from the new-toys-are-all-made-in-china dept.
China has launched a satellite that will beam entangled photons to base stations on Earth:
China has successfully launched the world's first quantum-enabled satellite, state media said. It was carried on a rocket which blasted off from the Jiuquan Satellite Launch Centre in China's north west early on Tuesday. The satellite is named after the ancient Chinese scientist and philosopher Micius. The project tests a technology that could one day offer digital communication that is "hack-proof". But even if it succeeds, it is a long way off that goal, and there is some mind-bending physics to get past first.
The satellite will create pairs of so-called entangled photons - tiny sub-atomic particles of light whose properties are dependent on each other - beaming one half of each pair down to base stations in China and Austria. This special kind of laser has several curious properties, one of which is known as "the observer effect" - its quantum state cannot be observed without changing it. So, if the satellite were to encode an encryption key in that quantum state, any interception would be obvious. It would also change the key, making it useless.
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For the first time in the history of quantum mechanics, scientists have been able to transmit a black and white image without having to send any physical particles. The phenomenon can be explained using the Zeno effect, the same effect that explains that movement itself is impossible.
The journal article is in Proceedings of the National Academy of Sciences of the United States of America (DOI: 10.1073/pnas.1614560114)
Wikipedia has an article about the quantum Zeno effect.
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Quantum Satellite Links Extend More Than 1,000 Kilometers
A space-based, virtually unhackable quantum Internet may be one step closer to reality due to satellite experiments that linked ground stations more than 1,000 kilometers apart, a new study finds.
[...] In 2017, scientists in China used the satellite nicknamed Micius, which is dedicated to quantum science experiments, to connect sites on Earth separated by up to roughly 1,200 kilometers via entanglement. Although those experiments generated about 5.9 million entangled pairs of photons every second, the researchers were able to detect only one pair per second, an efficiency rate far too low for useful entanglement-based quantum cryptography.
Now, the same researchers have achieved their goal of entanglement-based quantum cryptography using the Micius satellite. The scientists, who detailed their findings [DOI: 10.1038/s41586-020-2401-y] [DX] online in the 15 June edition of the journal Nature, say they again connected two observatories separated by 1,120 kilometers. But this time, the collection efficiency of the links was improved by up to four-fold, which resulted in data rates of about 0.12 bits per second.
The scientists employed two ground stations, in Delingha and Nanshan, in China. Each site had a newly built telescope 1.2 meters wide that was specifically designed for the quantum experiments.
To boost the efficiency of the quantum cryptography links, the researchers focused on improving the systems used to acquire, orient toward and track targets at both the satellite and ground stations. They also made sure to improve the receiving and collection efficiencies of the lenses and other optical equipment on the ground.
Also at New Scientist and NYT.
Previously: China's "Quantum-Enabled Satellite" Launches
China's Quantum Communications Satellite Beats Record
Unbreakable: China Doubles Down On Quantum Internet
Quantum Video Chat Links Scientists on Two Different Continents
Why This Intercontinental Quantum-Encrypted Video Hangout is a Big Deal
Related: Quantum Ghost Imaging Spy Satellites
(Score: 0) by Anonymous Coward on Wednesday August 17 2016, @02:25PM
I'm not a physicist but... (you know good stuff is coming now)
If a photon is both a particle and a wave, the latter behaving (conceptually) as waves of water
If I 'beam down' a photon
Doesn't that mean that the wave will cover a huge area on earth?
Now If observation of the wave 'collapses' the wave-function and basically makes the encryptors go "hnnggg... someone else is watching this, this is not secure" (basically the equivalence - if I understand correctly - of flipping a bit in a blob of encrypted data making the algorithm go "I can't decrypt this, something's wrong")
Wouldn't I be able to do a DoS this communication by just watching the wave anywhere on earth where the wave would hit?
Inquiring minds would like to know...
(Score: 2) by wonkey_monkey on Wednesday August 17 2016, @03:36PM
Doesn't that mean that the wave will cover a huge area on earth?
Nope. It'll be tightly focused. Has to be.
