Not Operation

In quantum computing, the NOT operation (also called the **X gate**) flips the state of a qubit: it turns (|0⟩) into (|1⟩) and (|1⟩) into (|0⟩). Mathematically, it’s represented by the Pauli-X matrix, which swaps the probability amplitudes of these basis states. On the Bloch sphere, it corresponds to a 180° rotation around the X-axis.