How Einstein and/or Schroedinger should have discovered Bell's theorem in 1936

TL;DR

This paper explores how Bell's theorem could have been derived in 1936 through considerations of quantum steering and local theories, highlighting the conceptual pathway that links quantum states to underlying real states.

Contribution

It demonstrates a possible derivation of Bell's theorem from quantum steering concepts, emphasizing the role of local theories and the impact of measurement choices.

Findings

Quantum steering can lead to Bell's theorem under local theories.

Adding a third measurement breaks the local description.

The derivation aligns with historical nuances of Bell's original work.

Abstract

This note shows how one can be led from considerations of quantum steering to Bell's theorem. The point is that steering remote systems by choosing between two measurements can be described in a local theory if we take quantum states to be associated many-to-one with the underlying "real states" of the world. Once one adds a third measurement this is no longer possible. Historically this is not how Bell's theorem arose - there are slight and subtle differences in the arguments - but it could have been.