Fix AncillaQubits added via .add_bits to be included in .qubits.

qiskit/circuit/quantumcircuit.py

@@ -1091,7 +1091,8 @@ def add_bits(self, bits):
         for bit in bits:
             if isinstance(bit, AncillaQubit):
                 self._ancillas.append(bit)
-            elif isinstance(bit, Qubit):
+
+            if isinstance(bit, Qubit):
                 self._qubits.append(bit)
                 self._qubit_set.add(bit)
             elif isinstance(bit, Clbit):

test/python/circuit/test_registerless_circuit.py

@@ -55,7 +55,7 @@ def test_circuit_constructor_on_bits(self):
 
         qc = QuantumCircuit(qubits, clbits, ancillas)
 
-        self.assertEqual(qc.qubits, qubits)
+        self.assertEqual(qc.qubits, qubits + ancillas)
         self.assertEqual(qc.clbits, clbits)
         self.assertEqual(qc.ancillas, ancillas)
 
@@ -98,6 +98,16 @@ def test_addding_individual_bit(self):
         self.assertEqual(qc.qubits, list(qr) + [new_bit])
         self.assertEqual(qc.qregs, [qr])
 
+    def test_inserted_ancilla_bits_are_added_to_qubits(self):
+        """Verify AncillaQubits added via .add_bits are added to .qubits."""
+        anc = AncillaQubit()
+        qb = Qubit()
+
+        qc = QuantumCircuit()
+        qc.add_bits([anc, qb])
+
+        self.assertEqual(qc.qubits, [anc, qb])
+
 
 class TestGatesOnWires(QiskitTestCase):
     """Test gates on wires."""