I Do Bell Experiments Show Local Overlap of Wave Functions Before Measurement?

[Fra]

I'll try to explain...

This still doesn't help me to match up what you say with what Bell said.

My point is that I don't accept the equipartion assumption, which is rarely discussed, it's just uncritically "put in there", and it is part of the old legacy of the mechanical causal logic.

As I see it, there can be a hidden variable, $\lambda$ that is set when the entangled pair is created, and this explains the statistical correlation in without violating locality! So we have the explanation of correlations.

But howto escape the Bell inequality:

IMO (in my qbist inspired agent interpretation) it does not logically follow that the observations at say Alice detector, is a function of alice detector settings and $\lambda$. My argument is a combination of informationlocality of agent action and that an interaction is a resulting form an action and reaction. Informationlocality suggest that Alice's detectors rection to the incoming entangled particle must be independent on $\lambda$ as the entangled pair by construction is ISOLATED From everything until it hits the apparatous(which Alice has set as she wishes). So the apparatous REACTION of the incoming particle, follow the expectations - which is determined not by lambda, by by the preparation procedure where the entangled pair is created. EXACTLY how the action is determined by a systems expectations of it's environment, is technically an open question. I do not have the explicit math. But that is exactly what I expect from future research (it follows from my own interpretation and understanding of physical law and QM).

So that is in short why I think the equipartition assumption is wrong to start with. Equiparition assumption holds only for the most naive old style causal mechanisms. This is what i referred to as causal mechanisms. I guess one can also associate this with the "naive realism". As I entertain a form of "subjective HV", there is still a form of reality, but reality is relative, and this influences interactions. This type of mechanism is not ruled out by Bell.

/Fredrik

 

[DrChinese]

1. As I see it, there can be a hidden variable, $\lambda$ that is set when the entangled pair is created, and this explains the statistical correlation in without violating locality! So we have the explanation of correlations.

2. Information locality suggest that Alice's detectors rection to the incoming entangled particle must be independent on $\lambda$ as the entangled pair by construction is ISOLATED From everything until it hits the apparatous(which Alice has set as she wishes). So the apparatous REACTION of the incoming particle, follow the expectations - which is determined not by lambda, by by the preparation procedure where the entangled pair is created.

1. If correct, this is exactly what Bell demonstrates requires explicit nonlocal action. Why? Because there is no $\lambda$ dataset that yields the quantum expectation values unless you FIRST know how Alice plans to measure.

2. This is not a requirement of a Bell test. Bell tests do not require that entangled particles ever interact with each other, and they do not need to have ever existed in the same spacetime cone. They can be created from fully independent sources sufficiently distant that no signal can propagate between them.

https://arxiv.org/abs/0809.3991
Abstract: "Entanglement swapping allows to establish entanglement between independent particles that never interacted nor share any common past. ..."

Consequently, there are no hidden variables from a common source as you imagine, since there is no common source, nor point of contact between the particles that Alice and Bob observe.

 

[PeterDonis]

My point is that I don't accept the equipartion assumption, which is rarely discussed,

What is the "equipartition assumption"?

 

[vanhees71]

1. If correct, this is exactly what Bell demonstrates requires explicit nonlocal action. Why? Because there is no $\lambda$ dataset that yields the quantum expectation values unless you FIRST know how Alice plans to measure.

2. This is not a requirement of a Bell test. Bell tests do not require that entangled particles ever interact with each other, and they do not need to have ever existed in the same spacetime cone. They can be created from fully independent sources sufficiently distant that no signal can propagate between them.

https://arxiv.org/abs/0809.3991
Abstract: "Entanglement swapping allows to establish entanglement between independent particles that never interacted nor share any common past. ..."

Consequently, there are no hidden variables from a common source as you imagine, since there is no common source, nor point of contact between the particles that Alice and Bob observe.

