Quantum entanglement

[little_monkey]

How spooky does it get?

A ..........← ●● →.......... B

1) Observer A, called Alice, will measure the spin of incoming particle. If it has spin, say, up then she knows that observer B, called Bob, will measure its counter-part particle’s spin to be down.This is like Alice tossing a coin, heads or tails, and say it comes down heads. Her counterpart Bob who may be light years away on the other side of the galaxy, who is also tossing a coin, and now his must come out in this case as tails!

2) Not only that, but Alice can choose whatever axis, an infinity of possibilities, along which the particle spin must quantize as spin up or spin down. Now Bob’s particle, on the other side of the galaxy, must also quantize along the same axis, with the opposite spin. But how does the particle know that?!?

3) Furthermore, a third observer C, called Claude, might be moving towards either Alice or Bob. Suppose that Claude is moving towards Alice, then according to him, she is measuring first, and she decides along which axis the particle spin will quantize. However if at the same time another observer D, called Donna, is moving towards Bob, then according to Donna, it is Bob who makes the first measurement and he decides along which axis the particle will quantize. How can this be??!?? Which is the cause and which is the effect? Accordingly Quantum physics makes no distinction between the two cases?!?

[Engyo]

Originally Posted by little_monkey

How spooky does it get?

A ..........← ●● →.......... B

1) Observer A, called Alice, will measure the spin of incoming particle. If it has spin, say, up then she knows that observer B, called Bob, will measure its counter-part particle’s spin to be down.This is like Alice tossing a coin, heads or tails, and say it comes down heads. Her counterpart Bob who may be light years away on the other side of the galaxy, who is also tossing a coin, and now his must come out in this case as tails!

As long as the two coins are entangled.........

2) Not only that, but Alice can choose whatever axis, an infinity of possibilities, along which the particle spin must quantize as spin up or spin down. Now Bob’s particle, on the other side of the galaxy, must also quantize along the same axis, with the opposite spin. But how does the particle know that?!?

Maybe the particles don't know that they are on opposite sides of what to us looks like a very large galaxy - maybe to the particles they are still next to each other, and the distance is all in our minds.

3) Furthermore, a third observer C, called Claude, might be moving towards either Alice or Bob. Suppose that Claude is moving towards Alice, then according to him, she is measuring first, and she decides along which axis the particle spin will quantize. However if at the same time another observer D, called Donna, is moving towards Bob, then according to Donna, it is Bob who makes the first measurement and he decides along which axis the particle will quantize. How can this be??!?? Which is the cause and which is the effect? Accordingly Quantum physics makes no distinction between the two cases?!?

Again, I think the whole problem is that we confuse our sense-experience of the universe with reality. I believe that the reality the particles are operating in is vastly different from what humans perceive.

[little_monkey]

Originally Posted by Engyo

I believe that the reality the particles are operating in is vastly different from what humans perceive.

There are 10ˆ80 particles in the universe, each having its own reality?!?

[Kungfuzed]

Action at a distance is a mystery to me. Magnetism and gravity make no sense, since objects don't need to touch to affect each other. Considering this, quantum entanglement doesn't seem any less bizzare, it can just work at a greater distance, theoretically.

[silvermoon383]

Bear in mind though, this doesn't necessarily imply the passing of information between the 2 particles (coins in the example). We know that of the pair one has to spin up, the other has to spin down. To figure out both, all we have to do is measure 1 of the particles then use the process of elimination to determine the qualities of it's partner.

[little_monkey]

Originally Posted by Kungfuzed

Action at a distance is a mystery to me. Magnetism and gravity make no sense, since objects don't need to touch to affect each other. Considering this, quantum entanglement doesn't seem any less bizzare, it can just work at a greater distance, theoretically.

Action at a distance (Newtonian physics) has long been replaced by Quantum Field Theory, oh say, about 80 years ago.

OTOH, Quantum entanglement is so weird that even Einstein was spooked by it.

[little_monkey]

Originally Posted by silvermoon383

Bear in mind though, this doesn't necessarily imply the passing of information between the 2 particles (coins in the example). We know that of the pair one has to spin up, the other has to spin down. To figure out both, all we have to do is measure 1 of the particles then use the process of elimination to determine the qualities of it's partner.

Take two people. Place them in different rooms. Both know when they toss their coins, it's either head or tail. Now, let one tosses a coin, let`s say it is head, the second person in the other tosses his coin, but now according to QE, it must turn up tail! If you don't consider that as weird, you've been watching too many episodes of SUPERNATURAL...


BTW, by the principle of relativity, particle A cannot transfer its information to B faster than the speed of light. So the second particle`s spin will be observed way before the information can arrive.

[Engyo]

Originally Posted by little_monkey

There are 10ˆ80 particles in the universe, each having its own reality?!?

No, I said that I believe the reality the particles are interacting differs from what we as humans percieve. I didn't say that each one get's its own reality.....although I wouldn't find that necessarily impossible, just improbable.

[Troublemane]

when you factor in relativity its really quite simple....anyone recall the "time dilation effect"? As a particle approaches light speed time slows down to zero, and so does space. (because time and space are actually one thing, called SPACETIME. its not 3 dimensions of space and one of time, its 4 dimensions of SPACETIME, one thing).

so space and time contract to zero, so from the perspective of the particles travelling in opposite directions, no time has passed from the moment they left the device to the time they arrive at A and B, and therefor no space between them. They are effectively ONE particle. Its only after they strike the detector(s) that they differentiate and become separate, but thats due to their deceleration from lightspeed/transfer of energy to the detectors.

see, its not all that difficult when you think of it from their perspective, instead of trying to wrap your mind around it from our inertial frame, here on earth.