Physics:Quantum No-cloning theorem
The no-cloning theorem is a Book I topic in the Quantum Collection. It states that an arbitrary unknown quantum state cannot be copied perfectly by any physical process allowed by quantum mechanics. The reason is the linear structure of quantum evolution: a device that copies two known states cannot also copy every superposition of them. No-cloning is a basic difference between quantum and classical information. It underlies the security of quantum key distribution, limits error correction strategies, shapes teleportation protocols, and clarifies why measurement generally disturbs unknown quantum states.
Overview
Placeholder: explain why linear quantum evolution forbids perfect copying of an arbitrary unknown quantum state.
Key ideas
Placeholder: cover linearity, unknown states, quantum copying limits, cryptography, measurement disturbance.
Statement of the theorem
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Simple linearity argument
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Consequences for cryptography
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Relation to measurement
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See also
Table of contents (217 articles)
Index
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References
Source attribution: Physics:Quantum No-cloning theorem
