Time-delocalised variables violating causal inequalities

A piece accessible to a broader public on collaborative work between Julian Wechs and Ognyan Oreshkov  (Université libre de Bruxelles) and Cyril Branciard (CNRS) has been posted on several different portals. Read it at the following links

phys.org, eurekalert, alphagalileo, ULB press

A team of researchers from the Université libre de Bruxelles and the French National Centre for Scientific Research has shown for the first time that an exotic type of process violating causal inequalities can be realized with known physics. A violation of a causal inequality proves under theory-independent assumptions that certain variables in an experiment cannot be assigned a definite causal order. This phenomenon has been known to be possible in theory but widely believed impossible in practice, at least in the known regimes of physics. The new study, published in Nature Communications, shows that such processes can be realized in standard quantum mechanics using variables delocalized in time. The finding may have far-reaching implications for our understanding of causality in physics.