DZ
DefZone.Net

Kien thuc cong nghe & giai tri

Wiki Article

Talk:Uncertainty principle

Nguồn dữ liệu từ Wikipedia, hiển thị bởi DefZone.Net

Xem trên WikipediaBài ngẫu nhiên khác

Observer Effect

[edit]

Is the quoted statement correct? Didn't the modern double-slit experiment, conducted sometime after the sited reference, reveal that it was not simply detecting the particle that collapsed the wave function but rather the observation of the result? Please help!

"It must be emphasized that measurement does not mean only a process in which a physicist-observer takes part, but rather any interaction between classical and quantum objects regardless of any observer." — Preceding unsigned comment added by 2a02:c7d:784d:5500:2c4b:22cc:fce5:28c0 (talk)

The ideal of the detached observer -iatrogenic Building Blocks

[edit]

Hello there. In the section entitled 'The ideal of the detached observer', though Pauli mentions that he disagrees with Einstein's refutation of the uncertainty principle with respect to the observer influencing the thing observed, adding that he hopes his memory accurately reported their conversation, we do not hear Pauli's corrective to Einstein's attempt to refute the idea of something changing while/upon being observed. I'm sure his recall was perfectly good and it probably doesn't matter as the example cited, the position of the moon being unchanged whether we observe it or not (a bit like Bishop Berkeley's kitchen vanishing once he moves into the living room) is exactly (with all due respect to Einstein) the wrong scenario with which to test the hypothesis. A simpler scenario whereby an inspector is observing a junior teacher teach captures the theory a little more firmly. The inspector's presence distorts the lesson being given though s/he perhaps is unaware to what extent his presence changes the thing that he is observing. Descartes x/y axis assumes a new dimension Z, 'the catalytic observer' or perhaps better 'the subjective correlative' (to finesse T.S. Eliot), it seems to me (though I know nothing about physics). Another scenario might see an art gallery visitor standing before a classical painting and then an abstract painting, the former demanding no participation to consummate its meaning, the latter requiring some. (Unwelcome to settled tastes, the idea of the public participating in art is anti-elitist but nonetheless considered a necessary corrective to self serving elites.) Likewise, developments like Le Nouveau Roman require readers to augment their missing chapters to complete them, thereby assigning or allowing a role for the reader/observer (as Detective fiction does). These simple examples are part of an index of much heavier (complex) applications with respect to the manner in which our judgement is or becomes skewed in certain situations where we passively participate in let's say condemning lust while living a life of unwelcome and enforced celibacy. Our often failure to see that our own pathology (sorry) influences our view of the thing observed can get us into all kinds of trouble. Psychoanalysts have something called the object oriented question which is 'employed' on particularly resistant/ repressed individuals who will only surrender an image of their ego unwillingly and so such people speak through objects (as we all invariably do) to express themselves, so enabling the therapist to get an idea of their psychic composition. The therapist him or herself may possess all kinds of blocks to observing the patient in a clear light. These iatrogenic blocks provide a term which may help differentiate between Einstein's Moon and more subtle examples where the presence of the observer does impact the thing observed. So, I think this section needs a little finessing to either include Pauli's refutation or a better example might be found to expound the actual beneficial application whereby a scenario is altered by virtue of being a participant. I hope I haven't confused matters. Thank you. M.H. p.s. If you doubt the role of the observer, consider the oft told story of King Faisal waking disguised in the market to find out what his people were thinking, and saying. He knew that if he showed up as himself, he'd get a very different reception. 'The Deferential Equation', maybe. — Preceding unsigned comment added by 37.125.41.223 (talk)

Order of contents

[edit]

I think the qualitative sections on different relations should be grouped together and the math section moved below that. The section "Critical reactions" is evidently part of History and should set underneath. I notice that @Roffaduft has been rearranging so I will leave this as a suggestion rather than edit now. Johnjbarton (talk) 16:14, 3 November 2024 (UTC)[reply]

