Analysis of Coincidence-Time Loopholes in Experimental Bell Tests

TL;DR

This paper applies a novel distance-based analysis method to experimental Bell test data, revealing violations and loopholes that standard methods may miss or falsely identify, thereby improving the reliability of Bell inequality tests.

Contribution

It introduces a distance-based Bell-test analysis approach that reduces assumptions and uncovers loopholes in experimental data.

Findings

Identifies a classical source exploiting a coincidence-time loophole falsely indicating Bell violation.

Confirms previous Bell violation results with fewer assumptions using the new analysis.

Detects a strong Bell violation in data where standard analysis shows no violation.

Abstract

We apply a distance-based Bell-test analysis method [E. Knill et al., Phys. Rev. A. 91, 032105 (2015)] to three experimental data sets where conventional analyses failed or required additional assumptions. The first is produced from a new classical source exploiting a "coincidence-time loophole" for which standard analysis falsely shows a Bell violation. The second is from a source previously shown to violate a Bell inequality; the distance-based analysis agrees with the previous results but with fewer assumptions. The third data set does not show a violation with standard analysis despite the high source quality, but is shown to have a strong violation with the distance-based analysis method.