Talk:Open quantum system

Untitled

At the beginning I 'fixed' 'bath' to 'both'. But I see from the Quantum dissipation article that 'bath' is possibly correct. If so the wording needs clarification.

It's called "bath" in physics. --Glentamara (talk) 18:48, 15 October 2020 (UTC)[reply]

Wiki Education Foundation-supported course assignment

This article is or was the subject of a Wiki Education Foundation-supported course assignment. Further details are available on the course page. Student editor(s): Rronk96, Jleamer1. Peer reviewers: Dylanhecht, Wadams3.

Above undated message substituted from Template:Dashboard.wikiedu.org assignment by PrimeBOT (talk) 09:18, 18 January 2022 (UTC)[reply]

So many problems

Further reading is too long. Any source on the list that is useful here is should be summarized in the article. This deep technical topic should not have further reading.
Sourcing is terrible (related to abuse of Further reading).
History mixed up with discussion. The date-annotated material should be gathered in one section, History.
The second paragraph of the intro implies an Applications section which does not exist.

Johnjbarton (talk) 20:39, 14 September 2025 (UTC)[reply]

Further reading can always be trimmed or removed, if somebody cares then that person will re-add whatever is important. Sourcing is terrible because this started from a terrible article. History should be its own section. Again this article was a mess that was shortened to make it less of a mess, it still is a mess.--ReyHahn (talk) 08:35, 15 September 2025 (UTC)[reply]

Please look at my page: User:Harold Foppele/sandbox-2 as per suggestion of @Johnjbarton I rewrote the article. After having bad expirience wtih edit wars, i did all edditing in the sandbox. If yall agree to that version i copy it to the original page. Or delete the sandbox if no consensus is reached. Cheers Harold Foppele (talk) 10:13, 15 September 2025 (UTC)[reply]

I do not agree to such a replacement. There has been no suggestion or proposal that this page is so bad that complete replacement is needed. This is not how Wikipedia improvements are made. I would revert such a large undiscussed change immediately and I believe other editors would back me up.

The pageUser:Harold Foppele/sandbox-2 is not a suitable alternative to the current article. The way you find out what is suitable is to make a small self-contained edit with a short clear edit summary and let other editors review it. If they disagree, they may revert your change with an explanation. Try not to get disheartened or enraged, but rather open a polite discussion topic in the Talk page. Alternatively you can suggest a small change in the Talk page first. Johnjbarton (talk) 16:38, 15 September 2025 (UTC)[reply]

Am i glad it is only in my sandbox. Your comments on Sept, 14, ReyHahn Sept.15 looked like it should be sorta re-editted. I am not disheartened nor enraged, just want to understand whats the scope is of the remarks above. Trust me, i shall never endup in an edit war again. Thats is exactly why i did put it in my sandbox. Any suggestions of part(s) that could be merged? This is what you asked me to do: "I would like to propose a challenge to you: set your draft aside and fix an existing article, for example Open quantum systems." So i tried :) Harold Foppele (talk) 17:03, 15 September 2025 (UTC)[reply]

I suggested working on an existing article as a way to avoid your previous experience. The vast majority of Wikipedia editing is one small change at time, ideally a self-contained change. I gather you have experience programming computers. You must have noticed that debugging or improving large computer programs goes more smoothly if one makes small changes that compile, run, and test, followed by more small changes. Team programming add reviews by others on top, so each small change can be checked. That is how Wikipedia works. All-at-once, take-it-or-leave-it tactics are not helpful. Johnjbarton (talk) 17:43, 15 September 2025 (UTC)[reply]

Ok :) I did among other things HP Business Basic back in 1976, so no compile needed, maybe thats why :) But i hear you and am very much willing to learn. In the page itself it says "Lacks sufficient corresponding inline citations" that is one of the major things i did. How about i start there? It does not change the text, just add to it. Harold Foppele (talk) 18:25, 15 September 2025 (UTC)[reply]

