This page is still in progress.Experimental test of local observer independence. M. Proietti, A. Pickston, F. Graffitti, P. Barrow, D. Kundys, C. Branciard, M. Ringbauer and A. Fedrizzi in Science Advances 5: (2019).  What the paper says!?

A pioneering experiment on Wigner's friends.

The question whether the observers’ narratives can be reconciled has only recently been made accessible to empirical investigation, through recent no-go theorems that construct an extended Wigner’s friend scenario with four observers.