“While observer-independence has long remained inaccessible to empirical investigation, recent no-go-theorems construct an extended Wigner’s friend scenario with four entangled observers that allows us to put it to the test.
“In a state-of-the-art photon experiment, we here realise this extended Wigner’s friend scenario, experimentally violating the associated Bell-type inequality by 5 standard deviations. This result lends considerable strength to interpretations of quantum theory already set in an observer-dependent framework and demands for revision of those which are not.”
Referring to two alternate realities, study co-author, Martin Ringbauer, told Live Science that “you can verify both of them”.
Article source: https://www.express.co.uk/news/science/1103044/alternative-reality-news-science-duel-realities-theory-Martin-Ringbauer-wigner-physics