Why I hope QM is incomplete


by kebugcheck
Tags: bohr, double slit, einstein, erp, quantum collapse
DennisN
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#19
Feb19-13, 01:55 PM
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Quote Quote by kebugcheck View Post
But (some)QM literature makes the act of observing by a human unique.
I would personally choose other literature (at least at first). I see no reason to cloud one's objectivity by introducing humans as special. But it's my personal opinion of course. A quite interesting question (from a psychological perspective IMO) is why some people seem to resort to the human perspective when discussing QM. It seems... unusual. We don't seem to need any human perspective when discussing, let's say, thermodynamics or relativity.
Quote Quote by kebugcheck View Post
why should the non-determinism (even in form of probabilities) exists at microscopic level ? Am I the only one who finds it absurd ?
No, you are not alone . But I would personally not call it absurd, but interesting, because:
Quote Quote by atyy
I don't believe there is any consensus as to whether any interpretations are satisfactory.
I agree with atyy.
Quote Quote by kebugcheck View Post
This is so interesting :)
Yes!
mfb
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Feb19-13, 02:20 PM
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Quote Quote by kebugcheck View Post
I get that quantum phenomenon is not macroscopic.
I would like to add Bose-Einstein condensates to the counterexamples of DennisN.
Quote Quote by kebugcheck View Post
But (some)QM literature makes the act of observing by a human unique.
That literature is bad then, unless this option is just mentioned as one of many interpretations (and I don't think it has many supporters).
*why should the non-determinism (even in form of probabilities) exists at microscopic level ? Am I the only one who finds it absurd ?
There are interpretations where the time-evolution of the universe is deterministic, in particular the de-Broglie-Bohm theory and many worlds.

Cat is dead or it is alive. why does it needs to be both ?
Superpositions exist in all interpretations in some way. Otherwise, you could not perform double-slit experiments.

A photon "knowing" that "ahead-lies-a-slit-and-I-should-behave-like-wave" makes more sense.
No, it does not fit to experiments. You can decide what you want to measure even after the photon passed the slit(s).

Quote Quote by micky_gta
How would you explain the double slit experiment where a 'measuring device' was left on but the information leaving the measuring device was not allowed to reach its destination and viewed (by humans) AND STILL resulting in a an interference pattern?
To get an interference pattern, this information has to be destroyed in a very fundamental way - in a way not even a rock could "observe" it.
The_Duck
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Feb19-13, 02:24 PM
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Quote Quote by kebugcheck View Post
But (some)QM literature makes the act of observing by a human unique.
Unfortunately there's a lot of nonsense written about QM. Your instincts that human consciousness should not be special are correct. Anyone who tries to associate QM with human consciousness is talking nonsense.

Quote Quote by kebugcheck View Post
*why should the non-determinism (even in form of probabilities) exists at microscopic level ? Am I the only one who finds it absurd ?
No, many people have an instinctive reaction against non-determinism. But keep in mind that the universe doesn't particularly care what you find absurd.

Quote Quote by kebugcheck View Post
Cat is dead or it is alive. why does it needs to be both ?
All we can do is look at the world and try to describe what we see, and what we see is that it is possible for things to be in "superpositions" of different states.

Quote Quote by kebugcheck View Post
*what point do QM laws give up and classical laws start ?
Classical mechanics arises gradually from quantum mechanics as you consider larger systems, in the same way that Newtonian mechanics arises gradually from special relativity as you consider slower speeds.
DennisN
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Feb19-13, 02:37 PM
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Quote Quote by kebugcheck View Post
I get that quantum phenomenon is not macroscopic.
I also forgot the Tunnel diode, which makes use of quantum tunnelling.
bhobba
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Feb20-13, 02:10 AM
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Quote Quote by kebugcheck View Post
Source suggestions ? I have background in higher math and physics being an engineer.
Then the book to get is - Quantum Mechanics - A Modern Development by Ballentine:
http://www.amazon.com/Quantum-Mechan.../dp/9810241054

An observation is any device capable of recording an outcome - it has nothing to do with a conscious observer. But don't take my word for it - it's all explained in full detail in the reference above.

Thanks
Bill
micky_gta
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Feb20-13, 11:58 AM
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Quote Quote by mfb View Post
To get an interference pattern, this information has to be destroyed in a very fundamental way - in a way not even a rock could "observe" it.
I do not understand your answer to my question?

my question: "How would you explain the double slit experiment where a 'measuring device' was left on but the information leaving the measuring device was not allowed to reach its destination and viewed (by humans) AND STILL resulting in a an interference pattern? "

People argue that its the measuring devices that causes the double slits to appear instead of an interference pattern when clearly experiments have shown that its not. Its where the information ends up and 'who' knows about it.
mfb
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Feb20-13, 12:01 PM
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Quote Quote by micky_gta View Post
I do not understand your answer to my question?

my question: "How would you explain the double slit experiment where a 'measuring device' was left on but the information leaving the measuring device was not allowed to reach its destination and viewed (by humans) AND STILL resulting in a an interference pattern? "

People argue that its the measuring devices that causes the double slits to appear instead of an interference pattern when clearly experiments have shown that its not. Its where the information ends up and 'who' knows about it.
If the environment knows about it (and we get decoherence), it is a measurement (and we destroy interference), otherwise it is not (and we get interference). It does not matter if a human, a dog, or a rock might receive the measurement result.

