Talk:Measurement in quantum mechanics

Philosophical problems of quantum measurements

I have blanked the section "Philosophical problems of quantum measurements". While I wouldn't object to a section on this topic, I didn't feel that the section as it currently exists adds value to the article. I found the following to be problematic:

• The subsection "What physical interaction constitutes a measurement" was unsourced.
• The subsection "Does measurement actually determine the state?" I thought was weak in the sense that the question is answered as a clear "no" in the case of POVM and degenerate measurements, and the other cases are somewhat covered by the other questions posed.
• The question "Is the measurement process random or deterministic?" should at least mention the Kochen-Specker theorem which shows it is impossible to think of quantum measurements as revealing underlying properties of the state. Obviously there are deterministic models- like De Broglie-Bohm. These should at least be mentioned if this topic is going to be mentioned in the article.
• The subsection "Does the measurement process violate locality?" overstates the importance of determinism: due to Fine's theorem, and indeed Bell's theorem, randomness cannot be used to explain quantum nonlocality. I'd rather have an explanation from the realist perspective rather than relying on counterfactual definiteness, but I accept that that at least is a personal opinion

Porphyro (talk) 11:51, 27 April 2017 (UTC)

No complaints here. I started following this page when I was remembering a claim that, as well as I remember "The biggest case of pseudo-science being taught as science in school today is the Copenhagen interpretation of quantum mechanics." I have been trying to find the source of that claim, but it seems pretty obvious now that the Copenhagen interpretation is wrong. It works well enough, often enough, to be useful, but sometimes gives the wrong answer, and much of where it is wrong is related to wave function collapse. Keep the discussion going, though. Gah4 (talk) 21:52, 27 April 2017 (UTC)

I agree that the article leans a little heavily on the Copenhagen interpretation. Thanks for your feedback- hopefully more people will chime in too. Porphyro (talk) 10:27, 28 April 2017 (UTC)

I am learning a little more about this. I had the book What is Real? from the library, but it got recalled. It seems (maybe from that book) that the reason CI is so popular is because of Bohr. He would, for example, give negative recommendations to anyone who disagreed with his interpretations. Gah4 (talk) 01:08, 12 December 2019 (UTC)

What Bohr actually wrote differs from a lot of the things that were in later days called "the" Copenhagen interpretation. The term "Copenhagen interpretation" originated with Heisenberg in the 1950s, and people like Popper and Feyerabend promoted the idea that the founders of quantum mechanics were unified under that banner in order to have something to argue against [1][2]. XOR'easter (talk) 19:20, 31 July 2020 (UTC)

Your point is correct: Bohr himself did not always agree with what we now take to be the Standard interpretation. The basic problem with the 1927 Copenhagen (revised, perhaps) interpretation is that it rests on a set of axioms that seemed reasonable at the time but that, since they are axioms, successfully avoid proof. Since these axioms are somewhat mysterious in meaning, all of QM has remains mysterious (confirmed by Feynman's famous quotation, which was clearly expressing his annoyance with the interpretation, rather than with the underlying mathematics, which work well, including his own remarkable many-path integration).

If we must, along with most physicists, accept the Standard interpretation, and continue to ignore David Bohm's 1952 2-part paper in Physical Review, John Bell's public support for it twelve years later, and its confirming published weak measurement experiments fifty years later, then it is somewhat difficult to write a good introduction to quantum measurement that any high school graduate will understand, because the mysteries run so deep.

I have done my best, in several replies here and in the archived talk page to write such an introduction, and so have others. Some are much better at complaining and objecting than to actually contributing to this process themselves.

Do we give up? Or do we keep attempting until we can get general agreement on such an introduction?

If we wish to make progress, let's not get derailed in the process by the sharp and rather predictable complaints from certain editors. Let's get it done.