If it wasn't, for some reason, and you were able to detect a photon at some remote site, that wouldn't have been one of the ones that would end up being used in the encryption key anyway, as it woudn't have been received at the receiving station.
systemd is Roko's Basilisk
(Score: 2) by Capt. Obvious on Wednesday August 17 2016, @06:04PM
A single photon is both a wave and a particle. However, the spotlight from a flashlight is not a single photon/single wave. It is made up of tons of photons. In fact, one of the big concerns in this system is that multiple photons are sent for any given bit. Each photon can only be "read" once and cannot be reproduced (oversimplification, reproduction is accurate 50% of the time). But if you send 2 photons with the same bit, and I intercept one of them, then I can read that one and you cannot detect it.
You can DOS this communication by taking a similar laser, pointing it at the receiver, and turning it on.
(Score: 2) by maxwell demon on Thursday August 18 2016, @10:11AM
I am a physicist, so let me explain.
First: Yes, a wave spreads, but the spread can be controlled to a good extent. For example, a laser pointer emits a wave, yet if you pointed a laser pointer to the moon, you'd get a spot of merely 40 meters diameter. A satellite is much closer than the moon, so it should certainly be possible to limit the spread basically to the receiver.
Second: It is not really accurate to say that the photon is both a particle and a wave. Rather some of its properties are as we would expect particles to behave, and others are as we would expect waves to behave. But a photon is neither a particle nor a wave; it just shows behaviour we know of those. In particular, the wave-like behaviour only describes the probability of finding it at some place. So a photon you've found outside the receiver would not have found inside the receiver anyway, and therefore would anyway have been lost for key generation. So you cannot do a DoS attack that way. You could, of course, do a DoS attack by going in between the satellite and the receiver, but then it would probably be easier to just send your own photons to the receivers so that the entangled photons from the satellite no longer can reliably be detected.
Third: In typical quantum cryptography protocols, the photons don't transport the encrypted message, they are just used to generate a one-time pad that is then used to classically encrypt the message. One-time pads are provably secure (indeed, they are the only cryptographic method that is proven to be so), and all the quantum stuff does is to ensure that the pad is truly random, and that nobody but the sender and the recipient have the one-time pad.
The Tao of math: The numbers you can count are not the real numbers.
(Score: 2) by wonkey_monkey on Wednesday August 17 2016, @02:36PM
This special kind of laser has several curious properties, one of which is known as "the observer effect" - its quantum state cannot be observed without changing it.
It's not a quantum state that you need to observe, though, is it? - it's a classical one. To do so means collapsing the quantum state which (as I understand it) breaks the entanglement.
Once one measurement has been made on the photon, any subsequent measurements (unless they happen to be exactly the same kind of measurement, of which there is no guarantee) will result in uncorrelated results. The parties concerned will notice this (because they randomly make different kinds of measurement and only use the results where they happened to make the same measurement).
For that matter, can you even make the measurement without causing the destruction (absorbing) of the photon? Never been clear on that.
systemd is Roko's Basilisk
(Score: 0) by Anonymous Coward on Wednesday August 17 2016, @05:20PM
Like this won't make Denial Of Service the choice for horking up these "quantum secure channel" communications systems...
(Score: 2) by bob_super on Wednesday August 17 2016, @05:25PM
How would the satellite know whether the person observing the photon is legit or not?
I'm wondering whether China just launched yet another boring spy satellite, and just decided to distract us by trolling everyone...
(Score: 2) by Capt. Obvious on Wednesday August 17 2016, @06:07PM
There's an unencrypted side-channel. No secret information there, but (a) it is required to read the encrypted data and (b) it includes information from the receiver on whether the data was eavesdropped.
(Score: 3, Informative) by Capt. Obvious on Wednesday August 17 2016, @06:16PM
If you could, then this encryption would be worthless. It's postulated as impossible, but sometimes in physics that just means "not yet". There has been some announcements about the ability to do so, but they have the credibility of cold fusion: those who claim it's there/almost there are huckseters, and those who claim to be working on it but are serious are looking at career defining/decades long work/Nobels.
