Measurements work well if you want to know what quantum state something is in. Or alternately, you could prepare the state from scratch—we can do it with quite a few atoms now.
Yes, ok, but what about the state of the people doing the measurements or the preparation? You can’t have perfect information about them as well, that’s second thermo for you. You could just as well skip the step that mentions information and say that “If we had a state of zero entropy we could make it do a lot of work”. So you could, and the statement “If we had a state that we knew everything about we could make it do a lot of work” is equivalent, but I don’t see where one is more fundamental, useful, intuitive, or correct than the other. The magic insertion of information is no more helpful than a magic reduction of entropy.
Yes, ok, but what about the state of the people doing the measurements or the preparation? You can’t have perfect information about them as well, that’s second thermo for you. You could just as well skip the step that mentions information and say that “If we had a state of zero entropy we could make it do a lot of work”. So you could, and the statement “If we had a state that we knew everything about we could make it do a lot of work” is equivalent, but I don’t see where one is more fundamental, useful, intuitive, or correct than the other. The magic insertion of information is no more helpful than a magic reduction of entropy.