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The Viterbi Algorithm and Quantum Communications

Posted by ScuttleMonkey on from the sneaky-states dept.

eldavojohn writes "There have been a lot of tests in using quantum mechanics to communicate across large distances. But a student & a professor at USC have proven that the Viterbi algorithm can be applied to quantum communication. In the traditional Alice sends Bob a message scenario, 'Bob can reliably spot errors, and knows which message qubits are bogus before he opens the message — crucial, because opening it destroys it; and if it is garbled, he has nothing.'"

3 of 91 comments (clear)

  1. When Eve isn't listening by Anonymous Coward · · Score: 1, Interesting

    > So . . . when is ANYTHING Alice says not garbled?

    Whenever Eve isn't listening. Of course, given that our government is spying on everyone, you're right. You can simply DoS the connection by spying on them all the time.

    Crap, did I just break quantum encryption?

    1. Re:When Eve isn't listening by hairyfeet · · Score: 2, Interesting

      I know that you are probably joking,but that is exactly why quantum communications will never take off. There is no major government in the world that will allow communications that they cannot spy on,and since doing a MitM attack on quantum breaks it they will simply never let it get past lab stage. The second anyone tries to roll something out in a big way using quantum the governments will scream "its for teh terrorists and the kiddy pr0nographers! Think of teh childrens!" and that will be the end of that. So while I think it is interesting research,I doubt you will ever see it in real life unless they figure a way to copy everything sent and received without the subjects being spyed upon knowing it. But as always this is my 02c,YMMV

      --
      ACs don't waste your time replying, your posts are never seen by me.
  2. This could be huge by xZgf6xHx2uhoAj9D · · Score: 4, Interesting

    I'm not smart enough to figure out the details of what they've done, but it sounds like really promising work. "Communication" is perhaps too narrow a term for the applications, though.

    A big part of the problem with building quantum computers right now is keeping the qubits stable. The real world is constantly trying to "observe" (or interfere with) the qubits. When that happens, your quantum states break down and you lose your computation. This is a bit reason why we've only been able to build small (5-qubit) machines: it's very hard to keep things isolated and stable.

    If you have a practical error correction code scheme (using a Viterbi decoder, like in this article), then things might be a bit easier. Maybe instead of 5 very stable qubits, you could have 20 sort-of-stable qubits, where you expect that half of them will be lost to noise. It would still be a net win.