That said, because that would break this encryption wide open, I doubt the government of whomever discovered this would allow it to be published.
(Score: 2) by Scruffy Beard 2 on Wednesday August 17 2016, @08:07PM
According the the Quantum Eraser Experiment, you are allowed to observe, so long as you throw away the observation.
(Score: 2) by Scruffy Beard 2 on Wednesday August 17 2016, @08:10PM
Should have used pre-view :P
How the Quantum Eraser Rewrites the Past | Space Time | PBS Digital Studios [youtube.com]
(Score: 0) by Anonymous Coward on Wednesday August 17 2016, @10:13PM
The canonical (aka "Copenhagen") explanation is that, before a measurement has been made on the photon, it is in a nebulous superposition of states. For instance, if you're talking about polarization, it is in a linear combination of states where it has a probability of 0.5 of being in either state (just like Schrodinger's Cat). When a polarization measurement is made, the wavefunction "collapses" and the photon has a well-defined polarization. Now, since it was one-half of an entangled pair, that means the other photon's wavefunction colllapses and the other photon instantly gets the other polarization state. Here, when they say that its quantum state cannot be observed without changing it, they are talking about measuring one of its quantized states, such as its polarization or spin, which takes on discrete values (as differentiated from, say, its position). The "spooky action-at-a-distance" comes in when you consider how can the other photon ever know what polarization it is supposed to have because if nothing can travel faster than light, how can the information get from the measured photon to the other one?
You are correct in that once the measurement has been made, the state of the two particles have been fixed, and the fates of their QM states are no longer tied together. You cannot measure its state without affecting its QM state.
(Score: 2) by EQ on Wednesday August 17 2016, @04:30PM
Beecause by intercepting/observing it you change the state. OK. Then this makes it rather simple to deny service or jam, depending on what sort of access is needed to alter the observational status of the quantum pair.
*If* that is the case, then for anything other than a well hidden channel, this becomes far to easy interfere with to be reliable.
(Score: -1, Troll) by Anonymous Coward on Wednesday August 17 2016, @05:07PM
I have been an astrophysicist by profession for the past 10 years. This is neither a flamebait nor a troll post. Space does not exist the way space agencies want you to believe it does.
'Space' missions do take place, but most are underwater or in Antarctica. This light you see orbiting the Earth is no 'International Space Station'. Stalk it, and you will realize that it is self-luminescent.
This is a lot to take in, I know, but it is the truth. See for yourselves.
(Score: 0) by Anonymous Coward on Wednesday August 17 2016, @06:05PM
Looks like it turned out to be offtopic instead of flamebait or troll, so you're correct!
(Actually, very curious that it's at 0, offtopic. Who modded this underrated?)
I've seen the videos of these "bubbles." I've never seen bubbles behave as though the "water" doesn't have any turbulence from the man in the suit. This has to be quite simply the stupidest conspiracy theory I've ever come across. The electric universe one and the weather war one were much better. Please try to keep some level of quality with your next conspiracy theory. I do love a good conspiracy theory, but this particular one just plain sucks.
(Score: -1, Offtopic) by Ethanol-fueled on Wednesday August 17 2016, @06:07PM
Fact: they named that launch center after your White daughter's Black boyfriend. I hear she giggles and calls him "daddy" in front of you at family barbecues.
(Score: 0) by Anonymous Coward on Wednesday August 17 2016, @07:44PM
Oopsy. Seems like you forgot to tick your AC box, dear Ethanol-fueled. Maybe that #2792 ID influence of yours can retract the comment? (a.k.a. "Who's giggling now, bitch?)
Thank you SO MUCH for this opportunity to expose you for the shit commander that you are.
(Score: 0) by Anonymous Coward on Thursday August 18 2016, @03:15PM
I see you're new here. AFAIK, Ethanol-fueled does not believe in ticking the AC box. Unlike you, he proudly stands behind each and every of his trollish comments, and I salute him for that.
Troll long and prosper, Ethanol-fueled.