I did a small edit. I edited the first paragraph and added an info box. Please comment :)Harold Foppele (talk) 19:35, 15 September 2025 (UTC)[reply]

I removed the infobox for two reasons: 1) it links WP:User space and 2) I don't think it is helpful and it's not a common practice. We could discuss the value of a non-user space infobox, but I guess {{Quantum mechanics}} might be appropriate if the article is eventually strong enough to include it. Johnjbarton (talk) 20:22, 15 September 2025 (UTC)[reply]

Thank you, your comment(s) help me !!! Harold Foppele (talk) 20:34, 15 September 2025 (UTC)[reply]

I saw that you removed the info box. Is that not allowed? Or improperiate ? Harold Foppele (talk) 20:17, 15 September 2025 (UTC)[reply]

Did a minor edit in citing Harold Foppele (talk) 06:26, 16 September 2025 (UTC)[reply]

Quantum system and environment

Can you please see if you like my version better (shorter) than the original ? Harold Foppele (talk) 10:47, 16 September 2025 (UTC)[reply]

Edited this section Harold Foppele (talk) 11:35, 17 September 2025 (UTC)[reply]

May I suggest: This motivated the formalism of density matrices ^[1] Harold Foppele (talk) 16:52, 23 September 2025 (UTC)[reply]

Position of image in article

This edit by @Harold Foppele reverts my edit to move the system-bath image.

I believe the best location for this image which defines $H_{\rm {S}},$ $H_{\rm {B}},$ and $H_{\rm {SB}}$ is close to the formula $H=H_{\rm {S}}+H_{\rm {B}}+H_{\rm {SB}}$ . It has no particular value in the earlier location. I propose to move it back. Johnjbarton (talk) 17:51, 17 September 2025 (UTC)[reply]

Moved it back and added citation#4 as you said, 1 step at the time Harold Foppele (talk) 18:13, 17 September 2025 (UTC)[reply]

Page numbers

In this edit by @Harold Foppele the page numbers were alter from 358 to 95-108. The content sourced was summarized from page 358. According to the table of contents for the source, pages 95-108 are part of " Introduction to quantum mechanics pp 60-119". Thus I wonder why the page numbers were changed? Johnjbarton (talk) 23:21, 17 September 2025 (UTC)[reply]

Page# corrected Harold Foppele (talk) 10:27, 18 September 2025 (UTC)[reply]

Next citation

The combination would again be a quantum system and the complete description of that system would again require inclusion of its surrounding environment. The eventual outcome of recursively embedding a system in its environment is that the state of the whole universe would be a single quantum system.[citation needed] I would suggest: The Physical Basis of the Direction of Time by H. Dieter Zeh. or Houri Ziaeepour. Quantum state of Yang-Mills fields in SU(∞) Quantum Gravity (SU(∞)-QGR). Academia Quantum, 2025, 2 (1), pp.1. �10.20935/AcadQuant7579�. �hal-04523223� The only closed—and thereby static—quantum system is the Universe itself. Do you agree? Harold Foppele (talk) 10:38, 18 September 2025 (UTC)[reply]

Sorry I do not agree. These sources are primarily about other topics unrelated to the article. Essential core aspects of the article need sources about the topic.

In my opinion we should not be looking for sources to justify that content. Rather we should be starting on page 358 of Nielsen and Chuang and summarizing what they say about open quantum systems.

We could use Nielsen and Chuang pg 82 to add a single sentence about the relationship between open/closed and the universe. But this key source makes it completely clear that the study of "open quantum systems", our topic here, is specifically about quantum systems embedded in a environment modeled by a bath. The topic is not about the universal wavefunction, which therefore deserves at most a mention. I suggest that belongs later perhaps in a subsection summarizing Universal wavefunction. These sources might be useful there IDK. Johnjbarton (talk) 16:32, 18 September 2025 (UTC)[reply]

