Universidade Estadual de Campinas, Brazil, rabelo@ifi.unicamp.br
(joint work with Peng Xue, Lei Xiao, Gabriel Ruffolo, André Mazzari, Tassius Temistocles, Marcelo Terra Cunha)
Bell nonlocality and Kochen-Specker contextuality are two remarkable nonclassical features of quantum theory, related to strong correlations between outcomes of measurements performed on quantum systems. Both phenomena can be witnessed by the violation of certain inequalities, the simplest and most important of which are the Clauser-Horne-Shimony-Holt (CHSH) and the Klyachko-Can-Binicioglu-Shumovski (KCBS), for Bell nonlocality and Kochen-Specker contextuality, respectively. It has been shown that, using the most common interpretation of Bell scenarios, quantum systems cannot violate both inequalities concomitantly, thus suggesting a monogamous relation between the two phenomena. In this work, we show that the joint consideration of the CHSH and KCBS inequalities naturally calls for the so-called generalized Bell scenarios, which, contrary to the previous results, allows for their joint violation. In fact, this result is not a particular feature of such inequalities: we provide very strong evidence that there is no monogamy between nonlocality and contextuality in any scenario where both phenomena can be observed. Also, we have implemented a photonic experiment to test the synchronous violation of both CHSH and KCBS inequalities; our results agree with the theoretical predictions, thereby providing experimental proof of the coexistence of Bell nonlocality and contextuality in the simplest scenario, and shedding new light on further explorations of nonclassical features of quantum systems.