tsirelson’s bound – a theorem of quantum mechanics – from the three axioms of relativistic causality, nonlocality, and the existence of a classical limit.  But is it reasonable to derive (a part of) quantum mechanics from the unreasonable axiom of nonlocality?!  I consider replacing the nonlocality axiom with an equivalent axiom that even Bell and Einstein might have considered reasonable:  an axiom of local retrocausality.

Rohrlich – Bell paper

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