Learning more about quantum computing and physics would (for most of us) result in more accurate models/beliefs/priors, so it seems on-topic to me.

Having said that though, we have to draw the line somewhere, otherwise any scientific topic would be on-topic, such as "analysis of proteins contained in the albumen of chicken eggs", which I doubt many of us think belongs on this site.

Since physics and computing are so foundational -- witness their frequent discussion and the long sequences that Eliezer devoted to quantum physics -- I think we could safely say that any general topic in physics or computing that has ramifications for rationality in other contexts (that we are likely to make use of), as is the case here with quantum computing, is welcome to be discussed, and that suggests a broader criterion for scientific topics as those that have ramifications for rationality in other contexts and that we are likely to make use of.