Nevertheless all the interactions involved in the preparation are of course local. What's needed are the two entangled photon pairs, photons 1 and 2 as well as potons 3 and 4, both of which are created by parametric down conversion, i.e., local interactions of laser photons with the BBO crystals. The next perparation step is the filter measurement done with photons 2 and 3, which also are based on local interactions of the photons with the beam splitter BS and the polarizing beam splitters PBS. The resulting entanglement of photons 1 and 4 after selection based on the measurement on photons 2 and 3 are all due to local interactions of photons with the "equipment" needed to prepare the entanglement of photons 1 and 4 via entanglement swapping. Of course, indeed, the photons 1 and 4 themselves never interacted ever locally. Nevertheless that does not imply that the interactions used to prepare them were in any way contradicting the locality of interactions in standard QED.

 

[DrChinese]

Nevertheless all the interactions involved in the preparation are of course local. What's needed are the two entangled photon pairs, photons 1 and 2 as well as potons 3 and 4, both of which are created by parametric down conversion, i.e., local interactions of laser photons with the BBO crystals. The next perparation step is the filter measurement done with photons 2 and 3, which also are based on local interactions of the photons with the beam splitter BS and the polarizing beam splitters PBS. The resulting entanglement of photons 1 and 4 after selection based on the measurement on photons 2 and 3 are all due to local interactions of photons with the "equipment" needed to prepare the entanglement of photons 1 and 4 via entanglement swapping. Of course, indeed, the photons 1 and 4 themselves never interacted ever locally. Nevertheless that does not imply that the interactions used to prepare them were in any way contradicting the locality of interactions in standard QED.

I wish you would stop contradicting mainstream science on this subject, as we have discussed many times. I have provided may quotes in recent years from top scientists indicating the nonlocal nature of swapping - you are the lone voice contrary to them. Again I ask for a verbatim quote from a suitable reference that says swapping is merely local, and nothing nonlocal is occurring (contradicting the below quote).

Zeilinger et al: "Quantum teleportation strikingly underlines the peculiar features of the quantum world. We present an experimental proof of its quantum nature, teleporting [nonlocally] an entangled photon with such high quality that the nonlocal quantum correlations with its original partner photon are preserved. This procedure is also known as entanglement swapping. The nonlocality is confirmed by observing a violation of Bell's inequality by 4.5 standard deviations. Thus, by demonstrating quantum nonlocality for photons that never interacted our results directly confirm the quantum nature of teleportation."

The entanglement swap can be performed anywhere at any time. The Bell test particles can be measured by Alice and Bob anywhere and at any time. (Those particles need not have ever co-existed! And they can even be entangled AFTER they are observed!)

There can be no local description of the entire experiment with these options, since Alice and Bob were never local to each other. So we could have:

1. Alice created at T=1 and observed at T=1.5.
2. Bob created at T=2.
3. Distant Bob observed at T=3 to have perfect correlations with Alice at any desired measurement setting.
4. At a later time, the entanglement of Bob with Alice is created (yes, this seems impossible but see my reference).

 

[martinbn]

2. This is not a requirement of a Bell test. Bell tests do not require that entangled particles ever interact with each other, and they do not need to have ever existed in the same spacetime cone. They can be created from fully independent sources sufficiently distant that no signal can propagate between them.

Not very important, but they are in common light cones.

 

[martinbn]

I wish you would stop contradicting mainstream science on this subject, as we have discussed many times.

He does not contradict the science. He only objects to the use of the term nonlocal.

 

[Fra]

1. If correct, this is exactly what Bell demonstrates requires explicit nonlocal action. Why? Because there is no $\lambda$ dataset that yields the quantum expectation values unless you FIRST know how Alice plans to measure.

My point was that I question the whole ansatz of that $\lambda$ determines the interaction statistics. IMHO I think the anzats is flawed so is no need for nonlocal actions. The detector is "informed" about the preparation (~$\psi$) only - not about $\lambda$, so at least in my interpretation the total interaction must account for the uncertatiny from preparation. So in my interpretation it's inconsistent that $\lambda$ alone can explain the interaction. The idea that lambda can explain this is built on the old ideas of how interactions work, and it's that THIS does not work that Bell IMO proves. But I supposed this is an interpretation as well.

/Fredrik

 

[PeterDonis]

I question the whole ansatz of that $\lambda$ determines the interaction statistics.

That ansatz was made by Bell for the very reason you yourself state:

The idea that lambda can explain this is built on the old ideas of how interactions work

Exactly. And:

it's that THIS does not work that Bell IMO proves.

