In 1964 John Stewart Bell presented an inequality that was able to test the validity of quantum mechanics against local realist models. The inequality states that any theory that satisfies the conditions of local-realism cannot reproduce all the predictions of quantum theory. After that scientists design many experiments to test the Bell inequality.

In such experiments, for achieving reliable results, it is so important that you close all the loopholes such that a local realistic model cannot fake the quantum mechanical results.

In this seminar, I will introduce one of the most recent experiments that designed to tighten the “freedom-of-choice” loophole. In this cosmic Bell test high-redshift quasars’ photons, which were produced at least 7.8Gyr ago, were used as measurement settings. In that way we could push back any local-realist influences that could have exploited the “freedom-of-choice” loophole in order to engineer the observed Bell violation.