David Spector (talk) 10:42, 1 July 2023 (UTC)

Article is seriously incomplete

This article seems to be missing any discussion of Quantum nondemolition measurement. The latest thinking about QM is that wave function collapse and decoherence both happen through contact with a larger (quantum mechanical) environment, not through the destructive nature of most QM measurement techniques. This is a very important and basic point which, incidentally, further obviates any appeal to a need for human consciousness in the effects of measurement on quantum systems. David Spector (talk) 17:15, 11 December 2019 (UTC)

I, and maybe others, find claims like Article is seriously incomplete not so useful. With quotes likenobody understands quantum mechanic from Richard Feynman, it isn't surprising, but we work on it anyway. I think I agree with what you say, though. CI is way too entrenched in teaching, such that it isn't easy to get other ideas in. But yes, CI has wave function collapse in contact with a non-quantum system, which is obviously wrong. Gah4 (talk) 01:14, 12 December 2019 (UTC)

QM can be presented in a less mysterious way. Feynman's famous quotation was not due to QM (which is best expressed in mathematics), but to the Standard (Copenhagen) interpretation given as an explanation of QM. This interpretation is flawed by making its mysterious claims axioms instead of theorems, effectively preventing research (such as that finally done by John Bell and David Bohm) from showing that some of the axioms are misleading as stated. Bohm, for example, showed that particles through the double-slit experiment travel in paths just as deterministic as in classical (relatively large-scale) physics. And, fifty years later, this was confirmed in a published experiment.

But even putting this argument aside, it is always possible to describe Nature using simple words, as an introduction, before math is added to make precise predications possible. This is why there are several successful, well-known popularizers of physics. They, more so than us, have that ability.

David Spector (talk) 14:08, 1 July 2023 (UTC)

Another way this article is "seriously incomplete" is in its ignoring de Broglie-Bohm theory. Bohmian mechanics, while still making use of the Schrödinger equation (but interpreting it as a force instead of a position probability), eliminates the need to incorporate probability as a axiom (it can instead be derived statistically) and. more importantly, seems to eliminate the Measurement problem by eliminating the entire concept of wave function collapse.

In fact, recent double-slit experiments incorporating weak measurement show that the destructiveness of measurement in the atomic domain is indeed a viable explanation for apparent wave function collapse, even when Bohmian Interpretation is applied to the experiment. The more the measurement of which slit the particle came through is accurate, the more the interference pattern disappears. This effect seems to prove that momentum transfer from the measurement process is indeed the source of the effective blockage of a slit, with the extreme situation being that a very accurate momentum measurement acts exactly like blocking a slit: the interference pattern completely disappears because no particles are following the usual two-slit guidance equation.

It is my opinion that this article (as well as several others) should be modified to reflect the increasing doubt about some of the basic mystical features of the standard Copenhagen Interpretation. David Spector (talk) 15:40, 31 July 2020 (UTC)

I'm not sure that Bohmian researchers would agree that in the quantum domain conventional measurements, due to their relatively high energy, produce a wave function collapse. They are more likely to argue that there is no collapse at all, and insist that measurements are fundamentally probabilistic, not for this reason, but because of the strong nonlocal QM effects in the atomic regime. These effects, represented by a guidance equation derived from the Schrödinger equation, cannot be accounted for by hidden variables or by particle perturbation. How does the experiment "know" that there is a measuring device at a slit? Simply because it changes the geometry and energy, and hence the wavefunction. This change then effects the (deterministic) paths of particles through the experiment. David Spector (talk) 13:59, 1 July 2023 (UTC)

There is no such thing as a single, well-defined, "standard Copenhagen interpretation" (and historians of science have been saying this since 1974). This article is about practicalities and technicalities, not interpretations; we have Interpretations of quantum mechanics for that side. The significance or lack thereof of weak measurements for foundational matters is a topic of dispute which does not belong in a basic introduction to ordinary textbook matters. (It took years to clarify even partially what is genuinely anomalous about anomalous weak values....) Writing more about measurements that are backaction-evading, weak, etc., etc., makes sense, as does having more material about experimental implementations in general (technology has progressed since Stern and Gerlach!). But we should tread lightly when claiming conceptual implications for any given calculation or experiment, because there is vanishingly little consensus among the experts about what those implications might be. XOR'easter (talk) 03:09, 1 August 2020 (UTC)

