What does the Pauli-Z gate change?

Question: What does the Pauli-Z gate do to the state |1⟩? A) It changes |1⟩ into |0⟩ B) It changes |1⟩ into -|1⟩ C) It creates entanglement D) It measures the qubit Correct: B Explanation: The Pauli-Z gate leaves |0⟩ unchanged but adds a negative phase to |1⟩. This means Z|1⟩ = -|1⟩. The measurement probability may remain the same, but the relative phase can affect later interference. Topic: quantum computing / gates / phase