[[Classical Information]] is stored in the form of [[Bit|bits]]. These can be easily copied (and they are millions of times each day). If you send a picture to a friend, you obviously keep the picture, they just get a copy of it. Unfortunately, it is not as easy for quantum information. It is impossible to copy an arbitrary quantum state. In easy terms, this is related to the fact that measuring the quantum state will destroy any possible superposition. Since, in general, we cannot know which [[Basis|basis]] was used to encode the state, we cannot copy it. >[!read]- Further Reading >- [[Quantum Mechanics]] >- [[Quantum Key Distribution]] >- [[BB84]] >[!ref]- References > - W. K. Wootters and W. H. Zurek, A single quantum cannot be cloned, Nature **299**, 5886 (1982).