← Quantum Store · Guides · Lessons · Glossary · About · Türkçe
What is a quantum gate?
A quantum gate is a basic operation that reversibly changes the state of one or more qubits; quantum programs are sequences of gates.
Quantum gates are the quantum counterpart of classical logic gates such as AND, OR and NOT. Mathematically every gate is a unitary matrix, so every quantum operation other than measurement can be undone.
Common single-qubit gates are X (NOT), Y, Z (phase flip), H (Hadamard), S and T. The best-known two-qubit gate is CNOT; CZ and SWAP are also common. H, S, T and CNOT together form a universal gate set that can approximate any quantum operation to any desired accuracy.
Try it yourself
The lesson Bits and qubits: the smallest piece of information lets you try this concept in the browser, with no installation.
Related packages
Related concepts
- Hadamard gate (H) · The Hadamard gate is a single-qubit quantum gate that turns a qubit in |0⟩ into an equal superposition of 0 and 1.
- CNOT gate · The CNOT (controlled-NOT) gate is a two-qubit gate that flips the target qubit when the control qubit is 1; it is the basic tool for creating entanglement.
- Quantum circuit · A quantum circuit is a quantum program made of gates applied to qubits in order, followed by measurements.