Qubit computers

Discussion in 'General Science & Technology' started by Vkothii, Sep 16, 2008.

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  1. Vkothii Banned Banned

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    We have quantum mechanics, and information science. How close are we to the holy grail of a multi-qubit machine that can harness all the mechanics, and what will it take?

    A promising field could be trapped-ion qubits. The research in this area got into the last SciAm issue; they can cool ions down to a few mK with lasers, and keep them suspended in magnetic traps I think about 100 nm from the room-temp surface of a chip, these days. That's pretty cool.
    And they can line the ions up in a row and move them around without disturbing the qubits, because ions have a larger Coulomb interaction and so are more stable, or more tightly coupled.
    Apparently much of the groundwork has been laid by the electronics industry, with sophisticated fabrication methods, that means parts are available, or can be put together - we have the technology.

    Progress has been made, but the outstanding issue is quality, in both fabrication techniques, and in manipulation of the information - qubit flipping and reading, all at the required fidelity, or with a very high signal to noise ratio to avoid decoherence of the signal. Both are purity issues, signal purity depends on material purity.

    Gates that can perform logical operations on two qubits - quantum phase gates, are a key step to a qubit machine. Like logic gates made with transistors, two signals get 'mixed', one comes out.

    Apparently these jocks now have a reliable (97%) QP gate prototype using Be ions. Qubit logic is here; integrated devices that can control dozens or hundreds of qubits are up ahead somewhere.
     
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  3. Vkothii Banned Banned

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  5. CheskiChips Banned Banned

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    Yup; we're going to have so much data and information that no one will know anything.
     
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  7. Dinosaur Rational Skeptic Valued Senior Member

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    The last article I read about quantum computers bragged about one of them being able to factor 15.

    Great progress after about 10-15 years of effort. The article was written a few years ago. Perhaps they can facter 21 or 36 now.

    All I ever see are grandiose claims with little actual information about how they function and no prototypes that can do more than trivial calculations.
     
  8. BenTheMan Dr. of Physics, Prof. of Love Valued Senior Member

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    As dinosaur says, I think that quantum computers are only in the proof of principle stage, from what I understand.
     
  9. Vkothii Banned Banned

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    But they have working 2 and 3 qubit systems, which are already useful in certain measuring devices.
    FQHE devices are looking promising, too. It's mostly a technology problem - decoherence is like a S/N ratio of 0.
    Transistors only had thermal and material purity considerations. The problem is the size.
     
  10. dazzlepecs Registered Senior Member

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    eh? Is it still a binary system?


    BOolean algebra would be horrid otherwise.. Or impossible?
     
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