The heisenburg uncertainty principle

[ThomasT]

You ARE funni. That's exactly what I was thinking, and I am waiting in suspense for the answers...

Pretend I didn't say it. In fact, I'm going to delete the post.

 

[DevilsAvocado]

Hidden variable theories which try to explain the apparent randomness of quantum mechanics as a deterministic theory – is not dead, it just https://www.physicsforums.com/showpost.php?p=2860862&postcount=1493"...

 

[arkajad]

What's wrong with some randomness? I do not understand why some people can't admit that they do not have the same computing and descriptive power as the Universe. Is it because they are so proud of themselves? Who they think they are?

 

[DevilsAvocado]

What's wrong with some randomness?

Agree.

 

[DevilsAvocado]

And, by the way, I think you should pay attention to, and respect, Zonde's posts. He really is much more knowledgeable than both of us. And yes, I know, you're wondering how I know these things (like, eg., that billschnieder is a working scientist) -- well I just know these things and I'm not going to tell you how I know these things.

You ARE funni. That's exactly what I was thinking, and I am waiting in suspense for the answers...

Muhahaha! Yeah, ThomasT is a REAL entertainer!

Pretend I didn't say it. In fact, I'm going to delete the post.

What?? Why!?

I had some very interesting comments on that post...

Well, I know, you're wondering how I know these things, well I just know these things, and I'm not going to tell you how I know these things, but I know these things.

Let’s see now... first you said:

In fact, the quantum theory is ONLY about measurements, no more and no less. On what other basis would you develop a statistical probabilistic theory?

And then you retracted your assertion:

Ok, at this time I think I should retract my assertion that "the quantum theory is ONLY about measurements, no more and no less" (apologies to Heisenberg).

And then you changed your mind AGAIN...??

the quantum theory is about measurements, ie., the behavior of instruments ... this is what the qm matrix mechanics of Heisenberg is based on

I don’t know if I should answer here? Or start a new thread in the Philosophy forum called Gobbledygook...??

Naah, let’s have all the fun here instead!

Of course Heisenberg was only an experimental physicist. Instruments were all he cared about! In fact, some say there’s even physical proof:

– Don’t be sad Werner. We will get all your stolen gear back!​

And then you said something about that it makes more sense if nature is local than nonlocal, and I naturally agree. The only problem with that; is that what we have to choose between is locality or reality – not local or nonlocal.

Finally, Hawking supports MWI, and that’s also a different thing.


P.S. Thanks for the laughs TT! You make PF so much funnier!

Ohh, ahh, of course the great Nobel laureate Werner Heisenberg was a theoretical physicist, anything else is gobbledygook!

 

[tom.stoer]

I don't know if it makes sense to repeat this over and over again, so I hesitate to participate in this discussion ...

... anyway, the whole QM formalism does not care about the measurement process, does not explain this process, is not based on measurement and measurement process and does not reflect any limitations regarding measurement. QM says something regarding observables but does not explain how to do this in practice; it does not explain how to construct a "complete" set of such operators, it does not explain which set one one should use etc.

QM is not very precise about the measurement process itself; the statement that observables have a definite value after measurement which collapses the the state to an eigenstate is questioned today. Both orthodox / Copenhagen and MWI interpretation are interpretations only; they are not used as construction principles, but sit on top of the formalism as interpretations / speculations.

I know that the term "measurement" is used over and over again, but unfortunately it has never been explained. One can savely say that QM is about "accessable information on quantum systems" but one should be aware of the fact that measurement itself is still a mystery in QM.

 

[arkajad]

One can savely say that QM is about "accessable information on quantum systems" but one should be aware of the fact that measurement itself is still a mystery in QM.

Well, that depends on which QM you have in mind. There are many of them and they differ one from the other by the way they treat "measurements" and, more generally, "events".

 

[tom.stoer]

Well, that depends on which QM you have in mind. There are many of them and they differ one from the other by the way they treat "measurements" and, more generally, "events".

