What is the no-cloning theorem?

Question: What does the no-cloning theorem say? A) Unknown quantum states cannot be copied perfectly B) Classical bits cannot be copied C) Qubits cannot be measured D) Quantum circuits cannot contain gates Correct: A Explanation: The no-cloning theorem states that an arbitrary unknown quantum state cannot be copied perfectly. This is one reason quantum information behaves very differently from classical information. Topic: quantum computing / no-cloning theorem