Fix/max n qubits predicate

pytket/extensions/qiskit/backends/ibm.py

@@ -79,6 +79,7 @@
     GateSetPredicate,
     NoClassicalControlPredicate,
     NoFastFeedforwardPredicate,
+    MaxNQubitsPredicate,
     Predicate,
 )
 from pytket.extensions.qiskit.qiskit_convert import tk_to_qiskit, _tk_gate_set
@@ -323,6 +324,7 @@ def available_devices(cls, **kwargs: Any) -> List[BackendInfo]:
     def required_predicates(self) -> List[Predicate]:
         predicates = [
             NoSymbolsPredicate(),
+            MaxNQubitsPredicate(self._backend_info.n_nodes),
             GateSetPredicate(
                 self._backend_info.gate_set.union(
                     {

tests/backend_test.py

@@ -1198,3 +1198,18 @@ def test_sim_qubit_order() -> None:
     circ.X(Qubit("a", 0))
     s = backend.run_circuit(circ).get_state()
     assert np.isclose(abs(s[2]), 1.0)
+
+
+@pytest.mark.skipif(skip_remote_tests, reason=REASON)
+def test_requrired_predicates(manila_emulator_backend: IBMQEmulatorBackend) -> None:
+    # https://github.com/CQCL/pytket-qiskit/issues/93
+    circ = Circuit(7)  # 7 qubit circuit in IBMQ gateset
+    circ.X(0).CX(0, 1).CX(0, 2).CX(0, 3).CX(0, 4).CX(0, 5).CX(0, 6).measure_all()
+    with pytest.raises(CircuitNotValidError) as errorinfo:
+        manila_emulator_backend.run_circuit(circ, n_shots=100)
+        assert (
+            "pytket.backends.backend_exceptions.CircuitNotValidError:"
+            + "Circuit with index 0 in submitted does"
+            + "not satisfy MaxNQubitsPredicate(5)"
+            in str(errorinfo)
+        )