Quantum Entanglement and Time

[padren]

I was thinking about this while walking home yesterday, and it bugged me: how does quantum entanglement work in regards to time and relativity?

 

We know from relatively, if you have a watch on earth synched to a watch that goes around in orbit for a good while, the watch that has been accelerating and spinning around the earth in orbit, will show an earlier time, because time will have slowed during it's trip from it's vantage point.

 

But what happens if we have entangled particles instead of watches in the experiment.

 

Something you do to particle A has an instant result on particle B, and visa versa.

So, A) while undergoing the acceleration, would particle B appear to change its state more "quickly" since its rate of change is determined by a particle not undergoing the same acceleration...ie, if time was moving half the speed in orbit that it was on the earth, would changing the state of particle A 2 times a second appear to be changing 4 times per second in orbit?

B) When particle A and B were returned to the same location, but one having experienced slower time, would the entanglement still be instantaneous, even though they had different ages, or would there be a delay if you tapped the older particle, before it would show in the younger one? Of course, if that happened, then tapping the younger one would produce an effect earlier in time instead of later, which would really annoy causality.

 

Still I remember hearing a long time ago, about the idea of having a worm hole between points, and accelerating one to change its reference in time before returning them to the same area, to create a mini-time machine. That had a number of flaws stemming from wormhole theory issues, but what about quantum entanglement?

Wouldn't that have the same issues?

[swansont]

Something you do to particle A has an instant result on particle B' date=' and visa versa.

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If you measure the state of A, you know the state of B immediately; the information about both particles is included in the measurement. If you change the state of A, nothing happens to B, because this breaks the entanglement.

 

AFAIK time/relativity has no extra effect on this process. You can't get "more quickly" than instantaneous.

[gagsrcool]

Hi,

 

I think he means the EPR paradox.

 

But aren't we supposed to not confuse ourselves by co-relating Special Relativity 7 General Relativity to quantum mechanics and stuff? I mean. even though a few principles of special realtivity have been valid for at the quantum level at the same time quantum mechanics has theories of its own, right?

 

gagsrcool

[swansont]

I think it may be that the wave function of the entangled particles does not evolve in time, so there is no time-dependence to worry about.

[5614]

If there are two particles; one with up spin and one with down. You measure one particle and it is up. You know the other is down. It is independant of time.

 

It's not like you're waiting for a reading to come back from the second particle. You just know, without knowing anything about the 2nd particle.

 

Whether it is accelerating, in a chemical reaction, in a blackhole or if it has split into two seperate virtual particles we know what spin it has (or technically "had", as it could have changed as a result of interacting with other matter), totaly independant of anything to do with the particle (ie. time or anything physical).

[padren]

Thanks everyone, I think I have another way to say it:

 

Particle A stays on earth next to clock A, particle B accelerates and goes around the earth with clock B.

 

If you measure particle A to find it has z- while particle B is accelerating, when do you know that a measurement on particle B has 100% change of getting z?

Would that be, instantly, or when the clock B catches up to the same point as clock A?

 

If you wait to take the measurement until particle B is back on the earth next to particle A, with their respective clocks, would the entanglement between A and B be any different due to their different ages, or would they behave identically to any other pair of entangled particles?

[Klaynos]

instantly, as soon as you measure A you know what the measurement on B will yield...