Indeed, it’s remarkable they want to make a fuss out of something that I can undo entirely via unitary transformation. There have been a number of papers with

Indeed, it’s remarkable they want to make a fuss out of something that I can undo entirely via unitary transformation. There have been a number of papers with these kinds of “theorems” that seem to miss that proponents of the many-worlds interpretation would have explained (in this instance) Wigner’s friend in this way in the first place by eliminating all non-unitary evolution a priori.