Can superposition be tested by gravity?

[cryptist]

You need to learn a bit of quantum mechanics

:) I know quantum mechanics. (at least as undergraduate level) But I'm realist and I believe we do not know too much about the laws of the universe ;)

 

[ZapperZ]

:) I know quantum mechanics. (at least as undergraduate level) But I'm realist and I believe we do not know too much about the laws of the universe ;)

But one must know SOME things to be able to discuss things. If you lack certain parts of it, how are you going to understand the phenomenon? This is such a case in point. You were already focused on a misunderstanding that a measurement "collapses" everything, when in fact, this is not the case. It is not a coincidence that the commutation relationship between observables, i.e. [A,B] is often called the "First Quantization".

Presumably, since that was the ONLY thing that you quoted out of my post, that you've finally accepted not only the info that I gave you, but also have learned about the various experiments producing results in favor of the reality of superposition.

Zz.

 

[Demystifier]

Asking "where is it when we aren't measuring it" is an impossible question.

There are no impossible questions; there are only questions that cannot be answered by given epistemological tools. But questions that cannot be answered by one epistemological tool perhaps can be answered by another epistemological tool. In particular, questions that cannot be answered by a measurement (e.g., where is the Sun during the night) can be answered by a theory (e.g., Newton theory of gravity). The mistake that some scientists make is to assume that measurement is the ONLY epistemological tool. But it is not! Therefore, "where is it when we aren't measuring it" is a question that CAN be answered - by a theory.

 

[cryptist]

you've finally accepted

In fact I never said I do or do not believe superposition or your information. I just questioned its testability, and you gave some links of articles. Thank you very much about that.

 

[yoda jedi]

Every theory introduces different entities, some of them are physically measurable, some of them not. Superposition is not measurable physically as in the very end what you detect is not a superposition of particle states but a single particle in a detector at a certain location...

congratulations. very incisive.

Regarding quantum mechanics there is a mathematical apparatus which can partially be related to physical experiments and which can sometimes be interpreted ontologically* ("a particle is a ..."). Now we have to be careful how to ask the question:

a) can a quantum system be in a superposition of different classical states? (can a quantum particle be in two different locations in a superposition before being measured?)b) shall a quantum system be described by a superposition od states?

Question a) is the ontological version and - to be honest - nobody can answer this; it is interesting philosophically but irrelevant physically

Question b) is the phenomenological version; the answer is "yes, as long as the result agrees with experiment". From that time on it's a matter of taste if you believe in the superposition or if you try to construct a different theory w/o superposition but based on something else.

The majority of physicists believe in superpositions b/c the resulting theory is rather successfull (it is e.g. possible to explain the writing of this post on my laptop and the sending to the server by this theory) and b/c it explains a huge number of facts rather "naturally".

*maybe


Ontological Vs Epistemic, Theory

For you cryptist a good read:

Einstein, incompleteness, and the epistemic view of quantum states
http://arxiv.org/PS_cache/arxiv/pdf/0706/0706.2661v1.pdf

:) I know quantum mechanics. (at least as undergraduate level) But I'm realist and I believe we do not know too much about the laws of the universe ;)

me too.

I believe we do not know too much about the laws of the universe ;)

a lot ! we have to learn a lot.

 

[tom.stoer]

congratulations. very incisive.

thanks a lot

 

[tom.stoer]

Ontological Vs Epistemic, Theory

Are you referring to "some of them are physically measurable, some of them not"? That's not the same.

 

[yoda jedi]

Are you referring to "some of them are physically measurable, some of them not"? That's not the same.

please if can, read again my previous post.

 

[yoda jedi]

There are no impossible questions; there are only questions that cannot be answered by given epistemological tools. But questions that cannot be answered by one epistemological tool perhaps can be answered by another epistemological tool. In particular, questions that cannot be answered by a measurement (e.g., where is the Sun during the night) can be answered by a theory (e.g., Newton theory of gravity). The mistake that some scientists make is to assume that measurement is the ONLY epistemological tool. But it is not! Therefore, "where is it when we aren't measuring it" is a question that CAN be answered - by a theory.

or a deeper theory.

