[extropy-chat] Fortune: the future of computing

scerir scerir at libero.it
Fri Jul 28 14:30:14 UTC 2006


|Giu1i0 Pri5c0> quotes:
> Ask scientists to predict how quantum
> technology will change the world over
> the next 20 years or so, and their
> imaginations go wild.

Wild, yes.

Zeilinger, and his group, distributed (via an optical free-space 
link, using the 'Optical Ground Station' of the European Space 
Agency) pairs of entangled photons to independent receivers or
observers separated by 144 km between the two Canary Islands: 
La Palma and Tenerife. 

Needless to say the observed polarization correlations,
due to the entanglement, violate Bell's inequality (or, 
better, the usual, easier, CHSH inequality) by more than 
13 standard deviations. They have also used these 
correlations to establish a quantum cryptographic 
key between La Palma and Tenerife.

This long-range performance (Schoedinger, who invented the
term 'entanglement' (1935), believed it was a short-range 
quantish effect, but in QM formalism the 'entanglement'
does not depend on distance, and on delayed measurements)
demonstrates the feasibility of quantum communication 
in free space, involving perhaps satellites or even the 
International Space Station. (Notice that the feasibility
in free space is easier than the feasibility on the earth,
due to the strong atmospheric 'decoherence').
           ^^^^^^^^^^^^^^^^^^

Is this the first step to establish a world-wide network 
(or many world-wide networks) for quantum communication?

http://www.arxiv.org/abs/quant-ph/0607182





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