B Can Quantum Linked Signals Be Observed in Real-Time in Space?

Brad Jamison
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Can we send a quantum linked signal into space and be able to tell immediately whether or not it is ever observed?
 
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By "quantum linked system" do you mean one member of a pair of entangled particles? If so, the answer is no, there is no way of knowing whether the remote member of the pair has been observed, measured, or interacted with anything else in any way. Furthermore, the hypothetical remote observer won't even know that the particle is part of an entangled pair.
 
Welcome to PF!
We would know it was observed if we received a signal back...
 
No. We link the signal to a quantum affected action. Just like the old detector slits. Any observation of the signal will flag the event. Us looking for the flags is observation of the signals. So we do it in pulses. Send, check for flags, send again and so forth. I'm not sure that it matters when it is observed, just whether or not it is ever observed. Similar to the quantum communication systems that can flag whether or not a message has been observed prior to it's observation by the recipient.
 
Comeback City said:
Welcome to PF!
We would know it was observed if we received a signal back...
That takes too long.
 
Nugatory said:
By "quantum linked system" do you mean one member of a pair of entangled particles? If so, the answer is no, there is no way of knowing whether the remote member of the pair has been observed, measured, or interacted with anything else in any way. Furthermore, the hypothetical remote observer won't even know that the particle is part of an entangled pair.
I'm not sure about that. I think the problem is broadcasting half of these pairs out into the sky. Then we have to wait for any possible observations. What I'm saying is more real-time. (pun intended).
 
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Insights auto threads is broken atm, so I'm manually creating these for new Insight articles. Towards the end of the first lecture for the Qiskit Global Summer School 2025, Foundations of Quantum Mechanics, Olivia Lanes (Global Lead, Content and Education IBM) stated... Source: https://www.physicsforums.com/insights/quantum-entanglement-is-a-kinematic-fact-not-a-dynamical-effect/ by @RUTA
Is it possible, and fruitful, to use certain conceptual and technical tools from effective field theory (coarse-graining/integrating-out, power-counting, matching, RG) to think about the relationship between the fundamental (quantum) and the emergent (classical), both to account for the quasi-autonomy of the classical level and to quantify residual quantum corrections? By “emergent,” I mean the following: after integrating out fast/irrelevant quantum degrees of freedom (high-energy modes...
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