On Fri, Oct 28, 2022 at 1:09 AM Brent Meeker <[email protected]> wrote:
* > I was citing Carroll on the delayed choice quantum erasure...not on > anything Deutsch said. * > OK, then whatever Carroll was saying that you were referring to is irrelevant to what we were discussing. And by the way, Carroll is just as big an advocate of the Many World's idea as Deutsch is and wrote an excellent book about that very subject. > * > The problem I see in this is that the computer must make a measurement > that does two things1) it prints out a document that is causally dependent > on a distinct measured value existing (not just: there was an electron so > it prints "I measured it.") * > Yes, when the computer writes the document, writes it after the electron passes through the slits but before it hits the photographic plate, the machine knows which slit the electron went through but it reframes from including that bit information in the document, it retains that bit of information safely in its quantum memory and doesn't quantum erase it until a nanosecond before the electron hits the photographic plate. > > > *(2) the measurement must be quantum erased. I think this is impossible > because (1) depends on the measurement, being either LEFT or RIGHT* > No, the document is EXACTLY the same in both universes, that's why I kept emphasizing that it does not contain any information about which slot the electron went through, it just tells us if it was able to successfully make such a measurement and if it knows which slot the electron went through. So the only thing different about the two universes is the computer's memory about which slot the electron went through and if, unlike classical computers, that bit of information is stored quantum mechanically, then that bit of information can be erased quantum mechanically. At that point the two universes are identical again, that is to say they would have exactly the same quantum wave function, so it would be silly to pretend there are still two distinct universes. > *> and that specific distinct value being amplified to a classical > variable* > That's what usually happens and the amplification typically happens at enormous speed, that's why making any quantum experiment is difficult and making a quantum computer is even more difficult, but that's just an engineering difficulty caused by our limited technology, it is not a limitation imposed by scientific fundamentals. I'm talking about heroic engineering not impossible engineering, like a faster than light rocket or a perpetual motion machine. >* if the distinct variable is amplified to a classical value, a print > command, it can't be quantum erased.* It makes no difference if the electron went left or right, the EXACT same print command is issued in both universes in either case, and that results in the EXACT same document being printed in both universes. I agree that if you let the distinct knowledge of which slit the electron went through get amplified and spread into the classical realm then it's game over, you're never gonna be able to erase all of that, so you're going to have to arrange things so that doesn't happen, or at least delay it from happening for long enough to complete the experiment. To do all this would be very difficult but it would not be impossible. John K Clark See what's on my new list at Extropolis <https://groups.google.com/g/extropolis> 7vv -- 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/CAJPayv1LsV80H-vaJFU%2BdcRQ__9nw2jRW1chfD6T35%2BFm7bs-Q%40mail.gmail.com.
