As of now, is one of the most popular tags, with 351 questions and counting.

Thing is, I don't quite understand what is it for. Or rather, what is it not for.

The whole site is essentially about quantum information and quantum-information-related topics, so I don't see the point in keeping this tag. Looking at the questions tagged with it, I also don't see how this tag is helping categorise them in any way.

What do you think? Can we simply get rid of it? If not, can you provide a good rationale for keeping it?

As a tangential question, I guess this would be problematic for question that are currently only tagged with . Is there a way to look for such questions (I'm not well-versed with data.stackexchange, if that's what's needed)?

  • $\begingroup$ This is the SEDE query you're looking for: Find questions with a single tag (now case insensitive) $\endgroup$
    – Mithrandir24601 Mod
    Commented Aug 19, 2020 at 17:29
  • $\begingroup$ @Mithrandir24601 thanks. That gives just 11 questions, so not really a significant problem to retag them in case we decide to do this $\endgroup$
    – glS Mod
    Commented Aug 19, 2020 at 17:33
  • $\begingroup$ Most of those (now 10) questions could do with some retagging anyway, so no, I don't see them as an issue here at all $\endgroup$
    – Mithrandir24601 Mod
    Commented Aug 19, 2020 at 17:34
  • $\begingroup$ There may be new users that are unfamiliar with stackexchange and/or are very beginners in quantum computing. This tag may be useful for them, unless/until retagged? $\endgroup$ Commented Aug 26, 2020 at 23:28
  • $\begingroup$ @MarkS I'm not sure I get your point. How would the tag be useful for people unfamiliar with stackexchange? $\endgroup$
    – glS Mod
    Commented Aug 26, 2020 at 23:51
  • $\begingroup$ Isn't there a requirement that all questions must have at least one tag? If I'm a new user and am new to quantum computing, and I have a question to ask and I must tag the question, I start typing "quantum..." and "quantum-information" shows up as an option. I think "yeah, that'll work for me..." Without the option, if I am new and have to hunt around for the right tag, then I might get discouraged and demotivated from asking? Just throwing the hypothetical out there, I agree it's not the best tag but it might be a cushion for new users. $\endgroup$ Commented Aug 26, 2020 at 23:58
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    $\begingroup$ @MarkS there are plenty of tags already, I hardly think that someone would be discouraged by that. To name a few, mathematics and quantum-state would be easy targets, especially given the provided auto-complete (you start typing quantum and you get plenty of options). If someone cannot be bothered even finding a relevant tag, I'd argue that being discouraged from asking the question wouldn't be that bad of an outcome. $\endgroup$
    – glS Mod
    Commented Aug 27, 2020 at 0:00
  • $\begingroup$ OK, yeah you convinced me! $\endgroup$ Commented Aug 27, 2020 at 0:02
  • $\begingroup$ I don’t think so. It’s arguable that there are topics covered on the QC stack exchange that may have very little to do with quantum information. For example a lot of discussion around hardware implementations, specific software libraries, etc. may have little to do with the quantum information itself. As we look to the future this may even be more so the case — quantum information is a common tag because that’s perhaps the most democratized area of the field; as hardware and software mature, it’s popularity could that easily balance out as other areas come to the fore. $\endgroup$
    – Greenstick
    Commented Aug 27, 2020 at 18:05
  • 1
    $\begingroup$ @Greenstick that should probably be an answer, as we need to know how many people think one way or another. Also, the discussion in quantumcomputing.meta.stackexchange.com/q/281/55 and quantumcomputing.meta.stackexchange.com/q/362/55 might be related. But most of all, I feel like this is a matter of terminology. For me, "quantum information" comprises things such as quantum computation. The terms are not mutually exclusive. But this is not even what's relevant here. We need examples of questions for which the tag is actually useful, adding information. Can you provide any? $\endgroup$
    – glS Mod
    Commented Aug 27, 2020 at 23:40

3 Answers 3


Observations/Retag Guidance:

There's a tag that at least sounds like it's purpose is possibly what was actually originally intended for. If you see something tagged that should be tagged , then please re-tag as such.


The tag is in the process of being removed (and may potentially be burninated). You can help out by reviewing the questions with this tag, and...

  • editing questions to improve the question and remove the tag,
  • flagging/voting to close questions that are duplicates/off-topic/unclear/too broad/opinion-based
  • voting on questions with this tag,
  • voting to delete the questions with this tag (after they have been closed, and only if the entire Q&A contains nothing of value).

Here are some quick links to get you started:

Ask for help if you need it.

If you have any questions about specific questions you come across, or the process in general, please feel free to leave a comment on this post. You can also ask in QC chat.

This answer is adapted from the burnination process on SO

  • $\begingroup$ thanks. I interpreted information-theory as more specifically about questions related to classical information theory concepts (rather than all things quantum information, as quantum-information). There is no excerpt yet though, so this is mostly to be decided. Also, I don't quite what should happen now. For example, why should voting on questions with quantum-information help? Are you going to edit the tag excerpt to mark it being in the process of being removed? $\endgroup$
    – glS Mod
    Commented Sep 10, 2020 at 15:01
  • $\begingroup$ Yeah, that's what I'm interpreting it to be as too (the quantum version of classical info theory concepts). Voting helps (in principle) because questions <0 score get automatically deleted after a while when closed. Of course, we're small enough that such things probably won't matter and can be manually done anyway $\endgroup$
    – Mithrandir24601 Mod
    Commented Sep 10, 2020 at 15:25

There's currently no questions with only the tag. This query indicates that. That doesn't mean that it's not a useful tag though. There's probably not a lot of questions with only 1 tag, in general.

