Unsupported Circuits
MENOS refuses what it cannot represent rather than approximating it. Each entry is a symptom, its cause, and a solution; the messages are quoted from real runs.
Measurement followed by an operation
| Symptom | UnsupportedFeatureError: operation 1: qubit 0 has a non-terminal measurement (an operation follows a measurement of this qubit) |
| Cause | Measurements must be terminal |
| Solution | Move the measurement to the end. Mid-circuit measurement is not supported |
reset
| Symptom | UnsupportedFeatureError: operation 1 (reset): not a MENOS-supported named gate and has no matrix representation; unsupported. Try transpile(qc, backend) first. |
| Cause | reset is not a unitary |
| Solution | Restructure the circuit to avoid it |
Classical control
| Symptom | UnsupportedFeatureError: operation 2 (if_else): not a MENOS-supported named gate and has no matrix representation; unsupported. |
| Cause | Conditional gates need mid-circuit classical feedback |
| Solution | Not supported. Use deferred measurement where the algorithm allows it |
A gate on more than five qubits
| Symptom | UnsupportedFeatureError: operation 0 (qft): acts on 6 qubits, exceeding kMaxUnitaryQubits=5, and is not a MENOS-supported named gate. Try transpile(qc, backend) first. |
| Cause | Unitaries are limited to five qubits |
| Solution | transpile(qc, backend) lowers it into native gates |
Unbound parameters
| Symptom | InvalidCircuitError: operation 0 (rx): unbound parameter(s) [Parameter(t)]; bind all parameters before running (QuantumCircuit.assign_parameters) |
| Cause | A circuit still contains Parameters |
| Solution | qc.assign_parameters({...}) before running |
Parameterized circuits in the estimator
| Symptom | UnsupportedFeatureError: MENOSEstimator does not currently support parameterized circuits … |
| Cause | MENOSEstimator rejects any circuit with parameters, even when parameter_values are given in the pub |
| Solution | Bind first, as the EstimatorV2 example does |
Shots without a measurement
| Symptom | InvalidCircuitError: shots > 0 was requested but the circuit has no Measure operation |
| Cause | There is nothing to sample |
| Solution | Add measure, or set shots=0 and ask for a statevector |
Nothing to produce
| Symptom | InvalidCircuitError: request asks for neither counts (shots=0) nor a statevector nor an expectation; nothing to produce |
| Cause | shots=0 and want_statevector=False |
| Solution | Request an output |
An unsupported observable
| Symptom | InternalError: Tableau: num_qubits must be at least 1 from an expectation request |
| Cause | Every term of the observable was the identity, which MENOS does not currently handle |
| Solution | Add the constant yourself after the run. See Pauli Observables |
An unsupported gate in one engine only
| Symptom | A candidate is listed as infeasible with operation N (…) is not a Clifford gate or is not supported by Pauli propagation |
| Cause | Not an error: that engine does not support the gate, and another engine ran the job |
| Solution | None needed. See Execution Plans |
Silently dropped instructions
barrier, id and delay are dropped without error because they cannot change any output.