On Wed, Jul 7, 2021 at 6:29 AM 'Brent Meeker' via Everything List < [email protected]> wrote:
> > On 7/6/2021 12:49 PM, smitra wrote: > > On 06-07-2021 19:34, Jason Resch wrote: > >> On Tue, Jul 6, 2021 at 12:27 PM 'Brent Meeker' via Everything List > >> <[email protected]> wrote: > >> > >>> > >> > >> And you're never going to find a being that behaves intelligently > >> based on information that can be quantum erased. > >> You need only a quantum computer with enough qubits. > >> > >> Jason > > > > Indeed, the critics have to show how the laws of physics imply that > > decoherence cannot be limited to the extent necessary to run a good > > enough quantum computer simulation of an entire brain for this to > > work. And one has lots of elbowroom available for the thought > > experiment. Practical issue that would make this unfeasible for us to > > do play no role at all, but real physical limits would be valid > > objections. The amount of available resources that can be used > > physically is at least a large fraction of all the materials that are > > present in our galaxy. One can build Dyson spheres around a far > > fraction of all stars in the galaxy, the available time is at least of > > the order of tens of billions of years. The simulation does not have > > to run in real time, each simulated second can take a billion years, > > which may be necessary to perform enough quantum error correction to > > make this work. > > > > If it can be shown that under more generous conditions this is not > > feasible, so large scale quantum computing is not going to work even > > with most of the resources in the observable universe, and that a > > large scale computation needed for the thought experiment cannot be > > finished before the end of the universe, then the critics have a > > point. But even then it's only a hint of a problem, because the > > objection would only be consistent with the unproven hypothesis that > > unitary time evolution breaks down when a large enough number of > > degrees of freedom get entangled with a quantum system. > > > > Saibal > > Why are you worrying about enormous quantum computers? A quantum > computer should have much more computational power than a classical > computer and we already know of an intelligent classical computer fits > in a little more than a liter. The problem isn't computational power, > it's reaching definite answer. Quantum computers in general provide a > readout by decoherence, and then it's no longer erasable. > Exactly right, Brent. It is not resources that are necessary, it is an explanation of how a consciousness that records a definite result can have that information quantum erased. If one thinks that it is just a matter of overwriting some computer registers, then there is no way that you can ever demonstrate that a definite result was ever obtained. Definite results require decoherence and the formation of permanent records. Since thermodynamics assures us that nothing can ever be totally isolated from the environment, decoherence is ubiquitous. Then the fact that IR photos will always irreversibly escape from your set-up ensures that definite quantum results are always irreversible. As Bohr and others would have said, a definite result is always a classical object -- subject to the classical laws of relativity and thermodynamics. A quantum computer, no matter how many qubits it has, or what resources it utilizes, is never going to escape from these limits imposed by the laws of physics. The trouble with many computer scientists is that they live in some idealized world that has nothing to do with the laws of physics. 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/CAFxXSLSdd-Lar6yjZvfR42XNAU3APL%3DDqy35Cg_eBOO3TbvTsQ%40mail.gmail.com.
