Talk:Cat state

Completely different thing

GHZ state is a multipartite state (involves more than one party) that is entangled, but Cat state is a single-party state that involves superposition of (possibly macroscopic) components. These two are completely different things that should be described in two different articles. — Preceding unsigned comment added by 70.55.50.158 (talk) 21:37, 2 September 2014 (UTC)

Merge is not a good idea

GHZ and cat states both are non-classical superposition states, but this already the extent of their similarities. Experimental creation and verification protocols, and the communities dealing with either state are not the same. — Preceding unsigned comment added by 81.194.35.225 (talk) 11:24, 21 October 2013 (UTC)

If that is so, the first paragraph is clearly wrong, because it describes *exactly* a GHZ state. However the superposition given in the next section just as obviously isn't.

The Nature article referenced in the article actually contains a definition right in the abstract (which, unlike the actual article, is freely accessible):

Cat states are equal superpositions of two maximally different quantum states.

This certainly includes GHZ states.

That the name is used in different communities is no proof that it is a different concept, because it happens quite frequently that different communities have different names for the very same concept. In this case, the concept of "cat state" seems to include both GHZ states and non-GHZ states. --93.134.80.75 (talk) 08:29, 11 January 2014 (UTC)

Do not merge. There is a whole lot of confusion going on here. The GHZ is a maximally entangled state of three particles not two; the cat state is an entanglement of two coherent states. Measurement of one of the three states in a GHZ entanglement creates a mixed state; in 4-particle variants thereof, selective measurements can *restore* Bell states that "Wigner's friend" is entangled with (after performing a U-transform depending on the measurement outcome). This is not how the Cat state works -- coherent states do not have a well-defined particle number and so there is no effective way to say "measure this one particle", although you can do other neat things with coherent states -- quantum optics is replete with these. So the idea of a merger seems to be based on some sort of mis-information, or the superficial resemblance of some formulas, or something. Not sure where the problem crept in. 67.198.37.16 (talk) 17:05, 27 April 2016 (UTC)

I would like to add to this discussion that a GHZ state can be understood as a spin cat state, and therefore the two concepts are not completely unrelated as people here are suggesting. — Preceding unsigned comment added by 2.100.97.97 (talk) 18:00, 27 August 2018 (UTC)

Definition

I have a first degree in physics, and as far as I know a cat state is a (normalized) sum of two coherent states. The latters could be thought of as marcscopic states.--89.139.55.163 (talk) 15:10, 31 July 2010 (UTC)

Proposed merge

I know that Greenberger–Horne–Zeilinger state requires N > 2, unlike this article. But it is a weak excuse to existence of two separate articles. Incnis Mrsi (talk) 18:55, 12 February 2013 (UTC)

The fact that any two subsystems are unentangled in a GHZ state, although it is possibly maximally entangled as a whole, gives it a different conceptual status. This does not appear for cat states in N=2, which may justify a distinct entry.

That's a mis-apprehension. In GHZ, any one state is entangled with the union of the other two. This is used to perform the Wigner's freind trick to restore a Bell state after Wigner's friend measured it. So, again, don't merge. 67.198.37.16 (talk) 17:09, 27 April 2016 (UTC)

Do not merge

Do not merge this article with GHZ-states. Both topics are used rather independently in science and despite some similarities they are completely different things. For instance a GHZ-state consists of a distinct number of particles, whereas cat states can have any real α and are often described in terms of continuous variables. Both topics are important enough on their own to deserve distinct articles. Geek3 (talk) 23:05, 20 September 2015 (UTC)

Disambiguation problem: Wigner distribution

@Geek3: could you please confirm that "Wigner distribution" in figure one refers to Wigner quasi-probability distribution? Currently it is pointing to a disambiguation page Wigner distribution.--MaoGo (talk) 14:48, 11 June 2019 (UTC)

New layout

I've just made an edit that I hope is helpful... I found the article was a bit confusing since it started out discussing GHZ states in the lead, then suddenly jumped to optical mode cat states. So I've put the GHZ stuff in its own section and left the lead to be general.

On that note, there is this section on the Schrodinger's Cat article which is perhaps useful.

Previous comments seem to lean towards GHZ states not being counted as cat states, perhaps true, in which case this article might need a lot more work. But I wonder if this is a clash between different subcommunities of physics? --Nanite (talk) 06:41, 1 July 2020 (UTC)