View source for Talk:Measurement problem

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== Edit war ==

An editor, [[User:Naeemshahzada|Naeemshahzada]], has been repeatedly inserting a sentence into the Interpretations section
:"''It has been recently proposed that biological cells solve the measurement problem being the smallest agents capable of processing quantum information within the framework of the holographic principle, entropic gravity, and emergent dimensionality.''"
against a consensus of  [[User:SageGreenRider|SageGreenRider]], [[User:Tercer|Tercer]] and myself.  He has readded it 4 times [https://en.wikipedia.org/w/index.php?title=Measurement_problem&diff=1213084824&oldid=1211827857], [https://en.wikipedia.org/w/index.php?title=Measurement_problem&diff=1213227572&oldid=1213207067], [https://en.wikipedia.org/w/index.php?title=Measurement_problem&diff=1213433695&oldid=1213354984], [https://en.wikipedia.org/w/index.php?title=Measurement_problem&diff=1213614256&oldid=1213525586] within about 3 days  --[[User:Chetvorno|Chetvorno]]<sup><small>[[User talk:Chetvorno|<i style="color: Purple;">TALK</i>]]</small></sup> 06:56, 14 March 2024 (UTC)

:The problem with this addition is that it is inadequately sourced.  It is supported by only two [[WP:primary source]]s, research papers by the same author, Szymon Łukaszyk.  WP requires secondary sources ([[WP:PSTS]]).  After this was pointed out, [[User:Naeemshahzada|Naeemshahzada]] added two additional sources, also research papers by the same author, neither of which mention anything about the measurement problem, the previous papers, or the subject of the sentence.  Any relation of these papers to the topic is [[WP:SYNTHESIS]].  In addition this sentence gives [[WP:UNDUE|WP:UNDUE WEIGHT]] to a speculative theory with no support in a section that is limited to the main [[interpretations of quantum mechanics]] that have stood the test of time.

:These are the only edits [[User:Naeemshahzada]] has made; this seems to be a [[WP:single use account]] whose goal is to insert Szymon Łukaszyk's work into Wikipedia.  It seems likely that [[User:Naeemshahzada]] is Mr. Łukaszyk and he is using Wikipedia to promote his papers and his career, without the disclosure of [[WP:COI]] that Wikipedia requires.--[[User:Chetvorno|Chetvorno]]<sup><small>[[User talk:Chetvorno|<i style="color: Purple;">TALK</i>]]</small></sup> 17:02, 14 March 2024 (UTC)
::I've opened (yet another) SPI: [[Wikipedia:Sockpuppet_investigations/Guswen]]. [[User:Tercer|Tercer]] ([[User talk:Tercer|talk]]) 17:41, 14 March 2024 (UTC)
::The first two sources, in addition to being primary, were below the standard we should adhere to. One was an item in conference proceedings, which in physics typically means no meaningful peer review, and the second was a book chapter in a collection published by [[Nova Science Publishers|a company on Beall's List]]. The other two were in [[MDPI]] journals, which again means that we can't expect any meaningful degree of peer review to have been applied. [[User:XOR&#39;easter|XOR&#39;easter]] ([[User talk:XOR&#39;easter|talk]]) 15:23, 21 March 2024 (UTC)

::: You submit that [[Institute of Physics]] and [[MDPI]] lack credibility, while at the same time unpublished, non-peer-reviewed [[preprint]]s are commonly used on Wikipedia to debase and discredit valid scientific research, even if they are plainly false.
::: For example, this non-peer-reviewed preprint<ref name="Zenil2024">{{Cite journal |title= Assembly Theory is an approximation to algorithmic complexity based on LZ compression that does not explain or quantify selection or evolution|year=2024|last1=Abrahão |first1=Felipe |last2=Hernández-Orozco|first2=Santiago|last3=Kiani|first3=Narsis A.|last4=Tegnér|first4=Jesper|last5=Hector|first5=Zenil|journal= arXiv|arxiv= 2210.00901}}</ref> is an attempt to discredit [[assembly theory]] which has been experimentally confirmed through [[tandem mass spectrometry]], [[nuclear magnetic resonance]], [[infrared spectroscopy]], etc. The authors of this preprint claim, for example, (p.9), that an "object with a '''low''' assembly index (...) necessarily displays '''low''' [[Entropy (information theory)|entropy]]. In the opposite direction, an object with a '''high''' assembly index will (...) necessarily display '''high''' [[Entropy (information theory)|entropy]]". This is untrue (!). For example, two binary strings <math>C=[01010101]</math> and <math>D=[00010111]</math> have the same lengths <math>N=8</math>, [[Hamming weight]]s <math>N_1=N/2=4</math>, and therefore the same [[Entropy (information theory)|Shannon entropies]] <math>H(C)=H(D)=\log_2(2)=1</math> bit, but different assembly indices!
::: <math>a(C)=3</math>, while <math>a(D)=6</math>.
::: When does a fringe idea stop becoming a fringe idea? When it becomes more popular ([[User:Tercer]]), gets more support ([[User:Chetvorno]]), in particular from ''physical authorities'' ([[User:SageGreenRider]])?
::: Will a [[Modern flat Earth beliefs|flat Earth theory]] stop being a fringe idea when it becomes popular among physicists, as [[User:Tercer]] proposes? 

