Undergrad Decoherence and standard formalism

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SUMMARY

The discussion centers on the compatibility of decoherence with the Copenhagen interpretation of quantum mechanics and the standard mathematical formalism. It establishes that while the Copenhagen interpretation treats the environment classically, decoherence requires a quantum mechanical treatment of both the system and the environment. The conversation highlights the need for a master equation to model dissipative processes in quantum mechanics, particularly in systems like cavity field modes, and references the significant contributions of physicists Zeh and Zurek in this area.

PREREQUISITES
  • Understanding of quantum mechanics principles, particularly decoherence.
  • Familiarity with the Copenhagen interpretation of quantum mechanics.
  • Knowledge of density matrix formalism in quantum mechanics.
  • Basic concepts of Hamiltonians and quantum harmonic oscillators.
NEXT STEPS
  • Study the derivation and implications of the master equation in quantum mechanics.
  • Explore the works of Zeh and Zurek on decoherence and its implications for quantum measurements.
  • Investigate the differences between classical and quantum treatments of measurement devices.
  • Learn about the role of entanglement in the context of open quantum systems.
USEFUL FOR

Physicists, quantum mechanics students, and researchers interested in the foundations of quantum theory, particularly those exploring the implications of decoherence and the measurement problem.

  • #61
bhobba said:
The sbove shows many misconceptions eq an eigenstate is not in a superposition is simply wrong. You must be precice in what you are saying..

Now here is your task. You claimed to have read Maximilian's book. He disscusses MW on page 336.

How about giving us a precis of what he said then a well formulated question based on that precis. As it stands you query makes no sensse.

Thanks
Bill

In the double slit experiment. The eigenstate or eigenpositions are the spots in the detectors. So they are no longer in superposition because they are collapsed already. So why do you say eigenstate is still in superposition. Born rule is already applied when a system is in an eigenstate.

I already read page 336 a week ago.. It's mostly relative-state interpretation.. But in modern day. Most are into many worlds. I'll quote Maximilians:

"Each of these (physical) states can be understood as relative (a) to the state of the other part in the composite system (as in Everett's original proposal; see also [141,143]), (b) to a particular "branch" of a constantly "splitting" universe (the many-worlds interpretation, popularized by DeWitt (386) and Deutsch (387[), or (c) to a particular "mind" in the set of minds of the conscious observer (the many-minds interpretation; see, for example, [388])"

In (b), Dewitt many worlds are classical nut and bolt world, is it not? and most people refer to Dewitt now in Many worlds. The original Everette relative proposal is less popular.
 
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  • #62
fanieh said:
In the double slit experiment. The eigenstate or eigenpositions are the spots in the detectors'

States are destroyed in the double slit so the question is meaningless.

If not, and this is basic QM, all states are in superposition and in an infinite number of ways. An eigenstate of an observable is still in superposition - its just that an eigenstate will give a definite result if observed using the observable its an eigenstate of. Its in superposition as any state is.

Thanks
Bill
 
  • #63
fanieh said:
I already read page 336 a week ago..

Then read 337 - its the modern version.

It should be easy not to quote, which I asked you not to, but give us a precis. Whats going on in decoherence terms is very very simple - but I would prefer you to nut it out. If you want to study books at this level you must be prepared to THINK.

Thanks
Bill
 
  • #64
bhobba said:
States are destroyed in the double slit so the question is meaningless.

If not, and this is basic QM, all states are in superposition and in an infinite number of ways. An eigenstate of an observable is still in superposition - its just that an eigenstate will give a definite result if observed using the observable its an eigenstate of. Its in superposition as any state is.

Thanks
Bill

Is this Bohr's original formalism? Because I was referring to Bohr. His Eigenstate is classical already because the apparatus is classical.. so please specify if it is Bohr formalism.. or other formalism.
 
  • #65
fanieh said:
Is this Bohr's original formalism?

No.

Thanks
Bill
 
  • #66
bhobba said:
Then read 337 - its the modern version.

It should be easy not to quote, which I asked you not to, but give us a precis. Whats going on in decoherence terms is very very simple - but I would prefer you to nut it out. If you want to study books at this level you must be prepared to THINK.

Thanks
Bill

But most physicists still think apparatus is classical and there is a division between quantum and classical world. Only few realized even the apparatus is quantum. Hence for those who believe in many worlds. They refer to Dewitt Many World instead of the Everett original formalism. Don't you agree with it? Many physicists who study the mathematical formalism assumes apparatus is classical. How many percentage do you estimate think it is quantum? Therefore I need to consider the mindset of these people.
 
  • #67
fanieh said:
But most physicists still think apparatus is classical and there is a division between quantum and classical world.

Really.

You know this exactly how?

There is no division and I am not aware of mainstream modern practicing physicists that thinks so. And please don't quote thus or that they are either out of date, hold fringe ideas or you have the wrong context.

The modern view is Wienberg's:
http://scitation.aip.org/content/aip/magazine/physicstoday/article/58/11/10.1063/1.2155755

Both Bohr and Einstein were wrong, there is no classical quantum division and you will never learn QM from reading ancient texts.

Thanks
Bill
 
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  • #68
fanieh said:
most physicists still think apparatus is classical and there is a division between quantum and classical world

AFAIK this statement is egregiously false.

fanieh said:
I need to consider the mindset of these people.

I don't think you should. I think you should focus on understanding the basic math of QM, how it makes experimental predictions, and how those predictions actually compare with experiments. In other words, start with the "shut up and calculate" interpretation. Until you've mastered that, trying to understand what the other interpretations are saying is going to be beyond you.
 
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