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Math Supercomputing Science

Making Cesium Atoms Do a Quantum Walk 117

An anonymous reader recommends an Ars Technica account of a breakthrough in efforts toward quantum computing. German scientists have managed to get cesium atoms in a state called a "quantum walk": basically a superposition of all the possible states of a particle. "Quantum walks were first proposed by physicist Richard Feynman and are, in terms of probability, the opposite of a random walk. A random walk might be modeled by a person flipping a coin, and for each flip he steps left for heads and right for tails. In this case, his most probable location is the center, with the probability distribution tapering off in either direction. A quantum walk involves the use of internal states and superpositions, and results in the hypothetical person 'exploring' every possible position simultaneously." In the abstract of the paper from Science (subscription needed for full-text access), the researchers say: "Our system allows the observation of the quantum-to-classical transition and paves the way for applications, such as quantum cellular automata."
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Making Cesium Atoms Do a Quantum Walk

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  • Re:Encryption plan (Score:3, Insightful)

    by TiberSeptm ( 889423 ) on Tuesday July 21, 2009 @12:09AM (#28765805)
    A working AND cost effective quantum computer capable of decrypting your pr0n is still a ways off.

    If someone wants to spend that kind of money and resources to get you, then it doesn't matter what kind of decryption they have. If they can't ruin you by decrypting your secrets then they can just make something up. Fake compromising information is going to be the easier way to go for long enough that you shouldn't have to worry about it. I mean a planted local news story or thorough facebook+myspace+blogspot+whatever campaign calling someone a "pedophile" will drive them to hang themselves faster than stealing their identity anyways.
  • Re:Encryption plan (Score:3, Insightful)

    by fuzzyfuzzyfungus ( 1223518 ) on Tuesday July 21, 2009 @12:22AM (#28765875) Journal
    It's probably less about people "getting you"(I suspect that, today, relatively few people are actually being protected from a hostile superior power by the strength of their crypto) and more with things like the breakdown of electronic commerce security, the spoofability of cryptographic signatures(Goodbye SSL) and new difficulties in secure authentication(SSH would be about as useful as telnet).

    If a superior power simply wishes to ruin you that is, as you say, typically easy without any codebreaking. People who don't have that kind of power, but would love to compromise your secrets, are markedly more common and crypto is pretty much what keeps them at bay right now.
  • by Anpheus ( 908711 ) on Tuesday July 21, 2009 @01:27AM (#28766195)

    From what I've read on the issue, such as Feynman's books and other novels targeted toward those of us who do not have a complete grasp of quantum mechanics, you are wrong.

    Caveat emptor, this is merely what I've read:

    Classical mechanics as explained by Feynman were the result of the sum of all possible histories, among other interpretations. Regardless of one's interpretation, Feynman and others found that as you crunch the math for larger and larger quantities of particles, the results closer and closer approximate what we think of as classical physics. As a result, classical physics is an approximation of quantum mechanics, which is a theory of how the universe really works.

  • by radtea ( 464814 ) on Tuesday July 21, 2009 @03:54PM (#28773893)

    Nope. This is exactly the point I was trying to make: extremely short wavelengths explain why we don't observe interference phenomena. But they don't explain why we don't observe the cat as being in a superposition of ALIVE and DEAD.

    That is, they don't explain why the world of experience differs from the quantum world, and this is the central question.

    GIVEN that the only way we can detect the quantum world is via interference phenomena, then the really short wavelength of macroscopic objects explains why we don't detect interference phenomena.

    But WHY is interference the only way we can detect quantum phenomena? Why don't we just perceive the damned wavefunction? I think there is an essentially anthropic answer to this, in the form of an anthropic metaphysics: we experience a limited aspect of reality because the very fact of having such experience requires such a limitation. Kant would approve.

If the aborigine drafted an IQ test, all of Western civilization would presumably flunk it. -- Stanley Garn