Quantum information is like a dream—evanescent, never quite existing as firmly as a word on a printed page. “Many people can read a book and get the same message,” Bennett says, “but trying to tell people about your dream changes your memory of it, so that eventually you forget the dream and remember only what you said about it.” Quantum erasure, in turn, amounts to a true undoing: “One can fairly say that even God has forgotten.” As for Shannon himself, he was unable to witness this flowering of the seeds he had planted. “If
