The no-cloning theorem is a fundamental principle in quantum mechanics that states it is impossible to create an exact copy of an arbitrary unknown quantum state. This theorem was first formulated by physicist W. K. Wootters and W. H. Zurek in 1982.
More specifically, the no-cloning theorem states that given an arbitrary quantum state |ψ⟩, it is not possible to create another quantum state |ψ′⟩ that is an identical copy of |ψ⟩. Mathematically, it can be expressed as:
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