Those practically-minded, results-oriented physicists who prefer spending their time working out the predictions of quantum mechanics (QM) and comparing those predictions to laboratory data, instead of rambling endlessly about the philosophical implications of QM, are often said to belong to the “shut up and calculate” school. It seems to me that the advocates of the multiverse “many-worlds interpretation” (MWI) of QM belong to the less desirable school of “don’t shut up and don’t calculate”.
MWI was first proposed in 1957 by Hugh Everett. More than half a century later, it still hasn’t spawned any useful results. And that, in my opinion, is the biggest flaw of MWI: that it’s not very useful. Is it possible to explain or predict or calculate any laboratory observations much more simply or elegantly using MWI than not using it? No. Like I said before, useless.
The vast majority of people working in quantum computing have never used MWI in their work. QM can easily stand without MWI. I can’t stress this fact enough. I hope that those new to the field of quantum computing don’t get turned off from the field because they get the mistaken impression that it’s based on MWI.
David Deutsch claims that MWI is necessary in order to “explain” a quantum computer. He has no mathematical proof of this claim. He argues that the claim must be true because of philosophy (his philosophy). Yawn. He even claims that he has devised a test that singles out MWI as the one and only possible interpretation of QM. His test requires a bizarre self-aware quantum computer artificial intelligence. Nothing like proposing an impossible-to-do, cryptic experiment to prove your point.