Dear Sirs:    I am Jim Bell, the inventor and businessperson of daltonium.com.   I have a Bachelor's degree in Chemistry.   I was alerted to your recent article  https://phys.org/news/2019-12-entanglement-long-distance-free-space-quantum....  . DECEMBER 16, 2019   How to use entanglement for long-distance or free-space quantum communication   by Austrian Academy of Sciences I have invented a very new kind of silica single-mode silica optical fiber (waveguide)  that is isotope-modified.  Specifically, the silicon-29 isotope is removed from the core and cladding, and the germanium-73 isotope is removed from the doped core.  I explain the reason for this invention at:   daltonium.com/optical-fiber/      My hypothesis is that the Si-29 and Ge-73 isotopes, as well as the O-17 isotope atoms (the ones that have electromagnetic 'spin'), react to the passage of the infrared photons, and convert some of their energy into phonons, and thus cause what appears to be optical loss.   If I am correct, the loss can be reduced from the record held by Sumitomo Electric  of about 0.141 dB/kilometers.    https://global-sei.com/company/press/2017/03/prs029.html My understanding is that the maximum distance that can be exploited for purposes of quantum entanglement is inversely related to the value of optical loss.  I believe that the current record is about 50 kilometers.  https://phys.org/news/2019-08-entanglement-km-optical-fiber.html I expect that the eventual loss for my fiber, made with 99.99% Si-28, and perhaps 99.95% Ge (non-Ge-73) could be as low as 0.001 dB/kilometer.  (Although, achievement of this value might require use of O-17-free oxygen, created by the multiplate cryogenic distillation of liquid oxygen.)  This would be about 140 times lower than the best existing fiber.  This might allow quantum entanglement to effectively occur over a distance of 50 km x 140, or about 7000 kilometers.  (Perhaps, the distance between New York City and Eastern Europe.) My understanding is that a group of the Russian Academy of Sciences, headed by Andrey Bulanov, is proceeding with the prototyping of my fiber.   Are you interested in this fiber?  It should also allow optical fiber links over long distances with no or very few optical repeaters.                     Jim Bell     I am in Vancouver, Washington USA, in the Pacific Time Zone.   See below for some of my 'advertising'.   A message that I have sent to a couple thousand participants in the fiber optics industry: I am looking for a company to make an optical preform and draw it into optical fibers. It's a patented innovation, a silica single-mode optical waveguide with a loss of 0.001 dB/kilometer. https://www.linkedin.com/pulse/optical-waveguide-0001-dbkm-loss-even-10x-less-jim-bellhttps://daltonium.com/optical-fiber/Here's the US Patent for Daltonium.com's isotope-modified optical waveguide.http://www.freepatentsonline.com/9459401.html orIsotopically altered optical fiberForecast silica single-mode waveguide specifications:Optical loss 0.001 dB/kilometer at 1550 nmTransmission bandwidth: 400 nm-2000 nm (loss will be about 100x lower, at any given wavelength, than current single-mode silica fiber)Signal velocity: Optical signals will travel 5.6% faster than current silica optical waveguide.Chromatic Dispersion: If made to minimize loss, 'material dispersion' should disappear. What would be left would be 'waveguide dispersion.Can be made with EITHER a germania-doped silica core, OR a pure-silica core, fluorine-doped cladding.