Philipp TREUTLEIN

In 1935, Einstein, Podolsky and Rosen (EPR) conceived a Gedankenexperiment which became a cornerstone of quantum technology and still challenges our understanding of reality and locality today. While the experiment has been realized with small quantum systems, a demonstration of the EPR paradox with spatially separated, massive many-particle systems had so far remained elusive. In our experiment, we observe the EPR paradox with two spatially separated Bose-Einstein condensates containing about 700 Rubidium atoms each. Entanglement between the two condensates results in strong correlations between measurement outcomes of their collective spins, satisfying Reid’s criterion for the EPR paradox. Our results show that the conflict between quantum mechanics and local realism does not disappear as the system size is increased to over a thousand massive particles. Furthermore, EPR entanglement in conjunction with individual manipulation of the two condensates on the quantum level, as demonstrated here, constitutes an important resource for quantum metrology and information processing with many-particle systems.

P. Colciaghi, Y. Li, P. Treutlein, and T. Zibold, Einstein-Podolsky-Rosen experiment with two Bose-Einstein condensates, arXiv:2211.05101.