 

[yoda jedi]

Are you referring to "some of them are physically measurable, some of them not"? That's not the same.

refering to that

...All this must have come to Heisenberg as a scathing attack on what he regarded as his fundamental orientation, derived from reading Einstein's early works, and being guided by them from the start, right through his most recent triumph. But now, in this meeting, Einstein, whose development away from positivistic instrumentalism to a rational realism...


...Perhaps this discussion helped Heisenberg eventually to embark on his own epistemological pilgrimage, ending later with a kind of neo-Platonism in the description of nature through the contemplation of symmetries...

 

[tom.stoer]

OK, first of all I should say that "epistemic" and "phenomenological" are not quite the same - http://en.wikipedia.org/wiki/Phenomenology_(philosophy) - but they are rather close in our context.

It may be dangerous to use "phenomenological" b/c there is a confusing cross-reference to physics where one tries to construct phenomenological models which are not "the real world" but which capture some "aspects of reality" - e.g. the non-relativistic quark model.

All what I wanted to say is that according to realism "ontological entites" need not be grounded in measurements. Of everything that can be measured "does exist", but there may be entities that "exist", but can never be measured "e.g. wave functions".

I think we can never decide if a wave function does "exist" (not only b/c we do not know what "exist" really means; the wave function is not a phenomenon), but we can be sure that we "need it" in our models (we use it in orer to describe phenomena efficiently).

 

[yoda jedi]

OK, first of all I should say that "epistemic" and "phenomenological" are not quite the same - http://en.wikipedia.org/wiki/Phenomenology_(philosophy) - but they are rather close in our context.

not discussing that point, i agree with you to some degree.

It may be dangerous to use "phenomenological" b/c there is a confusing cross-reference to physics where one tries to construct phenomenological models which are not "the real world" but which capture some "aspects of reality" - e.g. the non-relativistic quark model.

agree, and rutherford model, landau theory...

All what I wanted to say is that according to realism "ontological entites"
need not be grounded in measurements.
Of everything that can be measured "does exist", but there may be entities that "exist", but can never be measured "e.g. wave functions".

of course, noway.
or entities that are no ontological "e.g. wave functions" ergo; no real.
like you say "MAY"

I think we can never decide if a wave function does "exist" (not only b/c we do not know what "exist" really means;
...the wave function is not a phenomenon),
but we can be sure that we "need it" in our models (we use it in orer to describe phenomena efficiently).

its unknown, because as you say:


Phenomenological Theory: A theory which expresses mathematically the results of observed phenomena without paying detailed attention to their fundamental significance.

or/and

from Greek: phainómenon "that which appears"
are wave functions real ?
represent reality (ontological entity) ? or our knowledge of reality (epistemic fact)?

is the wave function a phenomenon ? maybe.

 

[tom.stoer]

I think we should agree that from now on we are leaving physics and enter the philosophical domain. So this would be a good moment to pause, be happy about some agreement, and stop talking about philosophy (not that it's not interesting - but it's not the right place).

 

[yoda jedi]

I think we should agree that from now on we are leaving physics and enter the philosophical domain. So this would be a good moment to pause, be happy about some agreement, and stop talking about philosophy (not that it's not interesting - but it's not the right place).

read:

Quantum Physics
are wave functions real?
https://www.physicsforums.com/showthread.php?t=400515

..."epistemic -- of, relating to, or involving knowledge"

As opposed to

"ontic -- of, relating to, or having real being"

So, "psi epistemic" means the wave function is knowledge about ... , it doesn't necessarily "exist" or have "being." In BM, psi definitely exists and acts on the quantum particles, so psi is ontic. Of course, it could be both, but in RBW it's purely epistemic...