Controlled experiment with time.

[Lost in Space]

Yes. QED is fully relativistic. It includes both entanglement and relativity.

Thanks for your answer. So, given this, does it therefore mean that entanglement can exist across time as well as space? Could it be possible for example, that if one part of an entangled pair was to come under the gravitational influence of a black hole (without crossing the event horizon), that time dilation could split the pair by millions of years, yet they would still be connected? And if time dilation is caused by one part of the pair traveling faster relatively to the other would this also apply?

As relativistic effects can be measured at quite low speeds and in lower gravity fields, do you think that it's possible that we could ever experimentally confirm this?

 

[Dale]

Could it be possible for example, that if one part of an entangled pair was to come under the gravitational influence of a black hole (without crossing the event horizon), that time dilation could split the pair by millions of years, yet they would still be connected? And if time dilation is caused by one part of the pair traveling faster relatively to the other would this also apply?

Certainly. This happens to some degree with any entangled particles that are moved apart.

 

[Lost in Space]

Certainly. This happens to some degree with any entangled particles that are moved apart.

That's really interesting. So, if they are still entangled even though time dilation has separated them, will a change of state in the part moving relatively slower to the other or a change in state of the one not affected by the gravity field be carried backwards in time to the other?

 

[Dale]

What are you talking about? The two particles are a single quantum-mechanical system with a single state (wavefunction). They don't have separate states which can be independently changed or not changed at some time. If you interact with one particle then you change the state of the system.

 

[Lost in Space]

Please forgive my ignorance, but all I'm trying to establish is whether there is a time differential between the entangled pair and what is happening in each respective time frame if they are occupying two different time frames due to time dilation. If there is an interaction with one that is separated in time from the other how will this be reflected? Will any interaction be still be instantaneous even though they occupy different time frames? If both observers are separated relativistically, will the observation of the 'receiver' take time to register the change in state for example?

 

[Dale]

There is no receiver, there is no information transmitted, there is nothing to register. Your problem has nothing to do with relativity per se, it is a just a misunderstanding of enganglement.

Also, "separated in time" is not meaningful anyway. One particle may experience more or less proper time than the other, but they both exist any given time.

 

[Lost in Space]

Ok. Does this mean then that a change in state between entangled particles can't be confirmed by observers who are relativistically separated as they can't compare the state of the particles at the same instant of time? Would this also be true even at lower relative speeds or in differing weak gravitational fields?

And would the same thing also be true for quantum teleportation, if this is the case?

 

[Dale]

Ok. Does this mean then that a change in state between entangled particles can't be confirmed by observers who are relativistically separated as they can't compare the state of the particles at the same instant of time?

It cannot be confirmed at the same instant of time by observers that are separated in any way, relativistically or not.

Would this also be true even at lower relative speeds or in differing weak gravitational fields?

Yes.

 

[danR]

...observers who are relativistically separated...

'relativistically separated' has no meaning. In the real world (unless space and time are granular at Planck scales) every object/observer has a different frame of reference from every other object, even if the difference of velocities is only .0000000000...1 c.

quantum entanglement occurs in quantum world.

 

[Lost in Space]

It cannot be confirmed at the same instant of time by observers that are separated in any way, relativistically or not.

Sorry? Then how can experimenters confirm that entanglement exists? Isn't distance the same as separation?

 

[Lost in Space]

'relativistically separated' has no meaning. In the real world (unless space and time are granular at Planck scales) every object/observer has a different frame of reference from every other object, even if the difference of velocities is only .0000000000...1 c.

quantum entanglement occurs in quantum world.

Yes, but some physicists think that it may be possible to teleport a virus using entanglement before the end of this century and this would be on a macroscopic scale so apparently quantum effects are not just limited to microcosmic scales.

As quantum teleportation isn't superluminal, I would have thought that it would be theoretically possible to teleport information between differing relativistic time frames. If so, effectively this information would be being teleported backwards and forwards in time, relatively speaking.

 

[danR]

Yes, but some physicists think that it may be possible to teleport a virus using entanglement before the end of this century and this would be on a macroscopic scale so apparently quantum effects are not just limited to microcosmic scales.