Yes: Bell's Theorem proves that no model of the type Bell constructs using his ansatz can reproduce the predictions of QM, and also the experimental results, since those are consistent with the predictions of QM. You aren't proposing any alternative to Bell; you are simply agreeing with the implications of his theorem. What particular words you want to use to describe the class of models his ansatz covers is irrelevant.

 

[vanhees71]

I wish you would stop contradicting mainstream science on this subject, as we have discussed many times. I have provided may quotes in recent years from top scientists indicating the nonlocal nature of swapping - you are the lone voice contrary to them. Again I ask for a verbatim quote from a suitable reference that says swapping is merely local, and nothing nonlocal is occurring (contradicting the below quote).

Zeilinger et al: "Quantum teleportation strikingly underlines the peculiar features of the quantum world. We present an experimental proof of its quantum nature, teleporting [nonlocally] an entangled photon with such high quality that the nonlocal quantum correlations with its original partner photon are preserved. This procedure is also known as entanglement swapping. The nonlocality is confirmed by observing a violation of Bell's inequality by 4.5 standard deviations. Thus, by demonstrating quantum nonlocality for photons that never interacted our results directly confirm the quantum nature of teleportation."

The entanglement swap can be performed anywhere at any time. The Bell test particles can be measured by Alice and Bob anywhere and at any time. (Those particles need not have ever co-existed! And they can even be entangled AFTER they are observed!)

There can be no local description of the entire experiment with these options, since Alice and Bob were never local to each other. So we could have:

1. Alice created at T=1 and observed at T=1.5.
2. Bob created at T=2.
3. Distant Bob observed at T=3 to have perfect correlations with Alice at any desired measurement setting.
4. At a later time, the entanglement of Bob with Alice is created (yes, this seems impossible but see my reference).

Nothing I said, contradicts, what's said by Zeilinger above. There are of course nonlocal correlations, described by entanglement, but there are nowhere nonlocal interactions needed to explain entanglement swapping or teleportation.

My view is very mainstream physics: According to relativistic QFT all the Bell-test experiments can be described correctly using a theory based on the assumption that there are no faster-than-light causal influences, which is achieved by making the interactions described by this class of QFTs strictly local (i.e., the Hamilton density is commuting with all local observables at space-like differences of their arguments).

I don't understand, what you describe by 1.-4. To which experimental setup do you refer and what are the time (?) stamps T?

 

[DrChinese]

1. Nothing I said, contradicts, what's said by Zeilinger above. There are of course nonlocal correlations, described by entanglement, but there are nowhere nonlocal interactions needed to explain entanglement swapping or teleportation.

My view is very mainstream physics: According to relativistic QFT all the Bell-test experiments can be described correctly using a theory based on the assumption that there are no faster-than-light causal influences, which is achieved by making the interactions described by this class of QFTs strictly local (i.e., the Hamilton density is commuting with all local observables at space-like differences of their arguments).

2. I don't understand, what you describe by 1.-4. To which experimental setup do you refer and what are the time (?) stamps T?

1. And for the Nth time: you quote yourself when addressing the fact that your view is not mainstream. Where is that quote? And please, something verbatim is called for - not one of your "read any book" references. If you are mainstream, why haven't I seen anything like that in the last 100+ recent papers I have read? I won't respond further to you until you supply a suitable quote supporting your position.

There *is* "something" occurring (quantum) nonlocally. No one knows the mechanism. If it was simply a matter of correlations, as you say, then everyone would agree and we wouldn't be discussing. However, teleportation is a nonlocal effect from start to finish.2. Bell test with entanglement swapping to create the entangled pair. Read my reference, post #62 for example. You know this perfectly well, but deny its significance. You cannot entangle particles that have never existed in a common spacetime cone without a nonlocal effect of some type.

 

[PeterDonis]

Thread closed for moderation.

 

[PeterDonis]

Update: Thread will remain closed as the OP question has been addressed and there is no point in wrangling over what the word "locality" means when there does not appear to be any dispute over the actual physics--what is actually observed in experiments and the theoretical, mathematical machinery that predicts it.