What are Quantum Gates?

Beginner's Guide to Quantum: Quantum 101

A quantum gate is a reversible (unitary) operation applied to one or more qubits. Thus quantum gates change the state of the quantum qubit.

The various types of gates that are available in Qiskit include: 

  • Classical Gates: NOT, CNOT, Toffoli (CCX), SWAP, Identity (I)
  • Phase Gates: T, S, Z, T†, S†, RZ, 
  • Hadamard Gate: H
  • Quantum Gates: √X, √X†, Y, RX, RY, RXX, RZZ, U, 
  • Non-unitary Operators and Modifiers: Reset, Measurement, Control, If, Barrier, 

This system relies on building really reliable qubits where basic quantum circuit operations, or gates, can be put together to create any sequence, running more and more complex algorithms.