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FTL communication using quantum entangled particles.
https://www.esa.int/Enabling_Support/Preparing_for_the_Future/Discovery_and_Preparation/ESA_takes_steps_toward_quantum_communications
Not possible; entanglement collapse can't be used to send information
The idea is this:
2 particles are quantum entangled. Whatever happens to one instantly happens to the other regardless of distance.
So you establish a state that means "0" and a state that means "1" and you can send binary.
At a minimum, you have quantum Morse code.
If you change one of the particles it just breaks the entanglement. If you measure one, then you instantly know the state the other will have when measured, but the result of your measurement - and therefore the other one also - is random. The only way to correlate the two measurements of the two particles is to send the results (at C or slower) to the same place and compare them. Otherwise each just looks like a random result.
(I know nothing about this)
Could you to the sub-C measurement test enough times to show that it just empirically works, and then use it on that basis? Or are you saying that the sub-C measurement would prove that it doesn't work (and it produces random noise)?
I'm not sure what you mean by 'use it on that basis'. Yes, entanglement has been proven to work, but it can't be used to communicate FTL.
Read the link posted. They already did it. In 2007. At a distance of 144km.
I read it. Doesn't mention FTL, because that's not a possibility for actually transmitting info.
Edit: I think the way these quantum encryption systems work is that basically the photons (and I assume it's polarization being measured) become the encryption key to a message that is sent conventionally.
Like the sender generates a bunch of entangled photons, sends the paired ones to the recipient, measures their photons and uses the results to encrypt the message, the receiver measures theirs and gets the same results, the sender sends the encrypted message over email or whatever, and the recipient has the same key because of entanglement.
Meanwhile an eavesdropper measuring the photons would mess them up for the recipient so the message wouldn't decrypt.
I'm familiar with quantum entanglement. It doesn't work because you have no way of affecting which state you'll measure, and thus what state the other particle will be in.
Read the link posted. They already did it. In 2007. At a distance of 144km.
No they didn't, they sent a conventional signal that was encrypted with an entangled particle. Nothing was sent ftl, this is like if I had two boxes that I know have the same thing in them, an encryption key, and traveled across the world, and sent you a message, you have the other box, the information in that box didn't go ftl you just opened it later.
there is no path to ftl communication here.
have a basic video on the topic: https://www.youtube.com/watch?v=9oBiS_Yb9Ac
The FTL is the sci-fi component that is the subject of the thread, the quantum entanglement communication part is the real world piece they actually got working.
It will never be possible to use this for ftl communications. This is like saying in 100 years we will use very long steel rods to communicate ftl by pushing on them. The problem is fundamental.
That wasn't FTL
That's not the part you were trying to say couldn't be done. ;) You were trying to argue that quantum entanglement couldn't be used to communicate, clearly it can.
The FTL bit is the science fiction premise of the thread. ;)
That is indeed that bit I was saying couldn't be done. Entanglement alone can't be used to communicate; a signal has to be sent conventionally over the distance.
The FTL bit is physically impossible, so it's not really "achievable in a reasonable time-frame"
This you?
That's exactly the part they DID get working.