We already have page 358 of Nielsen and Chuang in #4, Now the next [citation needed] should refer to the text between #4 and the new citation. There it should refer to the universe beeing a single quantum system, but if you want Nielsen and Chuang pg 82, i can do that. Just let me know. Also i was looking for a sample of a professor at MIT. He stated at the end of his college: "When we want to know the position of every atom, we need a computer as big as the universe, and the universe is what we already have". He was a great guy. Stephen Hawking also published along these lines. Its fun to work with you! Harold Foppele (talk) 17:32, 18 September 2025 (UTC)[reply]

I made a change to move the content about recursive model way down the page. I think we should ignore it for now. Johnjbarton (talk) 20:03, 18 September 2025 (UTC)[reply]

This motivated the formalism of density matrices,^{[citation needed]} introduced by John von Neumann in 1927.......

If you agree i would write that alinea as:

This motivated the formalism of density matrices, first introduced by John von Neumann in 1927.^[2],^[3] and later employed extensively by Stephen Hawking in his analysis of black hole evaporation.^[4]. In this approach the state of a subsystem is described by the density operator

\rho

and the expectation value of an observable

A

by the scalar product

(\rho \cdot A)=\mathrm {tr} \{\rho A\}

. Stephen Hawking made famous use of it in his work on black hole radiation and the information paradox. In particular, he argued that tracing over inaccessible degrees of freedom leads to a mixed-state density matrix, which motivated huge parts of modern quantum gravity discussions.

The cite# will be corrected ofcourse. For some reason these end up now wrongly on the talk page. See below Maybe you want to add Von Neumann entropy as a source? [User:Harold Foppele|Harold Foppele]] (talk) 10:11, 19 September 2025 (UTC)[reply]

In my view, the "Quantum system and environment" section should introduce the concept and terminology of open quantum systems. It should not go off topic into history or black holes.

We could have a History section if we have a source that specifically discusses the history of open quantum system analysis. This might be a paragraph in a book or article rather than a dedicated history. The History and Further reading section on quantum noise in Nielsen/Chuang, page 397, might have lead to suitable sources.

We could have a section on application of open quantum system models to black hole. However we would need a different source to start it because the Hawking paper on the "Breakdown of predictability..." does not discuss the article topic.

Von Neumann entropy is a related topic which should be discussed, perhaps with references to Nielsen/Chuang. The page itself cannot be used as a source, per WP:CIRCULAR.

I will post a separate proposal for moving the section forward. Johnjbarton (talk) 15:56, 19 September 2025 (UTC)[reply]

References

^ Semin V, Petruccione F. Dynamical and thermodynamical approaches to open quantum systems. Scientific Reports. 2020 Feb 13;10(1):2607. doi:10.1038/s41598-020-59241-7
^ von Neumann, John (1927), "Wahrscheinlichkeitstheoretischer Aufbau der Quantenmechanik", Göttinger Nachrichten, 1: 245–272
^ Nielsen, Michael A.; Chuang, Isaac L. (2009). Quantum computation and quantum information (10. printing ed.). Cambridge: Cambridge Univ. Press. p. 82. ISBN 978-0-521-63503-5.
^ S.W. Hawking, "Breakdown of Predictability in Gravitational Collapse," Phys. Rev. D 14, 2460–2473 (1976).

Driven systems

While you are down there, can you look at that section? I think it has twice te same content. Harold Foppele (talk) 20:34, 18 September 2025 (UTC)[reply]

The section "Driven systems" is not duplicate, but it is about an advanced topic with a single primary source from 2025. The content is pretty minimal so despite it being about an advanced topic it appears to be almost trivial.

Normally I would simply delete this section and I'm ok if we do. But I suggest delaying to see if the sources referenced by the 2025 paper are useful. In addition to textbooks and reviews in journals, the introductory sections of peer-reviewed papers can be useful secondary sources even if the paper itself is a primary source. The paper is about the article topic just too early to be encyclopedic. Johnjbarton (talk) 23:11, 18 September 2025 (UTC)[reply]

Quantum system and environment

What content should we have in "Quantum system and environment"? I think it should lay out the basic concept of "open quantum system" and terminology. We have a start:

Open quantum systems are described by a composite system. The interior system of interest, or principal system, is surrounded by an environment and together they create a closed quantum system.

