Talk:Quantum entanglement

Wiki Education Foundation-supported course assignment

This article was the subject of a Wiki Education Foundation-supported course assignment, between 20 August 2020 and 23 November 2020. Further details are available on the course page. Student editor(s): MAllison5.

Above undated message substituted from Template:Dashboard.wikiedu.org assignment by PrimeBOT (talk) 07:35, 17 January 2022 (UTC)

Standard error of sign regarding information and entropy.

Short before the sentences:

″The reversibility of a process is associated with the resulting entropy change, i.e., a process is reversible if, and only if, it leaves the entropy of the system invariant. Therefore, the march of the arrow of time towards thermodynamic equilibrium is simply the growing spread of quantum entanglement.[83] This provides a connection between quantum information theory and thermodynamics.″

... all entropy formulas, whether Shannon's or 'von Neumann' tell about possibilities and/or bandwidth. Real data transferred via classic or quantum methods show always the reverse sign, because a single of the many possibilities has been chosen for transfer. In the same way growing quantum entanglement does not increase but reduces entropy. For sure the internal order by entanglement is even the reverse of disorder maximization by thermodynamic equilibrium. If [83] is indirectly cited, it tells simply non-sense. Please drop the sentences above and the reference from the article. Many thanks!

Spooky Action at a Distance

It is questionable whether Einstein was talking specifically about entanglement when he used this expression. Here is the relevant passage from his letter to Max Born (3 December 1947):

Meine physikalische Haltung kann ich Dir nicht so begründen, dass Du sie irgendwie vernünftig finden würdest. Ich sehe natürlich ein, dass die principiell statistische Behandlungsweise, deren Notwendigkeit im Rahmen des bestehenden Formalismus ja zuerst von Dir klar erkannt wurde, einen bedeutenden Wahrheitsgehalt hat. Ich kann aber deshalb nicht ernsthaft daran glauben, weil die Theorie mit dem Grundsatz unvereinbar ist, dass die Physik eine Wirklichkeit in Zeit und Raum darstellen soll, ohne spukhafte Fernwirkungen.... Davon bin ich fest überzeugt, dass man schliesslich bei einer Theorie landen wird, deren gesetzmässig verbundene Dinge nicht Wahrscheinlichkeiten, sondern gedachte Tatbestände sind, wie man es bis vor kurzem als selbstverständlich betrachtet hat. Zur Begründung dieser Überzeugung kann ich aber nicht logische Gründe, sondern nur meinen kleinen Finger als Zeugen beibringen, also keine Autorität, die ausserhalb meiner Haut irgendwelchen Respekt einflössen kann.

I cannot substantiate my attitude to physics in such a manner that you would find it in any way rational. I see of course that the statistical interpretation (the necessity of which in the frame of the existing formalism has been first clearly recognized by yourself) has a considerable content of truth. Yet I cannot seriously believe it because the theory is inconsistent with the principle that physics has to represent a reality in space and time without spooky action at a distance [phantom actions over distances] ... I am absolutely convinced that one will eventually arrive at a theory in which the objects connected by laws are not probabilities, but conceived facts, as one took for granted only a short time ago. However, I cannot provide logical arguments for my conviction, but can only call on my little finger as a witness, which cannot claim any authority to be respected outside my own skin.

Max Born - Eroica (talk) 10:43, 30 December 2021 (UTC)

I have a problem with the first sentence of the article.

The article begins with these words: "Quantum entanglement is the physical phenomenon ... " My problem is with the word "physical." In one way of looking at it, physical properties are involved. But there appears to be a metaphysical aspect to quantum entanglement that cannot be explained by ordinary principles of cause and effect. Cause and effect happens when things bump into each other, figuratively speaking. But quantum entanglement occurs when particles are separated by such extremes than they could not have a direct effect on each other. 2600:8801:BE24:1A00:78CA:B2D3:C552:115A (talk) 19:48, 14 October 2022 (UTC)

It can be observed in an experiment, so it is physical. Metaphysics is the study of the unobservable. Cause and effect have nothing to do with the definitions of these terms - and I think a lot of people would disagree with the definition you gave here anyway. MrOllie (talk) 20:00, 14 October 2022 (UTC)

I agree with the objection. Entanglement is then defined in terms of how states are described, and not directly as something physical. There is no experiment to determine whether a particular particle is entangled. 04:00, 9 November 2022 (UTC)

I also have a problem with the first sentence, though for a different reason. I don't claim the sentence is false but that is it unclear (at least to me) due to the words "share spacial proximity" followed by the words "separated by a large distance." Perhaps it could be rewritten without that first phrase? In other words: "Quantum entanglement is the phenomenon that occurs when a group of particles is generated or interacts in a way such that the quantum state of each particle of the group cannot be described independently of the state of the others, including when the particles are separated by a large distance." This version seems much more straightforward to me.Renejs (talk) 22:29, 12 March 2023 (UTC)

This article confuses entanglement with interference

"Quantum entanglement has been demonstrated experimentally with photons, neutrinos, electrons, molecules as large as buckyballs, and even small diamonds. The utilization of entanglement in communication, computation and quantum radar is a very active area of research and development."

The references cited for electrons and buckyballs do not experimentally demonstrate entanglement, only interference. As such this is overstating the demonstrated entanglement for massive particles. The vast majority of experiments, and the ones that are most informative, have all used photons. Unless there are citations for experiments that demonstrate ENTANGLEMENT of massive particles (electrons, or molecules/buckyballs/diamonds) I suggest that the first sentence be edited or deleted. Ralivingston1952 (talk) 20:11, 9 February 2023 (UTC)

The reference about electrons indeed demonstrated entanglement, but you are right that with buckyballs only superposition was demonstrated. Also, the experiment with neutrino oscillations also only demonstrated superpositions. I removed them. Tercer (talk) 10:29, 10 February 2023 (UTC)

I believe that the electron and diamond experiments also do not demonstrate entanglement of massive objects since the connection between them is via photons, not massive particles. However, since the articles claim entanglement and it is only my opinion that they do not, it is appropriate that my opinion not go into the Wikipedia article. Thank you for your prompt response. Ralivingston1952 (talk) 14:33, 10 February 2023 (UTC)

I think that massive objects are made of particles (known nowadays as fields). Kartasto (talk) 14:40, 10 February 2023 (UTC)