Fix global phase tracking around DAGCircuit.substitute_node.

qiskit/circuit/quantumcircuit.py

@@ -1916,7 +1916,7 @@ def global_phase(self, angle):
         Args:
             angle (float, ParameterExpression): radians
         """
-        if isinstance(angle, ParameterExpression):
+        if isinstance(angle, ParameterExpression) and angle.parameters:
             self._global_phase = angle
         else:
             # Set the phase to the [-2 * pi, 2 * pi] interval

qiskit/dagcircuit/dagcircuit.py

@@ -826,6 +826,12 @@ def _full_pred_succ_maps(self, pred_map, succ_map, input_circuit,
         return full_pred_map, full_succ_map
 
     def __eq__(self, other):
+        if (
+                self.global_phase != other.global_phase
+                or self.calibrations != other.calibrations
+        ):
+            return False
+
         return rx.is_isomorphic_node_match(self._multi_graph,
                                            other._multi_graph,
                                            DAGNode.semantic_eq)

qiskit/transpiler/passes/basis/basis_translator.py

@@ -151,12 +151,14 @@ def run(self, dag):
                     bound_target_dag = circuit_to_dag(target_circuit)
                 else:
                     bound_target_dag = target_dag
-                if bound_target_dag.global_phase:
-                    dag.global_phase += bound_target_dag.global_phase
+
                 if (len(bound_target_dag.op_nodes()) == 1
                         and len(bound_target_dag.op_nodes()[0].qargs) == len(node.qargs)):
                     dag_op = bound_target_dag.op_nodes()[0].op
                     dag.substitute_node(node, dag_op, inplace=True)
+
+                    if bound_target_dag.global_phase:
+                        dag.global_phase += bound_target_dag.global_phase
                 else:
                     dag.substitute_node_with_dag(node, bound_target_dag)
             else:

qiskit/transpiler/passes/basis/unroller.py

@@ -95,8 +95,5 @@ def run(self, dag):
                                       (str(self.basis), node.op.name))
                 decomposition = circuit_to_dag(node.op.definition)
                 unrolled_dag = self.run(decomposition)  # recursively unroll ops
-                if unrolled_dag.global_phase:
-                    dag.global_phase += unrolled_dag.global_phase
-                    unrolled_dag.global_phase = 0
                 dag.substitute_node_with_dag(node, unrolled_dag)
         return dag

releasenotes/notes/dagcircuit-fix-substitute-node-global-phase-usage-ee05476a7d0b24c6.yaml

@@ -0,0 +1,12 @@
+---
+upgrade:
+  - |
+    The ``DAGCircuit.__eq__`` method, which is used to check structural equality
+    of :class:`~qiskit.dagcircuit.DAGCircuit` and :class:`~qiskit.circuit.QuantumCircuit` instances, has been updated to
+    include the ``global_phase`` and ``calibrations`` attributes in fields
+    checked for equality.
+fixes:
+  - |
+    The :class:`~qiskit.transpiler.passes.BasisTranslator` and :class:`~qiskit.transpiler.passes.Unroller` passes, in some cases, had not been
+    preserving the global phase of the circuit under transpilation. This has
+    been fixed.

test/python/circuit/library/test_grover_operator.py

@@ -106,12 +106,11 @@ def test_custom_zero_reflection(self):
             self.assertGroverOperatorIsCorrect(grover_op, oracle)
 
         with self.subTest('circuits match'):
-            expected = QuantumCircuit(*grover_op.qregs)
+            expected = QuantumCircuit(*grover_op.qregs, global_phase=np.pi)
             expected.compose(oracle, inplace=True)
             expected.h(0)  # state_in is H
             expected.compose(zero_reflection, inplace=True)
             expected.h(0)
-
             self.assertEqual(expected, grover_op)
 
     def test_num_mcx_ancillas(self):

test/python/circuit/test_circuit_qasm.py

@@ -16,7 +16,6 @@
 
 from qiskit import QuantumRegister, ClassicalRegister, QuantumCircuit
 from qiskit.test import QiskitTestCase
-from qiskit.quantum_info import random_unitary
 