There is no need for a consistent and final "Copenhagen interpretation" to exist for physicists to believe, based on it, that QM is mysterious. And it is already true that physicists are already mostly ignoring the experiments confirming the predicted deterministic paths of particles in the double slit. As rightly they should, since these experiments need replication and more accurate forms of weak measurement to make them produce clearer results. The real shame is that they are also ignoring the theoretical results of both Bohm and Bell, which are compelling since they eliminate most of the mystery in the explanation of QM, making it easier to comprehend. David Spector (talk) 14:14, 1 July 2023 (UTC)

Proposed new on-ramp section for this article

Currently the article jumps right in to formalism, skipping a lot of basic but surprisingly non-intuitive stuff. As a start to remedy this I propose a new section in this draft:

User:Johnjbarton/sandbox/measurement in quantum mechanics Johnjbarton (talk) 18:35, 30 June 2023 (UTC)

Approve. This is an absolutely marvelous proposed addition! Such an introduction is actually needed for many other QM articles which jump right into a kind of mathematics that presupposes many definitions and explanations. I wholeheartedly support this proposal.

With that said, I would like to see two areas expanded a bit more:

1. The single sentence "Light momentum pushes atoms around, changing the very thing we are trying to measure" really calls for a paragraph or two of explanation.

Imagine that we are trying to count the number of coins in an opaque, sealed box that has an opening at the top. We can reach in and easily count them with our fingers. We don't have any trouble because touching a coin doesn't much affect its position. But counting grains of sand with our fingers would be much more difficult, because of the size difference between our fingers and the grains.

Well, the situation is far worse if we want to count individual electrons. These are unimaginably tiny, so that our fingers can't feel them. Even worse, sending into the box a single photon is not likely to work, since the photon will almost never happen to collide with the electron. So we send in a beam of trillions of photons. This beam looks like a narrow ray of light to us, but there are now so many photons, and their energy is so much greater than that of a single electron, that we can measure only the grossest of effects.

In fact, even if we send a single photon directly at the electron, it won't even be guaranteed to reflect back, due to the very similar energies of the electron and the photon. The situation, like a pool ball colliding with another, results in similar changes in direction (to a first approximation).

The greater the energy we put into our measurement beam, the more we perturb the system we want to measure.

But even if we correct for this perturbation mathematically, it doesn't explain all the actual (quantum mechanical) effects we observe at atomic dimensions. Quantum mechanics includes nonlocality. That is the first point.

2. Another phrase appearing in the proposal is "we expect that measurements of these objects will give a definite value and we can assign that measurement a definite time." This phrase is good to introduce the Heisenberg Uncertainty Principle, which is a relationship between two complementary measurements that prevents both measurements being done simultaneously to full precision. Neils Bohr, one of the founders of quantum mechanics, felt that this "complementarity" was basic to it.

In the case of a sound wave, amplitude and frequency are complementary. Using a single measurement, we can measure amplitude precisely, but not frequency. And using multiple, repeated measurements, we can measure frequency precisely, but not amplitude (since it varies). This same behavior applies to position and momentum (velocity). We can measure position precisely with one measurement, but not momentum. The reason is very simple: the two measurements are related. In the first example, frequency is defined as the rate of change (the derivative) of amplitude. In the second example, velocity is defined as the rate of change of position. This precision relationship was investigated by Joseph Fourier in the late 1700s.

David Spector (talk) 19:37, 30 June 2023 (UTC)

