Phys.org May 2, 2022
An international team of researchers (France, Germany, Spain) has discovered a new connection between superposition and entanglement that does not assume that quantum theory is correct. They proved that given any two general probabilistic theories (GPTs) the following are equivalent: (i) each theory is nonclassical, (ii) each theory satisfies a strong notion of incompatibility equivalent to the existence of “superpositions” and (iii) the two theories can be entangled, in the sense that their composite exhibits either entangled states or entangled measurements. Intuitively, in the post-quantum GPT setting, a superposition is a set of two binary ensembles of states that are unambiguously distinguishable if the ensemble is revealed before the measurement has occurred, but not if it is revealed after. According to the researchers this notion is important because just like in quantum theory, superposition in the form of strong incompatibility is sufficient to realize the secret key distribution…read more. TECHNICAL ARTICLE
A novel connection between entanglement and superposition in any physical theory has been discovered… Credit: Ludovico Lami