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> I accept that this coin-hypothesis has been disproved by people who actually knows what they're talking about. The classical idea is more like as follows: yo
by bowsamic 3y ago
> I accept that this coin-hypothesis has been disproved by people who actually knows what they're talking about.
The classical idea is more like as follows: you have a guy Charles who makes two letters each with a card in that has written on it either number 0 or 1, and gives one letter to Alice and another to Bob. Now, "entanglement" here is that if Charles writes 0 in Alice's letter he writes the number 1 in Bob's, and vice versa. Alice and Bob are also aware of this. This means that even at a distance, if Alice opens her letters and sees a 0, she knows that Bob's has 1 in.
For a long time, Einstein and co. through the "EPR paradox" (Einstein-Podolsky-Rosen) thought that QM would be something like this, but we just didn't know how to access the actual letter "in transit" yet, which they called an "element of reality". They were wrong.
It turns out that Bell's theorem basically says that in this situation the correlation between the two letters would be less strong than quantum theory predicts for entangled states, so this cannot be the full explanation.
Bell's theorem says you either need to give up the idea that there is no "spooky action", or give up determinism (no true "element of reality" that really holds what's going on), or you can retain both if you let go of another concept called statistical independence.
> Have an array of 8 particles at both locations. They represent measured/unmeasured rather than heads/tails. You got yourself a one-way single-use FTL byte.
You can't have a quantum state where something is the superposition of measured and not measured, this violates a fundamental postulate of quantum mechanics: that measurement "chooses" one of the states in the measurement basis. I think you touch on that later, in that you can't tell via entanglement if a measurement took place elsewhere, which is partly why we can't experimentally demonstrate a non-local theory yet.
Basically, it isn't that some signal is transmitted, it's that if they are entangled the states of each system cannot be independently known. That is, like in the letters example I gave: it can be either 0 for Alice and 1 for Bob, or 0 for Alice and 1 for Bob. Now, the reason why information is not transmitted is the same: Bob didn't know what was in his letter before he measured it, so it's randomly symmetric between 0 and 1, there is no information transferred. It turns out that this kind of symmetry between the two states tells you nothing that can be used to transmit information.
- vjerancrnjak 3y agoYes, Bell's theorem is such a strong result. 1. locality 2. (local) reality 3. statistical independence Only 2 can hold at once and there's consensus to have 1. and 3., with that we lose the hidden variables. Instead, having 1. and 2. hold would be so interesting.
- tsimionescu 3y agoIn some sense, MWI also gets rid of 3, though it's not commonly seen like that. Essentially in MWI any experiment has all possible results, so the concept of statistical independence jsut doesn't make sense. Either way, MWI is by far the most popular interpretation that is both local and realistic.
- jemmyw 3y ago> Bell's theorem says you either need to give up the idea that there is no "spooky action", or give up determinism Can you not also say that the determinism includes the observer, aka superdeterminism (which is just determinism because that would surely be global).
- bowsamic 3y agoThis quote from my post > or you can retain both if you let go of another concept called statistical independence. is superdeterminism
- ngcc_hk 3y agoThe key difference, unlike the usual sock example or your letter example, it is not about knowing. The superimposed quantum states have not been fixed. It is both colour or or letters or states at the same time all the time unlike it is measured. It is not the knowledge about a pre-existed, the individual state does not exist until measurement. That is the crazy part.
- bowsamic 3y agoYes they have, it's just that in quantum mechanics you can expand the state in different bases. The state still "exists" before it is measured, just in a non-separable superposition state (i.e. an entangled state)
- jacknews 3y agoI think it's more like 2 dice, which always land on opposite sides, so 1 and 6, 2 and 5 and so on. And then a measurement isn't just to land a die, but also to choose which axis to measure - ie ask the dice are you a 1 or a 6. The other die magically spins around to the same axis and gives the corresponding result. But I'm not sure this analogy is satisfactory and explains the 'spookiness' either.
- slfnflctd 3y agoI have a couple follow up questions. > a guy Charles who makes two letters So Charles at least knows the information on the cards. Are you essentially saying that there's no way for Alice or Bob to distinguish that information from 'background noise'? If so, that is not a great analogy other than to illustrate a historical & incorrect perspective. Which may have been what you were doing and if so is fine. > measurement "chooses" one of the states in the measurement basis Okay, say you 'do some entanglement of multiple particles stored in two separate tubes' where you know there is some kind of pattern in the entanglement. Is the issue that there is no way to know how to find that pattern without possessing both 'tubes'?
- bowsamic 3y ago> If so, that is not a great analogy other than to illustrate a historical & incorrect perspective. Read the next part, I was discussing the idea thought of by Einstein that was dismissed by Bell's theorem. > Okay, say you 'do some entanglement of multiple particles stored in two separate tubes' where you know there is some kind of pattern in the entanglement. Is the issue that there is no way to know how to find that pattern without possessing both 'tubes'? I'm not sure what you mean by this, can you elaborate?
- slfnflctd 3y agoWell, we know entanglement happens because of experiments. In those experiments, researchers had to somehow independently verify that the entangled states produced predictable results, thereby demonstrating the entanglement. If you set up the first part of experiment, wherein you know certain particles are entangled, would it be possible for someone on one side of that entanglement to read a pattern from that side alone (if they 'knew where to look') which matched a pattern on the other side? At this point, if my question even makes sense, we're only talking about a very impractical method of data storage... I'm just curious whether even that is possible.
- Arelius 3y agoSure, you could read the pattern on he other side, you could been use of as a one time pad to encrypt data you actually cared about