Quantum non-locality - It ain't necessarily so...

TL;DR

This paper clarifies misconceptions about Bell's theorem, arguing that its derivation requires assumptions beyond locality, and suggests that violations imply the need for a broader operational notion of locality rather than nonlocality.

Contribution

It demonstrates that Bell's inequalities require additional assumptions beyond locality, challenging common interpretations of quantum nonlocality.

Findings

Bell's derivation involves assumptions beyond locality.

Violations suggest the need for an operational no-signalling notion.

Local causality is not the sole premise in Bell's inequalities.

Abstract

Bell's theorem is 50 years old. Still there is a controversy about its implications. Much of it has its roots in confusion regarding the premises from which the theorem can be derived. Some claim that a derivation of Bell's inequalities requires just locality assumption, and nothing more. Violations of the inequalities are then interpreted as ``nonlocality'' or ``quantum nonlocality''. We show that such claims are unfounded and that every derivation of Bell's inequalities requires a premise -- in addition to locality and freedom of choice -- which is either assumed tacitly, or unconsciously, or is embedded in a single compound condition (like Bell's ``local causality''). The premise is equivalent to the assumption of existence of additional variables which do not appear in the quantum formalism (in form of determinism, or joint probability for outcomes of all conceivable measurements, or ``additional causes`'', or ``hidden variables'', ``complete description of the state'' or counterfactual definiteness, etc.). A certain irony is that perhaps the main message of violation of Bell's inequalities is that our notion of locality should be based on an operationally well-defined no-signalling condition, rather than on local causality.