Quantum radar and its implications

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    Quantum Radar
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Discussion Overview

The discussion revolves around the concept of quantum radar and its implications, particularly focusing on the mechanics of quantum entanglement and its potential advantages over traditional radar systems. Participants explore the theoretical underpinnings of quantum radar, its operational principles, and the nature of information retrieval through entangled photons.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants question the reliability of sources discussing quantum radar and its workings, particularly regarding the implications of entanglement for information retrieval.
  • One participant suggests that quantum radar allows for detailed information about targets through the behavior of entangled photons, while expressing uncertainty about its superiority over existing methods.
  • Another participant clarifies that the process of quantum radar requires the downrange photon to bounce back and combine with its partner, emphasizing that there is no faster-than-light (FTL) signaling involved.
  • Concerns are raised about the actual informational advantage of using entanglement in quantum radar, with questions about how it provides more information than simply measuring the phase of a reflected photon.
  • A participant presents an analogy involving entangled dice in black boxes to illustrate the challenges of using entanglement for signaling and the difficulty in discerning useful information from random sets of outcomes.

Areas of Agreement / Disagreement

Participants express differing views on the implications of quantum entanglement in radar technology, with no consensus reached on whether quantum radar offers significant advantages over traditional methods. The discussion remains unresolved regarding the practical applications and benefits of entanglement in this context.

Contextual Notes

Participants highlight limitations in understanding the mechanics of quantum radar and the implications of entanglement, with unresolved questions about the nature of information derived from entangled photons and the conditions under which it may be useful.

GTOM
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https://www.popularmechanics.com/military/a28818232/quantum-radar/
https://www.asiatimes.com/2019/09/article/stealth-killer-quantum-radar-actually-works/?_=3274804
I don't 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 can't 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.

https://www.sciencealert.com/scient...d-direct-counterfactual-quantum-communication
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?
 
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GTOM said:
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.
 
Strilanc said:
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?
 
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 can't use this for signalling, we can't 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 don't 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 can't 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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