The relation between classical from quantum vs measurement perspective

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Discussion Overview

The discussion explores the relationship between classical and quantum systems, particularly in the context of measurement and wavefunction collapse. Participants examine how classical objects, which are perceived as having definite properties, relate to quantum objects that exhibit probabilistic behavior until measured. The conversation touches on concepts such as decoherence and the nature of wavefunction collapse, as well as the implications for understanding atomic structure.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant questions the relationship between classical objects and wavefunction collapse, expressing confusion about the measurement problem in quantum mechanics.
  • Another participant argues that wavefunction collapse does not connect the quantum and classical worlds, suggesting that the Born rule serves this purpose instead.
  • A participant states that collapse is not a part of quantum mechanics but rather a feature of certain interpretations, proposing that classical properties emerge from constant observation and interaction with the environment through decoherence.
  • Concerns are raised about the implications of decoherence for atomic behavior, particularly regarding the position of protons and electrons within atoms.
  • One participant emphasizes that while classical objects exhibit classical behavior due to environmental interactions, all objects fundamentally remain quantum in nature.
  • Another participant highlights the difference in behavior between protons and electrons, noting that protons appear more localized compared to the more elusive nature of electrons.

Areas of Agreement / Disagreement

Participants express differing views on the role of wavefunction collapse and decoherence in bridging classical and quantum realms. There is no consensus on how these concepts relate to the behavior of classical objects or the implications for atomic structure.

Contextual Notes

Participants reference various interpretations of quantum mechanics and the challenges of explaining complex concepts at a lay level. The discussion includes mentions of specific literature and resources that may provide further insight, though the participants acknowledge the difficulty in understanding these topics.

ftr
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What is the relation between classical from quantum vs measurement problem. On one hand they seem to be related on the other they seem to be of different nature.

We always see our screens on front of us and not 100 meters away, that we say is classical object although the screen is a quantum object in the end and it exists even when we are not looking at it . But the measurement of quantum systems says it only takes reality when "measured". I am confused when people discuss wavefunction collapse in regard as to which problem is actually being addressed and the relation.

Edit by mentor. You cannot bump a thread in less than 24 hours, so your posts have been merged. Please read the rules. It's amazing that after all of this time here you have never bothered to read the rules.

Since I am not getting any response let me ask a simpler question. Are classical objects considered to be a collapsed wavefunction of the system or the subsystems or what?.
 
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Personally I think that wavefunction collapse does not connect quantum and classical worlds. I think it's rather Born rule that does that.
So my answer is no, classical system is not collapsed wavefunction. Classical system can be described by probability while quantum system by probability amplitude.
 
ftr said:
Are classical objects considered to be a collapsed wavefunction of the system or the subsystems or what?.

Well first of all collapse isn't part of QM - its only part of some interpretations.

The classical world emerges because classical objects are being 'observed' all the time by the environment which via decoherence gives them classical properties.

Remove that interaction with the environment, while quite difficult to do, has in recent times been done, and some strange phenomena emerge:
http://physicsworld.com/cws/article/news/2010/mar/18/quantum-effect-spotted-in-a-visible-object

All objects are quantum - but not all objects are interacting with the environment (the vast vast majority are of course - its very very hard to engineer a situation where it isn't) - those that do have classical behaviour. For example a few stray photons form the CMBR are enough to give a dust particle a definite position.

The detail of all of this can't really be explained at the lay level - at that level the following is about as good as can be done:
https://www.amazon.com/dp/0465067867/?tag=pfamazon01-20

If you are willing to actually do the hard yards and delve into the detail (which of course I think is the best course) then the following is THE book:
https://www.amazon.com/dp/3540357734/?tag=pfamazon01-20

Thanks
Bill
 
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Thanks Bill. Of course, I read the Wiki decoherance and hence my question. If you look at the part of measurement you find it brief and confusing, other articles give very hard to understand discussions and not real explanation.

Moreover, as for classical from quantum, in NRQM you find the proton sitting in one place(ie. well defined position almost) and it is the electron which is elusive. So for normal classical objects I don't know what is the big deal the protons are not allover the place like electrons. And so what does decoherence actually says. Now, if it says the electron's position gets defined, that sound like a disaster for the atoms. I guess I am not getting it.

My understanding is the decoherance tries to explain why we don't find atoms allover the place as to the description of their wavefunction, is that correct?
 
ftr said:
My understanding is the decoherance tries to explain why we don't find atoms allover the place as to the description of their wavefunction, is that correct?

No.

It explains apparent collapse.

Thanks
Bill
 
Thanks Bill. But I was hoping somebody addresses my proton argument.
 
ftr said:
Moreover, as for classical from quantum, in NRQM you find the proton sitting in one place(ie. well defined position almost) and it is the electron which is elusive. So for normal classical objects I don't know what is the big deal the protons are not allover the place like electrons.

The electron is much lighter than a proton so the model is we describe the system using the proton as the origin of our coordinate system. An atom as a whole is modeled quite well as a little ball.

You can probably find treatments that remove that assumption but the math would be a lot harder and I don't think particularly illuminating of anything.

Thanks
Bill
 

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