I will point out that the tag has only 5 questions, and surprisingly, none of them have the tag.

The main issue though, is that there's 26 people "watching" the tag who I think need to have a say in this. Do they want to instead watch 10 separate tags that combine together to reproduce the effect of watching ? Or would they prefer to keep things as it is? Who are the people that are watching the tag, and who are the people subscribed to get emails when questions with that tag are asked? I think I do not have the ability to see who they are, but perhaps some of them can speak up here.

  • $\begingroup$ there were some such questions, they were just edited in the meantime (they were all mistagged anyway). information-theory is a few months old, so it's not surprising it has few questions. Sure, I agree on having people having a say in this.. I mean that's the whole point of posting it on meta. $\endgroup$
    – glS Mod
    Commented Aug 30, 2020 at 20:58
  • $\begingroup$ when you say "there were some such questions" what do you exactly mean? $\endgroup$ Commented Aug 30, 2020 at 21:01
  • $\begingroup$ I mean that there were some questions with only the quantum-information tag $\endgroup$
    – glS Mod
    Commented Aug 30, 2020 at 21:02
  • $\begingroup$ Ok. It's hard to know what the tags were like in the past. $\endgroup$ Commented Aug 30, 2020 at 21:03

Quantum information is typically used as an umbrella term to include all quantum science that uses information in a quantum way. As such, I find it's used a lot of time for non-quantum-computing related things, like quantum communication, creation of entanglement, violation of bells inequality, and various experiments not related to computing.

If someone says they work in quantum information (this is actually what I typically tell people I do research in), I assume they do one of these non-computing-related research areas. (Otherwise they would say they do "quantum computing")

So my vote is to leave it alone. If you want maybe change the tag to "quantum information(not computing)"

If my advisor for instance joined this forum and followed exactly one tag, he would follow quantum information (because of his interest non-computing related quantum things).

  • $\begingroup$ I'm sympathetic to the reason of allowing people to follow a specific topic; I very much follow physics.SE and other sites by following this very tag there, which works fine. However, my problem is to use "quantum information" as complementary to "quantum computation". For example, would questions about gate decomposition count as "quantum information"? Are quantum algorithms about "quantum information"? They're definitely about quantum computing, but also very much used for e.g. quantum communication. Should we tag everything that is not programming with quantum-information? $\endgroup$
    – glS Mod
    Commented Aug 31, 2020 at 7:04
  • $\begingroup$ what about broader questions that are not specific to either (e.g. those asking about general metrics or concepts)? Should these be in quantum-information? If not, this means that quantum-information should have a more narrow scope. Which brings me to the core issue here: what exactly should be the scope of quantum-information? Because right now the only thing I'm positive wouldn't count as such are questions in programming. Being this site essentially about quantum information, having it as a tag feels redundant and hard to maintain to me $\endgroup$
    – glS Mod
    Commented Aug 31, 2020 at 7:08
  • $\begingroup$ " For example, would questions about gate decomposition count as "quantum information"? Are quantum algorithms about "quantum information"?" If both are written in the context of quantum computing, (and the plan would be to use QI as complementary to QC) then they wouldn't be included. For example, an entanglement swapping algorithm or QKD would count as quantum information. Shor's, grover's, or just learning how to write some sigma operators in the standard QC notation would be quantum computing. $\endgroup$ Commented Aug 31, 2020 at 19:33
  • $\begingroup$ that's still not answering the main question, which is, how exactly do you distinguish between "quantum information" and "quantum computation"? Because for me, the former is the general term encompassing, among other things, the latter. For what it's worth, the Wikipedia page agrees with me, see end of first paragraph. (also, OT but a pet peeve of mine: stackexchange is not a forum) $\endgroup$
    – glS Mod
    Commented Aug 31, 2020 at 20:49
  • $\begingroup$ You can just modify the tag to refer to "quantum information without computing", which I think is what most people are currently using this tag for. $\endgroup$ Commented Aug 31, 2020 at 21:05
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    $\begingroup$ well, 1) quantum-information-without-computing is definitely not a good name for a tag, and 2) you are proposing having a tag whose role is to essentially "negate" another tag. What's the point of that? You can just ignore specific tags if you don't want to see some questions. If anything, this would suggest that it might be worth creating a quantum-computing tag to more easily ignore those questions. Not that I'm suggesting that here; you can pretty easily avoid seeing quantum computation questions by ignoring programming and a couple other tags $\endgroup$
    – glS Mod
    Commented Aug 31, 2020 at 21:08
  • 1
    $\begingroup$ let me also point out that, from a practical perspective, tags aren't really very useful if they are not actively maintained, as most new users aren't familiar with the tagging system and what exactly we mean with the tags. So the way a tag is actually used, mostly reflects the way people maintaing the tags understand its scope $\endgroup$
    – glS Mod
    Commented Aug 31, 2020 at 21:12

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