Fix qpy import of circuit with StatePreparation (#9665)

* add StatePreparation to list

* add reno

* add test

* fix lint

* Reword release note

---------

Co-authored-by: Jake Lishman <jake.lishman@ibm.com>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>
(cherry picked from commit dc1737c)

qiskit/qpy/binary_io/circuits.py

@@ -267,7 +267,7 @@ def _read_instruction(file_obj, circuit, registers, custom_operations, version,
             gate.ctrl_state = instruction.ctrl_state
         gate.condition = condition_tuple
     else:
-        if gate_name in {"Initialize", "UCRXGate", "UCRYGate", "UCRZGate"}:
+        if gate_name in {"Initialize", "StatePreparation", "UCRXGate", "UCRYGate", "UCRZGate"}:
             gate = gate_class(params)
         else:
             if gate_name == "Barrier":

releasenotes/notes/fix-qpy-import-StatePreparation-e20f8ab07bfe39a3.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    QPY (using :func:`.qpy.load`) will now correctly deserialize :class:`~.StatePreparation`
+    instructions. Previously, QPY would error when attempting to load a file containing one.
+    Fixed `#8297 <https://github.com/Qiskit/qiskit-terra/issues/8297>`__.

test/python/circuit/test_circuit_load_from_qpy.py

@@ -624,6 +624,37 @@ def test_initialize_qft(self):
         )
         self.assertDeprecatedBitProperties(qc, new_circ)
 
+    def test_statepreparation(self):
+        """Test that state preparation with a complex statevector and qft work."""
+        k = 5
+        state = (1 / np.sqrt(8)) * np.array(
+            [
+                np.exp(-1j * 2 * np.pi * k * (0) / 8),
+                np.exp(-1j * 2 * np.pi * k * (1) / 8),
+                np.exp(-1j * 2 * np.pi * k * (2) / 8),
+                np.exp(-1j * 2 * np.pi * k * 3 / 8),
+                np.exp(-1j * 2 * np.pi * k * 4 / 8),
+                np.exp(-1j * 2 * np.pi * k * 5 / 8),
+                np.exp(-1j * 2 * np.pi * k * 6 / 8),
+                np.exp(-1j * 2 * np.pi * k * 7 / 8),
+            ]
+        )
+
+        qubits = 3
+        qc = QuantumCircuit(qubits, qubits)
+        qc.prepare_state(state)
+        qc.append(QFT(qubits), range(qubits))
+        qc.measure(range(qubits), range(qubits))
+        qpy_file = io.BytesIO()
+        dump(qc, qpy_file)
+        qpy_file.seek(0)
+        new_circ = load(qpy_file)[0]
+        self.assertEqual(qc, new_circ)
+        self.assertEqual(
+            [x.operation.label for x in qc.data], [x.operation.label for x in new_circ.data]
+        )
+        self.assertDeprecatedBitProperties(qc, new_circ)
+
     def test_single_bit_teleportation(self):
         """Test a teleportation circuit with single bit conditions."""
         qr = QuantumRegister(1)