www.popularmechanics.com/military/resear...antum-stealth-radar/

I'm sure many of you have seen this already under some title revolving around "Chinese Quantum Radar Renders Billions of Dollars Worth of Stealth Aircraft Useless" and were appropriately terrified for a brief moment.

So now that we've all read the articles, let's turn to the real experts on the subject matter: us. What do you guys think?

I haven't yet gone so far in Physics as to delve in to quantum mechanics, but after Mass Effect 2 with the "quantum entanglement communicator" thing which gave them the ability to communicate instantaneously anywhere in the universe, I was intrigued by the concept and spent a couple minutes reading some Wikipedia stuff about it. If I remember correctly, in theory it's all 100% plausible, but the only issue is that once you modify one quantum-ly-entangled particle (however you say it) you break the entanglement. But for one instant, whatever you do to one particle is matched by its pair. So either you would have to have a whole bunch of these entangled particles on hand for further communication or you're done because the only known way to entangle a pair of particles requires them to be in close proximity. At least that was the level of understanding I developed from a case of mild interest prompted by a popular science-fiction video game. If you guys know this stuff better than I do, please correct me. In the case of this radar, I can see how it would work because you only need that instantaneous reading of a photon hitting some object and then you'll send a new entangled photon out with the next "sweep" of the radar to run in to that object again.

Compared with those supposed "stealth killer" lower-band radars that Russia likes to talk up, this does seem like a much bigger threat to the viability of stealth. There are still issues in developing it in to an airborne or ground mobile product just like with VHF, but by it's nature it seems like it could be a decent candidate for generating an engagement-quality track to actually attack the target you can now see, at least much better than VHF radar. Obviously if this was any semblance of a real threat to stealth aircraft today, they wouldn't be talking about it. Even if it proves to live up to the wildest of expectations, I doubt it will be making an impact for a few decades to come.

So, Vampyre, shadow, other subject matter experts, or kind-of-subject-matter-experts-hopeful like Sweeper: What's the story? Are we screwed in the foreseeable future?

It's all about the big picture; its not just Raptors/Lightnings/Raiders out there...

But hey, internet's gotta internet.

You can sleep tight

1)''Quantum radars defeat stealth by using subatomic particles, not radio waves. Subatomic particles don't care if an object's shape was designed to reduce a traditional, radio wave-based radar signature. Quantum radar would also ignore traditional radar jamming and spoofing methods such as radio-wave radar jammers and chaff.''
FALSE a photon is the same as a wave, the efects you'll get depends on the situation, this was stated by einstein's Wave–particle duality in like 1905 or something
So, something that doesn't reflect radar will not reflect photons, as theyre the same thing.

2)You can only look at an entangled particle once, so if you want to range something, you look at it and than [maybe] you know if it hit something. Ok, nice, how far was it? Well you don't know, as you can only run the test once, so you need to send different sets, making ranging much longer (like, once set of particles/distance resolution unit). And than, thatMs for ONE azimuth location, you have all the other altitude/azimuth combinations to go.
That is, assuming you can keep your photons in the planes without being absorbed to look at them and can control which photons you are looking at...remember photons go at 3*10^8m/s at all time.
And than, nothing tells you how you can know IF you hit something, that's above my comprehension, but I'd doubt it is precisefull, as everything quatum-based is HIGHLY based on probabilities.
And I also have no idea how you'd detect it, quantum particles usually share position, momentum, spin, and polarization, which cannot easily say if you've hit something. Even if it does, you are back to non-doppler/non-look down radar, as you cannot filter what's coming back.

I'll write more after I'm done BFM'ing

Sweep:
So what you're saying is you love the Super Hornet now?

lol

Obviously we're not depending on a 100% stealth-based fighting force to get things done, but we do have a significant dependence on stealth to carry out our more impressive abilities which we've grown reliant on to offset the need to invest greater numbers of people and aircraft in a fight. There's a definite hype-train element to it, but the reason behind it is a little bit better than average.

Ktulu:
The issue as I understand it here though is that with entangled photons, you're not relying on a reflection being bounced off of the object. Once an entangled particle bounces off an object, it will experience certain changes that can be indicative of the object it bounces off of and things like the direction and speed at which it travels. Those same changes are imparted on its matching entangled particle which stays back at the radar site and should be readily observed when it occurs. As far as ranging, I can only imagine it would be very similar as with radar in the electromagnetic spectrum by using a known velocity for the particle and measuring the time of flight.

Well, first off, if we assume that both particles will share momentum, I'm not sure how you can send one and not the other, as if you manage to stop the one that is in the plane, you should stop the other.
Also. Let's say the one particle stays in the ship, by the time the particle sent away hits something, it is sure that the first one will have hit a corner in whatever is holding it back, which should change the direction/charracteristics of the 2cd one, rendering the process useless.

Than there's the issue of removing the ground/mountains from the rest, which might not be possible, by simply analysing velocity [direction] change. Now, it is possible that the frequency of photons would change together, but I can't confirm that and its pretty complicated stuff at this point.

The problem that comes with ranging is that you have to know when to measure the photon's characteristics, which isn't possible, so you'd have to run a new ''photon check'' for each of the smallest resolution, for each of the smallest azimuth and altitude deviation. And than there's the problem of measuring the photon's state, which could be quite complicated on a larger scale if you are not doing the ''tests'' one by one. One by one taking much more time than a normal radar sweep, meaning you cannot target anything.

I'm not saying it isn't possible, but i'm saying that it's unlikely to have a working radar when we know/are used to work with entangled particles as much as we understood light in the 1800s.
Also, assuming it's possible, you have the whole problem of analysing data and all that would make the whole process restricted to VERY large SAM sites and would be as usefull as english radars in WW2 : Oh...someone's at the door!

Good point with the reverse engineering. Let's remember China recently bought ~30 Su-35 because Russia refused to sell them engines, so it is likely that if China cannot make something as ''simple'' (more like casual) as an engine, the odds of going into particle physics are low.

Yeah I was curious how they arrived at that "62 miles" figure too. Thought they might've used it with their P.O.S. J-20s, but they should know better. Chengdu stealth is crappy stealth. Never heard about them building a Nighthawk mockup.

www.google.com/search?q=62+miles+in+km&a...=chrome&ie=UTF-8

62 miles is 100km...That's how. It sounds a lot more interesting when converted don't it?

Hah. Good catch. But do you think it's a totally arbitrary figure rather than an actual result of testing? Could've rounded it off to a nice and propaganda-friendly number.

Note "Japan F-35 Roll Out" in recent news, too.

Ahh, (counter)propaganda...Gotta love it, eh?

Guess: they did some basic equations with some low-end RCS guesses and got something near 100km. Totally pulling from my "six" on that one, but it does seem quite plausible...

IIRC Eurofighter (or one of the Euro LM-equiv's) pulled the same crap a good six or seven years ago after some basic F-35 RCS modeling.

One other thing, remember that infamous F-35 10Ghz RCS estimate picture? The one that shows it's something like -15 to -30 DbSM without RAM head on (it fluctuates from 0-45 AON)? That came from China (one of their universities, actually).

I'm sure they, militarily, have decent means of figuring the design stuff out - All they're missing is the coat of "paint."

Without getting into any specifics, in the near term I wouldn't be too concerned with this quantum radar, lower band radar are much bigger threat to LO a/c, that and maintenance.