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As a forward, I'm no a physicist or a student of it. In fact I'm pretty ordinary. So if I mischarecterize some concepts, bear with me.

So I was reading up on some of the new technologies and then I had a moment. I am wondering if you could use quantum entanglement to transmit data across a vast distance, theoretically even light years, in an instant. I was debating this in a youtube clip where there was a whistle blower from the antarctic and they were speaking on this.

My "opponent"(I guess?) Stated that measuring any entangled particle removes the connection, but quantum computers can use gates that flip an electron spin without disrupting the connection. Another objection was multi light year transmission, but I thought that should be fine since according to the theory, it's instant, no matter the setting.

So basically I'm wondering with the current tech that we have, technically couldn't we set up an experiment to send a byte of data via quantum entanglement by changing the state of an electron, using a gate to measure it on the other end, and translating that to a binary digit?

In other words, do we have Faster-Than-Light communication on the horizon?

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  • $\begingroup$ So basically since the quantum bits can't actually be a one to one send and receive, couldn't we encode the transmission to repeat the send multiple times with the same or slightly different info so that the receiving end can "ungarble" it? $\endgroup$ Commented Aug 15, 2023 at 3:22
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    $\begingroup$ You can't transmit data using entanglement, no Faster-Than-Light, no Slower-Than-Turtle. $\endgroup$
    – kludg
    Commented Aug 15, 2023 at 3:45

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Entanglement lets you become aware of the state of a location that is arbitrarily far away but it does not allow for communication. This can be treated classically suppose I promise you that either there is a (red ball, blue ball) in 2 boxes or a (green ball, green ball) those same 2 boxes (each box contains 1 ball).

Now I hand you a box and I travel very very very far away over centuries. We become light years apart. When you open your box you can “instantaneously” know what is in my box but in order to signal you need to be able to control to some degree what the outcome of my box is.

This unfortunately you have no way of doing without sending some kind of signal.

But quantum signals seem like they can do more. After all an entangled state between two points can remain entangled after applying a gate at each point (but how did they know which gate to apply? They either agreed ahead of time or both managed to communicate before applying it)

Quantum computers can also measure if a qubit has been measured before it arrives at its final destination. (Again this is less useful than it seems because it says ONCE you receive the qubit (say as a photon) you can check if it was measured along the way but this didn’t let you receive it any faster/allow for measurements that weren’t physically following the photon).

So now to your example, all that could be done is that we make that electron entangled system $e1, e2$. Then the person on one end applies a gate to their electron $g(e1), e2$ and the person on the other end is not aware of it unless they work together so no FTL communication happened here because simply no communication happened here. If they work together by either agreeing on a protocol or exchanging information to maintain the entanglement then it’s obvious nothing FTL has happened either because they already agreed on a protocol or traded information back and forth using light or electric signals to maintain that entangled state.

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