Einstein-Bohr "photon box" debate and general relativity

[Giulio Prisco]

I see this has been already discussed but the old threads are closed.

EPR before EPR: a 1930 Einstein-Bohr thought experiment revisited

"In this example, Einstein presents a paradox in QM suggesting that QM is inconsistent, while Bohr attempts to save consistency of QM by combining QM with the Einstein’s general theory of relativity."

The author presents an alternative derivation of Bohr's conclusion (that the time-energy uncertainty relation holds) without invoking general relativity.

But I have long been persuaded that, regardless of whether invoking GR is necessary or not, Bohr's point (which is quantitatively correct) is too big an elephant in the room to ignore. It seems to say that a result of GR, which has nothing to do with QM, "protects" QM against failure. It's difficult to escape the impression that this points to a deep relation between the two theories.

Thoughts please!

 

[PeterDonis]

EPR before EPR: a 1930 Einstein-Bohr thought experiment revisited

This paper is by our own @Demystifier , who might want to comment.

 

[Giulio Prisco]

I look forward to hearing from you @Demystifier !

Bohr's argument uses general relativity, yours uses non-local entanglement. The two arguments give the same quantitative results, and experiment agrees.

Shouldn't this be taken as an indication that gravitation and entanglement are related, the fabric of space-time being woven by entanglement, as suggested for example in "Building up spacetime with quantum entanglement" and follow-ups?

 

[Demystifier]

Yes, I also had a thought that my analysis of the photon-box experiment could be used as one additional argument for the currently modern conjecture that gravity and entanglement are related. Unfortunately, I was not able to make this argument more precise.

 

[Giulio Prisco]

Yes, I also had a thought that my analysis of the photon-box experiment could be used as one additional argument for the currently modern conjecture that gravity and entanglement are related. Unfortunately, I was not able to make this argument more precise.

I hope you'll do more work on this, and find a way to make the argument more precise. It would be a simple, physical entry point to the idea that entanglement is what weaves the fabric of space-time, an idea that is usually introduced by means of mathematical concepts alone.

One of your references (the quantum paradoxes book) suggests that Bohr's argument works because both he and Einstein are assuming the equivalence of inertial and gravitational mass, from which general relativity follows?

 

[Demystifier]

One of your references (the quantum paradoxes book) suggests that Bohr's argument works because both he and Einstein are assuming the equivalence of inertial and gravitational mass, from which general relativity follows?

Sort of.

 

[bhobba]

Yes, I also had a thought that my analysis of the photon-box experiment could be used as one additional argument for the currently modern conjecture that gravity and entanglement are related. Unfortunately, I was not able to make this argument more precise.

I thought Roger Penrose was the only one into that. Actually, I am inclined in that direction myself.

Thanks
Bill

 

[Demystifier]

I thought Roger Penrose was the only on into that.

Penrose tries to relate gravity with collapse, not with entanglement as such. His approach is not so much popular.

 

[bhobba]

Penrose tries to relate gravity with collapse, not with entanglement as such. His approach is not so much popular.

I have no doubt you are correct. Must brush up on some of his very thought provoking books - looks like my memory needs refreshing.

Thanks
Bill

 

[bhobba]

Sort of.

Indeed.

What GR follows from is a separate thread in itself.

Just one comment here - look into Lovelock's Theorem. It only work's in 4 dimensions which may or may not be telling us something important.

Thanks
Bill

 

[Demystifier]

Just one comment here - look into Lovelock's Theorem.

This theorem says nothing about the equivalence principle.

 

[bhobba]

This theorem says nothing about the equivalence principle.

No - but it shows GR follows from the fact the metric has a Lagrangian. That's basically it. Is that the Equivalence principle? Not for this thread though. Will start another and link to it.

As promised here is the link:
https://www.physicsforums.com/threads/what-is-the-physical-basis-of-lovelocks-theroem.945998/

Will be going to dinner soon. Will see what gets posted while I am away.

Thanks
Bill

 

[Giulio Prisco]

I thought Roger Penrose was the only on into that. Actually I am inclined in that direction myself.

Thanks
Bill

A good 2016 review of gravity-from-entanglement:
https://arxiv.org/abs/1609.00026

 

[Giulio Prisco]

I am thinking of this again after reading in Carlo Rovelli's last book Helgoland:

"[Bohr's] response to Einstein’s objection when presented with the ideal experiment of the light box is wrong. Bohr invokes general relativity, but this has nothing to do with the question, which is about an entanglement between two distant objects."

But if general relativity has nothing to do with the question then the fact that Bohr's argument works is an inexplicable coincidence. Why should general relativity "protect" quentum mechanics of the two are unrelated? It seems to me that this points very strongly to a link between gravity and entanglement.

Alain Connes makes the same point in his physics-fiction novel "Le Théâtre quantique."

Any recent developments on this?

 

[stevendaryl]

A good 2016 review of gravity-from-entanglement:
https://arxiv.org/abs/1609.00026

Is this related to the slogan ER=EPR, which I understand connects entanglement with wormholes.

 

[martinbn]

I don't understand why it is always said that Bohr used GR to resolve Einstein's paradox!? Nowhere in his respose he used the field equations! What is used is the equivalence principle, time delation, gravitational redshift, which are experimentally confirmed very well with or without GR!

 

[Demystifier]

I don't understand why it is always said that Bohr used GR to resolve Einstein's paradox!? Nowhere in his respose he used the field equations! What is used is the equivalence principle, time delation, gravitational redshift, which are experimentally confirmed very well with or without GR!

I would say he used kinematics but not dynamics of GR. This is like using QM, e.g. the Born rule $p(x)=|\langle x|\psi\rangle|^2$, without using the Schrodinger equation.

 

[Giulio Prisco]

Is this related to the slogan ER=EPR, which I understand connects entanglement with wormholes.

It is a framework whose development could eventually allow to prove ER=EPR and other deep links between quantum physics and general relativity.

 

[Giulio Prisco]

I would say he used kinematics but not dynamics of GR. This is like using QM, e.g. the Born rule $p(x)=|\langle x|\psi\rangle|^2$, without using the Schrodinger equation.

But still... the coincidence is too big to ignore and seems to point to deep links between QM and GR.

I'm reading your 2012 paper again. It shows that if one assumes QM (including entanglement and all four uncertainty relations) one can derive time stretching in a gravitational field as predicted by GR.

This doesn't rigorously prove that QM --> GR, but seems a very strong indication that it could be so.

 

[stevendaryl]

Yes, I also had a thought that my analysis of the photon-box experiment could be used as one additional argument for the currently modern conjecture that gravity and entanglement are related. Unfortunately, I was not able to make this argument more precise.

I just read your paper, and it seems to me that in your analysis, gravity doesn't play any role. The relationship between time and energy uncertainty holds no matter what method is used to determine the energy of the box after the emission of a photon.

So I'm a little unclear about what Bohr's argument says about QM and gravity.

 

[Demystifier]

I just read your paper, and it seems to me that in your analysis, gravity doesn't play any role.

Gravity also does not play any role in CFT theories. Yet there is (conjectured) duality between CFT and gravity on AdS. So by analogy, maybe ...