= Pauli-X gate
{c}
= Quantum NOT gate
{synonym}
{title2}
The <quantum NOT gate> swaps the state of $\ket{0}$ and $\ket{1}$, i.e. it maps:
$$
x \ket{0} + y \ket{y} \to y \ket{0} + x \ket{y}
$$
As a result, this gate also inverts the probability of measuring 0 or 1, e.g.
* if the old probability of 0 was 0, then it becomes 1
* if the old probability of 0 was 0.2, then it becomes 0.8
$$
\begin{bmatrix}
0 & 1 \\
1 & 0 \\
\end{bmatrix}
$$
{title=<Quantum NOT gate> <matrix>}
\Image[https://upload.wikimedia.org/wikipedia/commons/9/91/Qcircuit_CNOT.svg]
{title=<Quantum NOT gate> symbol}