| Forum Home | ||||
| PC World Chat | ||||
| Thread ID: 67125 | 2006-03-18 02:22:00 | "A non running computer makes fewer errors" | Graham L (2) | PC World Chat |
| Post ID | Timestamp | Content | User | ||
| 438976 | 2006-03-18 02:22:00 | A quantum computer can get a correct result without running its programme. (But it has to be turned on, and have a correct programme :( ). New Scientist (www.newscientist.com/channel/info-tech/mg18925405.700.html) has a readable description. The Nature (439:949) letter is heavy going. | Graham L (2) | ||
| 438977 | 2006-03-18 03:31:00 | I saw that a couple of weeks ago. Head has just recently stopped spinning and I am none the wiser. | mark c (247) | ||
| 438978 | 2006-03-18 03:49:00 | Ah but who says its the correct answer? It might just be giving the incorrect one... | pctek (84) | ||
| 438979 | 2006-03-18 08:14:00 | Thanks for that Graham, very interesting. I'll try Nature too. I can't quite grasp the concept of course and if the computer relies upon Schrodingers Cat then we are in for some fun. Cats are enormously self-determinative so they'll only run the computer if they feel like it. Then if Heisenburg is correct, we can't be certain the answer given is indeed the right answer. And it will be different again if no-one watches the computer. Go figure. :badpc: |
Winston001 (3612) | ||
| 438980 | 2006-03-18 08:32:00 | Thanks for that Graham, very interesting. I'll try Nature too. I can't quite grasp the concept of course and if the computer relies upon Schrodingers Cat then we are in for some fun. Cats are enormously self-determinative so they'll only run the computer if they feel like it. Then if Heisenburg is correct, we can't be certain the answer given is indeed the right answer. And it will be different again if no-one watches the computer. Go figure. :badpc: That's quite right, to ascertain where the photon is, and what it is doing, as the article suggested, sounds very dubious to me. |
Terry Porritt (14) | ||
| 438981 | 2006-03-19 02:25:00 | (Nature 439:950-1])To the best of our knowledge, we have achieved the most accurate (2.6% error) realization of Grover's search algorithm, albeit with a non-scalable single-photon implementation. Using this setup, we made the first proof-of-principle demonstration of CFC, inferring that a particular element was not the answer to the computation, even though the computer did not run (with efficiency approx 0.319). Then we showed in principle how to obtain complete information from the algorithm unconditionally, without the algorithm ever running, using a 'chained' Zeno effect. ... Decoherence in quantum computing occurs owing to coupling to uncontrolled degrees of freedom -- the environment -- and results in incomplete interference between qubit states, leading to errors. In CFC, although the algorithm does not run, it still needs to be ready to run correctly, for all the critical interference effects to occur. ... however, we show that by using a variant of the chained Zeno CFC, in certain cirtcumstances it is possible to protect computations against decoherence. When this scheme succeeds (that is, when the photon is not absorbed) the total probability amplitude that has actually run through the algorithm is very small (<< 1, though not zero). Consequently, coupling to the environment is small and decoherence errors are suppressed. It remains to be seen whether the success probability can be made arbitrarily close to unity regardless of the amount of error. (CFC is "counterfactual computation", which sounds as if it ought to be political.). | Graham L (2) | ||
| 438982 | 2006-03-19 03:10:00 | New Scientist is known to have a thrown a few snake-oil theories around. | Greg (193) | ||
| 438983 | 2006-03-19 08:17:00 | "A non running computer makes fewer errors" Sorry guys, but this is old hat. Microsoft has been working on this proposition for years, with quite some success I might add. |
Murray P (44) | ||
| 438984 | 2006-03-19 12:21:00 | Very funny. Murray P | mark c (247) | ||
| 438985 | 2006-03-19 23:10:00 | So its non-scaleable meaning this is a one-off computation . I suppose using only one photon would do that . :D And I've never heard of "decoherence" . Didn't know it was possible, in fact I thought one of the principles of quantum physics was coherence . Sheesh - they keep changing the rules . :waughh: Incidentally for anyone interested, here is the book I'm currently reading which is comprehensible for failed physics students like myself . . amazon . com/gp/product/0553342533/qid=1142806121/sr=2-1/ref=pd_bbs_b_2_1/002-6171693-1115258?s=books&v=glance&n=283155" target="_blank">www . amazon . com |
Winston001 (3612) | ||
| 1 2 | |||||