Quantum gates are the fundamental operations that quantum algorithms use to manipulate qubits. Just as classical computers build complex computations from simple AND, OR, and NOT gates, quantum computers compose algorithms from elementary quantum gates. Single-qubit gates (like the Hadamard gate, which creates superposition, or the Pauli-X gate, which flips a qubit) act on individual qubits. Two-qubit gates (like CNOT) create entanglement between qubit pairs. Together, a small set of these gates is sufficient to perform any quantum computation — a property called universality.
The physical implementation of quantum gates varies by hardware platform. In superconducting systems (IBM, Google), gates are performed by applying precisely timed microwave pulses to qubits. In trapped-ion systems (IonQ, Quantinuum), laser pulses manipulate the energy states of individual ions. Photonic systems use beam splitters and phase shifters to transform photon qubits. Each approach has characteristic gate speeds and error rates: superconducting gates are fast (tens of nanoseconds) but noisier, while trapped-ion gates are slower (microseconds) but more precise.
Gate fidelity — how accurately a gate performs its intended operation — is the critical quality metric. Current leading systems achieve single-qubit gate fidelities above 99.9% and two-qubit gate fidelities above 99.5%. However, even these tiny error rates accumulate over the thousands to millions of gate operations required by practical algorithms, which is why quantum error correction is necessary for large-scale quantum computing. For deeper coverage, see DeepTechIntel's quantum computing section.