Document generate_preset_pass_manager supports list for initial_layout (

#12214)

This commit updates the documentation for the
generate_preset_pass_manager() function to clearly indicate that the
function will accept a integer list for the initial_layout field. This
already was supported but it wasn't documented. As it's now a documented
part of the API a unittest is added to ensure we don't regress this
functionality in the future.

Fixes #11690

qiskit/transpiler/preset_passmanagers/__init__.py

@@ -136,7 +136,7 @@ def generate_preset_pass_manager(
         instruction_durations (InstructionDurations): Dictionary of duration
             (in dt) for each instruction.
         timing_constraints (TimingConstraints): Hardware time alignment restrictions.
-        initial_layout (Layout): Initial position of virtual qubits on
+        initial_layout (Layout | List[int]): Initial position of virtual qubits on
             physical qubits.
         layout_method (str): The :class:`~.Pass` to use for choosing initial qubit
             placement. Valid choices are ``'trivial'``, ``'dense'``,

test/python/transpiler/test_preset_passmanagers.py

@@ -1436,6 +1436,38 @@ def test_generate_preset_pass_manager_with_list_coupling_map(self):
         # Ensure the DAGs from both methods are identical
         self.assertEqual(transpiled_circuit_list, transpiled_circuit_object)
 
+    @data(0, 1, 2, 3)
+    def test_generate_preset_pass_manager_with_list_initial_layout(self, optimization_level):
+        """Test that generate_preset_pass_manager can handle list based initial layouts."""
+        coupling_map_list = [[0, 1]]
+
+        # Circuit that doesn't fit in the coupling map
+        qc = QuantumCircuit(2)
+        qc.h(0)
+        qc.cx(0, 1)
+        qc.cx(1, 0)
+        qc.measure_all()
+
+        pm_list = generate_preset_pass_manager(
+            optimization_level=optimization_level,
+            coupling_map=coupling_map_list,
+            basis_gates=["u", "cx"],
+            seed_transpiler=42,
+            initial_layout=[1, 0],
+        )
+        pm_object = generate_preset_pass_manager(
+            optimization_level=optimization_level,
+            coupling_map=coupling_map_list,
+            basis_gates=["u", "cx"],
+            seed_transpiler=42,
+            initial_layout=Layout.from_intlist([1, 0], *qc.qregs),
+        )
+        tqc_list = pm_list.run(qc)
+        tqc_obj = pm_list.run(qc)
+        self.assertIsInstance(pm_list, PassManager)
+        self.assertIsInstance(pm_object, PassManager)
+        self.assertEqual(tqc_list, tqc_obj)
+
 
 @ddt
 class TestIntegrationControlFlow(QiskitTestCase):