The Pauli-X gate swaps |0⟩ with |1⟩. It's the quantum equivalent of a classical NOT gate, and people often call it that. On the Bloch sphere, X is a 180° rotation about the x-axis.
Related concepts
- Pauli-Y: 180° rotation about y.
- Pauli-Z: 180° rotation about z (phase flip).
- Hadamard gate: the gate that creates superposition.
- What is a quantum gate? The umbrella concept.
Frequently asked questions
Is Pauli-X the same as a quantum NOT?
Yes. Pauli-X flips |0⟩ ↔ |1⟩, which is exactly the classical NOT operation. The two names are interchangeable.
Is X self-inverse?
Yes. X² = I. Apply X twice and you're back where you started.