Oppose as written. Too much personal opinion about what is "intuitive". If I measure how a cookie tastes by eating it, I can be as "careful" as possible (not leaving crumbs anywhere!) but the measurement is unrepeatable. Is "momentum" intuitive? Having taught Newtonian mechanics to first-year college students, I'm not convinced; moreover, it took a couple thousand years to go from Aristotle through theories of impetus to Newton's concept of momentum (and generations after that for momentum to be cleanly distinguished from kinetic energy). I doubt it is fair to say that the concept of a body possessing a definite momentum is "intuitive". Nor would I call it obvious that measurements of these objects will give a definite value and we can assign that measurement a definite time. What about ordinary, humdrum experimental error? Does a measurement that an actual physics student does in an actual lab give a definite value? I can see what this language is trying to get at — in classical physics, "uncertainty" is uncertainty about the values of pre-existing properties, etc. — but I don't think the language gets there yet. I'm also concerned that statements like a quantum state lists the properties and their values for all of the components of a quantum system load the reader with imagery that is interpretation-dependent or, at worst, just misleading. If the state of a spin is an "up" eigenstate, is the physical value of the spin direction prior to measurement actually "up"? Depends on which interpreter you ask. Take a coherent state for a harmonic oscillator — an infinite superposition of energy eigenstates. It yields no exact prediction for a measurement of position, momentum, or energy. What properties and their values is it listing? And what does it mean to say In the quantum world we cannot directly sense the objects? When I made myself breakfast this morning, I saw the heating coils of my stovetop start to glow with a pretty Planckian spectrum.

A mathematical representation of a measurement device, called an operator, modifies the solutions to, for example, Schrödinger's equation producing both an eigenfunction and an associated number called an eigenvalue. An operator doesn't do this by itself; knowing the operator and the wavefunction isn't enough to calculate what will happen. And why say for example, Schrödinger's equation? The Schrödinger equation hasn't been mentioned yet. How do readers who have just been introduced to what a wavefunction is parse that?

More generally, I'm still confused about what problem we're trying to fix here. Is there anything wrong, in principle, with an article that is all about the serious math? Why not just keep the lay introduction in the Introduction to quantum mechanics article and make that page as good as possible? What benefit to we get from spreading the introductory material across half a dozen pages, necessarily repeating most of it, duplicating the struggle to avoid oversimplifications and pitfalls again and again? This feels a bit like adding a section to every article on a specific topic within general relativity that begins, "Imagine an ant walking across an apple..." Remember that we're building an encyclopedia, not a textbook.

If this article does need a gentler on-ramp, I'd go with something like the opening paragraphs of Quantum mechanics#Overview and fundamental concepts. XOR'easter (talk) 21:24, 30 June 2023 (UTC)

The problem we are trying to fix is explaining measurement at the atomic scale (and involving entanglement) clearly to the casual reader who is not familiar with quantum mechanics.

You make some good points. The "opening paragraphs" you mention at the end are indeed well-written and free of math, but this article is specifically concerned with measurement, predicted nicely by the mathematics of QM but described ontologically very mysteriously in the Standard (Copenhagen) interpretation of QM, which doesn't even want to imagine any measurement happening until a system somehow "collapses" into a classical state where a measurement makes sense. This collapsing is then measurable (nicely) as eigenstates. (Some interpretations require no collapsing, and arguably this is better for learning QM, i.e., less mysterious.)

I see two problems for newcomers to QM with at least a good high school education: first, understanding clearly how Nature behaves differently in the large (classical) statistical limit, and in the small (quantum) reality, and then understanding how the mathematics of QM, such as but not limited to the Schrödinger equation, predicts the behavior of elementary particles and other QM systems from simpler considerations, such as the total energy of the system over time and space.

But, these general difficulties aside, the challenge for this article is in the introduction, to describe why intuitive classical measurement doesn't work in the quantum domain, and how QM works to do accurate measurement, without math. It would also be nice if we could explain how measurement scales up from the quantum level to large, classical systems. Again, without math, as an introduction.

David Spector (talk) 22:46, 30 June 2023 (UTC)

The problem we are trying to fix is explaining measurement at the atomic scale (and involving entanglement) clearly to the casual reader who is not familiar with quantum mechanics. Why? Wouldn't they be reading quantum mechanics (1.3 million views in the past year) and maybe introduction to quantum mechanics (150,000) instead of this (62,000)?

