 Pauli-X gate

The Pauli $X$ gate interchanges $|0⟩$ and $|1⟩$.

This gate acts by the corresponding Pauli matrix, viewed as a unitary operator on one qubit.

The quantum NOT gate swaps the state of $|0⟩$ and $|1⟩$, i.e. it maps:As a result, this gate also inverts the probability of measuring 0 or 1, e.g.