I Entanglement swapping, monogamy, and realism

[DrChinese]

Just to summarize: my point is that "pre-existing correlations" are not "pre-existing something", but a well-defined technical term that should not be used in a loose manner as its meaning may easily get altered completely when doing so.

Wow @Cthugha , I think your focus on the word "correlations" (or "something") is way overboard, quite out of the ordinary for you. If you want to make something of the significance of momentum entanglement (as opposed to polarization entanglement) in PDC pairs and how it relates to conservation rules: Start a thread and we can discuss. But you will quickly find that it is not a factor in swapping experiments (or their interpretation), at least not one that changes anything discussed in this thread. Entanglement is entanglement, regardless of basis. Conservation is conservation as well, and nothing I say challenges this. I have written enough in this thread that trying to french fry me over a word is ridiculous. If you have something of substance, then present it.
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So... I wasn't specifically trying to make the point about correlations when I wrote it, but if you want to press it: let me be explicit:

DrC: The final (1 & 4) correlations are not pre-existing independent of the BSM. Only the initial (1 & 2) correlations existed prior to that (due to MoE*). Correlations that violate CHSH are indicative of entanglement*, and vice versa.

Reference on "correlation" as you requested (the one we've been using and you apparently didn't read entirely):
https://arxiv.org/abs/0809.3991

"We confirm successful entanglement swapping by testing the entanglement of the previously uncorrelated photons 1 and 4. Violation of a CHSH inequality is not only of fundamental interest because it rules out local-hidden variable theories. It also proves that the swapped states are strongly entangled... The resulting correlations between particles that do not share any common past are strong enough to violate a Clauser-Horne-Shimony-Holt (CHSH) inequality."

Case closed, my words stand as written. You can argue with the authors over semantics if you like, but I'm done on your point in this thread. You aren't even disputing that the BSM is action at a distance.*Already referenced, and not a single counter-reference presented to date in these threads. I am not going to keep presenting references over and over.

 

[Fra]

I call this "skirting Bell" because these interpretations do not do a very strong job of rejecting EPR elements of reality (Bell realism). They keep with the idea that there was a single reality prior to the act of measurement.

I think most interpretations holds variations but I think that qbist stances(at least not all) does not strictly "keep the idea of objective reality". To me at least i would say it is compatible with objective reality but does not rely on it. This is a world of difference! I would even say objective reality cant be ruled out, so its allowed, but the agent interations is indifferent to it. A solid illusion is indistinguishable from objective reality from the perspective of any inferring agent.

This is to me the KEY to bypass/skirting? the premises of bells theorem - isolated HV may exist and add explanatory value, but they does not influence the physics as long as they are isolate not only from the physicist but from every part of the experimental setup.

But I see no problem with this "skirting"?

Realism is allowed, but wether its just an illusion doesnt matter. Its impossible to tell and that is fine. Also, the point for an agent is that even IF objective reality exists, that adds no value, unleas the agent has inferred it.

Otherwise its like say you know the answer to somerhing! Its only that you forgotten it. Or you have a superalgorithm that you clom gives the answer it just takes the lifetime of a universe to compute it.

Well then you dont know. And your decision must be made.

/Fredrik

 

[Nullstein]

We have established many times that the initial 1 & 4 state is uncorrelated and unentangled, and that there is no relationship between them - hidden or otherwise.

We also have established many times that the final 1&4 state is uncorrelated and unentangled.

Yes, it is trivially true that if you look at the 1 & 4 pairs and don't know their Bell state, no pattern pops out. I guess we need to tell this team that they are wasting their time when they run the experiment and announce: "We confirm successful entanglement swapping by testing the entanglement of the previously uncorrelated photons 1 and 4. Violation of a CHSH inequality is not only of fundamental interest because it rules out local-hidden variable theories. It also proves that the swapped states are strongly entangled and, as a result, distillable."

All I can say is "wow". Hundreds of teams out there are working to create quantum networks using swapping from point to point to point. They all seem to think there is entanglement, and they all seem to think the 2 & 3 BSM had something to do with it.

The aim of these teams is just to verify the predictions of QM, nothing more. Your personal goal, which is different from the goal of these teams, is to somehow infer causal relationships from the data. These teams have reached their goal, while you have failed to reach yours. Nobody doubts that there is entanglement swapping. The discussion in this thread is solely about causal inference.

I have quoted extensively on Monogamy and referenced papers.

We have already established that your application of MoE is wrong. You are trying to somehow show that the full ensemble of 1&4 is entangled after the BSM. We have established that it is in a product state. No appeal to MoE can invalidate this. The papers you quoted don't support your opinion.

 

[PeterDonis]

Thread closed for moderation.

 

[DrClaude]

We'll leave the thread closed. Thanks to all that have participated.