Talk:Quantum decoherence

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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)[reply]

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)[reply]

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)[reply]

“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)[reply]

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

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)[reply]

The full sentence is:

"In quantum mechanics, particles such as electrons are described by a wave function, a mathematical representation of the quantum state of a system; a probabilistic interpretation of the wave function is used to explain various quantum effects."

I assume your point is that quantum mechanics makes no predictions other than measurements. I don't think the sentence is really off base. A "state" is an abstraction so its interpretation is not set by the sentence. Johnjbarton (talk) 15:01, 1 September 2024 (UTC)[reply]