mok-kong shen wrote:It seems that both quantum error correction and quantum tomography are necessary for practical realization of quantum computing, since the hardware needs to be verified for correctness in design, manufacture and maintenance. Is that true? If yes, then since, according to Wiki, quantum tomography is practically infeasible for cases of more than a few qubits due to exponential increase of work with the number of qubits, the practical infeasibility of quantum computing would be a direct consequence IMHO.
minkwe wrote:A "gullible audience" or "clever magician"? The result is the same. I pick the former.
FrediFizzx wrote:http://www.marketwired.com/press-release/los-alamos-national-laboratory-orders-a-1000-qubit-d-wave-2x-quantum-computer-2072670.htm
Labs are still buying the D-wave system for some reason. ??? Perhaps because even though there is no speedup, they use less power than other super-computers?
Joy Christian wrote:***
Some somber thoughts on the infeasibility of quantum computing: http://www.huffingtonpost.com/steven-ji ... 04846.html
***
The [Quantum Computer] story says a lot about human nature, the scientific community, and the society as a whole, so it deserves profound psycho-sociological studies, which should begin right now, while the main actors are still alive and can be questioned.
A somewhat similar story can be traced back to the 13th century when Nasreddin Hodja made a proposal to teach his donkey to read and obtained a 10-year grant from the local Sultan. For his first report he put breadcrumbs between the pages of a big book, and demonstrated the donkey turning the pages with his hoofs. This was a promising first step in the right direction.
Nasreddin was a wise but simple man, so when asked by friends how he hopes to accomplish his goal, he answered: “My dear fellows, before ten years are up, either I will die or the Sultan will die. Or else, the donkey will die.”
Had he the modern degree of sophistication, he could say, first, that there is no theorem forbidding donkeys to read. And, since this does not contradict any known fundamental principles, the failure to achieve this goal would reveal new laws of Nature. So, it is a win-win strategy: either the donkey learns to read, or new laws will be discovered.
Second, he could say that his research may, with some modifications, be generalized to other animals, like goats and sheep, as well as to insects, like ants, gnats, and flies, and this will have a tremendous potential for improving national security: these beasts could easily cross the enemy lines, read the secret plans, and report them back to us.
Prospects for quantum computing: extremely doubtful
Abstract:
The quantum computer is supposed to process information by applying unitary transformations to complex amplitudes defining the state of qubits. A useful machine needing or more, the number of continuous parameters describing the state of a quantum computer at any given moment is at least which is much greater than the number of protons in the Universe. However, the theorists believe that the feasibility of large-scale quantum computing has been proved via the “threshold theorem”. Like for any theorem, the proof is based on a number of assumptions considered as axioms. However, in the physical world none of these assumptions can be fulfilled exactly. Any assumption can be only approached with some limited precision. So, the rather meaningless “error per qubit per gate” threshold must be supplemented by a list of the precisions with which all assumptions behind the threshold theorem should hold. Such a list still does not exist. The theory also seems to ignore the undesired free evolution of the quantum computer caused by the energy differences of quantum states entering any given superposition. Another important point is that the hypothetical quantum computer will be a system of qubits PLUS an extremely complex and monstrously sophisticated classical apparatus. This huge and strongly nonlinear system will generally exhibit instabilities and chaotic behavior.
Dirkman wrote:How about this ? It's IBM, its a big private company, it wouldnt mess around with it's money.
"How IBM’s new five-qubit universal quantum computer works"
http://arstechnica.com/science/2016/05/ ... ter-works/
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