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Single Photons Bounced Off Orbiting Satellite

Posted by CmdrTaco on from the pling-pling-pling dept.

KentuckyFC writes "If we're ever going to benefit from the perfect security of quantum communication, we're going to need ways of transmitting entangled photons around the globe and certainly further than the current record of 144km through the atmosphere. Anton Zeilinger at the University of Vienna and colleagues have taken an important step towards this by bouncing individual photons off the Ajisai geodetic satellite (essentially a space-based disco ball) which is orbiting at 1400km. The group says the experiment is an important proof of principle for satellite-based quantum communications."

4 of 131 comments (clear)

  1. Complicatedly Unacceptable by eldavojohn · · Score: 5, Funny

    Anton Zeilinger at the University of Vienna and colleagues have taken an important step towards this by bouncing individual photons off the Ajisai geodetic satellite (essentially a space-based disco ball) which is orbiting at 1400km. Big deal. Drunken frat boys at sports games bounce millions of "single photons" off of the opposing team members with pen lasers. *snort* You're a few zeptometers short of the goal.

    Not to mention photons are like words: you shouldn't use those you don't understand. Is it a wave or is it matter? Huh, Mr. Smarty Pants? Oh, what's that you say? A boson followed by a long explanation, how utterly predictable! Ha, you would say that. No. I want answers and I wanted them back when the church would persecute you for publishing them!

    We need something smaller. Go back to the lab, anything larger than a Planck Length is unacceptable. And only 1400km? So help me god, if you can't express the distance it travels in double up arrow notation or tetration, I don't want to hear about it. Come on people, this is real science, not some religious mumbo jumbo (6,000 years? Is that the absolute limit of your imagination!?) ... and if there's one thing I rely on from real science, it's announcements of experiments with inconceivable units performed in a totally contrived and intangible environment. The fact that I understood this experiment speaks libraries of congress about its complexity (or lack thereof). I'm encouraging you to go the extra yottameter here.
    --
    My work here is dung.
  2. Come clean by sleeponthemic · · Score: 5, Funny

    This is just an elaborate game of pong, isn't it...

    --
    I record my sleeptalking
  3. Re:Other than supposed security improvements... by kmac06 · · Score: 5, Informative

    Breaking quantum cryptography is not hard, it is impossible. The security is guaranteed by the laws of physics. Unless quantum mechanics is flat out wrong, it can never be broken, period. And saying quantum mechanics could be wrong is like saying gravity could be wrong.

    About quantum computing, it's actually closer to providing new computational powers than you might think. In terms of a powerful, programmable computer that can factor large numbers, we are a long way off. But in terms of being able to simulate certain quantum systems that current supercomputers cannot, we are fairly close.

  4. Re:Other than supposed security improvements... by kelpless · · Score: 5, Interesting

    no cloning principle are exactly right. You cannot read and then reemit a photon with the same polarization Hmm. I think you meant you cannot read and reemit with 100% fidelity. http://www.icfo.es/images/publications/J05-055.pdf, "Quantum Cloning", Valerio Scarani, Sofyan Iblisdir, and Nicolas Gisin. This is a late 2005 review and of eavesdropping techniques for QKD. Much of the terminology of quantum physics is unfamiliar to me but I think the paper states that Eve could theoretically get 5/6 of the bits through cloning and to keep this from happening, Alice and Bob have to assume an eavesdropper if more than 11% of the bits have errors. When dealing with single photons, read errors will happen. There is also work at the University of Tokyo, the Japan Science and Technology Agency, and the University of York (Sam Braunstein and Akira Furusawa) on telecloning (combined quantum teleportation and quantum cloning) that I have a reference to an experiment done two years ago where they cloned 58% of the photons successfully out of a theoretical 66%.

    Others have created quantum crypto systems that take the possibility of cloning into account, http://w3.antd.nist.gov/pubs/Mink-SPIE-One-Time-Pad-6244_22.pdf

    'basic' quantum cryptography that is taught can be hacked This is true but I think not for the reasons you believe. Basic quantum crypto provides confidentiality only. To keep from being hacked, you must provide authentication as well (Alice must be able to prove she is communicating with Bob and not Eve). I haven't heard of a way to do this without falling back onto more conventional cryptographic techniques such as RSA signatures - at least when doing quantum crypto over fiber. Maybe sending photons through the atmosphere means you can actually just see if somebody is acting as a man-in-the-middle.