I asked a question. It's getting downvoted and so far it's only been viewed 14 times. It's not obvious to me why it's being downvoted. Why is there disapproval against the question I asked?

I would understand if it was unclear and people were voting to close but this not happening. How can avoid this situation?

  • 3
    $\begingroup$ sorry to be brutal but did you actually “work” on this or is it “just” an idea? Maybe just rephrasing would help. The sudden approximation is full of pitfalls (see aapt.scitation.org/doi/10.1119/1.1976231) and you questions reads like “check my work and see if anything is wrong”. $\endgroup$ Dec 17, 2021 at 3:25
  • $\begingroup$ @ZeroTheHero I appreciate the honesty. I tried playing around with density matrices but your pointing towards the premise of the question of using the sudden approximation. I mean I could just ask the even more abstract question can we use non-unitary evolution to do any computation (but I think that would be another rollercoaster I suspect). If I am misusing the sudden approximation then by all means please post this as an answer? $\endgroup$ Dec 17, 2021 at 14:47
  • $\begingroup$ You seem to have misunderstood part of my point. I’m not going to check if your calculation is right or wrong. I will point to the fact that whereas the evolution operator is unitary, it’s approximations or truncations are not, this in addition to possible issues in the paper mentioned above. See also farside.ph.utexas.edu/teaching/qm/Quantum/node81.html for an example where the sudden approximation clearly leads to non-unitarity. $\endgroup$ Dec 18, 2021 at 20:16

1 Answer 1


A few personal thoughts:

  1. The title is highly unspecific. "Using non-unitary time evolution for a computation?" is not really a question. It says nothing about what is actually been asked. I also don't really understand where the "computation" bit comes from when reading the question.

  2. Notation is better than the previous iteration of the question (which, btw, why did you not simply edit the other question in the first place?), but still, the presentation could be improved. The main missing thing is why one should care about this sort of thing in the first place.

  3. You were already given other pointers/suggestions/criticisms in the comments of the question. Not directly addressing those by editing the question accordingly makes people think that you are not willing to accept constructive criticism and act on it. That, generally speaking, regardless of the merits of the comments themselves, tends to erode people's "good faith assumptions", which significantly increases the likelihood of getting downvotes, votes to close, and such.

    Case in point, you were asked "Why are you doing this?", and you answer in the comments with "As the title says: Using non-unitary time evolution for a computation?", which clarifies next to nothing, and might be construed as condescending.

  4. On a more general note, in my opinion, there are some types of questions for which Stack Exchange is simply not a great venue. You tend to ask questions about rather involved situations without giving sufficiently strong reasons why one should care about it. Such questions are imo rather hard to be put into a form that is well-fit for Stack Exchange. It would be much better to break up what you don't understand or find unclear about whatever problem you are working on, and ask more specific questions about specific points that might be of more general interest.

  • $\begingroup$ So this comment was posted at 1 in the night before the comment was posted after the meta-post and I've just come back from work. I was already exhausted by 1 and I didn't think I had any energy to rewrite an answer. Despite the comment it was unclear to me why there was lack of clarity. Now, to address the points you wrote $\endgroup$ Dec 17, 2021 at 14:30
  • $\begingroup$ 1. If the average converges to lets say (hypothetically) to pi. Then all I have to keep doing this experiment and take the average and I digits of pi upto which I have say 99% confidence. (P.S Im confused why you say "It says nothing about what is actually been asked" 2. I honestly would like to see the meta-post of providing "motivation for your question." I mean I'm just not very good at expressing motivation. "Using non-unitary time evolution for a computation?" $\endgroup$ Dec 17, 2021 at 14:40
  • $\begingroup$ 3. I believe the above comment addresses this. 4. I honestly personally thought asking about the convergence was a specific question. $\endgroup$ Dec 17, 2021 at 14:40
  • $\begingroup$ Sorry the first comment should not read " this comment" (in the first 3 words) but "this question" $\endgroup$ Dec 17, 2021 at 14:44
  • $\begingroup$ I don't fully understand what you are saying. I'm not saying you have to immediately address comments, but you asked here for reasons, and I see not addressing that comments more thoroughly as a pretty clear one. There is no timeline whatsoever here, so I don't understand why it matters that you were tired. You do it when you have time, simple as that. Sure, the question might get closed in the meantime, but if you address the problems it will get reopened. I cannot tell what your first point is addressing at all, sorry. I also don't understand which meta post you are asking for. $\endgroup$
    – glS
    Dec 17, 2021 at 14:46
  • $\begingroup$ I didn't say this question was not specific. The specificity is fine I think. It however lacks some clarity, and most importantly motivation. If you find it hard to make your point come across, maybe you just need to spend more time thinking of a good way to frame/word what you mean to say? Again, rushing things will only lead to people not understanding what you want to say $\endgroup$
    – glS
    Dec 17, 2021 at 14:46
  • $\begingroup$ the reason I mentioned I was tired was because in point 3 you clearly say: "Not directly addressing those by editing the question accordingly makes people think that you are not willing to accept constructive criticism and act on it." but by what timeline does it count as "Not directly addressing." I do intend to address them via edits. I just disagree with what was inferred. $\endgroup$ Dec 17, 2021 at 14:50
  • $\begingroup$ I don't know what you think I was inferring, but you cannot expect people to know how you personally feel in any given moment, now can you? People see the current situation and act accordingly. It doesn't really matter what anyone's "real intentions" are; at the end of the day, the only thing that can be judged is what you write, the instantaneous state of the post. Also, obviously I don't really know why anyone voted as they did, I'm just pointing out what might be potential reasons. $\endgroup$
    – glS
    Dec 17, 2021 at 14:52
  • $\begingroup$ You wrote they were inferring "makes people think that you are not willing to accept constructive criticism and act on it." Also I did not say "you inferred". But I do think we can be more welcoming as a community and give some leeway and benefit of the doubt? $\endgroup$ Dec 17, 2021 at 14:55
  • $\begingroup$ @MoreAnonymous ah, yes, you are right, sorry. Still, hopefully you can see my point about people judging the current state of the post and nothing else. Tbh I personally don't see the site as particularly unwelcoming, and I also often ask questions. People generally give you constructive criticism. I also don't really understand what's the big deal with downvotes either. Someone doesn't like the question and downvotes, so what? Why should anyone take that personally? If it happens often, clearly there is a reason for it, so it's more useful to address those reasons, no? $\endgroup$
    – glS
    Dec 17, 2021 at 14:59
  • $\begingroup$ I do get your point. I just don't have the privilege to dedicate as much time to physics as I'd like. The work hours in non-first world countries are well, crazy. I suspect I'm not the only one who has this problem. Also I hope it doesn't come off as I took this personally? The intent was as stated "How can avoid this situation?" But I must add the upvote and downvote systems are incentive systems. People are much less likely to even give your question a look if it has negative votes. And I do care about getting an answer. $\endgroup$ Dec 17, 2021 at 15:07
  • 1
    $\begingroup$ maybe if you took part of advice of @glS and carefully and slowly tried to clarify and research your question… it just looks like you’re shooting from the hip: someone already alluded to poor notation, I already pointed to the syntax, and you should budget time to properly research your question as well if only to make sure you understand other examples of this type of calculation. Asking good questions is not easy. $\endgroup$ Dec 18, 2021 at 21:49
  • $\begingroup$ … as to being welcoming: the onus is on posters to understand what makes a question “well received”, and craft questions as such. $\endgroup$ Dec 18, 2021 at 21:55

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