PR-box correlations have no classical limit

Understand

One of Yakir Aharonov's endlessly captivating physics ideas is the conjecture that two axioms, namely relativistic causality ("no superluminal signalling") and nonlocality, so nearly contradict each other that a unique theory - quantum mechanics - reconciles them.

• But superquantum (or "PR-box") correlations imply that quantum mechanics is not the most nonlocal theory (in the sense of nonlocal correlations) consistent with relativistic causality.
• Let us consider supplementing these two axioms with a minimal third axiom: there exists a classical limit in which macroscopic observables commute.
• That is, just as quantum mechanics has a classical limit, so must any generalization of quantum mechanics.