Quantum Mechanical Conceptual Problems

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Discussion Overview

The discussion revolves around conceptual problems in quantum mechanics (QM), particularly focusing on wave-particle duality, superposition, wave function collapse, and the relationship between quantum states and classical systems. Participants explore theoretical implications and challenges related to these concepts.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants express confusion about the nature of wave function collapse and its implications for superposition, questioning what causes this collapse and how it relates to classical observables.
  • One participant argues that the consequences of superposition can be observed through measurements of non-commuting observables, suggesting that superposition does not necessarily lead to a total collapse of the wave function.
  • Another participant raises concerns about how a dimensionless energy vector can be transformed into an observable particle in three-dimensional space, and how multiple quantum states can combine to form a classical system.
  • A different viewpoint is presented, asserting that wave-particle duality is a misconception and that superposition merely describes the distribution of properties without implying a real collapse of the wave function.

Areas of Agreement / Disagreement

Participants express differing views on the nature of wave-particle duality, the concept of wave function collapse, and the relationship between quantum and classical systems. There is no consensus on these issues, and multiple competing perspectives remain.

Contextual Notes

Participants reference various theoretical frameworks and experiments, such as decoherence and the Stony Brook/Delft SQUID experiment, to support their claims. However, the discussion highlights unresolved questions regarding the foundational aspects of quantum mechanics.

DMuitW
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Some straightforward problems I have encountered in QM; i'll post them gradually, otherwise it 'd be a little long, thanks

1a) Wave/particle Duality: A quantum wave as stated through Dirac and von Neumann is a probability wave expressed by Schrödinger equation and thus here implying a superimposed state. A first conceptual problem I encounter here is that the very being of superposition can never be observed. It can be derived from the interference of for example the double slit experiment. Logically, the superimposed wave function has encountered a "wave collapse" due to a certain form of measurement. Due to this wave collapse, the former probability wave will act as a single vector in Hilbert space, containing finite energy, thus being a point in Hilbert space.
If we keep on using this definition of the quantum properties, I am very curious what that exactly causes the wave collapse.

1b) The notion of the "particle"- being of the quantum as a single vector in Hilbert space with finite energy thus implies a major problem explaining classical "rest mass". Thus if a classical observable particle,if being fundamentally different in some way of the quantum vector,is observed, it could never generate an interference pattern (if we do a gedankenexperiment containing two slits and bowling balls), just because the quantum properties of the propability wave needed for interference avoid the classical notion of matter.
IF! on the other hand you don't make a difference of fundamental level between a single quantum system and a classical system, -what- does then "convert" your theoretical vector in Hilbert space to a classical observable system having a structural rest mass, in which E=mc² must play a major role?

1c) If indeed, you don't make a fundamental difference between a single quantum state and a "classical" system (as being build up by single quantum states), then what contains the information to collapse the wave function of a whole system, thus creating a logically structured classical system??
 
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DMuitW said:
Some straightforward problems I have encountered in QM; i'll post them gradually, otherwise it 'd be a little long, thanks

1a) Wave/particle Duality: A quantum wave as stated through Dirac and von Neumann is a probability wave expressed by Schrödinger equation and thus here implying a superimposed state. A first conceptual problem I encounter here is that the very being of superposition can never be observed. It can be derived from the interference of for example the double slit experiment. Logically, the superimposed wave function has encountered a "wave collapse" due to a certain form of measurement. Due to this wave collapse, the former probability wave will act as a single vector in Hilbert space, containing finite energy, thus being a point in Hilbert space.
If we keep on using this definition of the quantum properties, I am very curious what that exactly causes the wave collapse.

I'm going to risk sounding like a broken record (broken CD?), but here goes.

The consequences of superposition CAN be observed. When you make a measurement, you are only forcing a definite state only on that corresponding to the commuting observable. It means that the observable that do NOT commute will still be represented by a superposition of states. For example, when you make a measure of Lz, the other two orthorgonal observables, Lx and Ly, REMAINS in indefinite state. Lz do not commute with both Lx and Ly. This means that a measurement of Lz does NOT remove the superposition of states that may be describing Lx and Ly.

Thus, if something is in a superposition of states, if I can find a non-commuting observable, I can make that measurement and see if so-and-so values reflect the fact that there is some form of superposition going on. This is what has been observed in the Stony Brook/Delft SQUID experiment (I have made repeated references to this here and in my Journal entry).

Thus, you can still detect the effect of such superposition without causing a total "collapse" of the wavefunction.

Zz.
 
Ok, so according to that paper superposition also is also noted in macroscopic distant states. Thats a clear and straight answer , thanks.

But that leaves most of my other questions unanswered. I still have conceptual problems on how a dimensionless "energy" vector such as stated by Quantum Mechanics can in some way or another be altered and be converted in a "particle" observable in 3D, and Above all, can be combined in such a way that they form logically structured systems.
In other words, how a single quantum state can be collapsed in some way or another and form with numerous other similarly collapsed functions a "classical system".

Thank you
 
1c) If indeed, you don't make a fundamental difference between a single quantum state and a "classical" system (as being build up by single quantum states), then what contains the information to collapse the wave function of a whole system, thus creating a logically structured classical system??
Maybe this will help.

DECOHERENCE, EINSELECTION,. AND THE
QUANTUM ORIGINS OF THE CLASSICAL. Wojciech Hubert Zurek.

http://

Regards
 
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There is no wave particle duality.

The superposition is just a description of the space/time distribution of some of the particle or system's properties.These properties constitute a partial description of the particle and its fields.

There is no real collapse. There is just redistribution of particle or system properties over space/time.

juju
 

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