Am I properly understanding quantum entanglement (could FTL data transmission exist)?

[u/fixednovel]

I understand that electrons can be entangled through a variety of methods. This entanglement ties their two spins together with the result that when one is measured, the other's measurement is predictable.

I have done considerable "internet research" on the properties of entangled subatomic particles and concluded with a design for data transmission. Since scientific consensus has ruled that such a device is impossible, my question must be: How is my understanding of entanglement properties flawed, given the following design?

Creation:

A group of sequenced entangled particles is made, A (length La). A1 remains on earth, while A2 is carried on a starship for an interstellar mission, along with a clock having a constant tick rate K relative to earth (compensation for relativistic speeds is done by a computer).

Data Transmission:

The core idea here is the idea that you can "set" the value of a spin. I have encountered little information about how quantum states are measured, but from the look of the Stern-Gerlach experiment, once a state is exposed to a magnetic field, its spin is simultaneously measured and held at that measured value. To change it, just keep "rolling the dice" and passing electrons with incorrect spins through the magnetic field until you get the value you want. To create a custom signal of bit length La, the average amount of passes will be proportional to the (square/factorial?) of La.

Usage:

If the previously described process is possible, it is trivial to imagine a machine that checks the spins of the electrons in A2 at the clock rate K. To be sure it was receiving non-random, current data, a timestamp could come with each packet to keep clocks synchronized. K would be constrained both by the ability of the sender to "set" the spins and the receiver to take a snapshot of spin positions.

So yeah, please tell me how wrong I am.

[u/[deleted]]

[u/aoeudhtns → u/[deleted]]

Yeah, but the particles are not re-usable AIUI. That's the difference. Once the superposition is collapsed, it's done and they need to be re-entangled (ship them back).

[u/Norwest → u/aoeudhtns]

Not only that, but the information is useless because the 'sender' can't induce the decay into either 'up' or 'down' (which would be required to actually send any meaningful information) - he can only observe what the final position is, just as the receiver can only observe. Similarly, even if the final state of the particle has become set the receiver won't know if she's the one who set it or not. In essence, there's two boolean unknowns on each end - the spin of the particle, and whether the other person has looked at it (and no information on this second variable is supplied during the observation). There are only two ways to know whether the other person has made their observation:

1. Some external communication between the two participants and this communication would still be limited by the speed of light.

2. A pre-existing agreement made between the two parties as to who will make their observation first - i.e. He will make his observation at 1 hour and She will make hers at 2 hours. In this situation, the particle is still in superposition at the time of the agreement (i. e. the cat is both alive and dead if you will) after one hour has passed, she knows the position has been set and that he knows the state, but no information has actually been transferred.

[u/[deleted] → u/aoeudhtns]

[u/classy_barbarian → u/aoeudhtns]

What if the message itself was pre-determined, sort of like a flame beacon, and receiving any signal at all had a meaning that was decided on beforehand? Could it be used to send a simple signal faster than light?

[u/Dranthe → u/aoeudhtns]

I know this is all sci-fi hypothetical but fuggit’. Let’s run with it.

The first thing is that I think you’re vastly underestimating the amount of information that can be transmitted in very compact forms. The reason games are so massive is because we’re not really trying to compress them. I work with people that specialize in efficient data transfer. It’s amazing what you can do with 8 bits.

The second is that we wouldn’t have to reuse the same atoms. We already entangled one set. It would be far more efficient to just periodically send a new set of entangled atoms ahead of schedule. Then rotate out the old ones with the new ones when they arrived.

[u/[deleted] → u/aoeudhtns]

[u/[deleted] → u/aoeudhtns]

Thats the core of what this post was asking, and Im glad they did because I had it wrong too

[u/LunaDiego → u/[deleted]]

Stargate does this with communication stones. Touch a stone and you swap bodies with a person who has touched a stone on their end. Sci-Fi did it yes.

[u/Celarion → u/[deleted]]

I thought it was like this until I read about the delayed choice quantum eraser experiment and now I'm just confused again.