As the article is a bit of a hodgepodge, I've condensed the material a bit and attempted to place the subsections in chronological order. That is:
  1. Start with the quantum mechanical description
  2. Next, the general mathematical formalism (which is still pretty quantum mechanical as opposed to "truely" mathematical)
  3. Then "generalizations", "equivalent statements" (with a more controversial history), "extensions" etc.
The reason I placed "Harmonic analysis" (i.e. Fourier analysis) a bit higher was to emphasize that the mathematical origins (involving e.g. Cauchy–Schwarz inequality and Chebyshev's inequality) underlying the uncertainty principle actually predate the QM description (although that doesn't become very clear in said subsection).
Regardless, the main issue I have with the article is that it's borderline WP:NOTTEXTBOOK. The subsubsections of "Position-Momentum" are a great example of that.
Kind regards, Roffaduft (talk) 08:08, 4 November 2024 (UTC)[reply]
yes surely the qualitative QM description is the most notable and should come early. Maybe an early section devote just to that would make sense.
Maybe add material on the mathematical origins into History before Heisenberg is discussed. I think that would bring out your point more clearly. I wish a few paragraphs of History were earlier but the Heisenberg microscope and the Critical reactions section should be combined and then the section is long. It seems to have a fair number of refs so reduction would not be a priority.
I agree about Position-Momentum. "Proof of the Kennard inequality using wave mechanics" could move under Mathematical or frankly just be deleted as unsourced and undue. Most of the rest of that section is unsourced.
I think most readers would appreciate the different types of uncertainty relations (x-p, E-t, etc) group together. Johnjbarton (talk) 16:55, 4 November 2024 (UTC)[reply]

Better definition of concept needed.

[edit]

@Oblibion123 has suggested that we need a better description of the meaning of the uncertainty relationship. I agree, but I don't agree with the specific wording and its placement in the introduction. Two sources which give detailed descriptions in a clear way are

  • Ballentine, L. E. (1998). Quantum Mechanics: A Modern Development. Singapore: World Scientific. Page 225
  • Peres, A. (Ed.). (2002). Quantum theory: concepts and methods. Dordrecht: Springer Netherlands. Page 93

The Peres description:

  • If the same preparation procedure is repeated many times, and is followed either by a measurement of x, or by a measurement of p, the various results obtained for x and for p have standard deviations, ∆ x and ∆ p, whose product cannot be less than / 2.

Ballentine says the same in my opinion but with more words. Johnjbarton (talk) 17:16, 15 December 2025 (UTC)[reply]