::: And what does it mean that the main [[interpretations of quantum mechanics]] have stood the test of time? No consensus on any particular interpretation has been reached so far<ref>{{Cite journal |
title= A Snapshot of Foundational Attitudes Toward Quantum Mechanics|
volume = 44|
number = 3|
year=2013|
doi = 10.1016/j.shpsb.2013.04.004|
url = https://www.sciencedirect.com/science/article/pii/S1355219813000397|
last1=Schlosshauer |
first1=Maximilian|
last2=Kofler|
first2=Johannes|
last3=Zeilinger|
first3=Anton |
journal= Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics}}</ref>.

::: Perhaps life is an explanation of the measurement problem, then? 

::: I am convinced it is.
::: [[User:Guswen|Guswen]] ([[User talk:Guswen|talk]]) 16:55, 21 March 2024 (UTC)

:::: There are several important differences between [[MDPI]] journals versus [[arXiv]]. Journals published by the first two organizations '''claim''' to be peer-reviewed, when in fact they are not. (I have seen multiple articles in their journals that do not even appear to have been properly copyedited!) arXiv, however, has never claimed to be other than what it is: a publishing clearinghouse for non-peer-reviewed preprints, many of which subsequently are published in journals having a more rigorous review process (which becomes noted in the articles' publishing history). A second important difference is in their funding sources. MDPI journal article processing charges are generally paid for by the authors, whereas arXiv is funded by Cornell University Library, the Simons Foundation, and various member institutions. MDPI journals are hence considered to be predatory, and many academic institutions and scientific bodies actively discourage their members from publishing in those venues. Indeed, publication in such journals is often considered in a negative light in regards to academic promotion, etc. Crackpots, of course, couldn't care less. Publication in arXiv carries no negative stigma, provided that one has a decent publication history in properly peer-reviewed journals.
:::: And no, although it happens, Wikipedia discourages use of arXiv as a source. [[User:Prokaryotic Caspase Homolog|Prokaryotic Caspase Homolog]] ([[User talk:Prokaryotic Caspase Homolog|talk]]) 12:19, 22 March 2024 (UTC)

::::: I disagree. 
::::: G Perelman, for example, provided the solution to the Riemann hypothesis in a never-published [https://arxiv.org/abs/math/0303109 preprint].
::::: Here is a list containing examples of wikipedia relevant articles that rely on non-peer-reviewed preprints for relevant parts of the entry: -https://en.wikipedia.org/wiki/String_theory - https://en.wikipedia.org/wiki/Riemann_hypothesis -https://en.wikipedia.org/wiki/Generative_adversarial_network -https://en.wikipedia.org/wiki/Machine_learning -https://en.wikipedia.org/wiki/Modal_logic. 

::::: If we apply your logic, [[User:Chetvorno]], [[User:XOR&#39;easter]], and [[User:Prokaryotic Caspase Homolog]], Wikipedia will not have many of its most relevant articles, or they will be incomplete.  

::::: [[User:Guswen|Guswen]] ([[User talk:Guswen|talk]]) 13:58, 22 March 2024 (UTC)

:::::: You misunderstood what I wrote. First of all, Perelman did not publish in a predatory journal, but on arXiv, and his arXiv article was extensively reviewed over a several year period. Second, I did not say that citation of arXiv should be forbidden. I merely pointed out that such citations are discouraged. Sometimes there is no choice, but we editors have to use our best judgement, and ultimately the contributions have to meet consensus.  [[User:Prokaryotic Caspase Homolog|Prokaryotic Caspase Homolog]] ([[User talk:Prokaryotic Caspase Homolog|talk]]) 15:14, 22 March 2024 (UTC)

::::::: That makes perfect sense to me: had [[Grigori Perelman]] published his proof of [[Poincaré conjecture]] in a predatory journal, this proof would be invalid. [[User:Guswen|Guswen]] ([[User talk:Guswen|talk]]) 21:10, 22 March 2024 (UTC)
 
::[[User:XOR&#39;easter|XOR&#39;easter]] thanks, I should have caught that. --[[User:Chetvorno|Chetvorno]]<sup><small>[[User talk:Chetvorno|<i style="color: Purple;">TALK</i>]]</small></sup> 17:04, 21 March 2024 (UTC)

{{reflist-talk}}

== Bohr paragraph with refs. ==

The current article has this paragraph:
* Bohr offered an interpretation that is independent of a subjective observer, or measurement, or collapse; instead, an "irreversible" or effectively irreversible process causes the decay of quantum coherence which imparts the classical behavior of "observation" or "measurement".