I think our next job is to explain these terms and why this formulation is useful. I think things that belong here include: the idea that a closed quantum system can be modeled with standard QM, any alternative terminology (eg "bath" for environment), examples of "environments". With that in place we can start to discuss how open quantum systems are modeled. Johnjbarton (talk) 16:19, 19 September 2025 (UTC)[reply]

I am not so happy with the 3 options I did send to you. I try some better Harold Foppele (talk) 13:54, 20 September 2025 (UTC) Harold Foppele (talk) 13:54, 20 September 2025 (UTC)[reply]

Content should summarize sources. Central to Wikipedia is the idea of WP:Verifiablity. Without sources content is not useful. Johnjbarton (talk) 14:34, 20 September 2025 (UTC)[reply]

If I can source it, is there an alinea you prefer? Harold Foppele (talk) 14:40, 20 September 2025 (UTC)[reply]

https://en.wikipedia.org/wiki/User:Harold_Foppele/sandbox-2 I think i found a nice solution. Added Examples of environments. Hope you like it. If so, i copy it to "Open Quantum System" Harold Foppele (talk) 17:32, 20 September 2025 (UTC)[reply]

It is not practical to review an entire copy of the article with an unknown number of differences. I note two differences but unfortunately I don't have a positive reply on them.

Citing Fano, Ugo (1995). "Density matrices as polarization vectors". Rendiconti Lincei. 6 (2): 123–130. doi:10.1007/BF03001661. S2CID 128081459. This source is not an introduction to open quantum systems but rather it describes a generalization of Bloch's NMR equations. It could be used later in the article once we have a source that established the Bloch's NMR equations are an example of modeling an open quantum system.
The examples list. It is unsourced and consequently not useful.

I would say at this point we have a complete disconnect on the direction of this effort. I will post on your Talk page additional comments. Johnjbarton (talk) 04:25, 21 September 2025 (UTC)[reply]

== History ==

This formalism of the operators and matrices was introduced in 1927 by John von Neumann and independently, but less systematically, by Lev Landau and later in 1946 by Felix Bloch. Von Neumann introduced a matrix in order to develop both quantum statistical mechanics and a theory of quantum measurements. The term density was introduced by Dirac in 1931 when he used von Neumann's operator to calculate electron density clouds.

This is from Density matrix That is where I found the source and also:

The formalism of density operators and matrices was introduced by von Neumann in 1927 and independently, but less systematically by Lev Landau and Felix Bloch in 1927 and 1946 respectively. The density matrix allows the representation of probabilistic mixtures of quantum states (mixed states) in contrast to wavefunctions, which can only represent pure states.

found in John von Neumann

The examples list is not sourced i adjusted it.

The use of the sandbox was to prevent content beeing published that you do not approve in Open quantum system but if you dont want that, maybe i can propose text in the talk page. Harold Foppele (talk) 07:52, 21 September 2025 (UTC)[reply]

Johnjbarton (talk) 14:13, 21 September 2025 (UTC)[reply]

I understood so I only search for conformer ref's. Also I did send you what I read by e-mail. Harold Foppele (talk) 14:22, 21 September 2025 (UTC)[reply]

The introduction paragraphs of

Am-Shallem, M., Kosloff, R., & Moiseyev, N. (2015). Exceptional points for parameter estimation in open quantum systems: Analysis of the Bloch equations. New Journal of Physics, 17(11), 113036.

provide a good start for a History section.

The introduction in

Dann, Roie, and Ronnie Kosloff. "Open system dynamics from thermodynamic compatibility." Physical Review Research 3.2 (2021): 023006.

outlines two different approaches to open quantum systems (I've seen the idea of two different approaches discussed elsewhere). Roughly these would be characterizes as approximate physical models (eg Bloch's NMR) vs axiomatic models. This kind of information is important because two different sources on this topic may seem very different as a consequence of being based on one or another of these cases. Johnjbarton (talk) 14:33, 21 September 2025 (UTC)[reply]

Do you want me to make a History section? and use D R R to cite Q S E ? Harold Foppele (talk) 09:51, 22 September 2025 (UTC)[reply]

Most of the time a History section is better than including dates in the other sections. Mixing history with description is tricky and best left to professional authors. Encyclopedia content is clearer when only one topic is covered at a time.