Personally, I'm dubious that a clear explanation for the casual reader is even possible. To get true, honest clarity, one has to learn some amount of the math sooner or later. But if, for the general betterment of humankind and all that, we do our best to make some text that isn't completely useless to the lay person, is this the way to go about it? Does an article that jumps from "no math" to "quite a lot of math" make for anything but a confusing read? XOR'easter (talk) 23:36, 30 June 2023 (UTC)

The answer to your "why?" is that a high-school graduate might have already read another, more general article on QM and wanted to pursue understanding QM measurement. Naturally, they would read this article. They might even read this article first (your figures show that this has a good chance of being true).

Your doubts that such an intro to measurement can be written are useless. The fact that you appear unable and unwilling to do so is not evidence that it cannot be done. There is nothing wrong with jumping from no math to introducing and developing the math. I'll bet many articles in WP do this quite successfully. I just don't have the time to research this.

David Spector (talk) 10:57, 1 July 2023 (UTC)

I'm not unwilling to try. I simply share the doubt expressed by many people who have tried that the result will ever be fully satisfactory. As Feynman said in The Character of Physical Law: The layman searches for book after book in the hope that he will avoid the complexities which ultimately set in, even with the best expositor of this type. He finds as he reads a generally increasing confusion: one complicated statement after another, one difficult-to-understand thing after another, all apparently disconnected from one another. It becomes obscure, and he hopes that maybe in some other book there is some explanation.... Carl Sagan went so far as to say that in his opinion, Indeed, there are no successful popularizations of quantum mechanics (quoted in our quantum mechanics article).

I can appreciate the value of presenting expositions with increasing degrees of sophistication. What I am still trying to understand is what we might gain by splitting off measurement, a concept that is interrelated with all the other concepts in the fundamentals of quantum mechanics, and trying to write an introduction to it specifically. As the draft presented indicates, that means introducing everything else at the same level, too. The natural unit of exposition is the subject of quantum mechanics, not eigenvalues, Hilbert spaces, von Neumann observables, or positive-operator-valued measures. XOR'easter (talk) 15:48, 1 July 2023 (UTC)

For analogy, let's say that Wikipedia's coverage of calculus needs improvement (which it does). And someone makes a proposal to fix this by editing integration by parts, which begins very abruptly, to add a lengthy section that explains what a variable is. I wouldn't want to disparage the effort or the sentiment behind it, but organizationally speaking, it'd be a head-scratcher. XOR'easter (talk) 16:46, 1 July 2023 (UTC)

Dear XOr, thank you for your cogent and reasoned opinion. I agree that a common introduction would be best. How about starting Measurement, and all the other QM articles, with the same introductory section, which would conclude with a prominent link (I forget what these detail links are called) to a further and more lengthy non-mathematical article that contains no math. Then, in the next section of every QM subtopic article, the more on-topic discussion would begin, oriented toward the mathematical (correct) description of the subtopic? David Spector (talk) 17:49, 1 July 2023 (UTC)

That sounds interesting! Maybe what we should do is turn Introduction to quantum mechanics into a treatment that's as good as we can make it at the Scientific American-ish level, focusing on the concepts needed to apply the theory. The historical development could be covered in History of quantum mechanics, while Introduction to quantum mechanics would focus on the subject in its mature form. The lede for the latter article could then be something we re-use across multiple pages (with small appropriate edits), using a {{main}} notice. XOR'easter (talk) 18:09, 1 July 2023 (UTC)

@XOR'easter:

"If this article does need a gentler on-ramp, I'd go with something like the opening paragraphs of Quantum mechanics#Overview and fundamental concepts."

The problem with that approach (as reflected in the current intro) is that it treats 'measurement' as a problem of mathematics rather than one of physics. Nothing in the introduction even mentions a physics measurement. I think a lot of the wave-particle nonsense derives from the vacuum created by starting with a mathematical point of view. Johnjbarton (talk) 02:28, 6 July 2023 (UTC)

I mostly agree. I am frequently annoyed by the emphasis of physics on mathematics rather than ontology. ChatGPT says, "The question of ontology in quantum mechanics concerns whether the theory provides a complete and objective description of physical reality, or whether it is simply a mathematical formalism that describes our observations and measurements."

