Ignore global phase if unsupported (#156)

Author: speller26

qiskit_braket_provider/providers/adapter.py

@@ -32,6 +32,8 @@
 
 from qiskit_braket_provider.exception import QiskitBraketException
 
+_GPHASE_GATE_NAME = "global_phase"
+
 _BRAKET_TO_QISKIT_NAMES = {
     "u": "u",
     "phaseshift": "p",
@@ -63,6 +65,7 @@
     "gpi": "gpi",
     "gpi2": "gpi2",
     "ms": "ms",
+    "gphase": _GPHASE_GATE_NAME,
 }
 
 _CONTROLLED_GATES_BY_QUBIT_COUNT = {
@@ -108,12 +111,14 @@
     "ecr": lambda: [braket_gates.ECR()],
     "iswap": lambda: [braket_gates.ISwap()],
     # IonQ gates
-    "gpi": lambda angle: [braket_gates.GPi(2 * pi * angle)],
-    "gpi2": lambda angle: [braket_gates.GPi2(2 * pi * angle)],
-    "ms": lambda angle_1, angle_2, angle_3: [
-        braket_gates.MS(2 * pi * angle_1, 2 * pi * angle_2, 2 * pi * angle_3)
+    "gpi": lambda turns: [braket_gates.GPi(2 * pi * turns)],
+    "gpi2": lambda turns: [braket_gates.GPi2(2 * pi * turns)],
+    "ms": lambda turns_1, turns_2, turns_3: [
+        braket_gates.MS(2 * pi * turns_1, 2 * pi * turns_2, 2 * pi * turns_3)
     ],
     "zz": lambda angle: [braket_gates.ZZ(2 * pi * angle)],
+    # Global phase
+    _GPHASE_GATE_NAME: lambda phase: [braket_gates.GPhase(phase)],
 }
 
 _QISKIT_CONTROLLED_GATE_NAMES_TO_BRAKET_GATES: dict[str, Callable] = {
@@ -174,6 +179,7 @@
         Parameter("phi1") / (2 * pi),
         Parameter("theta") / (2 * pi),
     ),
+    "gphase": qiskit_gates.GlobalPhaseGate(Parameter("theta")),
 }
 
 
@@ -398,10 +404,11 @@ def to_braket(
     Returns:
         Circuit: Braket circuit
     """
-    basis_gates = basis_gates or _TRANSLATABLE_QISKIT_GATE_NAMES
     if not isinstance(circuit, QuantumCircuit):
         raise TypeError(f"Expected a QuantumCircuit, got {type(circuit)} instead.")
 
+    basis_gates = set(basis_gates or _TRANSLATABLE_QISKIT_GATE_NAMES)
+
     braket_circuit = Circuit()
     if not verbatim and not {gate.name for gate, _, _ in circuit.data}.issubset(
         basis_gates
@@ -460,8 +467,15 @@ def to_braket(
                         target=qubit_indices,
                     )
 
-    if circuit.global_phase > _EPS:
-        braket_circuit.gphase(circuit.global_phase)
+    global_phase = circuit.global_phase
+    if abs(global_phase) > _EPS:
+        if _GPHASE_GATE_NAME in basis_gates:
+            braket_circuit.gphase(global_phase)
+        else:
+            warnings.warn(
+                f"Device does not support global phase; "
+                f"global phase of {global_phase} will not be included in Braket circuit"
+            )
 
     if verbatim:
         return Circuit(braket_circuit.result_types).add_verbatim_box(

qiskit_braket_provider/version.py

@@ -1,3 +1,3 @@
 """Qiskit-Braket provider version."""
 
-__version__ = "0.1.0"
+__version__ = "0.1.1"

tests/providers/test_adapter.py

@@ -9,7 +9,7 @@
 from braket.devices import LocalSimulator
 from qiskit import ClassicalRegister, QuantumCircuit, QuantumRegister, transpile
 from qiskit.circuit import Parameter, ParameterVector
-from qiskit.circuit.library import PauliEvolutionGate
+from qiskit.circuit.library import GlobalPhaseGate, PauliEvolutionGate
 from qiskit.circuit.library import standard_gates as qiskit_gates
 from qiskit.providers.basicaer import BasicAer
 from qiskit.quantum_info import SparsePauliOp
@@ -242,14 +242,20 @@ def test_global_phase(self):
         """Tests conversion when transpiler generates a global phase"""
         qiskit_circuit = QuantumCircuit(1, global_phase=np.pi / 2)
         qiskit_circuit.h(0)
+        gate = GlobalPhaseGate(1.23)
+        qiskit_circuit.append(gate, [])
 
         braket_circuit = to_braket(qiskit_circuit)
-
-        expected_braket_circuit = Circuit().h(0).gphase(np.pi / 2)
-
-        self.assertEqual(braket_circuit.global_phase, qiskit_circuit.global_phase)
+        expected_braket_circuit = Circuit().h(0).gphase(1.23).gphase(np.pi / 2)
+        self.assertEqual(
+            braket_circuit.global_phase, qiskit_circuit.global_phase + gate.params[0]
+        )
         self.assertEqual(braket_circuit, expected_braket_circuit)
 
+        braket_circuit_no_gphase = to_braket(qiskit_circuit, basis_gates={"h"})
+        self.assertEqual(braket_circuit_no_gphase.global_phase, 0)
+        self.assertEqual(braket_circuit_no_gphase, Circuit().h(0))
+
     def test_exponential_gate_decomp(self):
         """Tests adapter translation of exponential gates"""
         aer_backend = BasicAer.get_backend("statevector_simulator")
@@ -303,6 +309,7 @@ def test_mappers(self):
             "rxx": "xx",
             "ryy": "yy",
             "zz": "zz",
+            "global_phase": "gphase",
         }
 
         qiskit_to_braket_gate_names |= {