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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 ggambett (611421) on Sunday February 13, 2005 @03:36PM (#11661713) Homepage
    Disclaimer : I know next to nothing about quantum computing.

    However, I wonder if we really need quantum bits. Sure, we probably can reproduce the same kind of circuitry that we have now with quantum gates and whatnot, but I fear that would be missing the point, or rather grossly wasting, the capabilities opened by quantum mechanics, by forcing these into our current paradigm. That is, using quantum stuff as a new mechanics for our current paradigm, instead of coming up with a new paradigm that actually utilizes quantum properties fully.

    In a word, this looks like evolution - will this cause a revolution?

    As I said, I know almost nothing about this, so excuse me if my post didn't make sense at all.
  • by Umbral Blot (737704) on Sunday February 13, 2005 @03:43PM (#11661762) Homepage
    Quantum computers have the capability to break most encryption schemes. This would definitely be a revolution.
  • What the hell? (Score:5, Insightful)

    by mcc (14761) <amcclure@purdue.edu> on Sunday February 13, 2005 @03:55PM (#11661836) Homepage
    They could be finding cures to cancer, or making better space shuttles, or doing a ton of things with applications that would be useful

    Uh.. wow.

    The people designing better computers aren't curing cancer because they aren't biologists. It isn't like intelligence is just something you can put in a pipe and direct it whereever you want. Some people are just better at certain things than others. Meanwhile the kinds of people who gravitate toward research fields tend to only be effective when they're doing things they find interesting and exciting. What they personally most enjoy or can best apply their talents toward may or may not be the most important thing in the world, but if it's productive and makes some sort of difference, who are we to question?

    And why target the people improving computing power, and not any other "nonuseful" field? In particular, why on earth target people like the ones from this article, who are improving computing power by expanding our understanding of and ability to harness basic physics, and working in an area where discoveries potentially have direct applicability to all kinds of other nanoscale technologies, like, I don't know, smart medicines.

    Even if your "couldn't they be doing something more useful" thing made sense, your examples are very poor. Better space shuttles aren't being built for a lack of ingenuity, they're being built for a lack of funding. And curing cancer in particular is a horrible example because much of the interesting expanding work in the medical research field at the moment is in bioinformatics. Meaning that cancer research would directly and seriously benefit from a major jump in the capacity of computing power, such as the one these nanocomputer people could make possible.
  • by ca1v1n (135902) <snookNO@SPAMguanotronic.com> on Sunday February 13, 2005 @04:09PM (#11661922)
    40% of the US economy is dependent on applications of quantum mechanics, and all of the rest of it indirectly feels the effects.
  • by wass (72082) on Sunday February 13, 2005 @04:34PM (#11662067)
    That is, using quantum stuff as a new mechanics for our current paradigm, instead of coming up with a new paradigm that actually utilizes quantum properties fully.

    That pretty much is what researchers in quantum computing are trying to do, it's a whole different ballgame. For example, In classical computing, 3 bits lets you put a system into exactly one of 8 (2^3) distinct states. However a quantum computer with 3 qubits will let you put the system into a superposition of these eight states, such that the superpositiong (ie, wavefunction) is properly normalized.

    Quantum mechanics works in a whole different mathematical basis (Hilbert Space or Fock Space). The algebras of these spaces is quite different from classical computing, so yes, it's going to be a whole new way of looking at computing, at least at the lowest level.

    On a side note, it sounds like you have just read some Thomas Kuhn, as per your frequent usage of 'paradigm', along with comparing 'evolution' to 'revolution'.

  • by wass (72082) on Sunday February 13, 2005 @04:47PM (#11662159)
    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?

    First a note - All of my experience with quantum dots is at cryogenic temperatures, eg 4.2K and below, so I'm not aware of the behavior of systems at higher temperatures.

    It sounds like this author is making very generalized hand-waving explanations about these fairly complex systems. And is vague enough so that if any effect is discovered, he'll claim that he "discovered" it first. But if he did claim that, it would be somewhat disingenuous because it's very difficult to predict what kind of coherent long-range many-body "emergent" patterns would manifest themselves. Ie, the low-level physics is hard, the fabrication is hard, determining large-scale effects is hard, etc. Heck, even describing a simple helium-atom is hard enough (the quantum-mechanical 3-body problem), with three interacting coulomb forces to work with in addition to the nuclear potential. So it sounds like he's handwaving, but in an attempt to claim prediction of any future discovery based on quantum-dots.

    On a side note, though, all matter is already programmable by default. Phase transitions, for example, will happen at specific temperatures, or magnetic fields, etc, such that the macroscopic behavior of the material can be 'programmed' by pushing through the phase transition.

  • by Garbonzo Pitts (249836) on Sunday February 13, 2005 @06:47PM (#11663068)
    "quantum dot" is entirely generic and its use predates any commercial interest by many years.

    Does anyone have a *real* reference for this, like a paper on arxiv.org? The popularized description doesn't make any sense to me, since the bandgap of the wetting layer is above that of the dot.
  • by Curl E (226133) on Sunday February 13, 2005 @10:10PM (#11664436)
  • by kholburn (625432) on Monday February 14, 2005 @04:45AM (#11665968)
    Wrong, viruses have been evolving for millions of years to use other life forms to survive and reproduce.

    There is a law of biology that says something like: any parasite evolves to be less harmfull to its host(s).

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