On Thu, Jan 28, 2021 at 12:11 PM Pierz Newton-John <[email protected]> wrote:
> On 28 Jan 2021, at 12:02 pm, Bruce Kellett <[email protected]> wrote: > > > You can utilize technology to maintain quantum coherence over ever larger > domains (as in quantum computers), but that domain can never extend to the > whole universe; not even beyond the laboratory to the wider earth. This is > not a technological limit -- the limit is in the laws of physics themselves. > > This actually has very little to do with the question of whether quantum > physics is universal or not -- quantum mechanics can be the correct > theory of everything in the universe, but it would still be the case that > decoherence is irreversible in principle. This does not bear on the > question whether Everett is correct or not. > > > I’m not saying decoherence is reversible. I’ve corrected myself (or > accepted your correction) on that point. > Good. But my understanding of proposals for disconfirming MWI involve extending > quantum coherence to larger and larger scales. > That is mistaken. The scale over which one can maintain quantum coherence has no bearing on the truth or falsity of MWI. Deutsch has argued that if we can get enough qubits into a quantum > computation, we’ve effectively “proved” MWI since “where did all that > information come from?". > Deutsch is simply wrong on this point. I know that he has been arguing that quantum computers "prove" many worlds, "or else where did all the computational power come from?". But other quantum computing experts, such as Aaronson, disagree, and make the obvious point that quantum computers work by interference, and interference necessarily all happens in this one world -- separate worlds do not interfere. Other proposals similarly involve reversibility at large scales. If QM is > not universal, then at some scale that will prove impossible not merely due > to technological limits, but limits of the laws of physics. If such a limit > were found, that would certainly disconfirm MWI. > This is very confused. In principle irreversibility of quantum decoherence occurs at all scales. As soon as some photons or air molecules hit the laboratory walls from an experiment on any scale, there is irreversible escape of thermal information to the wider environment, and ultimately to IR photons out into space. The scale has nothing to do with quantum universality, and such considerations can never confirm or disconfirm a quantum interpretation, such as MWI. Bruce -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/CAFxXSLS1foa7xhiK6qLdG7z17c3Kz3otO1PsKTqLk17rKRLOCw%40mail.gmail.com.
