Why the quantum internet should be built in space

[jim bell]

 This posting, below, actually refers to something relevant to my isotope-modified fiber optic invention.  See  www.daltonium.com .The article I cited, below, refers to using quantum links from satellites to points on the ground to create an untappable link.  The reason they think they need to use satellites is that these quantum links can go over optical fiber, but they cannot be augmented by the usual EDFA's (Erbium Doped Fiber Amplifiers) commonly used, or to be received and re-transmitted to the next fiber.  I believe that a recent record was set for an entangled fiber link, of 50 kilometers.  https://phys.org/news/2019-08-entanglement-km-optical-fiber.html  
They started by generating a photon of 854 nm wavelength, but the loss of the optical fiber would be nearly ((1550/854)**4) = 10.85 that normally found in a natural-isotope optical silica fiber, about 0.150 dB/kilometer.  So, they convert that entangled photon to a wavelength of about 1550 nanometers, which matches the best (lowest-loss) passband of the fiber.  

To the same end is this:
https://www.nature.com/articles/s41467-018-04341-2

But even at about 1550 nanometers, 50 kilometers of fiber has:  50 km x 0.15 dB/km  = 7.5 dB of optical loss
Some are working on the idea of a quantum-compliant optical repeaters.  

https://qt.eu/understand/underlying-principles/quantum-repeaters/

"Distributing quantum resources such as entanglement and qubits over long distance fibre optic networks represents an enormous challenge. If we send single photons over 1000km, even at rates of 10GHz, we would need to wait hundreds of years to detect just one, due to loss in the fibre. Not very practical! Modern telecommunication overcomes this problem with amplifiers that boost the signal along the way. However, these would destroy the quantum characteristics of the photons such as entanglement, and, even in principle, this quantum information cannot be copied – we call this “no cloning”. Therefore, a quantum approach to overcome transmission loss is required – the quantum repeater."    [end of quote from url]

  My isotope-modified silica fiber (fiber made of silica where the Si-29 isotope and Ge-73 and O-17 has been reduced or even nearly all removed) may have a loss as low as 0.001 dB/kilometer, about 150x lower than ordinary-isotope fiber.  If the frequency-modification technique used above is also used, perhaps a quantum link could be maintained which is 50 km x 150 = 7500 kilometers, which is nearly 1/5 of the circumference of the Earth at the equator.  
A team of Russian scientists, including chemist Andrey Bulanov, is working on building my fiber.http://www.freepatentsonline.com/9459401.html



  http://english.iop.cas.cn/ns/es/201803/t20180322_190984.html
As this url states:   "Since 1995 [Bulanov] is engaged in different aspects of preparation and investigation of the properties of monoisotopic varieties of silicon, germanium, iron, sulfur, selenium. He is a responsible executive on the part of IChHPS RAS in the International projects Avogadro, Kilogram-2 and Kilogram-3."
See also these:    https://www.researchgate.net/scientific-contributions/2129520086_Andrey_D_Bulanov
Therefore, he sounds like the perfect researcher to be working on this project.

                 Jim Bell


    On Saturday, January 4, 2020, 11:10:20 PM PST, jim bell <jdb10987 at yahoo.com> wrote:  
 
 https://www.technologyreview.com/s/614994/why-the-quantum-internet-should-be-built-in-space/

  
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