Entanglement: How Does it Work and Its Implications in Everyday Life?

[zonde]

And entanglement has to be explained as something else than what seriously conflicts with with established theories (FTL communication).

Where do you see serious conflict with with established theory? If entanglement is explained using FTL coordinated changes of quantum phase it does not lead to FTL communication. Absolute phase is unobservable but to observe relative phase you have to compare both ends. There is no way how you can use quantum phase to communicate FTL. And quantum phases are out of scope of relativity so it says nothing about them.

 

[anothergol]

Where do you see serious conflict with with established theory? If entanglement is explained using FTL coordinated changes of quantum phase it does not lead to FTL communication. Absolute phase is unobservable but to observe relative phase you have to compare both ends. There is no way how you can use quantum phase to communicate FTL. And quantum phases are out of scope of relativity so it says nothing about them.

No I'm not talking about "third party message communication" FTL, but about that "coordination" itself. Simply stating that the changes of phase are coordinated is stating the observation, it's not interpreting it. Such a coordination, if we accept that it exists (because it doesn't seem to have to in Everett's theory), requires FTL communication, or something else like a shared property in another dimention, but in any case it requires something. If entangled particles are -really- linked, and that link can't be made through space because it would imply it's FTL, then it's made from something/somewhere else. Well sure you can say "it's the way it is, just accept it" but that sounds a little religious to me.

 

[zonde]

No I'm not talking about "third party message communication" FTL, but about that "coordination" itself. Simply stating that the changes of phase are coordinated is stating the observation, it's not interpreting it. Such a coordination, if we accept that it exists (because it doesn't seem to have to in Everett's theory), requires FTL communication, or something else like a shared property in another dimention, but in any case it requires something. If entangled particles are -really- linked, and that link can't be made through space because it would imply it's FTL, then it's made from something/somewhere else.

Yes, this "coordination" requires FTL physical process. But where is this "serious conflict" with established theory (not interpretation or arbitrary extension of that theory)?

 

[anothergol]

Well define "process". Speed of light is supposed to be the speed of causality, and here you're describing a causality.. happening instantly.
Perhaps speed of causality is an interpretation, but it seems to be the way it is, what else violates it?
Seems simpler & safer to reword entanglement as not being a coordination, since it doesn't need to be. It has been established that it wasn't a local hidden variable, but that doesn't go against the idea of multiple universes.

 

[zonde]

Well define "process". Speed of light is supposed to be the speed of causality, and here you're describing a causality.. happening instantly.
Perhaps speed of causality is an interpretation, but it seems to be the way it is, what else violates it?

Yes, I agree that it is in conflict with our experience. But I do not agree that it is conflict with established theory.

Seems simpler & safer to reword entanglement as not being a coordination, since it doesn't need to be.

Go ahead, try to do that. This is the topic of this thread after all.

 

[Ken G]

Entanglement isn't any less mysterious is Everett's interpretation. Remember, the guts of entanglement is that two particles can share a property like "same polarization" even when the polarization of each particle is completely indeterminate. It doesn't matter if your interpretation includes collapse or not, the bizarreness of that fact is still there. Indeterminacy doesn't go away in many worlds-- you just have more versions of scientists who cannot predict what they will see. If you have many worlds, you escape the need for the particles to yield a single seemingly random result in just one world, but you still have to explain why in every world where one particle passed a polarizer at some arbitrary angle, the other one did too. Tack on as many worlds as you like, that still requires interpreting the outcome of the observations. (As for virtual particles, that's a whole other can of worms you don't want to get into, so let's stick to entanglement.)

 

[anothergol]

Entanglement isn't any less mysterious is Everett's interpretation. Remember, the guts of entanglement is that two particles can share a property like "same polarization" even when the polarization of each particle is completely indeterminate. It doesn't matter if your interpretation includes collapse or not, the bizarreness of that fact is still there. Indeterminacy doesn't go away in many worlds-- you just have more versions of scientists who cannot predict what they will see. If you have many worlds, you escape the need for the particles to yield a single seemingly random result in just one world, but you still have to explain why in every world where one particle passed a polarizer at some arbitrary angle, the other one did too. Tack on as many worlds as you like, that still requires interpreting the outcome of the observations. (As for virtual particles, that's a whole other can of worms you don't want to get into, so let's stick to entanglement.)

But isn't Everett's theory more deterministic?

but you still have to explain why in every world where one particle passed a polarizer at some arbitrary angle, the other one did too

ah, so that really implies that there is a link. A problem indeed

 

[zonde]

ah, so that really implies that there is a link. A problem indeed

Before attempting to solve the problem yourself you can try to look how others tried to do that. There are some references at the end of this article. In particular you can take a look at this reference (chapter 6.3).
It is attempting to make MWI local by introducing additional splits where future light cones meet. Well, because intersections of lightcones initially would be spacelike I would say you get ever increasing microsplits along this intersection and subsequent intersections. At the end you get very contrived mechanism that at single world level (if is conceivable at all in such a model) looks just like FTL coordination of outcomes.

 

[Ken G]

But isn't Everett's theory more deterministic?

Determinism isn't the issue with entanglement-- correlation is. All many worlds do is allow you to escape the question "which definite outcome occurs when you have an indeterminate state?", but the question with entanglement is "what maintains the tight correlation between polariation of two particles that can be widely separated even before the polarization angle is decided?" It's the nonlocality of the correlation that is the puzzle.

By the way, there are two very different flavors to "collapse" that often get confused. Let's take the case of two photons entangled to be in the same polarization state, but that state is indeterminate. You choose a random angle for your polarizer, and perceive both photons either going through, or not going through. The two different flavors of collapse happen in two steps-- first there is the "decoherence", which happens in any interpretation, it means that when you pass the photons through, the only realities that remain "coherent" are the ones where both photons pass through, and we perceive they both pass through, and where neither photon passes through, and we perceive neither photon passing through. What experiences destructive interference, so doesn't happen, is that the photons pass through, and we perceive them not passing through, and the inverse. The interpretations only kick in after that stage, when we wrestle with the issue of which of those allowed possibilities will happen, or will all of them happen. But the entanglement puzzle already appeared, which is how did the behaviors get bundled together in the first place.

ah, so that really implies that there is a link. A problem indeed

Exactly.

 

[bhobba]

Say those virtual particles are mathematical helps

That's exactly what they are. Specifically they are lines on a Feynman diagram which is just a pictorial representation of what's called a Dyson Series:
https://en.wikipedia.org/wiki/Dyson_series

They don't exist in the same sense as real particles.

Thanks
Bill