A circuit with no entropy loss is, at least theoretically, fully reversible. Of course even if we change how we design circuits we're still going to leak entrop

A circuit with no entropy loss is, at least theoretically, fully reversible. Of course even if we change how we design circuits we're still going to leak entropy due to how we design circuits, just less of it. A circuit that reverses intermittent computational values is partially reversible, and practically that's the best we're going to get.