Experimental investigation of the relation between measurement uncertainties and non-local quantum correlations

TL;DR

This study experimentally investigates how measurement uncertainties influence the strength of quantum correlations, demonstrating that the maximal Bell inequality violations are constrained by the minimal uncertainties in joint measurements.

Contribution

It provides empirical evidence linking measurement uncertainties to the limits of quantum correlations, specifically confirming the Cirel'son bound.

Findings

High-contrast correlations approach maximal quantum limits

Measurement uncertainties directly affect Bell inequality violations

Results confirm the Cirel'son bound is set by measurement precision

Abstract

Bell's inequalities are defined by sums of correlations involving non-commuting observables in each of the two systems. Violations of Bell's inequalities are only possible because the precision of any joint measurement of these observables will be limited by quantum mechanical uncertainty relations. In this paper we explore the relation between the local measurement uncertainties and the magnitude of the correlations by preparing polarization entangled photon pairs and performing joint measurements of non-commuting polarization components at different uncertainty trade-offs. The change in measurement visibility reveals the existence of a non-trivial balance between the measurement uncertainties where the probabilities of a specific pair of measurement outcomes approaches zero because of the particular combination of enhancement and suppression of the experimentally observed correlations. The occurrence of these high-contrast results shows that the quantum correlations between the photons are close to their maximal value, confirming that the Cirel'son bound of Bell's inequality violations is defined by the minimal uncertainties that limit the precision of joint measurements.