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Domain: qubit.org

Stories and comments across the archive that link to qubit.org.

Comments · 104

  1. Re:Open Qubit, more info by maphew · · Score: 2 · on Stepping to Solid State Quantum Computing

    Unfortunately openqubit.org is nothing but a "coming soon" sign. :( While we're waiting for that to open up we can go to www.qubit.org, particularily the "Introductions & Tutorials" page.

  2. Re:Open Qubit, more info by maphew · · Score: 2 · on Stepping to Solid State Quantum Computing

    Unfortunately openqubit.org is nothing but a "coming soon" sign. :( While we're waiting for that to open up we can go to www.qubit.org, particularily the "Introductions & Tutorials" page.

  3. Quantum computing-- not the end of the world by cryptogeek · · Score: 1 · on RSA slightly broken
    The situtation is both worse and better than this. If quantum computing could only be used to factor large numbers, the world wouldn't change much. We would stop using RSA encryption (which is only as secure as factoring is hard) and start using schemes based on the difficulty of the discrete log (such as El Gamal). However, Shor's algorithm can also be used to perform discrete logarithms in polynomial time, thus blowing away most of the remaining public-key algorithms and some very important key exchange schemes (particularly Diffie-Hellman). We might still be able to salvage some sort of public key scheme out of lesser known problems (like the knapsack problem), but it would take a lot of work.

    So how is the situation _better_ than this? First, these advances only apply to public-key encryption, not secret-key encryption schemes like DES. Second, quantum mechanics also opens up new possibilites for key exchange that were not available before. In particular, quantum mechanics can be used to distribute random key material for a one-time pad over a public medium. There's a good overview of the process in the Oct. 1992 Scientific American, but the main idea is this: Quantum entities (photon, electrons, fundemental particles) change when observed. Therefore, someone can send out the random key material in the form of a stream of photons, and the reciever can tell if they were observed in transit.

    This is a Good Thing, cryptographically speaking, because one-time pads are proven to be _unbreakable_. Furthermore, this type of key exchange has already been one, over distances as long as 30km (I believe).

    So quantum computing would change things, certainly, but it's not the end of the world.

    (For those interested, Schneier's _Applied Cryptography_ and the _Handbook of Applied Cryptography_ by Menzes, van Oorschot and Vanstone are good general references. As mentioned above, the quantum key distribution method can be found in Scientific American, Oct. 1992. Peter Shor's home page is here. There's lots of information on quantum computing on the web, but a good place to start is here.)

  4. The algebra? by SteveM · · Score: 1 · on Quantum Computing Using Quantum Dots

    This page is entitled Quantum Algebra, so you might find it interesting.

    I have not spent any time there. I found it as a link from here.

    SteveM