Collapse of Wavefunction

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  • #26
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If the photons took any random path ....
Just an observation:

Using the term "random" without specifying the probability distribution may be misleading. Determinism is a particular kind of randomness. And the term "completely random" can be also misleading, because we may not even be able to define it precisely (For instance there are no translation invariant probabilistic measures on R).
 
  • #27
zonde
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Zonde, about the first question,

say a torch or a laser light when it comes out of the source, does not know the destination. However at the macro level we know where the light is going to reach. If the photons took any random path, we wouldn't be able to predict the destination - would we ?
Yes, I see it the same way. Photons have quite certain trajectory at macro level.
 
  • #28
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That depends on how the photon state is prepared and on the interactions.
 
  • #29
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Nice discussion. Hope it carries on.
 
  • #30
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I agree with that.


Problems appear when one attempts to identify the photon with its wave function. What we need is to understand what exactly the relation between the two is. Unfortunately, different interpretations of QM offer different answers. The EV bomb is an example where the differences between various interpretations become particularly clear.
test
 
  • #31
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What about that: photon is an excited state of quantized EM field. Wave function is its mathematical representation?
 
  • #32
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What about that: photon is an excited state of quantized EM field. Wave function is its mathematical representation?
How would that help to solve the EV bomb problem?

Does the photon takes both paths or not? If not, then what you said above is not satisfying. If yes, then why do we never observe photon at both positions at once?
 
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  • #33
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What is your problem? You think of photons as of point particles that have paths. Stop thinking this way and you will have no problems. You can model your EV bomb on your PC and see how it works. You model using wave functions, bombs and detectors. Bombs and detectors are material, wave functions are not. Wave functions represent states of the EM field.
 
  • #34
Fredrik
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I'm also not a fan of the view that "the photon takes both paths". QM doesn't claim that it does. It just says that both paths contribute to the probability amplitude of a detection event. The claim that the photon takes both paths doesn't imply anything about results of experiments, so it doesn't qualify as a theory. That puts it in a gray area between science and pseudo-science. It's not science because it fails to meet the requirements of a theory, and it's not pseudo-science because it doesn't contradict any good theories. It's just a suggestion about what mental images you might want to use when you think about the theory. I don't think it's a bad thing that people are trying to develop such mental images, because some of them might be useful. I just don't think this one is.
 
  • #35
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What is your problem? ... Bombs and detectors are material, wave functions are not. Wave functions represent states of the EM field.
My problem can be presented in the following way: Are electrons material?
If they are, then how would you explain an EV bomb in which photons are replaced by electrons?
If they are not, does it mean that all materials are made of something which is not material?
 
  • #36
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You think of photons as of point particles that have paths. Stop thinking this way and you will have no problems.
Actually, when I think of photons and electrons as point particles that have paths, THEN I have no problems. But I have problems when I DON'T think that way. In my post above I am trying to convey that problem to you.
 
  • #37
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My problem can be presented in the following way: Are electrons material?
I think we have to let go this with the introductions of wave particle duality .. which is also not a right way of putting it. wavicle was term that was invented, but never stuck. Essentially it means at micro-level you have two ways of looking at things , material (particle) or non-material (wave).

If they are, then how would you explain an EV bomb in which photons are replaced by electrons?
This is a very good question. It would have the same effect, except for the fact that we need to have some other type of interferometer.
If they are not, does it mean that all materials are made of something which is not material?
As far as I understand this is what it finally boils down to. Everything (at least at micro-level) is connected to everything else. So, and photon or electron would not have a measurable location, at least until wavefunction is collapsed.

That brings me back to my original question. Wavefunction collapse is mathematical and probabilistic concept. I do understand that it conveys and supports most of the physical phenomenon. However - what is the physical meaning of this. And if you are asking to let-go physical meaning (forget visualization), it is not a good way proceed.
 
  • #38
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I do understand that it conveys and supports most of the physical phenomenon. However - what is the physical meaning of this.
Perhaps the physical meaning of this is the following one: quantum theory will be one day replaced by another theory that will save us from such dilemmas. They will be replaced by some other dilemmas on an even deeper level.
 
  • #39
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That brings me back to my original question. Wavefunction collapse is mathematical and probabilistic concept. I do understand that it conveys and supports most of the physical phenomenon. However - what is the physical meaning of this. And if you are asking to let-go physical meaning (forget visualization), it is not a good way proceed.
If you insist on having at least a CONSISTENT (not necessarily correct) understanding of a physical meaning of it, there is no other way than to adopt one of the specific INTERPRETATIONS of QM, such as objective collapse, many world, Bohmian, etc. Unfortunately, you cannot learn about them from textbook QM, so you must search elsewhere ...
 
  • #40
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objective collapse, many world, Bohmian, etc. Unfortunately, you cannot learn about them from textbook QM, so you must search elsewhere ...
Any links / sources where some of these could be ?
 
  • #41
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Any links / sources where some of these could be ?
Interaction-free measurement is part of the quantum liar paradox. Both are explained via the Relational Blockworld interpretation in “Reconciling Spacetime and the Quantum: Relational Blockworld and the Quantum Liar Paradox,” W.M. Stuckey, Michael Silberstein & Michael Cifone, Foundations of Physics 38, No. 4, 348 – 383 (2008), quant-ph/0510090.
 

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