Loophole-Free Bell Tests and the Falsification of Local Realism

TL;DR

Recent loophole-free Bell tests in 2015 provided strong experimental evidence against local realism, supporting quantum mechanics and closing previous experimental loopholes that allowed local realistic explanations.

Contribution

This paper reviews the theoretical background, experimental methods, and implications of the first loophole-free Bell tests conducted in 2015.

Findings

Strong violation of local realism observed

Support for quantum mechanics confirmed

Loopholes in earlier tests closed

Abstract

Quantum mechanics is strictly incompatible with local realism. It has been shown by Bell and others that it is possible, in principle, to experimentally differentiate between local realism and quantum mechanics. Numerous experiments have attempted to falsify local realism; however, they have consistently failed to close the detection loophole under strict locality conditions, thereby allowing local realistic explanations for their observations. In 2015, three experiments took place that tested local realism without the impediments of these significant loopholes. Between these three experiments, a substantial data set was collected. All of the collected data show a strong violation of local realism and strong support for quantum mechanics. This article reviews the theoretical basis of Bell tests and the affiliated loopholes, as well as the methods employed by these recent experiments and the implications of the results they observed.