Peres and Ballentine while good books are often considered to have non-standard interpretations.--ReyHahn (talk) 17:31, 15 December 2025 (UTC)[reply]
This definition of the uncertainty relation is not related to questions of interpretation as far as I can tell. Do you have any source which contradicts the description above? Johnjbarton (talk) 17:37, 15 December 2025 (UTC)[reply]
Maybe I am being too careful? I agree with the paragraph cited above. One just has to be careful because Ballentine chooses a statistical interpretation and Peres is known for calling the uncertainty principle an "ill-defined notion" and unnecesary to teach quantum mechanics (he even makes a joke about it in the index).--ReyHahn (talk) 18:12, 15 December 2025 (UTC)[reply]
Are you referring to the Peres book I listed above? He spends quite a bit of time looking at quantum uncertainty from different angles. I didn't get any sense that he considered it a joke except in the same sense as Ballentine: it is too often used in a lazy way.
To be sure, most sources do not go in to the details like these two sources. I don't think they are contradictory so much as in agreement without making a point of working out the details. I think we should use these sources to clarify the two points made by Ballentine: the uncertainty is not an error of measurement and the relation is not a result of simultaneous measurement.
Our current sentence
  • It states that there is a limit to the precision with which certain pairs of physical properties, such as position and momentum, can be simultaneously known.
seems technically correct, but could be implied to mean simultaneous measurement. I think we could clarify the serial nature of the setup. Johnjbarton (talk) 19:46, 15 December 2025 (UTC)[reply]
Yes, that same Peres book. If you go to the index and look for uncertainty principle it points to the index (indicating it is unnecessary). I agree that as used in the quote above is not controversial but one has to be careful the Heisenberg uncertainty principle is a basic topic of quantum mechanics and standard books might be preferable.--ReyHahn (talk) 12:15, 16 December 2025 (UTC)[reply]
Or it indicates that sometimes proofreading the index is not completely successful. Johnjbarton (talk) 16:10, 16 December 2025 (UTC)[reply]
I personally agree with Peres and Ballentine's descriptions, and I understand my wording was likely not clear enough. I'm not comfortable with the idea of stating that the uncertainty principle places limits on "simultaneous knowledge" because the way someone unfamiliar with the subject will (probably) understand the sentence as
"there is inherent fuzziness in quantum mechanics that prevents us from having an exact number to each one", that is measurement error.
This is, of course, false. The idea behind the uncertainty principle is more of a limit on quantum theory, that is, if we measure the same quantum state A over and over again (either measuring position or momentum) then the standard deviations of position and momentum will multiply to be above a certain value (no matter what the experimental set-up is). We can measure each one of those observables to arbitrary precision though.
Ballentine's view is also that you shouldn't measure position and momentum on the same particle, so perhaps not serial nature on the same particle but serial measurements of the same quantum state. It's still important to state that the uncertainty principle does not form any limits on measuring the position and momentum serially on a single particle to arbitrary precision; it's just not what the uncertainty principle was talking about.
Here is what Ballentine states about common misconceptions:
• The quantities ∆Q and ∆P are not errors of measurement. The “errors”, or preferably the resolution of the Q and P measuring instruments, are denoted as δQ and δP in Fig. 8.2. They are logically unrelated to ∆Q and ∆P , and to the inequality (8.33), except for the practical requirement that if δQ is larger than ∆Q (or if δP is larger than ∆P ) then it will not be possible to determine ∆Q (∆P ) in the experiment, and so it will not be possible to test (8.33).
• The experimental test of the inequality (8.33) does not involve simultaneous measurements of Q and P , but rather it involves the measurement of one or the other of these dynamical variables on each independently prepared representative of the particular state being studied.
Overall, I think it makes more sense to discuss the uncertainty principle as a limit of the predictive power of quantum theory and how much we can prepare a quantum state rather than give the idea that it's a limit to how much we can measure. Oblibion123 (talk) 21:17, 15 December 2025 (UTC)[reply]
The article does not say anything about "inherent fuzziness in quantum mechanics", so I don't know what to say about that.
I think there is no difference between a limit on predictive power and a predicted limit on measurement. But what we think is not relevant here, the only thing that matters is what reliable sources say. I think that for the purposes of this article, Peres and Ballentine are reliable sources: we could summarize them in the article. We could use such a summary to alter the introduction. For example we could say something like
  • For certain pairs of physical properties, such as position and momentum, the uncertainty principle says that a preparing a state precise in one property will result in a quantitative amount of imprecision in the measurement of the other property. This level of imprecision is unrelated to errors of measurement and cannot be eliminated through additional measurement.
Johnjbarton (talk) 01:35, 16 December 2025 (UTC)[reply]
I think the definition is decent, but I'm not sure the sources support the idea that "preparing a state precise in one property will result in the quantitative amount of imprecision in the measurement of the other property" as this current phrasing seems to imply that it reuslts into a measurement imprecision, which directly contradicts the sentence afterwards.
We could say like:
- For certain pairs of physical properties, such as position and momentum, the uncertainty principle says that a preparing a state more precise in one property will result in a quantitative amount of imprecision in preparing the other property (no matter the experimental set up (?)). This level of imprecision is unrelated to errors of measurement and cannot be eliminated through additional measurement.
Maybe stating "when measuring" could also be better phrasing.
A more laymen summary could also be given afterwards to say something like
"In essence, the uncertainty principle places limits on how much a state can be prepared in the parameters that define it." Oblibion123 (talk) 01:53, 16 December 2025 (UTC)[reply]
Both Peres and Ballentine refer to prepare/measurement pairs. I don't think state preparation has a meaning separate from measurement. Johnjbarton (talk) 02:02, 16 December 2025 (UTC)[reply]