Date: Sat, 15 Jun 1996 15:43:07 GMT
Subject: Hairballing Schrodinger's Cat
From: jya-AT-pipeline.com (John Young)


>----- Forwarded message (Jim Choate <ravage-AT-ssz.com>) -----< 
 
Forwarded message: 
>From physnews-AT-aip.org Fri Jun 14 18:39:08 1996 
Date: Fri, 14 Jun 96 16:45:16 EDT 
From: physnews-AT-aip.org (AIP listserver) 
Message-Id: <9606142045.AA11832-AT-aip.org> 
To: physnews-mailing-AT-aip.org 
Subject: update.275 
 
 
PHYSICS NEWS UPDATE                          
The American Institute of Physics, Bulletin of Physics News. Number 275,
June 14, 1996. By Phillip F. Schewe and Ben Stein. 
 
 
THE FIRST QUANTUM COMMUNICATION USES "TRITS" INSTEAD OF BITS. 
 
 
For the first time, physicists have exploited the laws of quantum mechanics
to send data, and with their technique have conveyed information more
efficiently than with 
traditional means. In contrast to a traditional computer, in which messages
consist of tiny electric pulses encoded in binary form (i.e., streams of 0s
and 1s), researchers at the University of Innsbruck in Austria send
messages consisting of single photons which can be coded as 0s, 1s, and 2s,
setting up a base three system called "trits." 
 
 
The Innsbruck group (Harald Weinfurter, harald.weinfurter-AT-uibk.ac.at)
converts a single ultraviolet photon into two photons whose properties are
quantum mechanically interlinked, or "entangled."  Devices then encode a 0,
1, or 2 onto one of the photons by performing an operation on it (such as
flipping its spin or shifting its phase); since the devices are blind to
the initial state of the photon, they change the overall properties of the
entangled photon pair without determining its final state. The two photons
are recombined and then the interlinked pair travels towards a network of
detectors.  Two-photon interference creates three different sets of
detection possibilities in the Innsbruck setup that reveal the quantum
state of the entangled pair and whether the photon was encoded with a  0,
1, or 2. 
 
 
The physics of entanglement has been exploited in numerous recent
experiments, 
to build quantum logic gates (Update 250) and perform an atom-level
demonstration of Schrodinger's cat (Update 273), but until now it has never
been used for quantum communication -- encoding a message at one location
and receiving it at another. Furthermore, the same information contained in
a typical ASCII character, normally requiring the use of 8 bits, can also
be transmitted using only 5 trits.  (K. Mattle et al, Physical Review
Letters, 17 June 1996.  More information and graphics can be found at: 
 
 
     http://www.uibk.ac.at/c/c7/c704/qo/photon/_qdc) 
 
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See also at that site links to "teleportation" research at IBM. 
 
 
All this reveals the recently Dromology-posted Paul Virilio interview
"Silence of the Lambs," from CTHEORY, to be quite prescient. 

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