The following answer was deleted by a mod despite containing a citation of an in-print textbook Notation for two entangled registers

Is it really the purpose of moderators to clamp down on potentially useful information?


I believe the Moderator acted correctly. The original answer was written with little more than:

"A more general answer to the question … can be found in Chapter 10 of [link to book]"
<period> <send>

Folks here will continue to work hard to build this site, so when someone finally finds this community through search, the last thing we want to do is send them elsewhere to find that information.

I understand your concern why someone would remove a link which would seem to satisfy the imperative to answer a question, but Stack Exchange was not built to be a search engine nor a list of links. The purpose of this site is curate an first-hand documentation of knowledge by authoring answers which add value to this site specifically — answers which can be vetted by the community with a wiki-style editing which allow us to edit and improve that content. You can't do that with a link.

Folks often describe how links can break etc, but I think that entirely misses the point of why links are not considered an "answer" in the context of this site.

  • $\begingroup$ The original answer did state the title and author of book, so to describe it as [link to book] is quite disingenuous. $\endgroup$ – Sideshow Bob Jan 18 '19 at 9:48
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    $\begingroup$ @SideshowBob Let me clarify: stating the name, author, publication details, etc. still doesn't make it an acceptable answer according this site's standards (unless it's a resource-request). And it's still a link-only answer, in the sense that the OP has to visit another castle to find out the answer to their question. If you don't like the term "link-only" being used here, we can call it a "reference-only" answer instead. But the point remains the same: not allowed! $\endgroup$ – Sanchayan Dutta Jan 18 '19 at 9:55

I'll be adding a bit to @Robert's answer.

This was your original answer (v1):

A more general answer to the question, why can't the state of the extra qubit be written in the form α|0⟩+β|1⟩ can be found in Chapter 10 of Rieffel & Polack, Quantum Computing - a gentle introduction (link to pdf).

And note that I had added this comment while deleting the answer:

Please do not post links without at least a basic summary of what they contain and how that content answers the question, since link-only answers become useless if the link rots away. Link-only answers are not considered answers here and will be deleted. I've converted it into a comment for the time being.

Your original "answer" is still available as a comment on the main question, so I don't think any useful information has been clamped down. In the future, if you get time and manage to edit and elaborate on the answer, according to the guidance given, consider flagging it for undeletion (click on "flag" → "in need of moderator intervention"). Meanwhile, if you have any minor additions to make or clarifications to ask for, use the comment section.

  • $\begingroup$ Yes, this - having a reference in an answer is great, as long as it (the answer) answers the question without requiring the reference $\endgroup$ – Mithrandir24601 Jan 17 '19 at 22:32
  • $\begingroup$ I appreciate the answer is still available as a comment but I would still rather have a reference-only answer than no answer at all $\endgroup$ – Sideshow Bob Jan 18 '19 at 9:49
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    $\begingroup$ @SideshowBob I can empathize with your point of view, but reference-only answers are not allowed on this site (except on resource-request threads). Mods only enforce the site's rules. They don't make rules unilaterally. If you only have time to point an OP to a specific textbook or paper, just mention it in a comment instead of an answer. $\endgroup$ – Sanchayan Dutta Jan 18 '19 at 10:03

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