Talk:Observable

Untitled

Changed it because the relative state interpretation is identical to the quantum operation formalism by the Choi structure theorem referenced in quantum operation. CSTAR 23:06, 12 Jul 2004 (UTC)

Coment on my commemnt: the relative state interpretation is not quite the same; even though Everett is a litle unclear in his 1957 paper what he means by normalization, the relative state should be thought of as the (isometric part of) the polar decomposition of the the compound state viewed as a linear map.CSTAR 16:25, 7 Aug 2004 (UTC)

Observables

Please see comment at bottom of article relating to observables and frames of reference. CSTAR 17:30, 15 Jul 2004 (UTC)

Perhaps an example of the math behind performing a measurement would be useful for me since i don't have a physics background. Showing the measurement operation on a state vector would be nice, thanks.

It would be useful in an article on Observables to firstly list what observables are. Other than position and momentum, what else qualifies? Secondly, to say how observable values are obtained in the wavefunction from the quantum numbers. Alas, too often in wiki, the contributors major on their preferred interpretations at the expense of providing encyclopedic data. The end result is confusion. For wiki to be of better use, some standards need to adhered to avoid the 'free for all' that pertains, much of it inexpert.

Additionally, the "eg. position and momentum" example does not clarify whether these are examples of observables or examples of states. The definition is valid, that they are a real valued function of the states, but this implies examples like "distance to a star = function(position, velocity, time)" where the distance is the observable and position and velocity are the system states, does it not? Most other references define an observable as a function that maps a point in phase space and time (ie position and momentum or position/velocity) to a real value, so observables include distance to a star, or the Doppler frequency of Voyager II, both functions of position and velocity. But this might be too specific too. What about temperature? It is measured and is a function of a set of classical thermodynamic state variables --Kpgokeef (talk) 17:36, 3 June 2024 (UTC)

Consciousness

There certainly are many frivolous speculations about consciousness and measurement in QM out there, but not all theories linking QM and consciousness are frivolous. For example, the work of Penrose and Hameroff is not frivolous. This article gives the wrong impression, namely, that a good physicist's eye is supposed to see through the mysteries in question. The fact of the matter is that the measurement problem, the basis problem, and many other issues related to measurement continue to puzzle anybody who is not sticking dogmatically to the Copenhagen interpretation or one of its derivatives (e.g. consistent histories).

You are certainly welcome to change it; I was the one that put the "offending sentences" in, (a) because I think they correctly represent the view of current mainstream science and (b) what was there when I first started editing this article was some unqualified gibberish about the observer.

A better solution might be to attenuate somwhat what you consider to be the offending sentences in this article, and start a new article discussing possible connections bewteen QM and consciousness. In order for that article to be fair and not POV, however, it should clearly state that the predominant view is what you seem to be implying is any one of the "crass" Cophenhagen - Consistent Histories - instrumentalist interpretations. But in that new article you could discuss also the work of Penrose and Hameroff and others. That would be informative.

The current article would then link to it. CSTAR 15:24, 5 Mar 2005 (UTC)

Link to control section?

I was looking here to find something about observable in control theory, turns out that this can be found under observability. Link there?

Imaginary Observables?

The quote:

One must note that the above definition is somewhat dependent upon our convention of choosing real numbers to represent real physical quantities. Indeed, just because dynamical variables are "real" and not "unreal" in the metaphysical sense does not mean that they must correspond to real numbers in the mathematical sense.

in the article is misleading I think.

The fact that observables are REAL NUMBERS is not an arbitrary choice, I'd say. Imaginary numbers have mathematical meaning and meaning in physical models, but the 'quantities' we observe are always represented by real numbers and complex (imaginary) numbers would be rather meaningless in that sense. — Preceding unsigned comment added by 93.62.17.241 (talk) 22:19, 19 April 2013 (UTC)

I must say that this article needs a lot of work. I mean a LOT. Because it is impossible to observe the Infinite (or measure it), I could argue that this article tries to hard too hard to provide a definition of Observability without a single clear example of how it can be achieved. My experience of Observability has to with a measure of Testability where sufficient input stimulus (a finite stimulus BTW) produces sufficient output response such that any internal fault (like digital open and short circuits) can be detected. But I know that even 100% Testability/Observability does not produce a truly perfect device - only a high probability of operation once it leaves the factory floor. It can still fail, and there can still be other defects that are not observable by the selected test method or by lack of time and resources.--68.188.183.91 (talk) 02:48, 20 February 2015 (UTC)

Quantum observable

Should quantum observable redirect here?