Is Einsteinian no-signalling violated in Bell Tests?

TL;DR

This paper investigates apparent violations of the no-signalling principle in Bell tests, attributing them to data selection procedures and proposing new experimental designs to conclusively test Einsteinian no-signalling.

Contribution

It identifies how outcome pairing procedures can cause apparent no-signalling violations and proposes experimental protocols to properly test the principle.

Findings

Selection procedures can mimic signalling violations.

Proper experiment design can conclusively test no-signalling.

Quantum correlations may be explained locally.

Abstract

Relativistic invariance is a physical law verified in several domains of physics. The impossibility of faster than light influences is not questioned by quantum theory. In quantum electrodynamics, in quantum field theory and in the standard model relativistic invariance is incorporated by construction. Quantum mechanics predicts strong long range correlations between outcomes of spin projection measurements performed in distant laboratories. In spite of these strong correlations marginal probability distributions should not depend on what was measured in the other laboratory what is called shortly: non-signalling. In several experiments, performed to test various Bell-type inequalities, some unexplained dependence of empirical marginal probability distributions on distant settings was observed . In this paper we demonstrate how a particular identification and selection procedure of paired distant outcomes is the most probable cause for this apparent violation of no-signalling principle. Thus this unexpected setting dependence does not prove the existence of superluminal influences and Einsteinian no-signalling principle has to be tested differently in dedicated experiments. We propose a detailed protocol telling how such experiments should be designed in order to be conclusive. We also explain how magical quantum correlations may be explained in a locally causal way.