Quantum communication

[Sparko]

Please, please don't let him play!

gotta get my entertainment somewhere.

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I thought scientists have said that you can't use entanglement to transmit information faster than light though. So I am not exactly sure how this all works. Or maybe they figured out how.

[seer]

gotta get my entertainment somewhere.

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I thought scientists have said that you can't use entanglement to transmit information faster than light though. So I am not exactly sure how this all works. Or maybe they figured out how.

And I thought nothing moved faster than light.

[TheLurch]

It's not so much that they become the same particle, but it's as if they act as a single quantum system.

Let me use an imperfect analogy - think of the old steam trains, where the wheels are connected by solid metal rods.

There are two wheels that we can still identify and distinguish, but the rod makes them act in a coordinated way - it takes separate wheels and makes them part of a single system. That's roughly analogous to what entanglement does to two separated particles.

As for the other issue that comes up, we've tested entanglement at a variety of distances, and its action is always indistinguishable from instantaneous. The only residual doubt is due to the imprecision of our hardware. Note that, because the two items are part of the same system, that doesn't require anything to travel faster than the speed of light. Again, thinking of the analogy, it's like having one wheel on earth, one in space, but a long enough metal strut to keep them connected.

[seer]

As for the other issue that comes up, we've tested entanglement at a variety of distances, and its action is always indistinguishable from instantaneous. The only residual doubt is due to the imprecision of our hardware. Note that, because the two items are part of the same system, that doesn't require anything to travel faster than the speed of light. Again, thinking of the analogy, it's like having one wheel on earth, one in space, but a long enough metal strut to keep them connected.

Ok, but what is connecting these particles?

[Sparko]

It's not so much that they become the same particle, but it's as if they act as a single quantum system.

Let me use an imperfect analogy - think of the old steam trains, where the wheels are connected by solid metal rods.

There are two wheels that we can still identify and distinguish, but the rod makes them act in a coordinated way - it takes separate wheels and makes them part of a single system. That's roughly analogous to what entanglement does to two separated particles.

As for the other issue that comes up, we've tested entanglement at a variety of distances, and its action is always indistinguishable from instantaneous. The only residual doubt is due to the imprecision of our hardware. Note that, because the two items are part of the same system, that doesn't require anything to travel faster than the speed of light. Again, thinking of the analogy, it's like having one wheel on earth, one in space, but a long enough metal strut to keep them connected.

makes sense.

so what connects them across any distance? and what does it connect them through? some other dimension?

[oxmixmudd]

makes sense.

so what connects them across any distance? and what does it connect them through? some other dimension?

Subspace. How is it we've gotten to 2 pages on this without the mention of that. So we have transparent aluminum, communicators, and now subspace radio.

Jim

[TheLurch]

so what connects them across any distance? and what does it connect them through? some other dimension?

I said it was an imperfect analogy

The connection isn't physical so much as both particles obeying the rules of quantum mechanics. And, according to those rules, the ability of particles to act as a single system doesn't depend on the distance between them.

[Sparko]

Subspace. How is it we've gotten to 2 pages on this without the mention of that. So we have transparent aluminum, communicators, and now subspace radio.

Jim

awesome. We also sort of have replicators and don't forget warp drive is coming.

[seer]

I said it was an imperfect analogy

The connection isn't physical so much as both particles obeying the rules of quantum mechanics. And, according to those rules, the ability of particles to act as a single system doesn't depend on the distance between them.

No, that does not make sense. If we do something to cause particle A to change its spin then at that moment particle B changes its spin. Is that correct? If so how does particle B know what to do?

[oxmixmudd]

awesome. We also sort of have replicators and don't forget warp drive is coming.

The list is long. The motivation for the development of automated, sliding doors. At one point a vaccine injection system was developed that used compressed air. I got one of my school age vaccines with way. I thought it was so cool to get a shot using a device sort of like the one Bones used. The desktop computer, voice recognition. It would be interesting to look at all the ideas from star trek that either became reality or that have been seriously researched in an attempt to bring them to reality.

But I'm dragging the thread off point.

Of course the real driver for this technology is not the possibility of instantaneous communications, but rather the possibility of completely secure encrypted communications. That is why the Chinese government is willing to make the investment in the technology.

Jim

[JimL]

No, that does not make sense. If we do something to cause particle A to change its spin then at that moment particle B changes its spin. Is that correct? If so how does particle B know what to do?

Possibly because you are not the cause of particle A's changing its spin. Particularly if the change in particle A and particle B is simultaneous with your observation of them. It could be all determined, including your own observations and actions. Nothing has to know what to do if its all determined.

[seer]

Possibly because you are not the cause of particle A's changing its spin. Particularly if the change in particle A and particle B is simultaneous with your observation of them. It could be all determined, including your own observations and actions. Nothing has to know what to do if its all determined.

But we are the cause of the spin, that is why we are able to get the other particle to do what we want.

[JimL]

But we are the cause of the spin, that is why we are able to get the other particle to do what we want.

Well, keep in mind that I don't really know enough about it, but my thought is that if we are all part of the same system, and the system itself is determined, then we aren't really the cause of anything.

[Leonhard]

This 'effect' cannot be used to transmit information faster than the speed of light.

Tired and depressed, and this requires a bit much headroom and energy to write about. If I have a good sleep and I'm well rested I might write a longer post explaining what's going on.

[TheLurch]

No, that does not make sense.

If i had a dollar for every time someone said quantum mechanics does not make sense...

If we do something to cause particle A to change its spin then at that moment particle B changes its spin.

That's not quite right. One, it doesn't have to be us. Any interaction with the environment (and we're part of the environment) can cause the particle's spin to switch from indeterminate to determinate. And, since it's a single system composed of two particles, spin is conserved, so the other particle is compelled to adopt the opposite spin. And again, it's not changing its spin - its spin is just going from a superposition of all possible spins to a specific one.

Another analogy: you have two cards, the ace of spades and the ace of hearts. You don't look at the cards, but place one in a box and ship it to california. While it's shipping, both cards are in an indeterminate state - you have no idea which one is which. Once it arrives, you look at your card and find it's the ace of spades. The card in california has to be the ace of hearts then. That's similar to how this works, although the mechanism is entirely different.