Bell correlations and equal time measurements

TL;DR

This paper discusses how certain measurement setups can mimic quantum correlations and argues that avoiding coincidence monitors is essential to exclude local hidden variables, highlighting a subtlety in testing Bell inequalities.

Contribution

It introduces simple binary apparatuses that replicate quantum correlations and emphasizes the importance of measurement methods in Bell tests.

Findings

Coincidence measurements can mimic quantum correlations.

Avoiding coincidence monitors is crucial to exclude local hidden variables.

Simple apparatuses can reproduce quantum predictions under certain measurement schemes.

Abstract

According to the Bell theorem, local hidden variable theories cannot reproduce all the predictions of quantum mechanics. An important consequence is that under physically reasonable assumptions quantum mechanics predicts correlations that seem impossible to obtain from a realistic system. In this paper, two simple binary apparatuses are discussed that can accurately mimic correlations predicted by quantum mechanics \textit{if} the correlations are determined by a coincidence measurement as is commonly done. It is argued that in order to exclude local hidden variables, coincidence monitors should be avoided.