> On 21 Sep 2019, at 14:29, Alan Grayson <agrayson2...@gmail.com> wrote: > > > > On Saturday, September 21, 2019 at 6:23:18 AM UTC-6, John Clark wrote: > There is a rumor that a team of researchers at Google led by John Martinis > have performed a calculation on a Quantum Computer in three minutes and 20 > seconds that would have taken Summit, the most powerful conventional > supercomputer in the world, 10,000 years to perform. The rumor started when a > paper stating that was posted by the Google team, apparently accidentally, on > a NASA website and then quickly taken down. It's not clear exactly what the > calculation was about, they just said it “marks the first computation that > can only be performed on a quantum processor". My guess is it was probably a > weird function of some sort that would not be of much use to a scientist or > engineer, but even so if true it would be a first proof of concept and be > earthsharing. I suppose they want to check and recheck their work before they > make a official announcement this important and that's why they took the > article down. > > What I don't understand is why a computer programmed to assume a > superposition, say of two states, represents a system in both states > simultaneously (which I find to be false for reasons previously stated), > would speed up any calculation. Can anyone answer this question? AG
That is not obvious at all, but has been very well illustrated by some quantum algorithm which does more quickly what we can conceive (perhaps wrongly) hard to do classical. For example, with a quantum computer you can do 2^1000 different computations (but having the same length). Of course, you are not able to gain anything by looking a the result, but the quantum mechanism allows you to extract information from a Fourier transform made on all (2^1000) results, and this might give some information not accessible by a classical computer in any reasonable time, and speed some computation. This is illustrated with the quantum algorithm to factorise large numbers (Shor). Mathematically, it is still an open problem if a quantum computer really speed-up the computations, but like with P = NP, most experts have few doubt that this is the case. Now, Imo, just the double slit experiment, or the study of the hydrogen atom, shows that the superposition are physically real. It is the “one universe” idea which seems to me quite speculative, and just added for ideological coquetry. It is a form of 1p-plural solipsism. Bruno > > > -- > 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 everything-list+unsubscr...@googlegroups.com > <mailto:everything-list+unsubscr...@googlegroups.com>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/everything-list/9d4c2cb2-efc7-4664-860f-f7b68031128a%40googlegroups.com > > <https://groups.google.com/d/msgid/everything-list/9d4c2cb2-efc7-4664-860f-f7b68031128a%40googlegroups.com?utm_medium=email&utm_source=footer>. -- 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 everything-list+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/3BAF5EAE-72A9-4731-AE5D-287FF279D7A8%40ulb.ac.be.