I believe this is incorrect. I believe this is actually (at most) Rosenfeld's rationalization, not something Bohr ever said. But I don't have access to the primary ref (Bohr collected works) @[[User:ReyHahn|ReyHahn]] WDYT? [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 22:35, 30 April 2024 (UTC)
:I got access to the book. The page referenced is a letter from Bohr to Pauli where Bohr discusses measurement. I will take a look, but I need a few days.--[[User:ReyHahn|ReyHahn]] ([[User talk:ReyHahn|talk]]) 00:02, 3 May 2024 (UTC)
::{{ping|Johnjbarton}} I read Bohr to Pauli letter (16 May 1947). Bohr does discuss the role of irreversibility and microscopic dynamics but it is far from clear that it refers to measurement and observation. It mentions measurement/observation three times in the letter, once to say that [[Edward Teller]] was looking into the connections between irreversibility and observation, influenced by [[John von Neumann]]. The second time it is mentioned it says:
:::"After reconsidering the question, I feel myself that the whole question is purely epistemological and therefore of qualitative rather than quantitative character. On the one hand, it is evident that any practical observational arrangements, making use of photographic plates, cloud chambers or direct sensual impressions, involve a mechanism of amplification in the working of which free energy is spent in amounts out of all proportion with the energy exchanges characterizing the individual atomic processes under investigation. On the other hand, it is equally clear that, for the interpretation of [the] quantum mechanical formalism and the elucidation of the paradoxes involved, the problem is how to account consistently for the phenomena defined by means of measuring agencies and recording devices which serve to fix the external conditions and register the experimental results and which, for this purpose, are to be treated as ideal classical instruments."
::the next time it is mentioned he proposes some sort of thought experiment:
:::"The irreversibility in any observational problem has its root in a certain degree of complication of the interaction of the object with the measuring agencies and, trying to make the situation more clear to me, I have considered experimental arrangements where the critical element of irreversibility may be arbitrarily far removed from the final macroscopic recording. For instance, we may, for the localization of a particle, instead of catching it directly on a photographic plate, allow it to enter through a small hole in a box from which the probability of escaping is vanishingly small and where, therefore, the presence of the particle can be ascertained in some suitable way at a later time. The degree of irreversibility here depends on the complicated character of the state of motion of the particle in the box, and the problem presents a certain analogy with the entropy increase accompanying irreversible expansion of a gas from a smaller volume ''v'' to a larger volume ''V'' which pro gas molecule is given by <math>k \log V/v</math>."
::The phrase in this wiki article uses modern language that is not at all coherent with Bohr's view of old quantum mechanics. At best he says that it is an epistemological issue.--[[User:ReyHahn|ReyHahn]] ([[User talk:ReyHahn|talk]]) 11:05, 3 July 2024 (UTC)
:::@[[User:ReyHahn|ReyHahn]] Excellent, thank you! I rewrote the paragraph to avoid using "quantum coherence" in connection with Bohr. That is the part that struck me as uncharacteristic. In addition his comments about amplification are good to know because this concept is used in modern quantum decoherence papers but without reference. Please review. Based on what I've read, summarizing Bohr is famously challenging. [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 16:38, 3 July 2024 (UTC)
::::Yes that is more reliable. It would be nice to investigate what Teller said about it, but Bohr provides no reference.--[[User:ReyHahn|ReyHahn]] ([[User talk:ReyHahn|talk]]) 16:58, 3 July 2024 (UTC)

== Interpretations ==

The "Interpretations" section is really just a repeat or summary of the interpretations. As far as I can tell the discussion and refs never cover "the measurement problem" as considered from each interpretation.

This ref covers how each interpretation deals with the measurement problem:
* {{Cite journal |last=Schlosshauer |first=Maximilian |date=2005-02-23 |title=Decoherence, the measurement problem, and interpretations of quantum mechanics |url=https://link.aps.org/doi/10.1103/RevModPhys.76.1267 |journal=Reviews of Modern Physics |language=en |volume=76 |issue=4 |pages=1267–1305 |doi=10.1103/RevModPhys.76.1267 |issn=0034-6861|arxiv=quant-ph/0312059 }}
It's not perfect because the starting point for the discussion is to assume decoherence in action. [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 22:51, 30 April 2024 (UTC)

