@Mithrandir24601 Why did you delete the N&C answer listing post and not the original post? I am new to the meta side of SE, so do not really understand the reasoning you give.

Because it would seem to me to have been better to not have the listings on a post discussing whether or not to make them. It's waaay cleaner that way

@SLesslyTall A few um, 'higher-level' reasons - the original post is asking if a certain thing is allowed, which is a perfectly good post. This first post also makes it clear that these questions are on-topic (which the second one doesn't and can't without becoming a duplicate of the first) even if there are questions (such as that one that someone pointed out isn't normally relevant to QC) that would normally involve some sort of argument as to whether it's truly on-topic here or not

(and it makes it clear these questions specifically are on topic)

Ok, but I still think that it would be better to have the directory of questions listed somewhere that isn't the original post. Where could this be?

Generally, on other SE sites, similar question series exist and these are also perfectly good. However, what apparently tends to happen is that these types of posts tend to fall into disarray with time

(which just makes things a bit of a mess)

Isn't the deleted post exactly the kind of thing the "community wiki" option is meant to address?

@Mithrandir24601 @SLesslyTall what about havintga dedicated tag for these posts? We could have the list in the associated wiki page

That would work

And what do you mean exactly by "associated wiki page" (I'm new)

Although one could argue that as the community develops and other textbook exercises are listed, having a tag per book seems sub-optimal

@SLesslyTall If you do want a list of questions, for the minute, the original post is the best place to put them (although I don't think even this is a good idea to be honest and I might end up having to get rid of that as well). Also, can you do that thing where you leave a header in each question saying that it's part of the series? I'm sorry this had to happen but I do really think that the idea of having the questions and answers from N&C is a good one

But where should this list go in the long run then?

And yes, I will add a header when the list has a proper home.

@glS Is this a meta tag? I'm not sure. I'll have to discuss with the other mods about whether this is a good idea or not

@SLesslyTall As in, a header to the original post that says we're OK with this

@SLesslyTall SE is trying very hard to remove new community wiki posts

I am going to wait until a permanent place for the list is found before adding the headers

Otherwise all the links will have to be changed each time the list location moves and I cba to do that

@SLesslyTall It's not about linking to the list of questions but about linking to the original meta post where you asked if such a thing would be OK

What's the point of that?

@SLesslyTall It's not necessary but it would prevent having potential issues about whether or not a question in that series is allowed (such as that one saying that maths questions about vectors that are only tangentially related to QC shouldn't really be on QC [I'm simplifying this a bit]) go away. It also serves the purpose of showing that they're part of a series

Ok, but a better solution would be to a) Leave both meta posts up, but with the listing page linked to the post discussing the exercises, b) Link all exercises to the listing meta post. That way if people see the posts and question the validity, they can click through the links to find the first meta post and comment away without having all users that just want to list be directed to the first post.

@SLesslyTall No can do, I'm afraid. Normally I'd like alternative suggestions like that but I don't think I've really got much wiggle room on this :/

Says who? Surely this is something we can decide on and define as a community?

@Mithrandir24601 I thought about that, yes. I don't know whether it qualifies as a meta tag. I mean, it doesn't have to I guess, as it's just a tag collecting questions about a specific topic (exercises from N&C). Maybe one could make it more general than N&C and have it include also other similar questions referring to other books, I don't know

@Mithrandir24601 I don't understand what you are saying here, and why the second post is a bad thing to have. I agree that it is hard to maintain these, but they still remain valuable resources imo

@SLesslyTall each tag has associated a wiki describing the tag. One could put the summary of the questions/answers in there (although the rep requirements to edit those are more strict than regular questions)

see e.g. quantumcomputing.stackexchange.com/tags/quantum-computer/info

@glS Ah, ok. Thanks for the clarification!

@glS It might be the case that, because it's so specific, it might not be a meta tag? I'm not really sure on the differences and more importantly, what makes a meta tag bad in the first place, so I'll need to find this out first

@glS Yeah, those are faq questions, which are treated differently. There are other examples over SE, which often have their own issues and aren't well organised and get worse with time

I think an "exercise" tag would work for this, with the listings of each exercise updated in the tag wiki

Although, I really don't know why that post exists as everything is already there thanks to the faq tag

@Mithrandir24601 Just because some are badly maintained on another SE isn't an argument that this wouldn't be a good solution here

one thing we do need to be really careful of here is the bane of a lot of other science/math sites is homework questions.

we need to kind of consider our attitude towards those in advance.

@Mithrandir24601 This is exactly the solution I am advocating. I think it is clear from this post that it's not violating any rules and performs the purpose it's supposed to well

@heather yeah, this is true, which is why I'd particularly like the header linking to the meta post here

I would like to suggest that until a consensus is reached, we undelete the second meta post

@SLesslyTall It's not so much 'on another SE' and more 'on SE' in general

Well, unless there is a prescribed way to handle these sorts of things, this seems like an ideological dispute more than anything. In lieu of any such prescription, I think the most practical option must be taken on a case by case basis, surely?

So, seeing as this seems to be how maths SE does It, I'm gonna go ahead and undelete the listings post until it is otherwise resolved

@SLesslyTall Please don't. We think that a tag for these questions might be OK. Would you be happy with that instead?

question about this question: $T_2$ is a matrix, right? because if so, * is probably just referring to the conjugate transpose, right?

@heather Ah, no - $T_2$ is the dephasing(?) time of a qubit (it's been a while since I've looked at this so might have gotten the type of error wrong), $T_2^*$ is related but slightly different

they were saying $T_2$ was a rotation about the block sphere, so I thought, 'oh, matrix'

but it didn't match what i was reading in the paper they sent, so.

thanks!

@heather $T_2$ is the time taken for 'the decoherence in that direction to occur' ('s used as that sentence doesn't really make sense, but hopefully gets the gist across)

@Mithrandir24601 okay, that makes a little more sense now.