make simulator native target respect noise_model for gate selection

qiskit_ionq/ionq_backend.py

@@ -118,6 +118,8 @@ def __init__(
 
         # Target (basis & connectivity)
         self._target = self._make_target()
+        # Track noise_model for native simulator target caching
+        self._cached_noise_model: str | None = None
 
         # Apply initial options if any
         if initial_options:
@@ -141,6 +143,11 @@ def _default_options(cls) -> Options:
 
     @property
     def target(self) -> Target | None:
+        if self._simulator and self._gateset == "native":
+            current_noise_model = getattr(self.options, "noise_model", "ideal")
+            if self._cached_noise_model != current_noise_model:
+                self._target = self._make_target()
+                self._cached_noise_model = current_noise_model
         return self._target
 
     @property
@@ -321,7 +328,14 @@ def _make_target(self) -> Target:
                 tgt.add_instruction(gate)
 
             # 2q native
-            if "forte" in self.name.lower():
+            noise_model = getattr(self.options, "noise_model", "ideal")
+            name_lower = self.name.lower()
+            name_is_forte = "forte-" in name_lower or name_lower.endswith("forte")
+            noise_model_is_forte = isinstance(noise_model, str) and (
+                noise_model.lower().startswith("forte")
+            )
+            use_zz = name_is_forte or noise_model_is_forte
+            if use_zz:
                 theta = Parameter("θ")
                 tgt.add_instruction(ZZGate(theta))
             else:

test/ionq_backend/test_base_backend.py

@@ -30,7 +30,7 @@
 from unittest import mock
 
 import pytest
-from qiskit import QuantumCircuit
+from qiskit import QuantumCircuit, transpile
 
 from qiskit_ionq import exceptions, ionq_client, ionq_job
 from qiskit_ionq.helpers import get_user_agent
@@ -314,3 +314,47 @@ def test_backend_memory(
     job = ionq_job.IonQJob(mock_backend, job_id)
     with pytest.raises(AttributeError):
         job.get_memory()  # pylint: disable=no-member
+
+
+def test_simulator_native_target_respects_noise_model(provider):
+    """Test that simulator native target uses ZZ gate for Forte noise models.
+
+    Args:
+        provider: A test IonQProvider.
+    """
+    sim_backend = provider.get_backend("ionq_simulator", gateset="native")
+
+    target_ops = [op.name for op in sim_backend.target.operations]
+    assert "ms" in target_ops
+    assert "zz" not in target_ops
+
+    sim_backend.set_options(noise_model="forte-1")
+    target_ops = [op.name for op in sim_backend.target.operations]
+    assert "zz" in target_ops
+    assert "ms" not in target_ops
+
+    sim_backend.set_options(noise_model="aria-1")
+    target_ops = [op.name for op in sim_backend.target.operations]
+    assert "ms" in target_ops
+    assert "zz" not in target_ops
+
+
+def test_forte_noise_model_transpiles_rzz_to_zz(provider):
+    """Test that rzz gates transpile to zz (not ms) with Forte noise model.
+
+    Regression test for issue #210.
+
+    Args:
+        provider: A test IonQProvider.
+    """
+    native_simulator = provider.get_backend("ionq_simulator", gateset="native")
+    native_simulator.set_options(noise_model="forte-1")
+
+    qc = QuantumCircuit(2)
+    qc.rzz(1, 0, 1)
+
+    transpiled_qc = transpile(qc, backend=native_simulator, optimization_level=3)
+    ops = transpiled_qc.count_ops()
+
+    assert "zz" in ops
+    assert "ms" not in ops