No-cloning theorem

I quantum physics the no-cloning theorem is the statement that there cannot be physical processes which produce “copies” of quantum states in the way known from classical physics. Quantum theoretically, this effect is ultimately due to the non-cartesian nature of the tensor product of vector/Hilbert spaces of quantum states (category theoretically it refers to this tensor product lacking natural diagonal morphisms) and as such is a direct cousin of the fundamental phenomenon of quantum entanglement.