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China Says It Has Developed a Quantum Radar That Can See Stealth Aircraft (digitaltrends.com)
An anonymous reader quotes a report from Digital Trends: At a recent air show in the city of Zhuhai, state-owned Chinese defense giant China Electronics Technology Group Corporation displayed what it claims to be a quantum radar that's able to detect even the stealthiest of stealth aircraft. The company claims to have been working on the technology for years, and to have tested it for the first time in 2015. In principle, a quantum radar functions like a regular radar -- only that instead of sending out a single beam of electromagnetic energy, it uses two split streams of entangled photons. Only one of these beams is sent out, but due to a quirk of quantum physics both streams will display the same changes, despite being potentially miles apart. As a result, by looking at the stream which remains back home it's possible to work out what has happened to the other beam. According to a brochure from the China Electronics Technology Group Corporation, the new quantum radar could "solve the traditional bottleneck [of] detection of low observable target detection, survival under electronic warfare conditions, [and] platform load limitations."
They wouldn't admit this to the world if they really had it, and it really worked. Sounds like another Chinese hack to me.
A beam seems like a really inefficient way of searching for something in 3D space. Also, if only one beam is sent out what happens to the second entangled beam? Photons aren't known for sitting still.
I'm fairly certain entanglement is incredibly easy to break. While you can, in practice, beam stable entangled photons to a satellite, requiring enough going sideways through the atmosphere to then bounce off an object to then be read out without breaking the majority of entanglement seems unlikely. It's hard to enough to maintain entanglement in the extremely isolated confines of a quantum computer, just flinging it out into the atmosphere seems a lot harder?
Dwave also has developed a 1000 qubit quantum computer. And Musk is building a hyperloop tunnel system and a Mars colony. And soon we will have AI and self-driving cars. We live in exciting times, my friends.
Awesome, so this disproves bell's theorem and thus re-writes the laws of WM as we currently understand them.
Or at least the simplified description of this does. perhaps the real process is different.
Bell's entanglement experiment results in a rather cool result that even though one can have spooky actions at a distance, you cannot use it to transmit information. That is you can if you compare results at each end see that there was a measurement induced correlation in the photons but you can't determine this from the statistical distribution of measurements at either end by themselves.
Thus you can't possibly see the aircraft in the local beam due to changes in the remote beam.
Some drink at the fountain of knowledge. Others just gargle.
That isn't how quantum entanglement works. China Electronics Technology Group Corporation is betting that readers are stupid or ignorant or both. That's a relatively safe bet, too.
The radar might still work, since there are other ways to design good radar.
If I'm reading this correctly, the exact same technology also enables faster-than-light communication.
They had a similar story last year, and the year before. It's not true. If it was, the last thing they would do is tell everyone that they can see stealth plans (or at least how they did it so it could be duplicated/nullified.) But it's not true. It's designed to impress someone, I'm not sure who.
Your ad here. Ask me how!
yes it is what Bell's theorem shows.
Here's how. Bell's theorem requires acting on the entangled pair in a way that will change the pair relationship. If you simply force one of the particles to a specific state then it breaks the entanglement and the other particle becomes independent. (thus no FTL info). And if you act on the entangled pair, then when you measure the local particle's state you also break the entanglement (thus no FTL).
here's a layman's description:
https://www.forbes.com/sites/c...
Some drink at the fountain of knowledge. Others just gargle.
First photos revealed.
When all you have is a hammer, every problem starts to look like a thumb.
First let's not argue what or what not is in Bell's theorem given that we violently agree that you can't transmit information faster than the speed of light.
THe work surrounding bell's theorem seems to establish two things
1. state changes can be transmitted faster than the speed of light (as we both agree)
2. That the nature of the state changes cannot transmit information faster than the speed of light (I aver and I think you agree).
So however you want to state it, information can't be transmitted the way that was described in the article.
Some drink at the fountain of knowledge. Others just gargle.
It detects the plane if you don't look at the radar screen
Some drink at the fountain of knowledge. Others just gargle.
PLA: We have not been able to figure out how to make stealth aircraft. We know our currently illegal expansion into the South China Sea will result in conflict in the next few years, with aircraft we cannot see. And our enemies will be able to see everything we have. So we have to figure out a way to make them think we're on equal footing, at least in terms of seeing aircraft, so they will delay stopping our imperial march through Southeast Asia.
Browsing at +1 - no ACs, I ignore their posts. So refreshing!
The article gives a pretty poor, if not outright wrong, explanation of what quantum radar is supposed to be. The idea behind quantum radar is that the microwave signal sent out by the radar system is first generated by one half of an entangled photon beam, and this is done in a way that maintains the quantum state as the photon beam is converted into a microwave signal. When the microwave signal returns after bouncing off a target object, the system is then able to use a comparison to the other half of the entangled photon beam in order to filter out any background noise. This would prevent an enemy from being able to using signal jamming to interfere with your radar. It would also make it easier to detect a stealth aircraft because no stealth aircraft is 100% invisible to radar, and quantum radar would, in theory, be able to pick out very small radar returns, that would normally be lost in the background radiation.
