Where is the quantum system prior to measurement?

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Discussion Overview

The discussion centers on the question of the location or position of a quantum mechanical (QM) system prior to measurement. Participants explore various assumptions and implications regarding the nature of reality in quantum mechanics, particularly whether location is an inherent property of a system before it is measured. The scope includes theoretical interpretations of quantum mechanics and the implications of these interpretations on our understanding of physical reality.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants propose that the universe is spatially extended and that a quantum system is a subset of this universe, leading to questions about its location prior to measurement.
  • There is a suggestion that one of two propositions must be true: either location is an 'element of reality' prior to measurement, or it is not.
  • Some argue that it makes sense to assert that a system prepared in one lab (e.g., Paris) is located there, but caution against negative assertions about its absence in another lab (e.g., Rome) due to potential nonlocal correlations.
  • Participants discuss the implications of asserting that a system is not everywhere in the universe, with some questioning the usefulness of such assertions if they do not lead to observable consequences.
  • There are differing views on whether a complete description of physical reality must include the location of a quantum system prior to measurement, with references to interpretations of quantum theory such as pilot-wave theory.
  • Arguments are presented regarding the necessity of a location for a quantum system to interact with measurement devices, with various conditional statements about the implications of location on measurement outcomes.

Areas of Agreement / Disagreement

Participants express a range of views on the nature of location in quantum mechanics, with no consensus reached. Some agree that location is a necessary component of a complete description of reality, while others challenge the implications of such assertions. The discussion remains unresolved with multiple competing interpretations and perspectives.

Contextual Notes

Limitations include the dependence on interpretations of quantum mechanics, the ambiguity of terms like 'location' and 'element of reality', and the unresolved nature of the arguments presented. The discussion also highlights the complexity of nonlocal correlations and their implications for assertions about location.

  • #151
Lynch101 said:
Remaining agnostic on what route is taken renders a 3D model incomplete.
Lynch101 said:
then either our model is not a complete description of 'the physical reality'
WernerQH said:
I admire your persistence. It may not be obvious to you, but ironclad logic loses its force when a flawed assumption is included. ... Probably you'll never be able to make sense of quantum theory.
My impression is that Lynch101 ignores the connection of "complete description" with the original thermodynamical riddles: If there were a more complete description, then there must be more local degrees of freedom, but then you have to explain why those local degrees of freedom don't show up in the entropy.
OK, an atom actually has internal degrees of freedom, so why are those invisible in the entropy? Because their excitation energy is so high that they would only start to contribute to the entropy in a really really hot plasma.
But those unique paths he wants the interpretation to describe, why would those not constitute degrees of freedom, and why would those not show-up in the entropy?
OK, the de Broglie-Bohm interpretation actually has such paths, so why are those invisible in the entropy? Because those are not local degrees of freedom.
 
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  • #152
WernerQH said:
I admire your persistence. It may not be obvious to you, but ironclad logic loses its force when a flawed assumption is included. You have achieved reductio ad absurdum of the idea that quantum theory can be understood in terms of quantum "objects" (or what you call "systems"). Probably you'll never be able to make sense of quantum theory.
In effect all I have done is set out some very basic principles of 3D modelling. From this we can deduce/infer certain rules which must apply to anything which operates within such a model. One such rule relating to the propagation of anything from one region to another spatially separated region.

For a complete 3D model we should be able to represent everything in the universe at all times. If we don't specify i.e. remain agnostic on the unique path/route of propagation taken by anything within our 3D model then we are left with an incomplete 3D model. If we say that no unique path is taken, then either that 'thing' is not in the universe or it operates in other dimensions.
 
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  • #153
Lynch101 said:
It's not simply a matter of opinion. It's the application of basic principles of 3D modeling to the experimental set-ups and making inferences/deductions about the implications.
This claim about "basic principles of 3D modeling" is just your opinion.

Lynch101 said:
Physicists also commit to the propagation of causal influences at a finite speed, don't they?
No. Not all interpretations of QM require causal influences to "propagate".
 
  • #154
WernerQH said:
I admire your persistence. It may not be obvious to you, but ironclad logic loses its force when a flawed assumption is included. You have achieved reductio ad absurdum of the idea that quantum theory can be understood in terms of quantum "objects" (or what you call "systems"). Probably you'll never be able to make sense of quantum theory.
And this seems like a good note on which to close the thread.
 
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