A quantum circuit is the model of quantum computation used by most quantum SDKs. It consists of a set of qubits (wires in the diagram), quantum gates applied in time order (left to right), and measurement operations at the end. Circuits are described using the gate model of quantum computation. The circuit depth is the number of sequential gate layers (time steps) — shallower circuits are less affected by noise. The circuit width is the number of qubits. A quantum circuit must be transpiled to match the native gate set and qubit connectivity of a real device before execution. Tools like Qiskit, Cirq, PennyLane, and HLQuantum all use the circuit abstraction.
Related Terms
Quantum Gate
GatesA unitary operation that transforms the state of one or more qubits.
Transpilation
HardwareThe process of compiling a quantum circuit into the native gate set and qubit connectivity of a specific device.
Measurement
FundamentalsThe act of observing a qubit's state, which collapses the superposition to a definite 0 or 1.
Qubit
FundamentalsThe fundamental unit of quantum information — the quantum analog of a classical bit.