If China is claiming the technology to " see " stealth aircraft is now a reality, why are they still spending big $$$$ on building stealth aircraft ?
China is fixated on image. They took that whole " fake it till you make it " saying to heart and desperately wants the entire planet to believe they are the most amazing, powerful and capable country in history.
It should be noted the term " Paper Tiger " originated in China. They should be all too familiar with what it means since they are basically the very definition of the word.
There are three parts to their claim and they're all pseudo-babble junk:
1. A "stream of photons" can detect a stealth aircraft from some useful distance
2. Photons can be entangled on the fly (in real "stream" speed)
3. The entangled stream at home can be analyzed on the fly (same speed)
1.
Can photons be entangled? Sure. Can they be entangled at the speed of light such that a "stream of photons" (going out sequentially at the speed of light) are all entangled... possibly, but not with current technology and not with 2015 technology.
Think of it this way... physicists spend days setting up a quantum entanglement experiment where they entangle ONE or even TWO and sometimes FOUR (http://iopscience.iop.org/article/10.1088/1402-4896/aa736d) photons. To entangle enough to create a "stream of photons" and then sweep the skies two or three dimensionally for stealth aircraft is orders of magnitude beyond current tech.
2. It takes experiments ages (in photon time) to get photons entangled. Our primitive tools (electronics) uses electrons in a wire, which are slower than photons in air or in vacuum. Our tools simply cannot hammer these fast-moving nails fast enough... so what we do is fire a crap-ton of nails at our slow moving hammer and hope we can hit one into the other into the detector.
3. See #2. We don't have the speed with our slow-moving tools to analyze a photon stream.
I'm calling physics bullshit.
Ehud
Actually I remain unconvinced of the impossibility of transmitting information faster than light - all the proofs I've seen all rely on assumptions which seem overly conservative to me. Not that I'm expert enough to fully understand the proofs, but I'll trust the experts when they say "these are the assumptions this proof depends on"
--- Most topics have many sides worth arguing, allow me to take one opposite you.
China both has and does not have a quantum radar.
They won't know until they open the box.
We've got quantum BLOCKCHAIN radar. It not only detects stealthy aircraft, it can detect aircraft you don't even have but wish you did.
Don't disappoint your bird dog. Go to the range.
Harnessing that fact to transmit classical information faster than light is a completely separate question. But nobody is claiming that is happening here.
That is exactly what the summary is claiming is happening:
As a result, by looking at the stream which remains back home it's possible to work out what has happened to the other beam.
That is precisely what you cannot do: examining the photons you have doesn't tell you any information about what has happened to the photons you sent out, the only "information" it gives you is (basically) the what the state the photons you sent out will be if they haven't interacted with anything (you don't, however, know if they have interacted with something or not). Since the point of radar is to interact with whatever you're looking for, that makes it rather pointless.
Note that a "quantum radar" could maybe improve on classical radars by comparing reflected photons to give you more information about what exactly reflected them, but it's still only useful if you get some of the photons you send out back. Even then I doubt you could actually make such a system (I'm not entirely sure it's physically or even theoretically possible). I am sure, however, the Chinese don't have such a system: they would never publicly disclose it if they did. The only reason to brag about it's existence is to either convince other countries to waste time trying to replicate it, or to convince them their stealth fighters will be useless against the Chinese. Either way, it's a purely psychological move.
"None can love freedom heartily, but good men; the rest love not freedom, but license." --John Milton
The article's description is flat our wrong. The idea behind quantum radar is that the photons used to generate the microwave signal are first entangled with photons that are kept inside the system, and then when the system receives returning microwaves, it's able to compare them to the entangled photons and filter out background noise and enemy jamming signals. The filtering out of background noise is what in theory would allow quantum radar a greater chance to detect stealth aircraft, which normally rely on background noise to obscure their small radar cross section. That being said, just because the Chinese say they've invented it, obviously doesn't mean they have. In fact, I would guess if any major power does develop a working quantum radar, they'd keep it secret.
In particular, the quantum radar does not claim any FTL nonsense. A beam is sent out, and reflected from the target. A very weak reflection, in case of a stealth plane. The quantum radar is not faster, it is merely able to see that extremely weak reflection because it is not hampered by background noise (natural microwave noise or electronic warfare jammers).
Read the wikipedia article on quantum radar. The principle is so old it has a wikipedia page - the only "new" here is that China claims they have a working device. I would guess some others have these devices too, but are quiet about them.
Even if I'm wrong, I'm 50% correct
Fucking millennials.
To have a right to do a thing is not at all the same as to be right in doing it
A breakthrough in basic physics would also be helpful because the energy cost of producing a muon is 6 GeV while each D-T fusion yields .0176 GeV of heat and is captured by a helium nucleus on average once per 1-200 reactions. Generating electricity costs another factor of 2.5, so the energy gap is nearly an order of magnitude.
Store muons? I think that's a fanciful embellishment of your own, and thank you for explaining the length of a microsecond.
When all you have is a hammer, every problem starts to look like a thumb.