B Quantum radar and its implications

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I dont know, whether the above sources are reliable, or not, that is why i ask.

"Quantum radars involve pairing photon particles together, shooting one downrange while keeping the second captive for observation. The downrange particle will act in a certain manner as it bounces off certain objects, behavior that can be observed in the captive particle. The result is much more detailed information about the target than seen in previous radars. "

This is from the first article. What makes it really fantastic for me, that as far as i know, we cant use quantum entanglement for FTL signalling, since the effect is unobservable directly, we can be only sure what happened, when we compare results of the endpoints of entanglement.
But the above part implicates for me, that actually there is a way to observe something has happened to the entangled pair, with only a measurement of the emitter.


That third link also about that possibility, if i understand correctly.

Of course i can totally misunderstand theese parts, but in this case, what makes that quantum radar and imaging any superior to existing methods?
 

Strilanc

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But the above part implicates for me, that actually there is a way to observe something has happened to the entangled pair, with only a measurement of the emitter.
The photon sent downrange has to (conditional on an object being present) bounce back and get combined with its partner in order for the process to work. There's no FTL signalling going on.
 
804
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The photon sent downrange has to (conditional on an object being present) bounce back and get combined with its partner in order for the process to work. There's no FTL signalling going on.
I also thought about that, but then how it gives any more information than simply measure the phase of the reflected photon? What is the point of entanglement?
 
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I try to write down my thoughts without saying that its high time to rewrite physics books, or saying that i am the expert of the field, instead of simply a curious one.

I have the analogy of black boxes with dice in it.

So classic example of entanglement is like, we have two boxes with entangled dice. We turn one box upside down, open the boxes, and voila we see the same numbers. The problem is, we break entanglement when we open the boxes, so we cant use this for signalling, we cant tell, whether the other one turned the box or not.

Now, we have a box, send out entangled pairs to an object. We receive some dice, either the ones we sent out and reflected, or from a random noise.
So we compare the ones in the box, and what we received. If we dont know anything about what should be in the box, how does it helps us? How it help us to compare two random set of numbers showed by the dice?
Does the numbers of the box have any clear pattern? In this case cant we make a difference between a clear pattern (like most numbers are 1, or even) and a random set of numbers if the other party shaked the other box with the entangled pairs?
 

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