NOVA Show on Einstein and Quantum Entanglement

[jedishrfu]

NOVA presents a show on Einstein and Quantum Entanglement:

 

[bhobba]

Watching it now.

As usual they fail to explain its just a correlation and try to sensationalize it. No wonder the general public gets confused.

Thanks
Bill

 

[DarMM]

What are you talking about @bhobba ? It needs more sensationalization not less.

Bohr and Einstein in a cage fight, maybe with velociraptors over a volcano. Get Bohr to deliver a cool line at the end.

"Sorry Albert, the world isn't predetermined, but this fight was!" before he throws Einstein into the volcano.

If you agree with Einstein's take on QM maybe "In all frames of reference, you lose!" and Bohr is thrown into the raptor pit.

EDIT: How can you throw somebody out of a closed cage? Quantum Tunneling.

 

[bhobba]

What are talking about @bhobba ? It needs more sensationalization not less.

Its just Bertlmann's socks with a twist - ie different statistical properties of the correlation than classically. And as far as locality goes to me the cluster decomposition property of Weinberg suggests you preclude correlations anyway.

Other issues are they do not make clear QM does not say objects do not exist before measurement and the other stuff along those lines - QM is silent on the issue. Reading things like that into is interpretation territory.

However I do agree on the fundamental importance of entanglement right at the foundations of QM:
https://arxiv.org/pdf/0911.0695.pdf

Thanks
Bill

 

[DarMM]

Other issues are they do not make clear QM does not say objects do not exist before measurement and the other stuff along those lines - QM is silent on the issue. Reading things like that into is interpretation territory.

I think this is a real issue. What do you actually say to non-experts?

Let's say in QFT you have particle observables only defined at asymptotic times, at other times most states don't admit a particle decomposition (Hilbert space is non-Fock). Now combine that with not wanting to say anything that isn't interpretation neutral.

All I can say is "QFT models the statistics of field like observables". The End. I'm never sure what to say to non-experts.

And as far as locality goes to me the cluster decomposition property of Weinberg suggests you preclude correlations anyway.

What do you mean by preclude correlation?

 

[bhobba]

Bohr and Einstein in a cage fight, maybe with velociraptors over a volcano. Get Bohr to deliver a cool line at the end. "Sorry Albert, the world isn't predetermined, but this fight was!" before he throws Einstein into the volcano.

Sorry Bohr we do not know if is predetermined or not. It is generally thought Bohr defeated Einstein in the famous Bohr Einstein debates, but I am of a different view - Bohr convinced Einstein QM was consistent and a valid theory, which Einstein never should have doubted - but the issues he raised about its completeness are still with us today. We are closing in on how it may be made complete eg:
https://arxiv.org/abs/1312.7454

But we are not there yet. One can still validly hold the view QM is incomplete (as at least one mentor here does) or one can be like me and think completing it will come. Only time will provide the answer.

Thanks
Bill

 

[bhobba]

I think this is a real issue. What do you actually say to non-experts?

Feynman struggled with that one also. He finally reached the view you can't tell the truth initially - you have to build up to it. As long as the people watching shows like Nova realize that then its not an issue. The only issue is when they come to places like here and argue about the 'semi' truths they were told. This is particularly bad in the area of virtual particles - for some reason once they have been told they are real you can argue until the cows come home they are simply lines in the diagrammatic representation of a Dyson series and they will not believe. You can have professors like Dr Neumaier write detailed papers explaining it - all to no avail. It is probably the most maddening thing I have come across on this forum.

What do you mean by preclude correlation?

Here is the statement of the Cluster Decomposition Property:

'It is one of the fundamental principles of physics (indeed, of all science) that experiments that are sufficiently separated in space have unrelated results'

If you allow correlated systems then it logically breaks down. Of course by a simple rewording of it you can still have correlated systems so those holding different views than me on entanglement correlations can stick to those - but for me simply exclude it and you don't have these issues.

Thanks
Bill

 

[DarMM]

Doesn't the cluster decomposition principle say that if the connected part of the S-matrix has only a single delta/kronecker function then the S-matrix factorises?

In other words it's not concerned with entangled states that do have these additional deltas?

This is still important because it shows that factorisable states that are initially spatially separated and stay separated as they evolve remain factorisable. Otherwise QFT would have superluminal signalling basically. However my understanding was that it says little about entanglement as it excludes it.

Perhaps I am misunderstanding.

 

[bhobba]

Yes yes all true. It depends on how you state the principle. The one I gave is from Weinberg from which he develops the full technical version. Its easy to modify so you do not have the issue - its purely up to you the way you want to go. As I said I took the easy way out and just excluded correlations so you do not have to worry about entangled systems. You can include them if you want - but then you have all the other issues.

Thanks
Bill

 

[DarMM]

Sorry @bhobba I parsed your original statement incorrectly, shouldn't read this stuff when tired!

You're saying the CDP shows you that locality is best discussed in terms of systems where there are no correlations (even classical ones) to begin with, i.e. the fact that distant initially uncorrelated systems remain uncorrelated is a good definition of locality.

I thought you were saying the CDP says something about entanglement.