Chinese Satellite Breaks Distance Record For Quantum-Key Exchange (sciencemag.org) 42
slew writes: Science Magazine reports a team of physicists using the Chinese Micius satellite (launched back in August 2016) have sent quantum-entangled photons from a satellite to ground stations separated by 1200 kilometers, smashing the previous world record. Sending entangled photons through space instead of optical fiber networks with repeaters has long been the dream of those promoting quantum-key exchange for modern cryptography. Don't hold your breath yet, as this is only an experiment. They were only able to recover about 1000 photons out of about 6 billion sent and the two receiving stations were on Tibetan mountains to reduce the amount of air that needed to be traversed. Also the experiment was done at night to minimize interference from the sun. Still, baby steps... Next steps for the program: a bigger satellite for more power and moving to quantum teleportation instead of simple key exchange. The results of the experiment were published in the journal Science.
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Yay, rather than celebrate the advance of science for all mankind, we can whine, moan and troll about politics.
That's just his defense mechanism. It kicks in whenever China is better than the USA at something.
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Did they get the consent of the Tibetans before emplacing their receivers on Tibet's mountains?
They didn't have to, which is why that should be where we put the Thirty Meter Telescope. The seeing is better at 17,000 ft anyway.
And the other "valid" signal?? (Score:1, Interesting)
So they sent entangled photons to ground, and there was a second signal, one that says "entanglement successful, photon is valid", and that was send how exactly? The signal they use to filter out all the other photons detected. That signal, the one that's actually carrying the real information here.... the one any attacker would attack if this was ever used in main stream use.
Look, I have a space based machine that fires ping pong balls at the earth, it paints them with random paint, and spins them in rando
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Since it is a telecom experiment, the Bell 202 inequality is the most appropriate.
Finding the few thousand good pairs out of the billions of bad is looking for a needle in a Hayes stack.
Re:And the other "valid" signal?? (Score:5, Informative)
Mods, before modding this up, be aware the poster(s) posts the same misunderstood garbage to nearly every Slashdot story involving anything quantum mechanics related. The poster fundamentally misunderstands entanglement experiments and the variety of possible setups that have been in use for decades now. Yet the poster always disregards any detailed and/or cited reply showing how wrong it is, while taking time to attack others replies that are less intelligent and acting as if that validates their armchair disproof of quantum mechanics. Mean while, those with backgrounds in the subject realize it is a waste of time trying to correct the same mistakes when it gets spammed on so many articles, and yield not because the parent is correct, but because the parent has too much free time and is too dense to argue with.
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Don't play on his level--don't post AC.
Re:And the other "valid" signal?? (Score:5, Informative)
The satellite generated entangled photon pairs, sending them down to two separated ground stations in the Himalayas.
One out of every 6 million pairs was received properly (how they could tell, I don't know. Time codes?). Polarization measured at each ground station and correlated (via normal phone or perhaps Internet). Correlation was nonrandom due to Bell's Inequality, demonstrating that entanglement survived the transmission from space.
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Actual communication? (Score:2)
Did this include actual communication? How closer is humanity to having a working ansible?
I'm talking about the so-far science fiction device for instantaneous communication, not the open-source automation engine.
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None of these experiments have actual communication faster than light.
https://en.wikipedia.org/wiki/... [wikipedia.org]
In physics, the no-communication theorem is a no-go theorem from quantum information theory which states that, during measurement of an entangled quantum state, it is not possible for one observer, by making a measurement of a subsystem of the total state, to communicate information to another observer.
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Oh Wikipedia said so? It must be an immutable fact...
No, it's not a fact, it's a theory. And the Wikipedia article isn't meant a definitive proof. It's a starting point to learn more about it. You are encouraged to check out the references at the bottom.
Quantum Entanglement != Instant Communication (Score:2)
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What interests me... (Score:2)
is that they're publishing it in Science.
Not an example of instantaneous communication? (Score:1)
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Nice result (Score:2)
"They were only able to recover about 1000 photons out of about 6 billion sent"
My cellphone provider's electrons also only achieve a similar result, judging by the quality of the talks.
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Um, actually, (Score:2)
Are 1000 out 6 billion distinguishable from random chance, or even useful?
Is it faster than light or not? (Score:2)
SHUT THE FUCK UP (Score:2)
"Quantum teleportation" is not teleportation. You cannot use entanglement to violate causality. You are not exceeding c.
STOP REPEATING THIS BULLSHIT.
Chinese Satellite Breaks Distance Record For Quant (Score:1)
That's a bit of pocket loss :p (Score:1)