Detection-Loophole-Free Test of Quantum Nonlocality, and Applications

TL;DR

This paper reports the first loophole-free Bell test with photons, demonstrating high-quality entanglement, closing the detection loophole, and enabling secure quantum random number generation at unprecedented rates.

Contribution

It introduces a photon source that closes the detection loophole and verifies entanglement quality through multiple Bell tests, advancing quantum nonlocality experiments.

Findings

Violation of Bell inequality over 7 standard deviations without fair-sampling assumption

Achieved enough efficiency to perform fully loophole-free tests

Generated secure quantum random numbers at rates 10,000 times faster than previous work

Abstract

We present a source of entangled photons that violates a Bell inequality free of the "fair-sampling" assumption, by over 7 standard deviations. This violation is the first experiment with photons to close the detection loophole, and we demonstrate enough "efficiency" overhead to eventually perform a fully loophole-free test of local realism. The entanglement quality is verified by maximally violating additional Bell tests, testing the upper limit of quantum correlations. Finally, we use the source to generate secure private quantum random numbers at rates over 4 orders of magnitude beyond previous experiments.