Talk:Quantum decoherence

pedagogical lecture on decoherence and quantum measurement

I'd like to add a reference to a recent arXiv paper relevant to this article. It is a short pedagogical lecture aimed at students of quantum mechanics which explains the modern viewpoint on decoherence and its relation to the measurement problem.

Perhaps a more experienced editor (like @StarryGrandma) can suggest a place to add it to the article, with a description similar to the above or to the abstract below.

https://arxiv.org/abs/2212.02391

Title: Decoherence and Quantum Measurement: The Missing Lecture

Abstract: We give an elementary account of quantum measurement and related topics from the modern perspective of decoherence. The discussion should be comprehensible to students who have completed a basic course in quantum mechanics with exposure to concepts such as Hilbert space, density matrices, and von Neumann projection (``wavefunction collapse''). Zenmach (talk) 21:01, 3 January 2023 (UTC)

@Zenmach, Wikipedia is an encyclopedia, not a place to publicize someone's unpublished lecture. See Wikipedia:What Wikipedia is not, particularly the section on textbooks, which says "The purpose of Wikipedia is to summarize accepted knowledge, not to teach subject matter." StarryGrandma (talk) 22:10, 3 January 2023 (UTC)

Intro section way to long.

The intro tends attract additions in articles but per WP:SO it should be "a concise summary of the article". Johnjbarton (talk) 02:01, 27 February 2024 (UTC)

I made a series of organizational edits so address this issue. Some of the content here deleted as duplicate or too detailed and unreferenced (meaning we can't judge if the detail is important or not). Johnjbarton (talk) 02:32, 27 February 2024 (UTC)

Puzzling and incorrect lede

The first sentence says:

• Quantum decoherence is the loss of quantum coherence, the process in which a system's behaviour changes from that which can be explained by quantum mechanics to that which can be explained by classical mechanics.

The sentence makes no sense: does "the process" refer to coherence or decoherence? We can infer the latter, but then the sentence would be disputed. See

• A J Leggett 2002 J. Phys.: Condens. Matter 14 R415 DOI 10.1088/0953-8984/14/15/201

Johnjbarton (talk) 17:16, 4 May 2024 (UTC)

“lost” energy doesn’t exist

The end of the second paragraph in the Concept section says "As a result of this process, quantum behavior is apparently lost, just as energy appears to be lost by friction in classical mechanics." Classical mechanics are governed by laws of thermodynamics, the first of which is energy conservation. Hence, energy doesn't get "lost" by friction. The example should be revised, or if no classical mechanic equivalent exists, removed Jpcarbod (talk) 04:49, 6 July 2024 (UTC)

I revised the sentence but it could be removed as unsourced. Johnjbarton (talk) 15:29, 6 July 2024 (UTC)

Concept

I believe the phrase " a mathematical representation of the state of the system" should be changed to "a mathematical representation of the probable state of the system after measurement".

Though often forgotten, that is just what the Born law tells us. There are many, many authoritative publications to confirm this understanding, starting with Born's original analysis: M. Born. Z. Phys. 37, 863 (1926). One among the many others is Wigner's 1952 article in Z. fur Physik, 133, 101, "Measurement of Quantum Mechanical Operators" where he explains that each of the eigenfunctions of the present wavefunction is a probable result of a measurement, with its accompanying eigenvalue.

I believe this understanding is not at all trivial, since the present wavefunction is often believed to collapse at measurement. D bar x (talk) 21:11, 31 August 2024 (UTC)