As quantum teleportation isn't superluminal, I would have thought that it would be theoretically possible to teleport information between differing relativistic time frames. If so, effectively this information would be being teleported backwards and forwards in time, relatively speaking.

You've quite lost me. quantum effects were never limited to microscopic scales (unless you mean 'microcosmic' in some special way, but I don't think it's a formal physics term). For example, the Aharonov-Bohm effect.

Some physicists that think it may be possible...

This goes too far beyond Douglas Hofstadter's 'subjunctive replay', for me. As a layperson, I need to hear:

Most physicists agree that it has been demonstrated or calculated as likely...

 

[Lost in Space]

You've quite lost me. quantum effects were never limited to microscopic scales (unless you mean 'microcosmic' in some special way, but I don't think it's a formal physics term). For example, the Aharonov-Bohm effect.

Some physicists that think it may be possible...

This goes too far beyond Douglas Hofstadter's 'subjunctive replay', for me. As a layperson, I need to hear:

Most physicists agree that it has been demonstrated or calculated as likely...

I used the term 'microcosmic' because 'microscopic' scales are still really 'macroscopic' when talking of quantum reality. There's a borderland between these scales and just how far each overlaps into the other is yet to be fully resolved.

 

[Dale]

Then how can experimenters confirm that entanglement exists?

They compare the data from both particles after the fact. With only the information from one particle there is no way to detect entanglement. You must have the data from both.

 

[Lost in Space]

They compare the data from both particles after the fact. With only the information from one particle there is no way to detect entanglement. You must have the data from both.

Yes, I realize that they have to compare 'after the fact', but if one of them is further in the future relative to the other, how could this be done without accurately compensating for the time dilation? The instant of time at which any change occurred in time would be different for each of them even if it wasn't for the particles.

 

[Dale]

one of them is further in the future relative to the other

What exactly do you mean by this and why do you think it would be a problem for an entanglement experiment?

 

[danR]

I used the term 'microcosmic' because 'microscopic' scales are still really 'macroscopic' when talking of quantum reality. There's a borderland between these scales and just how far each overlaps into the other is yet to be fully resolved.

Well, I'm not certain of the borderline scales, but you can read this and decide whether it satifies your criterion:

http://en.wikipedia.org/wiki/Aharonov–Bohm_effect#Mathematical_interpretation

I'd say the scale of an electron going around a solenoid is fairly macroscopic.

 

[Lost in Space]

What exactly do you mean by this and why do you think it would be a problem for an entanglement experiment?

I don't know if it would be a problem. That's why I'm asking. Observers with different running clocks don't share the same instant of time even if the particles still do. If the entangled particles' state can be changed, then maintained and compared later, will the observer with the slower running clock have seen the change at a different time in comparison with the other observer? Will it be possible for both observers to compare the result later, if they then move back into the same synchronous time frame after carrying out the experment? More time would have passed for the observer with the faster clock.

The instant of change as far as I can tell is different for each observer as their clocks are running at different rates even though as far as the particles are concerned the change is still instantaneous as they are one system. So as far as the observer with the slower running clock is concerned the instant of the change of state in the other part of the entangled pair has happened in the future relative to him. If the particles are unaffected by this it seems to me that they are acting independently of relative time even if they aren't physically sharing the same time frame.

But in the case of quantum teleportation, coherent information is teleported subluminally from one relative time frame reference to another if the same kind of experiment is carried out so relativity does have an effect. The particles are physically separated by time dilation as well as spatial separation. So, if the spaceship was traveling fast enough for a substantial time or stayed in a strong gravity field for long enough, the time dilation between it and observers on the ground would be significant and any contact made by passing information via teleportation would be across time as well as space.

 

[Lost in Space]

Well, I'm not certain of the borderline scales, but you can read this and decide whether it satifies your criterion:

http://en.wikipedia.org/wiki/Aharonov–Bohm_effect#Mathematical_interpretation

I'd say the scale of an electron going around a solenoid is fairly macroscopic.

I suppose it comes down to comparison. An electron would be macroscopic in comparison to a string, I guess.

