Melf/fix max n qubits (#434)

* fix max qubit predicate * update changelog and version * add test * Update docs/changelog.md Co-authored-by: Callum Macpherson <[email protected]> * fix mypy --------- Co-authored-by: Callum Macpherson <[email protected]>
CQCL · Dec 13, 2024 · d0cee1c · d0cee1c
1 parent 46bdddf
commit d0cee1c
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diff --git a/_metadata.py b/_metadata.py
@@ -1,2 +1,2 @@
-__extension_version__ = "0.61.0"
+__extension_version__ = "0.62.0"
 __extension_name__ = "pytket-qiskit"
diff --git a/docs/changelog.md b/docs/changelog.md
@@ -4,6 +4,10 @@
 
 # Changelog
 
+## unreleased
+
+- AerBackend now reject circuits with too many qubits 
+
 ## 0.61.0 (December 2024)
 
 - Restrict qiskit version to ~= 1.2.4, to avoid breaking changes in 1.3.0

diff --git a/pytket/extensions/qiskit/backends/aer.py b/pytket/extensions/qiskit/backends/aer.py
@@ -48,6 +48,7 @@
     ConnectivityPredicate,
     DefaultRegisterPredicate,
     GateSetPredicate,
+    MaxNQubitsPredicate,
     NoBarriersPredicate,
     NoClassicalControlPredicate,
     NoFastFeedforwardPredicate,
@@ -695,6 +696,7 @@ def __init__(
         self._required_predicates = [
             NoSymbolsPredicate(),
             GateSetPredicate(self._backend_info.gate_set),
+            MaxNQubitsPredicate(n_qubits),
         ]
         if self._crosstalk_params is not None:
             self._required_predicates.extend(

diff --git a/tests/qiskit_backend_test.py b/tests/qiskit_backend_test.py
@@ -22,6 +22,7 @@
 from qiskit_aer import Aer  # type: ignore
 
 from pytket.architecture import Architecture, FullyConnected
+from pytket.circuit import Circuit
 from pytket.extensions.qiskit import (
     AerBackend,
     AerStateBackend,
@@ -59,6 +60,15 @@ def test_samples() -> None:
         assert all((r[0] == "1" and r[1] == r[2]) for r in counts)
 
 
+def test_maxnqubits() -> None:
+    backend = AerBackend(n_qubits=1)
+    with pytest.raises(Exception):
+        backend.run_circuit(
+            circuit=Circuit(2).CX(0, 1).measure_all(),
+            n_shots=1,
+        )
+
+
 def test_state() -> None:
     qc = circuit_gen()
     b = AerStateBackend()