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Chinese Satellite Breaks Distance Record For Quantum-Key Exchange (sciencemag.org)
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.
Did they get the consent of the Tibetans before emplacing their receivers on Tibet's mountains?
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 random ways. There is no stastical correlation between spin and paint color and each parameter is totally randomly selected.
Sometimes a machine ejects two at the same time, I call these "entangled". They have the same paint as a consequence of being ejected at the same time from the same machine, and they have related spins because they were ejected at the same time from the same machine imparting the same spin.
I send Alice below ping pong balls from a group of these ball firing machines, if I get two at the same time of the same color. (My entangled ones). I keep one and tell her below that this one is a valid entangled ping pong ball. I tell her this "valid" signal via a more reliable link. She uses it to select the subset of valid ping-pong balls from invalid ones.
My ping pong ball machines pass a nice Bells test, as long as I prefitler so we only consider "entangled" ping pong balls.
If I go check my spin for these "valid" balls, I know that stastically significantly the spin on hers will correlate.
There is no quantum magic in my ping pong ball machine. It is doing exactly what you expect it to do. The act of filtering the subset of pingpong balls by properties likely to select ones ejected from the same machine at the same time, is what lifts the few events and makes them stastically significant.
Don't worry, a legal team won't help you anyway.
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.
As much as I love the idea of an ansible, and while I'm no physicist, I have seen it stated time and time again that quantum entanglement doesn't get you instantaneous communication.
is that they're publishing it in Science.
"I don't know, therefore Aliens" Wafflebox1
Absolutely, and free Tibetan Gerbils too.
Quantum teleportation is the even that's theoretically faster than light by way of being instant, regardless of distance, correct? Am I correct in thinking this is more of that a quantum entangled signal was transmitted in a waveform and they successful read the spin on roughly 1000 of the point resolved photons?
"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.
Are 1000 out 6 billion distinguishable from random chance, or even useful?
deleting the extra space after periods so i can stay relevant, yeah.
It's simply sending light from 1 satellite to 2 ground stations in form of key exchanges (duplicated messages in very few bits). And there are not any another vectors as the bidirectional communication.
It was made at night and without clouds, because the Sun and the clouds suppress these light's signals. All it is classical physic.
If a station loses the reception of this key then the another station might not know that the former station had lost this key. And it sounds a fatality.
It gives nothing special about quantum.
So they sent them to the space station and now a satellite and I think the space station one blew up on launch but have they determined yet if it's faster than light transmission? The theory is that you had to physically move the particles at least once away from each other so you can't violate causation or something like that. But has it been proven?
"Quantum teleportation" is not teleportation. You cannot use entanglement to violate causality. You are not exceeding c.
STOP REPEATING THIS BULLSHIT.
Bell's inequality is incomplete. It does not hold for all possible hidden variables. It holds only for those hidden variables that repeat under different experimental configurations (device orientations). But there are other hidden variables that do not repeat. Hidden variables belonging to the reals do not repeat. Every instance of a real random variable is unique. The probability of two instances being equal is zero, exactly zero. What this means for the Chinese news story is that nothing special has been demonstrated. It is expected that a local model based on real hidden variables will violate Bell's (and other) inequalities. Quantum entanglement has not been demonstrated by the Chinese project. Local entanglement can reproduce their results.
DGDanforth
The more chaff there is the harder for any decryption to find the real data.
Just a slight pocket loss there kek...