If it's possible to teleport molecules using quantum teleportation, or use quantum computing, I understand that it requires many coherent particles in order to do this. Whether it is possible to maintain coherence or not is another question.

 

[Dale]

Observers with different running clocks don't share the same instant of time even if the particles still do.

You still haven't explained what you mean by this.

 

[Lost in Space]

You still haven't explained what you mean by this.

If an instant of time is separated by time dilation, how can it be verified as the same instant? Surely an instant can only be compared and verified by synchronous clocks running in the same time frame? Isn't this why there has to be adjustments made in communication satellites etc for even tiny relativistic effects? An instant of time has zero duration or length.

 

[Dale]

If an instant of time is separated by time dilation

How can an instant become separated by time dilation?

Time dilation is something that happens to physical clocks, an instant is something that is defined by a mathematical coordinate system. A particular accurate physical clock may or may not agree with a given valid coordinate system, but that doesn't impact the operation of the physical clock one bit and it doesn't cause the mathematical coordinate system to become "separated" in any way.

I don't even have any idea how you could apply the word "separated" to the concept of an "instant". This is what is confusing me.

 

[Dale]

For an entanglement experiment, an ensemble of entangled particles are generated and separated. Whether it is at a high rate of speed or not is irrelevant. Then each set of particles are measured and two completely random sets of data are obtained. Whether some nearby clock reads the same time as any other clock is irrelevant. Then the sets of data are brought together and compared to find a perfect negative correlation.

 

[Lost in Space]

An instant of time cannot be separated by time dilation. However, observers can be separated by time dilation. If one observer is in a separate time frame which has been caused by time dilation, his measurement of time is different to that of the other observer. Each measures his own time with his own clock. Each observer sees time moving normally in their own respective time frame. But relatively speaking the clocks are running at different rates. Therefore, the instant at which a change is caused in the state of the particles will, for each observer, be at a different time relative to the other.

If one observer is further forward in time relative to the other, he cannot compare his set of data with the other whilst occupying this different time frame. When he makes his measurement it is at a different time and at a different rate of time relative to the other. And if the opposite case is taken and the other observer makes his measurement it is going to be behind the other's time, comparatively speaking.

Ergo, both observers would have to know each other's clock to be able to compensate for the time difference between them and to know when the 'instant' of change happened for each, when recording any change in state and on later making a comparison, and this could only be done at all having first regained synchronisation in the same time frame.

 

[Dale]

If one observer is in a separate time frame which has been caused by time dilation, his measurement of time is different to that of the other observer. Each measures his own time with his own clock. Each observer sees time moving normally in their own respective time frame. But relatively speaking the clocks are running at different rates.

True, but as I already said above, completely irrelevant to an entanglement experiment. Before comparison the individual ensembles will be found to be completely random regardless of any time dilation, and after comparison the ensembles will be found to be perfectly correlated regardless of any time dilation. The time dilation is irrelevant. It makes no difference to the individual measurements nor to the comparison between measurements.

If you wish to discuss something new then I would be glad to do so, but I am done with repeating this stale discussion.

 

[Quickless]

The OP seems to be alluding to The Faster Than The Speed of Time experiments of Gene Denler and Fred Denef.

 

[Lost in Space]

True, but as I already said above, completely irrelevant to an entanglement experiment. Before comparison the individual ensembles will be found to be completely random regardless of any time dilation, and after comparison the ensembles will be found to be perfectly correlated regardless of any time dilation. The time dilation is irrelevant. It makes no difference to the individual measurements nor to the comparison between measurements.

If you wish to discuss something new then I would be glad to do so, but I am done with repeating this stale discussion.

I have a problem in accepting that with time dilation the instant of time for both particles is simultaneous and is therefore instantaneous. I don't seem to be getting this point across so I apologise for this.

For example, if changes in states are instituted at 1 second intervals and then time dilation takes effect, those intervals will become distorted in comparison to each other so any change of state in the faster time frame cannot be happening instantaneously in the other as the difference between the faster time frame and the slower time frame means that what is happening in the faster time frame cannot have happened yet in the slower time frame.