I promised some links about the 5/6 cloning figure. You've had a few experimental ones, here are some theory ones.
Cloning machines: http://www.fi.muni.cz/usr/buzek/mypapers/96pra1844.pdf Theoretically optimal cloning machines: http://www.gap-optique.unige.ch/Publications/Pdf/PRL02153.pdf 1/6 disturbance is theoretically optimal, both as a QC interception strategy and "it's an optimal cloning machine": http://www.gap-optique.unige.ch/Publications/Pdf/PRA04238.pdf A different approach to the 1/6 figure (2/3 cloned correctly, the 1/3 imperfectly cloned still has a 50% chance of being right): http://arxiv.org/PS_cache/quant-ph/pdf/0012/0012121.pdf That lot is pretty much indisputed... ...except for the "optimal" part; and that's a sideways argument anyway - the math and physics theory are right as far as they go, just that they didn't consider everything. It may be possible to clone better than those "optimal" solutions, especially in the classic QC case, or get more information like which photons were cloned correctly, and perhaps to as near perfection as you like, but that is in dispute. Actually it's a pretty friendly dispute, people mostly say "I don't know"*. I'll post some more links on that later. *unless someone mentions non-linear transformations. Which is a different dispute really. -- Peter Fairbrother --------------------------------------------------------------------- The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to [EMAIL PROTECTED]