X Gate

X Gate (bit-flip)

qc/gates

Flips a qubit: |0⟩→|1⟩, |1⟩→|0⟩. Quantum analog of classical NOT. Geometrically: 180° rotation around the X-axis of the Bloch Sphere.

$X=\left(\begin{array}{cc}0& 1\\ 1& 0\end{array}\right)$

Related

• Pauli Operators
• H Gate
• Bell States — X is used to reach the other three Bell states from the base one
• Bloch Sphere

Self-Check

• Could you explain the X gate to someone who’s never heard of it, using the classical NOT analogy?
• What rotation does X correspond to on the Bloch Sphere?
• How is X used to move between the four different Bell States?