The fact is that the mathematical formalism describes all the behavior we observe at the atomic scale perfectly. Hilbert spaces and the rest serve to define what we mean by "measurement" or "observation" at this scale.

So there is nothing intrinsically wrong with mathematics. But I dropped out of a PhD program in physics because learning about Nature had ceased at the graduate level, replaced by mathematical physics in every class except foreign language. And, more relevant to our discussion, most newcomers to quantum mechanics cannot understand the mathematics, even when explained gradually.

They may understand complex numbers and vectors, but we lose them at complex functions, states, eigenvalues, and the very basic definition of a Hilbert Space, which has nothing to do with what we commonly mean by space. Not to mention Green's Theorem or Bessel Functions, which are sometimes relevant yet opaque to the understanding.

They want to know what it would look like if we could visualize the atomic scale, perhaps if we were very tiny. The truth is that such a visualization is physically impossible, no matter what our size. Our common sense is just too rooted in our common reality, which has little in common with the equally real reality of the atomic scale. There is much talk about QM being based on probabilities, but our classical physics is partially based on statistics (such as temperature), which is arguably more complicated in its ontology.

I'm inclined to agree with what XOR has been saying about requiring readers to read an introductory article first, with a summary in the lead of each more specific article, as he has been proposing. You, John, and XOR basically agree, it seems to me. There are plenty of specialist articles and courses diving deep into the mathematics. WP needs to start with more accessible, although incorrect, intuitive descriptions, then point out the rather enormous corrections.

My feeling is that such an article should start with a statement about mathematics similar to what I've said above, then present a classical picture of what we expect, but what we actually find when we do QM experiments involving light/polarization, fundamental particles and the double slit, and sequential 90 degree measurements of electron spin. We should discuss perturbation due to collisions (measurement), but also point out that QM is nonlocal, and wave/particle, which have nothing to do with perturbation.

Only then should we attempt to talk about the wavefunction. If we had the courage, we should take the Bohm interpretation as our guide, since it is more intuitive and less mysterious than the Standard interpretation. This would allow us to talk about deterministic particle paths and spins, yet show how they are based completely on a simple energy equation (the Schrödinger equation), which takes into account the entire experimental geometry in a nonlocal way. We should always emphasize how Einstein, representing all of us, searched in vain for a local realistic ontology, which only finally failed in the mid-1960s with the work of John Bell, who proved that locality via hidden variables is mathematically impossible. And we have a variety of different proofs of that now. QM has nonlocal and quantum reality, unlike our common reality.

David Spector (talk) 10:56, 6 July 2023 (UTC)

Regarding QM experiments: one aspect of my attempt on eigenstates that I think worth considering: coupling each concept with a key experiment. This invites the reader to evaluate the concepts in terms of its ability to explain results rather than a collection of paradoxes. Outlining the experiment and explaining the results is not simple but also need not be mathematical. Johnjbarton (talk) 14:48, 6 July 2023 (UTC)

(Too deeply nested) Agree. Sounds very good to me. It would be nice to get some buy-in from the other active editors here. David Spector (talk) 18:26, 1 July 2023 (UTC)

Another issue: we shouldn't bring position and momentum "eigenstates" into the story just to have to un-teach them later. XOR'easter (talk) 23:54, 30 June 2023 (UTC)

I agree. Eigenvalues should only be introduced when Hilbert Spaces and quantum state vectors are explained. David Spector (talk) 10:51, 1 July 2023 (UTC)

To me, this issue is just another symptom of the math-first mentality. Somehow we don't have a name for "the state of a physical system after a measurement" so we call it an eigenstate, then conflate that physical state with the mathematical eigenfunction which we cannot normalize. The results of physical measurements have no normalization problem and thus do not need to be unlearned. And yet they are eigenstates. Johnjbarton (talk) 02:57, 6 July 2023 (UTC)

I don't understand what you mean by "the math-first mentality". It's a mathematical term! And even textbooks for physicists that aren't hung up on mathematical rigor (e.g., Cohen-Tannoudji) explain that there's no such thing as an eigenstate of a position or momentum operator—they simply can't live within the Hilbert space of physical states. And, in practical terms, the "results of physical measurements" aren't even necessarily pure states. They can be thermal density operators, for example. XOR'easter (talk) 15:16, 6 July 2023 (UTC)

