We consider an entangled two-particle state that is produced from two independent down-conversions by the process of "entanglement-swapping", so that the particles have never met. We prove a GHZ (Greenberger-Horne-Zeilinger) type theorem, showing that the quantum mechanical perfect correlations for such a state are inconsistent with any deterministic, local, realistic theory. This theorem holds for individual events with no inequalities, for detectors of 100% efficiency. Furthermore, for detectors of arbitrarily poor efficiency, we can show that at certain angles no events at all can take place, in complete contradiction to the quantum case. This result is also independent of any "random sampling" hypothesis, and we take it as a refutation of such realistic theories, free of these usual "loopholes".
(This work was done in collaboration with Mike Horne and Anton Zeilinger.)

Contact: Luis A. Orozco.