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Toward a Quantum Internet

Continued from page 1

By Kate Greene

Tuesday, April 15, 2008

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To use this gate, Kumar needs photons that are identical in every way except polarization, or the orientation of their electromagnetic fields.These "identical" photons are sent through optical fiber to the gate itself, a small maze of devices that route photons in different directions depending on their polarization. Passing through the maze causes certain photon pairs to become entangled. But not all photons make it through the gate; only when photons reach detectors on the other end, and the researchers can measure whether or not they are entangled, do they know the gate succeeded.

The only way to know whether or not the gate worked is to wait until a collection of photons has been fired at it, says Carl Williams, coordinator of the quantum information program at the National Institute of Standards and Technology. "Most of the time the gate fails," he says. "It's a probabilistic thing." But when the gate fails, the researchers simply disregard the unentangled photons.

"The great thing about this work," says Williams, "is that it's in fiber. This is a big deal because it could lead to distributed networks. ... The obvious application is for long-distance quantum communication between two smaller quantum computers." One of the crucial elements in a conventional optical network is a device called a repeater, which amplifies signals that have degraded over distance. Williams says that a quantum logic gate, such as the one that Kumar built, could be used in a circuit that amplifies a signal without losing the entanglement of the photons.

"This is an important step toward constructing a quantum Internet," says Seth Lloyd, a professor of mechanical engineering at MIT and a leading researcher in quantum computation. "Such a network would have powers that the ordinary Internet does not," he says. "In particular, communication over the quantum Internet would be automatically secure."

Lloyd notes that Kumar's paper illustrates how a simple quantum logic operation can be performed using individual photons. "The current paper represents a significant advance in the technology of quantum computation and quantum networks," he says.

Comments

  • Reliability
    I'm assuming that the chance of the photons not being entangled would have to be lowered before this can be put into a production environment.

    also, with the qubit, is it simply taking the X^2 of binary we know and love and making it X^3 by adding a 3rd option? or is there more that I'm not understanding?
    Rate this comment: 12345

    Shiladie
    04/16/2008
    Posts:55
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    • Re: Reliability
      with the qubit, is it simply taking the X^2 of binary we know and love and making it X^3 by adding a 3rd option?

      not really. from what i understand, a qubit is kind of like a bunch of regular bits blurred together. each of those bits can only be a 1 or 0.

      and a quantum computer is kind of like a bunch of classical (binary) computers blurred together, all running the same algorithm at the same time. each one comes up with a different answer, and if the algorithm is set up right, the one answer you're looking for will stand out above the rest.
      Rate this comment: 12345

      brunascle
      04/16/2008
      Posts:68
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  • Clarification
    No no, the end result of the gate would have to be 100% entangled, I would imagine for total security in the environment. And the X^2 binary we know would double, becase the quibit it both a "1" and "0" at the same time. So it would be x^4
    Rate this comment: 12345

    Maverick Pag...
    04/16/2008
    Posts:1
    • Re: Clarification
      I don't know much about quantum computation. However the article says that quantum computers can deal with exponentially more information than classical computers. x^2, x^3, x^4 are all polynomials. Exponential implies something of the form a^x, with constant a.
      Rate this comment: 12345

      bugme
      04/16/2008
      Posts:29
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      • Re: Clarification
        Yeah, I think the original poster probably meant the 2^x binary we know, since the number of possible values that can be expressed by x bits is 2^x. So x qubits can express all those values simultaneously; a calculation performed using eight qubits, for instance, is the equivalent of 256 separate calculations on a classical computer.
        Rate this comment: 12345

        LarryH
        04/17/2008
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  • Supplemental Reading
    http://www.cs.caltech.edu/~westside/quantum-intro.html

    This article really helped me wrap my head around the basics of quantum computers. And this article is just a bit more challenging but provides a great basis:

    http://antoine.frostburg.edu/chem/senese/101/quantum/

    Enjoy :)
    Rate this comment: 12345

    warplayer
    04/16/2008
    Posts:2
  • [no subject]
    This article defines qubit just a bit inaccurately. A qubit is 1, 0, and a superposition between 1 and 0. So it isn't that it is 1 and 0 at the same time, it embodies all values between as well. At least, from my reading, that is how I understand it.
    Rate this comment: 12345

    warplayer
    04/16/2008
    Posts:2
  • This just in!
    This just in ... Comcast researchers discover a way to increase rates on a quantum level by acting as internet gate keepers.  Comcast calls this the "Quantum Net", and promises to charge every website a toll per visitor, thus Quantumly enhancing their profits and decreasing user satisfaction simultaneously. 
    Rate this comment: 12345

    jmaximus9
    04/17/2008
    Posts:83
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  • Quantum rewards ...
    Wow!, some progress ... finally. This article does give hope that I'll someday have some kind of Apple computer device in my arthritic hands for my Alzheimered mind to play with before I croak. Though I suppose I'll probably be long gone dead when the throw the switch to turn on the first commercial fusion engine. I mean, talk about snail's pace.

    When was the word quantum first uttered in relation to the atomic world? More than eighty years ago?

    Geez, let's get going, fellas! God forbid some Bangladeshi, or heavens to Mergatroid, a North Korean brilliantly writes the paper of Papers ...! The humiliation we'll pass on to future generations, and it'll never lie down.
    Rate this comment: 12345

    mergatroid
    04/18/2008
    Posts:20
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    2/5
    • Re: Quantum rewards ...
      Don't worry too much, we've got them all working in our research labs already, so we can just take the credit when they find something.

      Unfortunately, quantum computing is one of the areas I've started to allow other people to learn about instead of taking it on myself. I may be able to wrap my head around it all with enough effort but I'm beginning to realize how little impact I have on the subject compared with other areas. The amount of effort it takes to become an expert in this particular field is better left to someone more passionate about it than myself. It's basically become the next subject ignored in a line that started with Greek Tragedy.
      Rate this comment: 12345

      desolation0
      04/19/2008
      Posts:13
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