Talk:Quantum entanglement

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!

Did he say "spooky action at a distance" or "spooky actions (plural) at a distance"? 2600:8801:BE1C:1D00:FA07:6031:AB4E:440C (talk) 16:34, 12 January 2025 (UTC)

It's plural in the original letter: "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." It should be on p155 of The Born-Einstein Letters, but the book is no longer accessible vie archive.org; I've found a pdf in German here (p 162 of the German edition). --Qcomp (talk) 11:11, 13 January 2025 (UTC)

The lede says:

• Quantum entanglement is the phenomenon of a group of particles being generated, interacting, or sharing spatial proximity in a manner 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 definition implies an interpretation, "a group of particles being generated", which is inconsistent with orthodox QM. In all experiments with entanglement, the "particles" only appear in the final observations. Describing QM in terms of little flying things is the source of much confusion. This is difficult topic so I'll leave this up for discussion and look for a good source. Johnjbarton (talk) 23:38, 22 March 2025 (UTC)

It is kind of odd. Maybe shorten it:

• In quantum mechanics, quantum entanglement is a physical phenomenon were a group of particles cannot be described independently of the state of the others after interacting, including when the particles are separated by a large distance.

• --ReyHahn (talk) 10:53, 23 March 2025 (UTC)

  Good, I agree that the key bits that need to be in the sentence (as was in the original) is the "cannot be described independently of the state of the others". What if we left the "interacting" for later in the article and used a concrete distance rather than the relative "large":

  • In physics, quantum entanglement refers to a quantum state of multiple particles in which each particle of the group cannot be described independently of the state of the others, even when the particles are detected kilometers apart.

  Johnjbarton (talk) 17:06, 23 March 2025 (UTC)

  I put my version in and it was changed to a misleading sentence by @Tercer and @ReyHahn. The misleading version is:

  Quantum entanglement is the phenomenon where the quantum state of each particle in a group cannot be described independently of the state of the others, even when the particles are separated by a large distance.

  The claim "that the particles are separated by a large distance" is a form of local realism which has been disproven. We have no information on the separation of the particles. If we knew the separation of the individual particles, we would describe them independently. Entanglement means exactly that we do not have this information. The particles are detected at a large separation. This the fact observed experimentally and why I used "detected" in my version. This is not a trivial issue, but the very heart of the concept discussed in the article. Johnjbarton (talk) 14:36, 3 April 2025 (UTC)

  So you want to change "are separated" by "are detected". It sounds off, because the state is previous to measurement.--ReyHahn (talk) 14:55, 3 April 2025 (UTC)

  Yes, the sentence is abbreviates the process. State characterizes what we might measure. How about

  • Quantum entanglement is the phenomenon where the quantum state of each particle in a group cannot be described independently of the state of the others, even when the state describes experiments in which particles are detected kilometers apart.

  Johnjbarton (talk) 15:32, 3 April 2025 (UTC)

  That's incorrect. It's perfectly possible to know the position of two particles with high precision without breaking their entanglement. For the 100th time, you shouldn't write about things you don't understand. Tercer (talk) 15:29, 3 April 2025 (UTC)

  Perhaps your 100th aggressive statement without a source to back your claim. Johnjbarton (talk) 15:33, 3 April 2025 (UTC)

This article suddenly uses the term "qubit" in the middle of an edification without any explanation or reference link, and goes on to use it extensively. Room for improvement! Go-in (talk) 22:15, 16 January 2026 (UTC)

The first use is now linked to the qubit article. Rehashing at length what a qubit is in this article would be out of scope. Stepwise Continuous Dysfunction (talk) 00:47, 17 January 2026 (UTC)