A strong loophole-free test of local realism

TL;DR

This paper reports a loophole-free Bell test with entangled photons, closing major experimental loopholes and providing strong evidence against local realism through high-efficiency measurements and rigorous statistical analysis.

Contribution

It demonstrates a loophole-free violation of local realism using advanced photon sources, detectors, and spacelike separation, with robust statistical validation.

Findings

Achieved a p-value as low as 5.9×10⁻⁹ for Bell violation

Maintained spacelike separation of measurement events

Rejected local realism hypothesis with a p-value as low as 2.3×10⁻⁷

Abstract

We present a loophole-free violation of local realism using entangled photon pairs. We ensure that all relevant events in our Bell test are spacelike separated by placing the parties far enough apart and by using fast random number generators and high-speed polarization measurements. A high-quality polarization-entangled source of photons, combined with high-efficiency, low-noise, single-photon detectors, allows us to make measurements without requiring any fair-sampling assumptions. Using a hypothesis test, we compute p-values as small as $5.9\times 10^{-9}$ for our Bell violation while maintaining the spacelike separation of our events. We estimate the degree to which a local realistic system could predict our measurement choices. Accounting for this predictability, our smallest adjusted p-value is $2.3 \times 10^{-7}$. We therefore reject the hypothesis that local realism governs our experiment.