Preserve layout in optimize_single_qubit_gates.

src/iqm/qiskit_iqm/iqm_transpilation.py

@@ -19,6 +19,7 @@
 from qiskit.circuit.library import RGate
 from qiskit.dagcircuit import DAGCircuit
 from qiskit.transpiler.basepasses import TransformationPass
+from qiskit.transpiler.layout import Layout
 from qiskit.transpiler.passes import BasisTranslator, Optimize1qGatesDecomposition, RemoveBarriers
 from qiskit.transpiler.passmanager import PassManager
 
@@ -53,6 +54,8 @@ def __init__(self, drop_final_rz: bool = False, ignore_barriers: bool = False):
 
     def run(self, dag: DAGCircuit) -> DAGCircuit:
         self._validate_ops(dag)
+        layout = Layout.generate_trivial_layout(*dag.qregs.values())
+        self.property_set['layout'] = layout
         # accumulated RZ angles for each qubit, from the beginning of the circuit to the current gate
         rz_angles: list[float] = [0] * dag.num_qubits()
         if self._ignore_barriers:

tests/test_iqm_transpilation.py

@@ -127,3 +127,22 @@ def test_submitted_circuit(adonis_architecture):
         'measure:2',
         'measure:4',
     ]
+
+
+def test_optimize_single_qubit_gates_preserves_layout():
+    circuit = QuantumCircuit(3)
+    circuit.h(0)
+    circuit.cx(0, 1)
+    circuit.x(2)
+
+    transpiled_circuit = transpile(circuit, basis_gates=['r', 'cz'], initial_layout=[0, 1, 2])
+    optimized_circuit = optimize_single_qubit_gates(transpiled_circuit)
+
+    # Check if the layout is preserved
+    assert optimized_circuit.layout is not None
+    assert optimized_circuit.layout.initial_layout is not None
+
+    expected_layout = {0: 0, 1: 1, 2: 2}
+    actual_layout = {qubit._index: optimized_circuit.layout.initial_layout[qubit] for qubit in optimized_circuit.qubits}
+
+    assert actual_layout == expected_layout