From the article: they are planning to do this, and hopeful that it will work. Not actually using it yet.

Also, if they got it to work they would surely keep it secret.

Also, if they didn't get it to work they would surely keep it secret.

Yes, and if the military was involved at all, they wouldn’t even talk about the possibility.

Yea, you have to explain this. It made no sense when I first read it, and it still makes no sense.

Here is how radar works: You shine a flashlight somewhere. If there is an object within range, some of the light is reflected back at you and you know there is an object. This is literally what radar does.

So, what part of this, and how, does this "quantum" magic affect?

Think of the quantum state as another measurement to make on the incoming signals. The receiver already measures many characteristics of incoming waves, like frequency and amplitude, and now it has yet another measurement that can be helpful. It's helpful specifically because they kept a reference wave with the same quantum state. With more data you can get higher fidelity which means you can perhaps see further or see the same distance with less power.

It works like normal radar, except that they send one entangled photon towards the plane and keep the other.

When the reflection returns, they can use the entanglement to sort out signal from noise much better and radar is safe from jamming and spoofing.

Thanks, this helps a lot, but just to clarify:

Originally "We 'shine' a bunch of photons at an object, and see if they come back. Except there could be dragged decoy spamming photons back at us, and we don't know if there is. Or it could be sending out so much light, our photons coming back are lost in the mix."

With quantum: "We can verify that any photons that get reflected are the ones that we sent out and check only our photons when flooded with photons from enemy flashlights."

Right?

Right. Oversimplifying a lot, it's putting a name tag on the photons. Then you can sort out the tagged ones from all the others, drastically reducing the practical noise floor.

Except that photons don't have tags.. Each time a story talk about entanglement, I'm stuck: what does it mean experimentally to verify that two particles are entangled? I don't know..

Interesting. Is generating entangled protons so trivial that this is feasible now?

It seems like it would take millions (more?) of entangled protons per second to achieve this. And then these can be sensed, verified, and measured at such speed that it could be used as radar?

It sounds far fetched, but I would love to know if this process is already that quick and easy.

I understand the core concept of quantum radar but does it actually work in practice as a radar? i.e. you can resolve targets with a small range and angular resolution.

Theoretically you would combine the new tech with the old tech. Quantum state would be another measurement to make on the incoming wave on top of measurements like frequency and amplitude.