What does the no-cloning theorem say?

Question: What does the no-cloning theorem state? A) Unknown quantum states cannot be copied perfectly B) Classical bits cannot be copied C) Qubits cannot be measured D) Quantum circuits cannot use more than one gate Correct: A Explanation: The no-cloning theorem says that an arbitrary unknown quantum state cannot be copied perfectly. This is very different from classical information, where bits can be duplicated easily. Topic: quantum computing / no-cloning theorem