Reference Frame of Quantum Entanglement

[TheFaithfulStone]

Okay - so I was reading digg.com this morning, and that Dark Energy Star thing came up. There were links to a couple of blogs that basically said that George Chapline is a quack. One of their objections was his statement that quantum entanglement requires an absolute frame of reference - but no one explained why it DIDN'T- they just tossed off a "no it doesn't."

 

So - correct my understanding.

 

If I am travelling at some fraction of c in ship A, and you are travelling at the same speed in the opposite direction in ship B, and we both have entangled particles, and I measure my particle, your particle instantly assumes the measurement of my particle. Now, there is no way we can communicate with this system, granted - but the action is instananeous. Observer C, who is closer to me than you, will observe my particle changing first, and then yours changing second. Observer D, who is closer to you than me, will observe your particle changing before mine.

 

The simultaneity of the reaction is in question, obviously, but doesn't there HAVE to be a universal frame of reference for causality NOT to be violated? If the "switch" occurs simultaneously in multiple frames, then there must be an absolute frame of reference - but if it DOESN'T, then your particle could change BEFORE mine (the trigger) does, and you could predict what I would change mine too.

 

Okay - so where am I screwed up on this? Neither way makes much sense, frankly. And if we could answer this question without tensor calculus, that'd be good.

 

TFS

[arkain101]

I got lost in the details but I understand where you are going with this.

 

Using the SR theory it seems that the invisible field of space is at rest, because if you move through it your are supposed to experience dialations.

 

Now, tests have been done on particle accelerators and they assume they can only make a particle go so fast in cirtain directions because of a mass increase. Well lets say earth is traveling generally north at .25 C. If we shoot the particle south and it still only goes .99990C in reference to earth it is kind of irrelevant. Because, in space it actually slowed down...then should end up going south around .7499 percent C. It seems that SR requires an absolute frame of reference too.

[Erasmus00]

The simultaneity of the reaction is in question, obviously, but doesn't there HAVE to be a universal frame of reference for causality NOT to be violated? If the "switch" occurs simultaneously in multiple frames, then there must be an absolute frame of reference - but if it DOESN'T, then your particle could change BEFORE mine (the trigger) does, and you could predict what I would change mine too.

 

This is exactly what bothered Einstein about quantum mechanics. Him, and his buddies Podolsky and Rosen wrote a now famous paper on the issue.

 

Here is the thing, you assume that one measurement "causes" the other. This isn't necessarily true. The two measurements are certainly correlated, but correlation does not mean causation.

-Will

[TheFaithfulStone]

This is exactly what bothered Einstein about quantum mechanics. Him, and his buddies Podolsky and Rosen wrote a now famous paper on the issue.

 

Here is the thing, you assume that one measurement "causes" the other. This isn't necessarily true. The two measurements are certainly correlated, but correlation does not mean causation.

-Will

Okay, but if the correlation is 100% and is "triggerable" how is that NOT causality?

 

It's not like I'm simply screaming "Go!" everytime I step on the gas and thinking that makes the car go. (Well, I guess that COULD be it, but I think Quantum Mechanics is better understood than that by people smarter than I am.) The collapse of the wave function in MY particle ALWAYS leads to collapse of the wave function in YOUR particle at the EXACT same time. Right?

 

Under what circumstances are the measurements NOT correlated - because if something is always correlated with another event and there is no other event that is always correlated with it... that seems like a causal relationship. Of course - what place does logical thinking have in quantum mechanics, right?

 

The (likely) alternative is that I don't understand quantum entanglement.

 

TFS

[Erasmus00]

Okay, but if the correlation is 100% and is "triggerable" how is that NOT causality?

 

It's not like I'm simply screaming "Go!" everytime I step on the gas and thinking that makes the car go. (Well, I guess that COULD be it, but I think Quantum Mechanics is better understood than that by people smarter than I am.) The collapse of the wave function in MY particle ALWAYS leads to collapse of the wave function in YOUR particle at the EXACT same time. Right?

 

We assume so. But given that if we are widely seperated, in my frame I could make a measurement before you, and in your frame you could make a measurement before me. So who triggered the collapse?

 

This whole thing has to do with the troubleing non-locality of quantum mechanics.

-Will

[sanctus]

To solve your problem it's enough to look at the two correlated particles as one state of one pseudo-particle.

[TheFaithfulStone]

So, there's a particle that's in two places at once?

 

Whaaaat??

 

If I've got one aboard spaceship A, and one aboard spaceship B, doesn't that imply that said pseudo-particle is in two reference frames at once? Or no? Or - if it's only in a single frame, which one is it?

 

Actually, I just want to know under why quantum entanglement doesn't require a universal time coordinate - it wasn't properly explained in the critique of Chaplain.

 

edit:

Or maybe it was, and I'm just dumb. Anyway, I still don't get it.

 

TFS

[Tarantism]

what do yall know about super positions?

[Erasmus00]

Actually, I just want to know under why quantum entanglement doesn't require a universal time coordinate - it wasn't properly explained in the critique of Chaplain.

 

Quantum entanglement only requires a universal time coordinate if you want to look at entanglement causaly. If you don't think like "measurement of A causes the collapse" or "measurement of B causes the collapse" and instead think like "the two measurements are correlated." Also note, there is an entire theory mixing special relativity and quantum mechanics (quantum field theory).

-Will

[TheFaithfulStone]

Quantum entanglement only requires a universal time coordinate if you want to look at entanglement causaly. If you don't think like "measurement of A causes the collapse" or "measurement of B causes the collapse" and instead think like "the two measurements are correlated." Also note, there is an entire theory mixing special relativity and quantum mechanics (quantum field theory).

-Will

Ahh... Got it.

 

Is the causality of that in question, or is it settled that the measurement doesn't CAUSE the wavefunction collapse?

 

What I'm thinking is that in order for the relationship to NOT be causal, then there must be "hidden-variables" - which would be against Bell's theorem.

 

I guess maybe I have trouble drawing an intellectual distinction between "100% correlated & triggerable" and "causes." Like pulling the trigger of a gun does not nessecarily cause the gun to fire, but the action is just very highly correlated.

 

I suppose I'm thinking that locality is on one hand, and causality is on the other.

 

TFS

 

edit: BTW, I know very, very little about quantum field theory - so if you'd care to enlighten...

[Erasmus00]

I guess maybe I have trouble drawing an intellectual distinction between "100% correlated & triggerable" and "causes." Like pulling the trigger of a gun does not nessecarily cause the gun to fire, but the action is just very highly correlated.

 

I think the thing is that its hard to think of wave function collapse as "triggered" by either of the measurements, as its hard to say which measurement happens first. The problem of measurement in quantum mechanics is very worrisome to many. I had a professor who was fond of saying that anyone who wasn't worried about quantum measurements had rocks in his head.

-Will

[TheFaithfulStone]

Got it. Now I understand. Thanks for clearing it up for me Will.

 

TFS

[TheFaithfulStone]

As long as we're talking edge physics, could you explain something about the Alcubierre Metric to me?

 

I was reading something that said that it enable CTCs. and I went and looked up the reference, but it was again with the math I don't understand.

 

http://www.if.ufrj.br/~mbr/warp/etc/prd53_7365.pdf

 

That's the paper that was talking about it. I don't see how you could use a warp drive like Alcubierre's to travel back in time, since the ship is always at rest in regard to it's local space time, and thus doesn't experience Lorentz-contraction or time dilation, or any other of those nasty things.

 

Gratzi,

TFS

[Little Bang]

Is it possible to have three entangled particles?