# China quantum telecom [closed]

Perhaps did you read this information :

China’s Latest Leap Forward Isn’t Just Great—It’s Quantum

Beijing launches the world’s first quantum-communications satellite into orbit

State media said China sent the world’s first quantum-communications satellite into orbit from a launch center in Inner Mongolia about 1:40 a.m. Tuesday. Five years in the making, the project is being closely watched in global scientific and security circles.

The quantum program is the latest part of China’s multibillion-dollar strategy over the past two decades to draw even with or surpass the West in hard-sciences research.

main question : Is this project credible in regard of the state of the art as known in the universities?

Not important optional question : As for the d-wave solution, must we classify quantum computation and cryptonics as technologies which will be as such, shrouded in secrecy ?

You may answer that it is not the classical $q$-cryptography that is described in, for example, wikipedia. If so, what are the new principles?

edit : to answer to the relevant Zeldredge comment: sending a satellite is plausible, nobody doubts. But this implies to have an efficient technology, here, since at least 5 years. Following nearly all the informations on the subject, I don't see how a team got this technology 5 years ago in secret ! As today, a lot of engineers which spent a lot of time ( and money ), helped by great profs of great universities, didn't succeed to establish a valid protocol of communication ( as the theory we know states ). The alternate not polite question is , Is it not some kind of bluff ? or merely just a weak quantum application. By analogy with d-Wave which is not able to do today what we wait from a Quantum computer.

• There's a paywall on the article. Can you provide a summary? – Jim Aug 16 '16 at 13:37
• no paywall from Europe, I'll update the post. I don't care about secret. What is the state of this art ? this may imply an open door on thousands of new ideas ( I recycle comments to minimize their quantities ) – user46925 Aug 16 '16 at 14:02
• I'm not clear what you're asking precisely. If your question is whether a quantum-communication satellite is technologically viable, the answer is yes, this satellite is real (or at least seems quite plausible). If you'd like to know about the applications and security implications of quantum information technology, perhaps ask that directly as a separate question. – zeldredge Aug 16 '16 at 14:08
• @zeldredge : for me , the state of the art in teleportation is not clear. Many experiments has different conclusions and many new ones are in preparation with big grants. It is a subject similar to the irruption of d-Wave in the quantum computation, no one ( or at least me :) ) knows exactly how they do – user46925 Aug 16 '16 at 14:14
• This wikipedia page of quantum networks worth reading. Also notice, since the year 2003 goverments had been using operational and functional quantum networks. According to this wikipage, there are 5 in the world right now (one of them, in china). Apparently, China has decided to expand it a little bit (to space)...... – Physicist137 Aug 16 '16 at 16:00

I believe the best possible answer to your question is given in this Nature News article. As the article explains in detail, this type of technology has been established before, and indeed it doesn't require a special "quantum satellite":

Last year, the team showed that photons bounced back to Earth off an existing satellite maintained their quantum states and were received with low enough error rates for quantum cryptography

What this satellite does have is an on-board source of entanglement (I believe a single-photon parametric down converter):

At the heart of their satellite is a crystal that produces pairs of entangled photons

As to how they did this, there's no secret Chinese intelligence going on here that the rest of the world wasn't aware of. They just were willing to put up the money for it. The article goes into some of the organizational details, notes that Anton Zeilinger (European) is a major part of the collaboration, and details some other efforts that have taken place around the world.

• a better link ! could I refer to it in the question please ? That makes feel better seeing the names – user46925 Aug 16 '16 at 15:09
• @igael The intention of the site is that questions are asked and then have definitive answers, rather than working like a discussion forum. If you want to point people toward the link and feel it answers the question, the best you could do is accept the answer by clicking the check mark next to it. This marks the question as answered. Otherwise, you continually edit the question and the answers become superfluous. – zeldredge Aug 16 '16 at 15:14
• I asked your choice politely and i'll respect it ! You know , in general, I'm not qualified to say if a question is well answered. I downvote rarely but I trust the community. However, in this particular case, the questions are very precise for someone which works in the domain : how they do the impossible ? What will you think if tomorrow you read on your favorite newspaper that Strangersland realized a water engine ? To laugh or to be afraid ? – user46925 Aug 16 '16 at 15:21
• @igael Well, in general the idea is that you asked the question, so you decide whether it is answered :) admittedly, this is not a great answer from a SE perspective because it's mostly a reference, but I hope it cleared up the scientific context of this -- it certainly isn't "out of nowhere" and as an expert I wasn't surprised to see it (though I am excited) – zeldredge Aug 16 '16 at 15:23
• @igael As far as I know, the key technology to achieve the control of photons have been tested a few years ago through free space on ground with a distance of 100km. So now they just put the equipment on the satellite to test if it will work under a different scenario. – XXDD Aug 17 '16 at 9:23