Quantum theory predicts the existence of so-called tripartite-entangled states, in which three quantum particles are related in a way that has no counterpart in classical physics. Theoretical physicists would like to understand how well new theories, alternatives to quantum theory, might be able to reproduce the behavior of these states
John Clauser, Alain Aspect and Anton Zeilinger, whose work was recently recognized by the Nobel Committee, have experimentally proven Bell’s theorem, showing that no local hidden-variable alternative to quantum theory can reproduce this behavior. In other words, they showed that quantum correlations are nonlocal.
Researchers at the University of Science and Technology of China, Institute of Photonic Sciences, Università della Svizzera Italiana and Perimeter Institute of Theoretical Physics have recently carried out an experimental study generalizing these findings, by considering new potential theories. Their findings, published in Physical Review Letters, suggest that the correlations achieved by the tripartite-entangled state used in their experiment cannot be explained by an hypothetical theory involving a generalization of bipartite entanglement, called “exotic sources of two particles,” in addition to a local hidden-variable theory.
“The main objective of our study was to prove that the behavior of a three particle quantum source (e.g., a source of three photons) cannot be reproduced by any new hypothetical theory (replacing quantum theory, yet to be discovered) which only involves exotic pairs of two particle described by new physical laws’ and a local hidden variable model,” Marc-Olivier Renou, one of the authors of the paper, told Phys.org.
Gaël Massé, a second author, explains: “To do this, we used the idea contained in the ‘inflation technique,’ invented by Elie Wolfe, one of our coauthor. If we imagine a pair of two particles described by new physical laws, then even if we have no idea how to describe them we can still create a copy of this pair and make all the particles interact together in a new way. While this technique seems elementary, it has often proved to be a very powerful tool to address theoretical abstract concepts.”