In other words, if you get an interference pattern, your measuring device did not really measure the position of the particle - it might have interacted with it, but there is no measurement result.
DrChinese
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Feb20-13, 12:15 PM
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Quote Quote by kebugcheck View Post
2>

My main issue with QM is :-

*why should the non-determinism (even in form of probabilities) exists at microscopic level ? Am I the only one who finds it absurd ?
Cat is dead or it is alive. why does it needs to be both ?
A photon "knowing" that "ahead-lies-a-slit-and-I-should-behave-like-wave" makes more sense. This "knowing" can be due to something we do not know. Maybe the structure of space. Makes more sense than accepting that the moon may have gone for a walk right now.
No one knows "why" the laws of physics are as they are. But being "reasonable" is not a requirement of those laws. Quantum mechanics is a great theory and it is very useful. The implications of it are subjective to each person, but it is certainly considered strange by most. That does not stop science from moving forward.

Many experiments have been performed to shed more light on things. So far, the basic theory from circa 1927 remains intact. You mentioned Bell's Theorem, this is a very important stepping stone to answering your original question.
DrChinese
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Feb20-13, 12:20 PM
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Quote Quote by micky_gta View Post
my question: "How would you explain the double slit experiment where a 'measuring device' was left on but the information leaving the measuring device was not allowed to reach its destination and viewed (by humans) AND STILL resulting in a an interference pattern? "

People argue that its the measuring devices that causes the double slits to appear instead of an interference pattern when clearly experiments have shown that its not. Its where the information ends up and 'who' knows about it.
The above is incorrect for a couple of reasons. If it is not observed by a human, we don't know what happened (interference or not). On the other hand, there is no evidence at all that human observation yields any special results - ie the opposite of what you are saying.
bhobba
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Feb20-13, 03:55 PM
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Quote Quote by DrChinese View Post
If it is not observed by a human, we don't know what happened (interference or not).
Why is that? What is so special about a human? Why, for example, if the outcome was recorded in a computer wouldn't knowledge of what had happened exist just as well as if it was observed by a human? Would not wave function collapse occur exactly the same? Indeed once decoherence has occurred regardless of if an outcome has been recorded or not, has not, for all practical purposes, an observation occurred? As far as I can tell once decoherence has occurred and a pure state has been transformed into an improper mixed state then in effect an observation has occurred - at least for all practical purposes - by which I mean no experiment can tell otherwise.

I am very uneasy about this introduction of human observers into the theory even in saying things like you said above as I think it introduces unnecessary obfuscation. I know you are not advocating consciousnesses causes collapse but why introduce issues of 'human' observation at all?

Thanks
Bill
DrChinese
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Feb20-13, 04:16 PM
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Quote Quote by bhobba View Post
Why is that? What is so special about a human? Why, for example, if the outcome was recorded in a computer wouldn't knowledge of what had happened exist just as well as if it was observed by a human? Would not wave function collapse occur exactly the same? Indeed once decoherence has occurred regardless of if an outcome has been recorded or not, has not, for all practical purposes, an observation occurred? As far as I can tell once decoherence has occurred and a pure state has been transformed into an improper mixed state then in effect an observation has occurred - at least for all practical purposes - by which I mean no experiment can tell otherwise.

I am very uneasy about this introduction of human observers into the theory even in saying things like you said above as I think it introduces unnecessary obfuscation. I know you are not advocating consciousnesses causes collapse but why introduce issues of 'human' observation at all?

Thanks
Bill
I think you misunderstood my comment. Logically, we NEVER know the result of ANY unobserved measurement. For if you did, you must have observed it! This has nothing to do with QM, it is just logic.

As to QM, there is NO element of it which says that there is anything special about human observers, consciousness, or similar. There are those who say there is that element, but that is just their own opinion. It is not generally accepted science.

Generally, in the double slit experiment, there is no interference pattern if it was even POSSIBLE for to know which slit even if the human didn't bother to try and collect that information. So I conclude that the physical presence of a conscious observer is NOT a primary determining factor in decoherence.
Maui
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Feb20-13, 04:22 PM
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Isn't this a similar case to the HUP and its dependence on what can be known about noncommuting observables, which introduces knowledge of the observer into where you clearly hate to see it? When people say knowledge, they always mean knowledge of the observer as there is no other knowledge.
bhobba
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Feb20-13, 04:33 PM
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Quote Quote by Maui View Post
When people say knowledge, they always mean knowledge of the observer as there is no other knowledge.
Now Dr Chinese clarified what he meant I am cool with it. But, as a point of semantics, I personally do not agree with your view of 'knowledge'. IMHO knowledge exists once it is recorded - not when an 'observer' knows about it. But this is a philosophical issue not of any real value IMHO - I simply mention it as something that's open to debate.

Thanks
Bill


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