This is what I don't understand: as I said, if you put the Heisenberg cut in Copenhagen/von Neumann far enough back (say, at the level of the person looking at the result of the quantum computation), then both are equivalent in their predictions, so I don't see how "Copenhagen" can predict anything different from MWI, UNLESS it is a specific version of Copenhagen where certain systems are declared being "classical" which turn out not to be so.setAI said:not according to Deutsch- the Copenhage interpretation predicts that in Deutsche's experiment the photons would appear at BOTH detectors at the end- MWI predicts just the right detector- and this was experimentally confirmed-
But the point is: MWI cannot be "somewhat" true. If it is "true up to a certain level of macroscopicity" then it is a form of Copenhagen !
Let us not forget that there are as many "Copenhagen" flavors (with DIFFERENT empirical predictions) as there are ways to put the Heisenberg cut (meaning: different ways of defining what are "measurement apparatus").
If you say that photons are "measurement apparatus" then you have a version of Copenhagen that is easily falsified because any interference experiment would do so.
If you say that "atoms" are measurement apparatus, but not photons, then optical interference is predicted, but not, say, Stern-Gerlach experiments.
If you say that not atoms and photons are measurement apparatus, but only buckeyballs, or golf balls, or humans or ... then you make these "Copenhagen" flavors come closer and closer to MWI predictions.
So when you say something about "Copenhagen predicts this, and MWI that", it is necessary to say WHAT FLAVOR of Copenhagen predicts this (in other words, what has been declared "measurement apparatus" in the given flavor). And it is sufficient to remove the culpable object from the list of "measurement apparatus" to find out that we have now a *different* prediction of Copenhagen.
In fact, von Neumann said that we have to put the Heisenberg cut "far enough" so that it doesn't make any difference anymore: if you do so, you will NEVER find a disagreement with MWI's predictions.