X-Message-Number: 20288
Date: Fri, 11 Oct 2002 23:32:57 -0700
From: Mike Perry <>
Subject: Re: Then a Miracle Happens?

In Message #20281, Mark Plus writes:

>Is it true that a quantum computer is working on your particular problem
>even if you observe it to be turned "off" in your universe, because the
>computer is "on" & running your program in parallel ones?

Well, you could say that every problem is being worked on in some parallel 
universes, infinitely many I would think, but whether that is significant 
to you is another matter.

>Seems like it
>could have practically "oracular" powers, if it can efficiently solve
>problems previously "proved" to have been unsolvable on realistic time
>scales.

That is what quantum computing up to now has apparently offered, that is, 
great speedups over classical computers on certain problems. But the new 
claim goes farther, inasmuch as some problems not solvable at all, in any 
amount of time, would now become solvable. One interesting possibility 
would be to circumvent the Godel limitations on consistency proofs. To 
decide the consistency of some mathematical theory you consider a 
(classical) Turing machine that starts enumerating all provable statements 
within the theory and halts iff it finds a contradiction (that is, proves 
both P and not-P for some statement P). Then use your oracle quantum 
computer to decide if that machine ever halts. On a more practical level, 
perhaps an oracle machine could more quickly determine the information 
content of a cryopreserved patient, for a reanimation scenario. I could see 
this becoming a nontrivial issue; the brain is complicated enough in its 
own right. Extracting the necessary information, at least in cases of 
substantial damage, could be computationally difficult, even if there is no 
deliberate "encryption."

Mike Perry

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