Transpilation (also called compilation or routing) converts an abstract quantum circuit into a form that can run on a specific physical quantum device. This involves three main steps: (1) Decomposition — translating gates into the device's native gate set (e.g., converting Toffoli gates into CNOT and single-qubit gates); (2) Routing — mapping logical qubits to physical qubits and inserting SWAP gates to accommodate limited qubit connectivity; (3) Optimization — reducing circuit depth and gate count to minimize errors. Transpilation can significantly increase circuit depth — a shallow logical circuit may become much deeper after routing. Qiskit's transpiler, Cirq's routing, and HLQuantum's built-in transpilation optimize for each target device. Transpilation is a major factor in circuit fidelity on real hardware.
Related Terms
Quantum Circuit
FundamentalsA sequence of quantum gates applied to a register of qubits, followed by measurements.
Quantum Gate
GatesA unitary operation that transforms the state of one or more qubits.
Fidelity
MetricsA measure (0 to 1) of how close an actual quantum operation or state is to the ideal target.
QPU
HardwareQuantum Processing Unit — the physical hardware chip that executes quantum circuits.