Commercial quantum crypto product - news article

[Hannes R. Boehm]

On Fri, May 31, 2002 at 08:57:46AM -0600, Kossmann, Bill wrote:
> Anybody familiar with this product?

Yes - a little.

As far as I know, they use phase coding of weak pulses
(meaning that a puls contains an average of less than a photon).
The average number of photons per puls depends on the probability 
you want to have that a puls carries more than one photon (as determined by
statistic calculations).

Phase coding works with an interferometer (actually it is a double interferometer)
setup. Alice and Bob are on different arms of the (Mach-Zehnder) Interferometer and 
are both aplying phase shifts on the wave function of the photon (randomly).

IMHO the weak puls method is not as beautiful as a
entangled photon implementation, since there is still the possibility
that more than one photon carries the information (even though, statistics
teaches us that this probability can be made abitarly small)
And: there have to be random number generators on Alice and Bobs side - whereas with 
entangled photons, the key is created simultaniously on both sides ("it never passes the wire").

But: it is available now, as far as I know there is no comercial systems with entangled 
photons to date - even though it has been demonstrated in the lab. I think that 
soon other systems will be available to choose from - lets wait and see.

What I can tell about the company "idquantique.com" is, that it was
founded as an offspring of the university of Geneva. Somehow Nicolas Gisin
is involved, who is one of THE experts on the field of Quantum Cryptography.
(I dont know wether it belongs to the university or not)

Hannes

 
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Hannes R. Boehm
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Institute of Experimental Physics
University of Vienna 
Boltzmanngasse 5 
1090 Wien
Austria

web  : http://www.quantum.univie.ac.at/
email: hannes.boehm at exp.univie.ac.at
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email:  hannes at boehm.org 
web  :  http://hannes.boehm.org
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