[14322] in cryptography@c2.net mail archive
Re: quantum hype
daemon@ATHENA.MIT.EDU (Peter Fairbrother)
Sun Sep 28 12:22:32 2003
X-Original-To: cryptography@metzdowd.com
X-Original-To: cryptography@metzdowd.com
Date: Sun, 28 Sep 2003 15:43:10 +0100
From: Peter Fairbrother <zenadsl6186@zen.co.uk>
To: <cryptography@metzdowd.com>
In-Reply-To: <BB9395BC.39F31%zenadsl6186@zen.co.uk>
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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