From: cjl <cjl@welchlink.welch.jhu.edu>
Date: Tue, 18 Jul 95 17:54:59 PDT
To: Cypherpunks mailing list <cypherpunks@toad.com>
Subject: Quantum computing/crypto
Message-ID: <Pine.SOL.3.91.950718201132.22080B-100000@welchlink.welch.jhu.edu>
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C-punx,

Before the list cratered I had been intending to respond to Doug 
Hughes post about the quantum computing news piece by James Glanz in 
SCIENCE magazine, 7th July, vol. 269, pg. 28-29.

If you are reading this thread you may be aware of Peter Shor's 
development of an algorithm that uses quantum logic to factor large 
numbers.  This was discussed on the list last year and the general take 
on it was that there was no way to build a functioning quantum computer, 
and even if there were the code-maker would end up ahead of the code 
breaker.  

Well, it seems that his work stimulated some further interest in 
the design and construction of quantum computers and even a conference in 
Torino, Italy a few weeks ago.  In the 15th May Physical Review Letters 
ther are a number of papers on QC's, including one by Ignacio Cirac & 
Peter Zoller that describes the construction of a quantum logic gate.  
This builds on an article in same issue of PRL by Artur Ekert, 
David Deutsch and Adriano Barenco describing how by trapping ions 
in an electric field just above zero degrees Kelvin one can build a 
"quantum wire" which will pass information without measuring it (and 
therefore collapsing the quantum uncertainty).  Chris Monroe and David 
Wineland at NIST in Boulder have already built a simplified version of 
this quantum logic gate device, and have written a proposal to factor 
the number 15 using the technique.  The hardware involved will be about 
10 mercury atoms.  

There is airtime at the end of the piece for skeptics citing the 
calculations showing that "small errors in a QC can accumulate 
exponentially and no one has figured out a satisfactory way of reaching 
into the quantum world to correct them".

As I mentioned before there is a sidebar talking about the successful 
demonstration of quantum cryptography over 14 kilometeres of fiber optic 
cable in Los Alamos by Richard Hughes and colleagues, apparently 
announced at a conference held last month at the Univ. of Rochester in 
New York.  Alice and Bob can swap bits encoded in the quantum properties 
of photons that can't be intercepted with out them knowing that something 
is amiss.
 

C. J. Leonard                     (    /      "DNA is groovy"
                                   \ /                - Watson & Crick
<cjl@welchlink.welch.jhu.edu>      / \     <--  major groove
                                  (    \
Finger for public key               \   )
Strong-arm for secret key             /    <--  minor groove
Thumb-screws for pass-phrase        /   )