The Dann-Kosloff source probably belongs at the beginning of a different section. I would rename Dynamics (since we have no "Statics"). Maybe "Models" with a paragraph outlining the two approaches. Johnjbarton (talk) 14:41, 22 September 2025 (UTC)[reply]

Please look at the sandbox, is this what you want and pick entrypoints where you want the text to be inserted, Harold Foppele (talk) 16:30, 22 September 2025 (UTC)[reply]

I agree please do not mix history and content.--ReyHahn (talk) 16:19, 22 September 2025 (UTC)[reply]

User:Harold Foppele/sandbox-2 please look at the history section it is just a rough edit but am i on the right track? Any comments welcome,(talk) 19:03, 22 September 2025 (UTC)[reply]

Open Quantum system link

User:ReyHahn removed the link on open quantum system should there be a link to Open system (systems theory) instead or as a referring ? Although we have already a link in ref <6> Harold Foppele (talk) 09:42, 22 September 2025 (UTC)[reply]

The article title should never be wiki-linked, that makes no sense. Johnjbarton (talk) 14:27, 22 September 2025 (UTC)[reply]

Check MOS:INTRO, Johnjbarton is right.--ReyHahn (talk) 16:17, 22 September 2025 (UTC)[reply]

Relationship to the universal wavefunction

Cited this section Harold Foppele (talk) 21:51, 22 September 2025 (UTC)[reply]

The content is

The eventual outcome of recursively embedding a system in its environment is that the state of the whole universe would be a single quantum system.

and the source is

Everett, Hugh (1973). Bryce Seligman DeWitt; Neill Graham (eds.). The theory of the universal wave function. Princeton: Princeton University Press. pp. 1–140. doi:10.1515/9781400868056-002.

but the majority of the content from pages 1-140 don't relate to this sentence. Does Everitt ever discusses recursive embedding? My understanding of Everitt's point of view was different. He was concerned with formulating a QM theory without quantum jumps (aka wave function collapse). He specifically asserted that pure wave mechanics would apply over the entire universe, that is he proposed a closed quantum system. To me, the idea of an open quantum system is specifically designed to study interaction between an interior system and an environment. Am I being too critical?

I think I wrote that sentence trying to make sense of previous content. Maybe it's just wrong. I think the whole section is dubious in the context of open quantum systems. That's the problem with unsourced content: making sense of it sometimes fails. Johnjbarton (talk) 23:11, 22 September 2025 (UTC)[reply]

Someone like Rudolf Peierls or Asher Peres would say that you can always "recursively embed" a system within its environment to make a bigger system, but you always have to have something on the outside to provide a vantage point from which to understand the bigger system. Without that vantage point, you can't do quantum physics. In other words, the idea that the recursive embedding always culminates in a single universal wavefunction is disputed. Right or wrong, it shouldn't be asserted in wiki-voice. Stepwise Continuous Dysfunction (talk) 01:05, 23 September 2025 (UTC)[reply]

I have provisionally cut the section. If we are to say anything on the topic, we need to start by finding reliable secondary/tertiary sources and summarizing them, rather than attaching sources to text ex post facto. Moreover, it is not clear whether the more philosophical questions, like "what is the right way to think about quantum mechanics?" and "does the notion of a 'universal wavefunction' make sense?", belong in the same article as a technical discussion of Markov conditions, the Lindblad equation, etc. Stepwise Continuous Dysfunction (talk) 01:35, 23 September 2025 (UTC)[reply]

