Testing Local Realism into the Past without Detection and Locality Loopholes

TL;DR

This paper reports a groundbreaking test of local realism using entangled photons separated by 183 meters, employing cosmic photons for measurement choices, and testing events from 11 years ago to close loopholes and challenge local hidden variable theories.

Contribution

It demonstrates a loophole-free test of local realism with high efficiency, utilizing cosmic photon randomness and historical event analysis to push the limits of such tests.

Findings

Achieved >78% efficiency in entangled photon separation

Closed both locality and detection loopholes simultaneously

Tested events from 11 years ago, strongly rejecting local hidden variable models

Abstract

Inspired by the recent remarkable progress in the experimental test of local realism, we report here such a test that achieves an efficiency greater than (78%)^2 for entangled photon pairs separated by 183 m. Further utilizing the randomness in cosmic photons from pairs of stars on the opposite sides of the sky for the measurement setting choices, we not only close the locality and detection loopholes simultaneously, but also test the null hypothesis against local hidden variable mechanisms for events that took place 11 years ago (13 orders of magnitude longer than previous experiments). After considering the bias in measurement setting choices, we obtain an upper bound on the p value of 7.87 * 10^-4, which clearly indicates the rejection with high confidence of potential local hidden variable models. One may further push the time constraint on local hidden variable mechanisms deep into the cosmic history by taking advantage of the randomness in photon emissions from quasars with large aperture telescopes.