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Science Technology

Scientists Find Flaw in Quantum Dot Construction 180

Posted by Zonk
from the you-changed-the-outcome-by-measuring-it! dept.
ThePolkapunk writes "Scientists have been having problems in predicting the behavior of Quantum Dots, which are considered to be the most likely material to be used to build nanocomputers. Physorg is reporting that physicists at Ohio University believe they've found the problem, and it's with a flaw in the construction of quantum dots. If their theory pans out, "It's one more step towards the holy grail of finding a better quantum bit, which hopefully will lead to a quantum computer."" We first mentioned this about six years ago.
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Scientists Find Flaw in Quantum Dot Construction

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  • by mcc (14761) <amcclure@purdue.edu> on Sunday February 13, 2005 @04:35PM (#11661701) Homepage
    to ask this...

    The guy who wrote "the wellstone" is convinced that quantum dots can also be used to create programmable matter [wilmccarthy.com], something he came up with in one of his science fiction books.

    I am just curious. Is this (programmable matter via quantum wells/dots) something that actual work is being done on anywhere, or that actual signs of progress can be seen in, or that Mr. McCarthy has the actual capacity to encourage actual science work to be done on? Or is this just a lone science fiction author running around trying to convince people to take him seriously?
  • by necama (10131) on Sunday February 13, 2005 @05:08PM (#11661909)
    Quantum key distribution is cryptographically equivalent to one time pads, but better -- it solves the key distribution problem; you don't need to take all the one-time pads with you when you leave.

    Go watch a fleet prepare for setting to sea, and you'll see them loading one time pads onto the ship by forklift.
  • by Anonymous Coward on Sunday February 13, 2005 @05:34PM (#11662071)
    Hmm, having problems with spray painting with energy on quantum dots at an atomic level because the current stabilization coating won't allow light through the "paint"? Seems like they need to look at a clear coat paint (read: possibly different energy frequencies that will not cause the overcoating effect).

    Alternately, how about doing something like sputtered thin film (a hard drive surface coating technology) on a quantum level, which might reduce the thickness of the stabilization coat and allow a enough light to trigger the switch (Can't fix the "paint"? Fix the "sprayer").

    And, of course, the obvious obligatory comment for this article - A computer the size of a grain of sand? Dots nice, but how do I connect the keyboard...
  • by Anonymous Coward on Sunday February 13, 2005 @06:32PM (#11662497)
    So your question (I think) was something like "why don't we just drop 'bits' and classical crap altogether and build quantum computers from the fundamentals of quantum mechanics?" And your first real response said something like "We already do that", threw in the word "superposition" and commented on your word choice.

    Anyway, so that you don't think all AC's are stupid people, I'll try to explain where I think maybe you understood quantum computing incorrectly.

    Your comment, I think, suggests that you think that if we went straight from quantum mechnics, we could maybe abandon the concept of a "bit" (from classical computing) and thus not be unduly encumbered by the "old stuff". But the idea of a quantum bit isn't just trying to wedge a classical concept in where it doesn't belong. A quantum bit is a fundamental unit of quantum information, and thinking about quantum computing in terms of manipulating these things doesn't "lose" anything conceptual at all. The trick is that quantum mechanics allows quantum bits to do some pretty nifty tricks, like being in *superposition* (where the quantum bit doesn't have to be oriented to be either exactly 0 or exactly 1, but some goofy combination of the two), or being *entangled* (where quantum bits can have correlations which can be manipulated in various ways "at a distance").

    So it's more a matter of developing a new "paradigm" by way of analogy, than constricting us to the current one.
  • by UnHolier than ever (803328) <unholy_&hotmail,com> on Sunday February 13, 2005 @11:33PM (#11664547)
    I think it's important to point out that what these people are doinmg is not the whole story about quantum dots. They use a particular technique, and they found a way to improve it, but other people are using completely different techniques that have different advantages and disadvantages. Using "Scientists Find Flaw in Quantum Dot Construction" as a title is very misleading; it's like if an amelioration to firefox was reported as "Scientists find flaw in networking that could fix the internet".
  • by lgw (121541) on Monday February 14, 2005 @12:22AM (#11664841) Journal
    >Shor's algorithm is in P, not NP
    Yikes. First of all, P is contained in NP. In other words, it's impossible for something to be in P but not in NP.
    Secondly, Shor's algorithm is NOT in P. P is the set of languages decided in polynomial time by a deterministic Turing machine. Shor's algorithm runs in polynomial time, but it is NOT in P.


    This is an important point for math geeks. The reason quantum computers solve these problems more quickly is that they are not deterministic. They can therefore solve Non-deterministic Polynomial problems in polynomial time. Assuming, of course, that it's actually possible to build a quantum computer.

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