Quantum Computing

Controlled NOT (CNOT) Gate

While the NOT gate switches the states of single qubits, the CNOT gate juggles two qubits simultaneously—an atom-sized expansion of the capability of quantum gates but a gigantic breakthrough for computing. Since quantum programming doesn’t have the direct equivalents of if-then statements, the CNOT gate fills that gap. Moreover, learning to deal with two qubits opens the path for handling even more qubits, which is important if we want to use quantum computing for complex computational tasks.

The two qubits that the CNOT gate operates on are labeled as control and target, respectively. The CNOT gate is drawn as shown.

The top gray line represents the control qubit and the bottom gray line represents the target ...