KIR
KIR (the Kernel Intermediate Representation) is the form every circuit takes inside MENOS. Whatever you submit, whether a Qiskit QuantumCircuit, a native menos.Circuit, or an OpenQASM file, is lowered to KIR first, and everything after that (analysis, planning, execution) sees only KIR.
Why an intermediate representation
- One input, many front ends. The converter is the only place that knows about Qiskit. The planner and engines never do.
- Validate once. KIR is checked at the boundary, so nothing downstream re-checks it.
- Engines stay simple. An engine knows only matrices and operand lists, not where a circuit came from.
What a circuit is
A KIR circuit has a fixed number of qubits, a fixed number of classical bits, a global phase, and a flat list of operations in program order. There are three kinds:
| Operation | Carries |
|---|---|
| Gate | An opcode, the qubits it acts on, and parameters |
| Unitary | The qubits it acts on and an explicit matrix (1 to 5 qubits) |
| Measure | A qubit and the classical bit it writes |
Nothing else exists. There is no control flow, no reset, no mid-circuit branching.
The gate table
Each opcode has a fixed name, number of operands and number of parameters, and a flag saying whether it is Clifford. That single table is what the stabilizer engine consults to decide feasibility, and what the converter consults to decide whether a Qiskit gate is native. See Supported Gates.
Validation
A circuit is validated for index ranges, arity, finite parameters, unitarity, terminal measurements, and a meaningful output request. See Analyze.
Native access
The same representation is available directly from Python as menos.Circuit, with append, append_unitary and append_measure; see Native API.