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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."
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.
If I'm reading this correctly, the exact same technology also enables faster-than-light communication.
Yep.
And if you can fling things around fast enough, faster-than-light communication enables future-to-past information transfer.
Bye, bye, grandma. (The grandfather paradox, female version, doesn't suffer from the "but it turns out grandpa was a cuckold" loophole.)
Fortunately for those of us who depend on causality for countinued existence, Bell's theorem says the radar doesn't really work.
(Though one that passes entangled photons past both sides of the plane, then measures their interference, might in principle detect the plane without exposing it to the photons. THAT one doesn't violate bell, lightspeed, or causality, but is pretty spooky.)
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
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!
It detects the plane if you don't look at the radar screen
Some drink at the fountain of knowledge. Others just gargle.
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.
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
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.
If a country believes that war is likely or inevitable, it is better to hide their capability so enemies are unprepared.
If a country is primarily interested in deterring war, it is better to advertise new capabilities so enemies are intimidated.
Historically, America has tended to follow the first strategy, and keeps new developments secret.
Most of America's adversaries have tended to follow the second strategy. During the Cold War, Russia often tried to look stronger than they really were. Today, China does the same.
That's not how entanglement works. Maybe they are using some other kind of quantum effect. But entanglement actually does work instantaneously, faster than light. It just works in such a way that you cannot use it for communication. If you measure the particles at both ends, you will get the same result instantaneously (while you can prove that the decoherence occurred at that exact moment, not earlier, and therefore some kind of "information" must have traveled FTL) but you have no control over that result, and you cannot tell whether or not the other party made a measurement. So you cannot use it to send a message.