Is there anyting really entangled in Quantum Entanglement ?

1. Jan 23, 2012

mkserkan

As an amateur, I have been reading about the EPR argument, and afterwards Quantum Entanglement recently. Then I thought that the bound between two particles is only the applicability of a physical rule of everyday reality. For instance, the momentum or energy must be preserved at all times, so they behave like they are entangled otherwise a definite rule of physics would be violated. Like Born said, ‘while the motion of particles follows probability rules, probability itself propagates according to the law of causality’. So if this is a valid reasoning, there is actually nothing special about entanglement in a sense. There is nothing travelling between them, no need for an extra dimension or something like that to enable the syncronization of the states. Only that they HAVE TO obey the general rules of physics at all costs.

Is this reasoning true and justifiable? If so, that would simplify things for me.

2. Jan 23, 2012

Demystifier

Yes, that reasoning is quite justified. In fact, I am not aware on any interpretation that claims that something does travel between them.

3. Jan 23, 2012

ThomasT

Then why do people speak of Bohmian interpretation (dBB) as being explicitly nonlocal? If nothing is travelling between entangled entities in dBB, then in what sense is the nonlocality of dBB a realist account (as some people would characterize it) wrt quantum entanglement?

Some of your statements regarding how to think about dBB seem to me to indicate that you think that dBB and standard QM should be regarded as neither local nor nonlocal, ie., nonrealistic (wrt quantum entanglement) -- which is how I currently think about both.

I'm not disagreeing with anything you've written, just trying to clarify for myself how to think about it. It seems to me that the value of dBB is that the Born rule (probabilistic interpretation) is more or less naturally accounted for, and that dBB offers a certain (realistic?) underlying picture wrt individual results that might (or might not) prove to be a heuristic which gives rise to more accurate or novel predictions.

4. Jan 23, 2012

ThomasT

If quantum entanglement is only due to an underlying relationship between entangled entities (and the measurement of that relationship by a global instrumental parameter), and if the underlying relationship is produced via local transmissions/interactions, then there's no need to assume any sort of communication between separated entangled entities.

However, one thing, maybe the thing, that makes quantum entanglement special is that there doesn't seem to be any way to formulate a quantitatively viable and clearly explicit local realistic account of entanglement correlations.

This has led some to assume that entangled entities are communicating via nonlocal (ftl) transmissions, or, in the extreme, to assume the existence of action at a distance.

The fact of the matter, afaik, is that it isn't known, and maybe can't ever be known, whether or not entangled entities are in some way communicating or not.

But the way you seem to be approaching it seems to me to be the most reasonable approach. And Demystifier seems to agree with this.

Last edited: Jan 23, 2012
5. Jan 23, 2012

rohanprabhu

I have a question myself regarding this. Haven't we established that any information that is to travel between two points will take a minimum time, determined by $c$?

So, in that case, aren't we sure that nothing travels between them, because the effects of entanglement are instantaneous? Or, if we are talking about providing a solution via dimensions, are we talking of higher dimensions offering a 'shortcut' of sorts for the communication signals?

6. Jan 24, 2012

ThomasT

That's a working hypothesis that hasn't yet been contradicted by experiment, afaik.

Not necessarily, afaik. Because there's no way to know if anything is travelling between them.

It's only known, or presumed, afaik, that if there are communications between entangled entities, then the speed of their propagation must have a lower bound.

7. Jan 24, 2012

Demystifier

dBB is REALISTIC in the sense that particle positions exist even when they are not measured.
dBB is NONLOCAL in the sense that the force on one particle depends on the positions of all other particles at the same time.
In dBB NOTHING TRAVELS between the entangled entities in the sense that the nonlocal force above between two particles is not propagated by a third entity.

Is it clearer now?

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