A testable prediction of the no-signalling condition using a variant of the EPR-Bohm example

Abstract

Predictive power of the no-signalling condition (NSC) is demonstrated in a testable situation involving a non-ideal Stern–Gerlach (SG) device in one of the two wings of the EPR-Bohm entangled pairs. In this wing, for two types of measurement in the other wing, we consider the spin state of a selected set of particles that are confined to a particular half of the plane while emerging from the SG magnetic field region. Due to non-idealness of the SG setup, this spin state will have superposing components involving a relative phase for which a testable quantitative constraint is obtained by invoking NSC, thereby providing a means for precision testing of this fundamentally significant principle.