Entanglement: is there 'action at a distance' due to measurement?

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Discussion Overview

The discussion revolves around the implications of measuring entangled particles in quantum mechanics, particularly focusing on the nature of particle B when particle A is measured. Participants explore concepts such as action at a distance, the interpretation of quantum mechanics, and the implications of measurement on entangled states.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants question whether particle B possesses definite spin properties before measurement, suggesting that this depends on the interpretation of quantum mechanics.
  • Others argue that after measuring particle A as spin-up, particle B is in a definite eigenstate of spin about the same axis, but its spin about other axes remains indeterminate.
  • A participant raises the idea that the concept of action at a distance may imply a mechanism that is not part of quantum mechanics, speculating about faster-than-light influences.
  • Some interpretations discussed include instantaneous collapse, many-worlds, superdeterminism, and retrocausal theories, each proposing different views on the nature of measurement and entanglement.
  • There is a mention of Bell's Theorem in relation to local hidden variables and the implications of experimental results on the nature of entanglement.
  • Clarifications are made regarding the relationship between eigenstates and eigenvalues, with some asserting that an eigenstate will yield a definite measurement outcome.

Areas of Agreement / Disagreement

Participants generally do not reach a consensus, as multiple competing views on the interpretation of quantum mechanics and the implications of measurement remain. The discussion reflects a variety of interpretations and uncertainties regarding the nature of entangled particles and measurement outcomes.

Contextual Notes

Limitations include the dependence on interpretations of quantum mechanics, the unresolved nature of action at a distance, and the varying implications of measurement across different theoretical frameworks.

  • #91
Fra said:
As there is at least one more critical constant to worry about if you like Einstein seems to see no way to avoid the spacetime continuum.

Can we expect that the next step in the work - in your spirit - to be something like "NPRF+c+h+G"?

/Fredrik

“‘Mysteries’ of Modern Physics and the Fundamental Constants c, h, and G,” W.M. Stuckey,
Timothy McDevitt and Michael Silberstein. Honorable Mention in the Gravity Research
Foundation 2021 Awards for Essays on Gravitation.

Quanta 11(1), 5-14 (2022).

https://dankogeorgiev.com/ojs/index.php/quanta/article/view/66
 
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  • #92
Morbert said:
A principles-based understanding of a physical theory is desirable, but I don't think it dissolves interpretational disputes. Even in relativity, these disputes persist (see e.g. Substantivalism vs Relationalism). It's simply the case that quantum theories are more protean than classical theories, with a richer landscape of successful interpretations.
What I have in mind is the intepretation of the principles and how that influence how we view and navigate in theory space.

If we view them as unexplainable fixed facts of nature for us to discover empirically, a typical theory ansatz has plenty fine tuning room. The challenge then is how to enlarge theory space without getting lost in the same.

Or if we see the principles that relate subsystems as emergent as having been tuned by nature itself. Then there may be deeper principles for how persistent principles emerge, that may allow for a more convergent approach to enlarge theory space that maintain stability over evolution. In this case principles likely has an hierarchy, some came about before others.

This is what i meant by principle and constructive principles can complement each other, or be different sides of the same coin.

/Fredrik
 

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