Can you elaborate on them? I know different interpretations, not formalisms. Can you explain what you by "treat"? Is it more than "interprete"?

I am not talking about interpretation which is still vague but about the formal basis of QM which is rather unique.

 

[arkajad]

Can you elaborate on them? I know different interpretations, not formalisms. Can you explain what you by "treat"? Is it more than "interprete"?

It is. But there is also an interpretation involved.

Quoting from J. A. Wheeler ("Geons, Black Holes & Quantum Foam", p. 343):

"I wanted to emphasize in this talk that the essential feature of act of 'measurement' is amplification from the quantum thing observed to the classical thing doing the observing, which need have nothing to do with human intervention or human consciousness"

Thus part of the interpretation is to accept that there are "quantum things" (e.g. electrons) and there are "classical things" (e.g. tables and chairs). Not everybody is ready to accept it. Are YOU ready. If you are, the next thing is to look for a formalism. If you are not - no formalism will help you.

 

[tom.stoer]

I am definately not ready to accept that nature distinguishes between quantum things and classical things!

Due to new approaches like decoherence it seems likely that the reason why only classical states (= vanishing off-diagonal elements of density matrices w.r.t. a basis defined by the measuring device) are observed becomes clear even quantitatively. That means that the time scale at which decoherence acts seems plausible or at least not incompatible with our observation.

Therefore I doubt that there are classical things and quantum things and that they are fundamentally different. They are fundamentally the same, and decoherence gives us a tool to understand the emergence of A classical world

[It is not a tool to understand why exactly THIS classical world emerges; in case of Schrödinger's cat decoherence explains to some extend why the cat we observe is either dead or alive - not some quantum superposition - but decoherence does not explain why a specific cat is dead instead of alive; it eliminates quantum superposition of macroscopic objetcs, but not randomness].

 

[arkajad]

Due to new approaches like decoherence it seems likely that the reason why only classical states (= vanishing off-diagonal elements of density matrices w.r.t. a basis defined by the measuring device) are observed becomes clear even quantitatively.

You are using the term "our observation". Is it a classical thing or a quantum thing. Can quantum things meaningfully "talk" and "write"? And interpret itself? And create quantum mechanics?

You wrote this comment. Is it a classical thing or a quantum thing? If it is a quantum thing - what kind of a thing? An operator? A state vector? Is Hilbert space a quantum thing or a classical thing? Or, say, "time"?

 

[tom.stoer]

I have problems with these questions. An "observation" is not a thing, neither classical nor quantum. I think this is a category mistake.

As I am consisting of quantum objects on a fundamental level I would say that I am a "huge quantum thing" that is able to talk and write.

I am definately neither an operator nor a state vector. This is the same as with "red" and "750 nm". Light with 750 nm appears as red, but the sentence "red is identical with 750 nm" is meaningless (again a category mistake).

 

[arkajad]

If you are not operator and not a state vector, and because I believe you wrote it only once - how do you describe your act of writing within your beloved "decoherence formalism"?
About decoherence formalism: is the separation between the "system" and "environment" a classical thing or a quantum thing? Who is doing this separation? Who is putting the borders or moving them ad hoc as it pleases the mover?

"I think this is a category mistake. "

We are not trying to use some formal theory. We are discussing reality and its description. These are not "mistakes". These are ncessary questions that need to be asked. Of course you can refuse to accept them. Up to you. You will have to pay for it by not getting answers. You will know less about reality.

 

[tom.stoer]

In the decoherence framework one describes the time evolution of mixed states. The Usually one decomposes the Hilbert space into "quantum object", "pointer of the measurement device" and "environment". Then decoherence explains why the ponter appears classical and where the quantum superpositions go to (namely into the environement).

 

[tom.stoer]

bt.w.: I don't think your questions are unreasonable, but they do not have anything to do with the QM formalism but with interpretation and philosophy. They should not be discussed in a thread "The heisenburg uncertainty principle".