Schr\"odinger's paradox and proofs of nonlocality using only perfect correlations

TL;DR

This paper presents nonlocality proofs based solely on perfect correlations, generalizing Schrödinger's argument without relying on Bell's inequalities, and discusses implications for quantum nonlocality and Bohmian mechanics.

Contribution

It introduces a novel nonlocality proof using perfect correlations and Schrödinger's generalization, avoiding Bell's inequalities and highlighting the role of non-contextual value-maps.

Findings

Nonlocality can be established solely from perfect correlations.

Non-contextual value-maps are impossible without additional quantum predictions.

Bohmian mechanics is compatible with the non-existence of non-contextual value-maps.

Abstract

We discuss proofs of nonlocality based on a generalization by Erwin Schr\"odinger of the argument of Einstein, Podolsky and Rosen. These proofs do not appeal in any way to Bell's inequalities. Indeed, one striking feature of the proofs is that they can be used to establish nonlocality solely on the basis of suitably robust perfect correlations. First we explain that Schr\"odinger's argument shows that locality and the perfect correlations between measurements of observables on spatially separated systems implies the existence of a non-contextual value-map for quantum observables; non-contextual means that the observable has a particular value before its measurement, for any given quantum system, and that any experiment "measuring this observable" will reveal that value. Then, we establish the impossibility of a non-contextual value-map for quantum observables {\it without invoking any further quantum predictions}. Combining this with Schr\"odinger's argument implies nonlocality. Finally, we illustrate how Bohmian mechanics is compatible with the impossibility of a non-contextual value-map.