*Quantum gates* are the elementary arithmetic operations that a quantum computer can perform. They are the equivalent to [[Logic Gate|logic gates]] on [[Classical Computer|classical computers]]. While [[Logic Gate|logic gates]] act on [[Bit|bits]] and process [[Classical Information|classical information]], *quantum gates* act on [[Qubit|qubits]]. The effect of one-qubit gates can be illustrated by rotations on the [[Bloch sphere]]. For example, the **Hadamard gate** rotates a qubit from the poles of the Bloch sphere to the equator. This gate is very commonly used in [[Quantum Algorithm|quantum algorithms]] to create [[Entanglement|entanglement]] when used together with a **CNOT gate**. ![[hadamard_gate.excalidraw.light.svg]] An arbitrary quantum operation can be decomposed as a sequence of single- and two-qubit gates. The **CNOT** is a standard two-qubit gate used for this task. A **CNOT gate** (short for controlled NOT) is a gate which acts on two qubits: two-qubit gates are needed arbitrary quantum operation. A CNOT gate flips the second qubit if the first qubit is at the south pole of the [[Bloch Sphere]]. It works a bit like a if-then condition. ![[cnot_gate.excalidraw.light.svg]] >[!read]- Further Reading >- [[Algorithm]] >- [[Quantum Algorithm]] >- [[Quantum Computer]] > [!ref]- References >