quantum hype

Peter Fairbrother zenadsl6186 at zen.co.uk
Sun Sep 28 10:43:10 EDT 2003


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

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