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From: "Frank Sudia" <[EMAIL PROTECTED]>
To: "Digital Commerce Soc" <[EMAIL PROTECTED]>
Subject: The Physics of Quantum Information
Date: Fri, 22 Dec 2000 15:36:12 -0800
Sender: [EMAIL PROTECTED]
Reply-To: "Frank Sudia" <[EMAIL PROTECTED]>
Bouwmeester, D., et al., "The Physics of Quantum Information: Quantum
Cryptography, Quantum Teleportation, Quantum Computation," Springer Physics
& Astronomy Series (2000). ($54, Amazon)
Good grief, buy this book. The quantum mechanical EPR states are now
becoming so well understood that "realizations" are merely years away. This
will allow us to deploy quantum states with strange properties in the design
of pretty much any other system. (We still need it to work in solid state,
with long decoherence times, but progress has been phenomenal since the
famous Aspect experiment put this on the map in 1982.)
[Also check out the tantalizing photos of multi-atom quantum computers
at the University of Innsbruck: http://heart-c704.uibk.ac.at/ This site
also has a lot of well written tutorial material, and is all in English, but
you will understand it better after reading the book.]
This volume is a survey of important recent results, with 43 authors, who
are members of a worldwide scientific study group. The first third is a
well written introductory text, intended for a wider audience, scannable at
the "Scientific American" / "Science Magazine" level of literacy. The rest
of it reviews the mathematics and (still primitive) experimental setups in
more detail.
My personal observations follow. I think I "got" all this, but
scientific accuracy is not guaranteed --
Many of the principles involve "cat" states, wherein photons or particles
are passed around (within a fiber network, or on a computer chip), carrying
not yet determined states inside them, which are paired with other such
particles far away. Each one is a little "Schroedinger's Cat," waiting for
someone to open the box and look in. At that point the state of the far
away particle is altered, and "classical information" is transferred
instantaneously from point A to point B.
Also, due to the immense complexity that can be represented inside a quantum
superposition of states, usually in a trapped atom, problems that currently
require exponential running times, in what is quaintly called "classical
mathematics," will henceforth be solvable in logarithmic time.
But presumably, even if factoring becomes easy, it won't matter, because
we'll all be communicating securely via long distance quantum teleportation.
A notional quantum telephone exchange is described. And believe it or not,
you can design network repeaters that could transport the entangled quantum
states over long distances. (This will be the second coming of optical
networking, in 2007.)
Quantum cryptography is discussed extensively, and one imagines that there
must be considerable interest by well funded government agencies.
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