Coherence, i.e., coherence

I find this sentence confusing: Typical observables of interest include things like energy and the robustness of quantum coherence (i.e. a measure of a state's coherence). It seems to be trying to "clarify" the idea of coherence by saying coherence again, like a tourist who repeats themselves more loudly and more slowly. If "robustness" is meant in the technical sense introduced by Napoli et al., then it's not an observable in the same way that energy is, a specific self-adjoint operator which has an expectation value given a quantum state. Instead, their "robustness" is something that is estimated from the expectation value of any one of many different self-adjoint operators, and the operator which gives the best estimate is state-dependent. Stepwise Continuous Dysfunction (talk) 01:21, 23 September 2025 (UTC)[reply]

History

Is there consensus about where in the article the best place is for ==History== ? Harold Foppele (talk) 10:08, 24 September 2025 (UTC)[reply]

Put it at the end.--ReyHahn (talk) 15:01, 24 September 2025 (UTC)[reply]

Please if you have time, look at User:Harold Foppele/sandbox-2 and comment. Maybe the ancient part is off topic. Harold Foppele (talk) 15:49, 24 September 2025 (UTC)[reply]

As I have tried to explain, reviewing sandbox edits is not practical. Please edit the page. For best results make each edit focus on one type of change. For example, if you want to add a History section, just add that section, but don't change other parts of the article. Johnjbarton (talk) 16:08, 24 September 2025 (UTC)[reply]

Ik will do Harold Foppele (talk) 16:30, 24 September 2025 (UTC)[reply]

Done Harold Foppele (talk) 18:05, 24 September 2025 (UTC)[reply]

Since i still make many mistakes, but try to do my best, it would be better to look at a "draft" before it is published. That is why i tried to use the sandbox. But, your call. :) Harold Foppele (talk) 20:19, 24 September 2025 (UTC)[reply]

No mention of Dieter Zeh?--ReyHahn (talk) 18:48, 24 September 2025 (UTC)[reply]

By no means I expect the history section to be complete and flawless but I am glad its not rejected😄 the editor tells ambigious links could you look at that? Harold Foppele (talk) 18:55, 24 September 2025 (UTC)[reply]

There is a big problem with the section, it uses mostly WP:PRIMARY sources, did you use a WP:SECONDARY source? If not it is better to wait.--ReyHahn (talk) 19:30, 24 September 2025 (UTC)[reply]

I take back the section. This is exectly why i asked to take a look first in the sandbox. Could you do that ? Harold Foppele (talk) 20:14, 24 September 2025 (UTC)[reply]

Sorry i didn't see that you where editing the section. I replaced is as it was. Until you say to edit it, i say put. Harold Foppele (talk) 20:25, 24 September 2025 (UTC)[reply]

Again I will point out a fundamental issue: trying to find sources for content is backwards. If you write content by summarizing a secondary source then you already have a source. If I find content in articles without sources I look for secondary sources to verify it. Often I remove the content if it proves too difficult to source. Johnjbarton (talk) 23:58, 24 September 2025 (UTC)[reply]

We need to look into (the few) textbooks for secondary history refs. I doubt we will find a really great one. Johnjbarton (talk) 23:50, 24 September 2025 (UTC)[reply]

I added more ref's can you please check if thats better? Harold Foppele (talk) 19:10, 1 October 2025 (UTC)[reply]

[1] Semin V, Petruccione F. Dynamical and thermodynamical approaches to open quantum systems. Scientific Reports. 2020 Feb 13;10(1):2607. doi:10.1038/s41598-020-59241-7

[2] von Neumann, John (1927), "Wahrscheinlichkeitstheoretischer Aufbau der Quantenmechanik", Göttinger Nachrichten, 1: 245–272

[3] Nielsen, Michael A.; Chuang, Isaac L. (2009). Quantum computation and quantum information (10. printing ed.). Cambridge: Cambridge Univ. Press. p. 82. ISBN 978-0-521-63503-5.

[4] S.W. Hawking, "Breakdown of Predictability in Gravitational Collapse," Phys. Rev. D 14, 2460–2473 (1976).

[1]

[2]

[3]

[4]