On 24 Sep 2003 08:34:57 -0400, Greg Troxel <[EMAIL PROTECTED]> wrote:
In Quantum Cryptography, Eve is allowed to not only observe, but also
transmit (in the quantum world observing modifies state, so the notion
of read only doesn't make sense).  Also, Eve is typically accorded
unlimited computational power.

The idea that observing modifies state is something to be approached with caution. Read-only does make sense in quantum world; implementations of early theoretical work by Elitzur and Vaidman achieved roughly 50% success on interaction-free measurements. Later work, relying on the quantum Zeno effect, raised the success rate significantly: "Preliminary results from new experiments at Los Alamos National Laboratory have demonstrated that up to 70 percent of measurements could be interaction-free. We soon hope to increase that figure to 85 percent."

The quote comes from a article by Kwiat, Weinfurter and Zeilinger published in SciAm, November 1996 -- if they were getting success rates like these back then, I wonder what the current status is.

The article is well worth a read. There's a copy online at:

Best regards,
Ivan Krstic

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