You should reread their post, libraries usage is incidental to what they’re talking about. Their point, that first sale should apply to ebooks, requires a fundamentally different approach to DRM. If I own my content and can put it on any device I want, how can the seller be sure I’m only using one copy at a time? Consider the case that I might have it on multiple different devices which aren’t connected to the internet, they’re saying I should be able to do that while keeping the requirement that only one copy be usable at a time.

My reference to quantum was saying that this usage pattern would require something like quantum entanglement to replicate the state of which copy is active among all copies.

I'm not sure if the librarians in the article meant this but that's beside the point. The publishers can enforce a DRM on their side such that only one reader gets it at a time and adjust the contracts with the libraries accordingly, no need for fancy quantum stuff for client-side DRM.

> If I own my content and can put it on any device I want, how can the seller be sure I’m only using one copy at a time?

They can't, which is the same as it is now. DRM is a farce and everything is on The Pirate Bay. Which is why restricting libraries like this is ridiculous -- anybody who doesn't care to follow the law doesn't need to get a copy from a library, they can just download it from a piracy site. The reason you go to the library instead is that you want to follow the law.

There is no justice in following unjust laws.