:I thought the paragraph on each major interpretation did a pretty good job of relating how it explains wavefunction collapse, and isn't wavefunction collapse what the measurement problem is all about? --[[User:Chetvorno|Chetvorno]]<sup><small>[[User talk:Chetvorno|<i style="color: Purple;">TALK</i>]]</small></sup> 23:36, 30 April 2024 (UTC)
::Thanks. I think your perspective clarifies to me why the section seems off to me. 
::Only some interpretations posit that "the measurement problem is about wavefunction collapse".  I think the paragraphs for each interpretation should explain how "collapse" addresses the "measurement problem" directly.
::To be sure, "wavefunction collapse" is so vaguely described that it sounds like "presto" most of the time.  Thus one can easily conclude that "collapse is the solution to the measurement problem" simply because collapse can be anything one wants. [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 01:17, 1 May 2024 (UTC)
::Section 3, The Measurement Problem Reconsidered in 
::* Bub, Jeffrey. "Why the quantum?." Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics 35.2 (2004): 241-266.
::clearly does not consider the measurement problem to be equivalent to collapse. [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 03:12, 1 May 2024 (UTC)

::::The section is a summary of the major interpretations, written for general readers, which is the main readership of WP.  To address general readers it can't include mathematics.  Given those limitations, I think it is an excellent summary. 

::::You say: "''I think the paragraph for each interpretation should explain how "collapse" addresses the "measurement problem" directly''".  I'm not sure what you mean, each paragraph does discuss collapse.  You say collapse is vaguely described: ''one can conclude that "collapse is the solution to the measurement problem" just because it can be anything one wants.''  The section makes clear that in some interpretations like many-worlds and De Broglie-Bohm there is no collapse, and in others like some versions of Copenhagen apparent "collapse" is just updating of information.  

::::I would agree that the article does not have a description of the measurement problem itself; of what the "problem of definite outcomes" is.  That would include a mathematical definition of eigenstates and what "reduction of the wavefunction" is, as found in [[Wavefunction collapse]].  And discussion of complicated stuff like preferred basis, objective vs subjective definiteness, etc.  But that does not belong in the Interpretations section.  I would suggest a separate section for that.--[[User:Chetvorno|Chetvorno]]<sup><small>[[User talk:Chetvorno|<i style="color: Purple;">TALK</i>]]</small></sup> 02:58, 3 May 2024 (UTC)

== The cat ==

I recently [https://en.wikipedia.org/w/index.php?title=Measurement_problem&diff=prev&oldid=1221606247 deleted] an unsourced section on Schrodinger's annoying cat. Since then I have found references for the Cat in the context of the measurement problem:
* Peres, Asher. "Schrödinger's immortal cat." Foundations of physics 18.1 (1988): 57-76.
* Bell, John. "Against ‘measurement’." Physics world 3.8 (1990): 33.
* Schlosshauer, Maximilian. "Decoherence, the measurement problem, and interpretations of quantum mechanics." Reviews of Modern physics 76.4 (2005): 1267. "A book has never been observed to be in a state of being both “here” and “there” si.e., to be in a superposition of macroscopically distinguishable positions, nor does a Schrödinger cat that is a superposition of being alive and dead bear much resemblence to reality as we perceive it."
* Bub, Jeffrey. "Why the quantum?." Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics 35.2 (2004): 241-266. "This is the measurement problem, or the problem of Schrodinger’s cat (where the cat plays the role of a macroscopic measuring instrument): it is impossible to extend the Hilbert space theory as a noncommutative mechanics to include the black box measuring instruments."
So there are plenty of refs to rebuild a section with that title. [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 22:44, 1 May 2024 (UTC)

::I have no objection to your deleting that unsourced section.  But I think the article certainly should have a section on the thought experiment.  Whether or not there are any current physicists who believe that any of the interpretations could result in an alive/dead cat superposition, the experiment was historically used to discuss the measurement problem, is a great way of explaining wavefunction collapse to general readers, and today is constantly referenced in articles about the subject.  And of course today the question raised by the cat, whether a macroscopic object or system can be in a superposition, is no longer hypothetical, it has been shown to be possible.  The issue has extreme practical importance: that is what is required to create a quantum computer.  --[[User:Chetvorno|Chetvorno]]<sup><small>[[User talk:Chetvorno|<i style="color: Purple;">TALK</i>]]</small></sup> 19:01, 2 May 2024 (UTC)
:::Thanks.  I will work on a Cat section. [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 01:38, 3 May 2024 (UTC)
::::Ok I put something back with refs. I will add more based on other refs shortly. [[User:Johnjbarton|Johnjbarton]] ([[User talk:Johnjbarton|talk]]) 19:59, 6 May 2024 (UTC)
:::::Looks great! --[[User:Chetvorno|Chetvorno]]<sup><small>[[User talk:Chetvorno|<i style="color: Purple;">TALK</i>]]</small></sup> 05:23, 8 May 2024 (UTC)