I mean that we can certainly create a quantum state where we have restricted the momentum or position to a range of values and according to A. Messiah such a thing would be an eigenstate of momentum. (Please see my article on introduction to eigenstates). It is not an eigenstate of a momentum operator, it's a physically realized state. But it seems clear that pressing this point will gain nothing. We'll have to settle for descriptions without the word "eigenstate". Johnjbarton (talk) 15:28, 6 July 2023 (UTC)

The reason I haven't responded yet about your proposed article on eigenstates is that it needs, in my opinion, too much work by someone more knowledgeable than I. For example, it talks confusingly about "preparing eigenstates" and "split eigenstates". I just don't resonate with the article as it is; even without mathematics it makes lots of assumptions that an average high school graduate would not understand. It mentions "magnetic angular momentum" without defining it or mentioning spin. And its description of the Heisenberg Uncertainty Principle seems wrong to me; compare with my description on this Talk page, where I show the precision tradeoff between momentum and position and explain it clearly. David Spector (talk) 19:37, 6 July 2023 (UTC)

@David spector just such a response is what I need to make improvements Johnjbarton (talk) 20:39, 6 July 2023 (UTC)

Introduction to quantum mechanics has a long redundant history section (~50% of the article). It supposedly summarizes History of quantum mechanics, but substantially out-weighs it. Most of the material (100% of the Bohr model for example) should not be included here. In fact, in my opinion, no history should included in an article with this title. History is a different and valuable learning path, but an introduction should seek to present a modern view first and focus on that goal. Johnjbarton (talk) 02:40, 6 July 2023 (UTC)

I wouldn't go so far as saying an introduction should contain no history; in practice, I'm not sure that's feasible, particularly on a site like Wikipedia where we necessarily follow the example set by the introductions that came before us. But I do think that Introduction to quantum mechanics should be concept-focused and contemporary in orientation, while History of quantum mechanics is more, well, historical. XOR'easter (talk) 15:22, 6 July 2023 (UTC)

Agree. Science works even without knowing who discovered what. David Spector (talk) 21:08, 6 July 2023 (UTC)

If it includes the Bohr model of the atom, that is a mistake, in my opinion, since it mostly predates quantum mechanics. It evolved out of the Geiger-Marsden/Rutherford experiments plus the observed quantization of electronic energy transitions. David Spector (talk) 21:06, 6 July 2023 (UTC)

:::I haven't looked at the Intro to QM article in awhile, but if I remember correctly, following the history is how one introduces QM. It has a purpose. So, I am not sure about this wholesale merging of history out of that article. What was wrong with the History of QM in the first place? ---Steve Quinn (talk) 14:19, 8 July 2023 (UTC)

work of Conte

I removed the line recently added by @Masegi: and removed by @Tercer:. It adds six references by Elio Conte. In my opinion, it is not suitable for two reasons: first, it's not an "interpretation" but a mathematically distinct approach to QM and thus does not belong in the paragraph on interpretations; second, the approach has not received widespread attention and therefore does not belong in the WP article at all (in my view), where the main approaches to quantum measurement should be explained.
In any case, I think the issue should be discussed here before the sentence is added a third time. --Qcomp (talk) 13:14, 5 September 2023 (UTC)

@Qcomp These are mathematical physics papers with low citation count. Off topic primary literature; should not be included. Johnjbarton (talk) 15:06, 5 September 2023 (UTC)

yes, I agree - I had hoped we could have explained that to @Masegi: here instead of having to repeatedly revert unwelcome and unjustified changes, but the user seems not willing to discuss. --Qcomp (talk) 15:34, 5 September 2023 (UTC)

I concur with the removal. Incidentally, one of the papers is in Int. J. Theor. Phys., which is on my list of iffy journals, while the others are in conference proceedings or journals even more obscure. XOR'easter (talk) 16:03, 5 September 2023 (UTC)