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Quantum Entanglement Demonstrated Aboard Orbiting CubeSat:
In a critical step toward creating a global quantum communications network, researchers have generated and detected quantum entanglement onboard a CubeSat nanosatellite weighing less than 2.6 kilograms and orbiting the Earth.
[...] The researchers incorporated their new instrument into SpooQy-1, a CubeSat that was deployed into orbit from the International Space Station on 17 June 2019. The instrument successfully generated entangled photon-pairs over temperatures from 16 °C to 21.5 °C.
"This demonstration showed that miniaturized entanglement technology can work well while consuming little power," said Villar. "This is an important step toward a cost-effective approach to the deployment of satellite constellations that can serve global quantum networks." The project was funded by Singapore's National Research Foundation.
Journal Reference:
Aitor Villar, Alexander Lohrmann, Xueliang Bai, et al. Entanglement demonstration on board a nano-satellite [open], Optica (DOI: 10.1364/OPTICA.387306)
Secure, as long as you trust the man in the middle...
(Score: 2) by Rupert Pupnick on Saturday June 27 2020, @03:06PM (2 children)
There’s no mention at all of ground stations in connection with these tests.
This statement in TFA raises a lot of questions in my mind:
“However, creating a global network for entanglement distribution isn’t possible with optical fibers because of the optical losses that occur over long distances.”
So free space is a better medium for quantum propagation than a dielectric waveguide? Why? How does one “direct” an entangled quantum particle to its destination in free space? Can that even be done, or does an entangled quantum have to suffer the same 1/r^2 free space losses as classical EM waves?
As an engineer, I’m also really bothered by the way these quantum communications systems are being developed and deployed. Why, for example, are researchers spending money on satellite deployment before having a reliable (whatever that means in quantum physics) ground based point to point quantum communications system that doesn’t have to concern itself with conserving power, ruggedness of design in the face of launch acceleration forces and so on? Why complicate the design problem? Do we already have fully developed terrestrial quantum links and somehow I missed the news?
Somebody clue me in.
(Score: 1, Interesting) by Anonymous Coward on Saturday June 27 2020, @03:43PM (1 child)
It isn't that there are 1/r^2 losses, but that there is 1/r^2 spreading of the photons, and yes, they do have the same issue. These things are verified statistically, not on a photon-by-photon basis, because you can't detect each photon all the time (even on the ground).
I think the main reason for doing it on a cubesat is that cubesats are cheap and make for nice demonstration platforms. There is also the student training angle, which I didn't follow any links here so I don't know if that is relevant. Combine the interests in quantum cryptography and the low costs of cubesats (and given that it was launched from the ISS, there is always the case where NASA provided a significant amount of support to justify the ISS as being something useful), it was probably pretty easy to get funded for this.
(Score: 2) by Rupert Pupnick on Saturday June 27 2020, @05:34PM
Thanks for that comment. I understand that quantum communications links have to be evaluated on a statistical basis, but when you get right down to it, you evaluate classical communications systems the same way, the prime example being BER curves as a function of S/N ratio. Why are there not similar metrics for the performance of a quantum communications link? Without some kind of metric, how does one make a comparison between two systems, or assess technical progress? How much performance degradation might one expect between a satellite and a ground based system, for example?
Which brings me to repeat my other point: Why aren’t they entirely focused on solving this very sophisticated problem in Earth based laboratories? Why do they want to complicate the design of a link by burdening it with the constraints of being a space worthy communications platform? It makes absolutely no sense to me, and can only be explained by things that you mention relating to availability of funding. Which means politics, which often comes with big helpings of BS.