 
 class TestCircuitQasm(QiskitTestCase):
@@ -176,8 +175,7 @@ def test_circuit_qasm_pi(self):
         """Test circuit qasm() method with pi params.
         """
         circuit = QuantumCircuit(2)
-        circuit.append(random_unitary(4, seed=1234), [0, 1])
-        circuit = circuit.decompose()
+        circuit.cz(0, 1)
         circuit.u(2*pi, 3*pi, -5*pi, 0)
         qasm_str = circuit.qasm()
         circuit2 = QuantumCircuit.from_qasm_str(qasm_str)

test/python/compiler/test_transpiler.py

@@ -438,7 +438,7 @@ def test_parameterized_circuit_for_simulator(self):
 
         transpiled_qc = transpile(qc, backend=BasicAer.get_backend('qasm_simulator'))
 
-        expected_qc = QuantumCircuit(qr)
+        expected_qc = QuantumCircuit(qr, global_phase=-1 * theta / 2.0)
         expected_qc.append(U1Gate(theta), [qr[0]])
 
         self.assertEqual(expected_qc, transpiled_qc)
@@ -455,7 +455,7 @@ def test_parameterized_circuit_for_device(self):
                                   initial_layout=Layout.generate_trivial_layout(qr))
 
         qr = QuantumRegister(14, 'q')
-        expected_qc = QuantumCircuit(qr)
+        expected_qc = QuantumCircuit(qr, global_phase=-1 * theta / 2.0)
         expected_qc.append(U1Gate(theta), [qr[0]])
 
         self.assertEqual(expected_qc, transpiled_qc)
@@ -472,7 +472,7 @@ def test_parameter_expression_circuit_for_simulator(self):
 
         transpiled_qc = transpile(qc, backend=BasicAer.get_backend('qasm_simulator'))
 
-        expected_qc = QuantumCircuit(qr)
+        expected_qc = QuantumCircuit(qr, global_phase=-1 * square / 2.0)
         expected_qc.append(U1Gate(square), [qr[0]])
         self.assertEqual(expected_qc, transpiled_qc)
 
@@ -490,7 +490,7 @@ def test_parameter_expression_circuit_for_device(self):
                                   initial_layout=Layout.generate_trivial_layout(qr))
 
         qr = QuantumRegister(14, 'q')
-        expected_qc = QuantumCircuit(qr)
+        expected_qc = QuantumCircuit(qr, global_phase=-1 * square / 2.0)
         expected_qc.append(U1Gate(square), [qr[0]])
         self.assertEqual(expected_qc, transpiled_qc)
 
@@ -636,7 +636,7 @@ def test_hadamard_to_rot_gates(self):
         qc = QuantumCircuit(qr)
         qc.h(0)
 
-        expected = QuantumCircuit(qr)
+        expected = QuantumCircuit(qr, global_phase=np.pi/2)
         expected.append(RYGate(theta=np.pi/2), [0])
         expected.append(RXGate(theta=np.pi), [0])
 
@@ -982,14 +982,16 @@ def test_delay_converts_to_dt(self):
     @data(1, 2, 3)
     def test_no_infinite_loop(self, optimization_level):
         """Verify circuit cost always descends and optimization does not flip flop indefinitely."""
-
         qc = QuantumCircuit(1)
         qc.ry(0.2, 0)
 
         out = transpile(qc, basis_gates=['id', 'p', 'sx', 'cx'],
                         optimization_level=optimization_level)
 
-        expected = QuantumCircuit(1)
+        # Expect a -pi/2 global phase for the U3 to RZ/SX conversion, and
+        # a -0.5 * theta phase for RZ to P twice, once at theta, and once at 3 pi
+        # for the second and third RZ gates in the U3 decomposition.
+        expected = QuantumCircuit(1, global_phase=-np.pi/2 - 0.5 * (0.2 + np.pi) - 0.5 * 3 * np.pi)
         expected.sx(0)
         expected.p(np.pi + 0.2, 0)
         expected.sx(0)