Talk:Wave function collapse/Archive 2

Rename to "Wave function collapse (Quantum Mechanics)", create "Wave Function Collapse (Algorithum)", and add a disambiguation page.
Recently over the past few years Wave Function Collapse has become an incresingly common algorithum used to store and search data, and especially prosedurally generate terrains. It hardly makes sense to group a semi dense article about quantum mechanics with one about data storage and terrain generation, thus this proposal. Tryoxiss (talk) 00:58, 26 April 2023 (UTC)


 * It's spelled "algorithm" and probably not, because the term in quantum mechanics is most likely the WP:PRIMARY topic. It is adequate to put a hat note at the top of the article pointing to Wave function collapse (algorithm) which does not even exist. Maybe you should work on such an article first and we can go from there. Changing what exists here at wave function collapse would break a lot of incoming links for no good reason. The algorithm has ~1700 mentions on google scholar while the term in quantum mechanics has ~6800 —DIYeditor (talk) 01:06, 26 April 2023 (UTC)


 * Oppose: Agree with DIYeditor. The quantum mechanical definition is clearly the primary one and should keep the current name.  I agree the algorithmic definition should be covered in a separate article, with a different name. --ChetvornoTALK 01:32, 26 April 2023 (UTC)
 * Also want to back up that the algorithm should be its own page, but leave QM here 2A02:C7C:C4CD:A500:469A:2158:97A7:247C (talk) 21:51, 11 June 2023 (UTC)

Wave functions collapse is not time evoluion.
The statement 'Collapse is one of the two processes by which quantum systems evolve in time' is false. The time evolution is described by the Schrödinger equation alone. (that is, when spin is disregarded and relativistic effects are absent ...). Aoosten (talk) 22:41, 28 July 2023 (UTC)

Lead sentence is misleading: "occurs" implies a physical event.
The current lead is:

In quantum mechanics, wave function collapse occurs when a wave function—initially in a superposition of several eigenstates—reduces to a single eigenstate due to interaction with the external world.

Later in this very same article we read:

''Heisenberg did not try to specify exactly what the collapse of the wavefunction meant. However, he emphasized that it should not be understood as a physical process.''

The word "occurs" in the lead makes it sound like wave function collapse is a physical process. As far as I am aware there is no observational evidence to support this. Wave function collapse is one of a series of steps connecting a model results to experiments, a highly successful connection. We don't understand this step: we can't assert that it "occurs". Johnjbarton (talk) 17:37, 3 August 2023 (UTC)


 * It is uncontroversial that collapse is not a physical process - as far as anything in quantum foundations is uncontroversial. I'm not sure if I would interpret physicality from the word "occur". In any case, do you have a suggestion on how to improve the lead? Tercer (talk) 19:13, 3 August 2023 (UTC)
 * Uncontroversial among physicists, but, as we write for any reader, I think some may come with questions. (As evidence I present the current state of the wave-particle duality article.) To my mind phrase "collapse occurs when" vividly reinforces a physicality, a reality, that “projection of rays in Hilbert space” (von Neumann) or even "wave packet reduction" (Heisenberg) does not.
 * BTW I am yet to find the phrase "wave function collapse" in any of the references that claim to cite the origin of the term.
 * The current lead is written well, so it is a challenge for me to do better but without the action. Here is a try that also attempts to say something less jargon-y in the first sentence.
 * Wave function collapse describes the experimental observation of a single probability-weighted value from among multiple values predicted by quantum mechanics. A wavefunction initially in a superposition of eigenfunctions reduces to a single eigenfunction in the calculation of the probability.'' Johnjbarton (talk) 01:13, 4 August 2023 (UTC)
 * I'm afraid you're making the language much more complicated for little gain. It is way too subtle for the reader to catch the distinction. I think it would be more helpful to explicitly state that collapse is not a physical process (with a source of course). Tercer (talk) 08:26, 4 August 2023 (UTC)
 * I don't think "occur" necessarily implies the kind of physicality in question here. For example, a math text might say Looking at any list of prime numbers, one sees that twin primes occur often . XOR&#39;easter (talk) 19:42, 3 August 2023 (UTC)


 * I don't think there is anything wrong with using "occurs". I am fine with the existing lead sentence.  "Occurs" usually implies an event in time, and wavefunction collapse appears as an event in time: a discontinuous increase in our knowledge of a measureable due to a measurement.  We don't know yet whether this is due to a physical process or not: whether a wavefunction "collapses", or whether it just represents an increase in an observer's knowledge.    If apparent wavefunction collapse is due to decoherence, as it seems to be, this is a physical process: the diffusion of phase information from a wavefunction into the environment.  Anyway, as XOR&#39;easter pointed out, the word "occurs" doesn't necessarily mean an event in time. --ChetvornoTALK 22:00, 3 August 2023 (UTC)
 * There are unverified theories that claim non-linear "magic" as a cause of "collapse", which might be discussed in the article. As generally used the term is refers to a step in matching a model to experiment, so I don't think it should be used in the lead.
 * In his review Quantum Decoherence Maximilian Schlosshauer gives his definition of collapse in his section 7:
 * Application of the unitary Schr¨odinger evolution to a measuring apparatus interacting with a system prepared in a quantum superposition state cannot dynamically describe the stochastic selection of a particular term in the superposition as the measurement outcome (the “collapse of the wave function”)
 * The remainder of his section 7 has a very readable discussion of how the theory called "decoherence" can't help with collapse. Johnjbarton (talk) 02:08, 4 August 2023 (UTC)
 * Would it be sufficient to change "occurs when" to "is when"? —DIYeditor (talk) 04:15, 4 August 2023 (UTC)
 * Thanks for the feedbacks. How about
 * ''In quantum mechanics, wave function collapse reduces a wave function—initially in a superposition of several eigenstates—to a single eigenstate; this step is part of the process of comparing theory models to experiments.
 * Johnjbarton (talk) 14:12, 4 August 2023 (UTC)
 * At the risk of coming across as negative, I don't see how this is a substantial improvement. If "occurs" sounded too physical, surely "reduces" does too. It keeps the opaque technical terms "superposition" and "eigenstates", and it adds a whole extra statement (containing the somewhat awkward construction "theory models"). XOR&#39;easter (talk) 15:49, 4 August 2023 (UTC)
 * Agree with XOR&#39;easter, not an improvement. Johnjbarton That is why I said "apparent wavefunction collapse".  --ChetvornoTALK 21:38, 6 August 2023 (UTC)
 * Johnjbarton (talk) 21:46, 6 August 2023 (UTC)