Recently a question was asked about a topic that is indirectly related to quantum computing.


Are topics that are indirectly related to quantum computing allowed on this stack exchange website?


By Indirectly I mean topics that have relevance to the field of quantum computing, but do not necessarily relate only to quantum computing.


While there is a physics Stack Exchange website, I believe some questions could benefit from being answered through the lens of quantum computation.

For example, while the linked question doesn't necessarily have direct relevance to quantum computing, I can see how - if it were answered in the context of quantum computing - it would likely become relevant to quantum computing.

  • $\begingroup$ suggest when the site is young less worry be given to borderline questions. as the site gets larger it can be more strict about scope. also voting can help determine scope/ interest (the question cited now has high 12votes, ie high interest by users here). another issue is that questions that dont get much attn do not really consume much user energy and seem harmless. a bigger issue might be "hot network questions" which a lot of sites find distracting/ annoying at times. but again smaller sites will rarely see those and they probably require little admin attn/ concern when the site is young. $\endgroup$
    – vzn
    Apr 15, 2018 at 14:35

1 Answer 1


Here is what I'd have to say based on previous discussion here.

Be very, very careful.

Remember that the idea of migration is for stuff that is

  1. explicitly off-topic here
  2. explicitly on-topic somewhere else, and
  3. is a good question.

So to answer your clarification:

By Indirectly I mean topics that have relevance to the field of quantum computing, but do not necessarily relate only to quantum computing.

That doesn't meet point #1. Now, the specific question you link too could very well be explicitly off-topic, and I'd agree that it meets points #2 and #3, so let's examine point #1.

The question states:

To be specific, imagine a one dimensional chain of qubits coupled by a Hamiltonian [insert Hamiltonian here; I don't think it bears repeating ...] Can you give a good (i.e. as tight as possible) upper bound for the Lieb-Robinson velocity v for the system?

and just how is the Lieb-Robinson velocity relevant?

The proofs of the Lieb Robinson bound typically show the existence of a velocity v (that depends on J). This is often really useful for bound properties in these sorts of systems. For example there were some really nice results here to do with, for example, how long it takes to generate a GHZ state using a nearest-neighbor Hamiltonian.

The article linked states:

We discuss several consequences of [the Lieb-Robinson velocity] in the context of quantum information theory. First, we show that the information that leaks out to spacelike separated regions is negligible and that there is a finite speed at which correlations and entanglement can be distributed. Second, we discuss how these ideas can be used to prove lower bounds on the time it takes to convert states without topological quantum order to states with that property. Finally, we show that the rate at which entropy can be created in a block of spins scales like the boundary of that block.

In other words, very much relevant to quantum computing. It meets #1.

Tl;dr: In my opinion the question is on-topic and we need to be a wee bit more careful about rejecting questions.


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