Enable use of qiskit ParameterExpressions for circuit conversion: qiskit to braket

qiskit_braket_provider/providers/adapter.py

@@ -8,7 +8,13 @@
 import braket.circuits.gates as braket_gates
 import qiskit.circuit.library as qiskit_gates
 from braket.aws import AwsDevice
-from braket.circuits import Circuit, FreeParameter, Instruction, observables
+from braket.circuits import (
+    Circuit,
+    FreeParameter,
+    FreeParameterExpression,
+    Instruction,
+    observables,
+)
 from braket.device_schema import DeviceActionType, OpenQASMDeviceActionProperties
 from braket.device_schema.ionq import IonqDeviceCapabilities
 from braket.device_schema.oqc import OqcDeviceCapabilities
@@ -19,9 +25,11 @@
 from qiskit import QuantumCircuit, transpile
 from qiskit.circuit import ControlledGate
 from qiskit.circuit import Instruction as QiskitInstruction
-from qiskit.circuit import Measure, Parameter
+from qiskit.circuit import Measure, Parameter, ParameterExpression
+from qiskit.circuit.parametervector import ParameterVectorElement
 from qiskit.transpiler import Target
 from qiskit_ionq import ionq_gates
+from sympy import sympify
 
 from qiskit_braket_provider.exception import QiskitBraketException
 
@@ -401,7 +409,10 @@ def to_braket(
     ):
         circuit = transpile(circuit, basis_gates=basis_gates, optimization_level=0)
 
-    # handle qiskit to braket conversion
+    # Verify that ParameterVector do not collide with scalar variables after renaming.
+    _validate_name_conflicts(circuit.parameters)
+
+    # Handle qiskit to braket conversion
     for circuit_instruction in circuit.data:
         operation = circuit_instruction.operation
         gate_name = operation.name
@@ -466,11 +477,32 @@ def to_braket(
 def _create_free_parameters(operation):
     params = operation.params if hasattr(operation, "params") else []
     for i, param in enumerate(params):
-        if isinstance(param, Parameter):
+        if isinstance(param, ParameterVectorElement):
+            cleaned_param_name = _rename_param_vector_element(param)
+            params[i] = FreeParameter(cleaned_param_name)
+        elif isinstance(param, Parameter):
             params[i] = FreeParameter(param.name)
+        elif isinstance(param, ParameterExpression):
+            cleaned_param_name = _rename_param_vector_element(param)
+            params[i] = FreeParameterExpression(sympify(cleaned_param_name))
+
     return params
 
 
+def _rename_param_vector_element(parameter):
+    param_name = str(parameter._symbol_expr)
+    return f"{param_name.replace('[', '_').replace(']', '')}"
+
+
+def _validate_name_conflicts(parameters):
+    renamed_parameters = {_rename_param_vector_element(param) for param in parameters}
+    if len(renamed_parameters) != len(parameters):
+        raise ValueError(
+            "ParameterVector elements are renamed from v[i] to v_i, which resulted "
+            "in a conflict with another parameter. Please rename your parameters."
+        )
+
+
 def to_qiskit(circuit: Circuit) -> QuantumCircuit:
     """Return a Qiskit quantum circuit from a Braket quantum circuit.
      Args:

tests/providers/test_adapter.py

@@ -1,5 +1,4 @@
 """Tests for Qiskit to Braket adapter."""
-
 from unittest import TestCase
 from unittest.mock import Mock, patch
 
@@ -9,7 +8,7 @@
 from braket.circuits.angled_gate import AngledGate, TripleAngledGate
 from braket.devices import LocalSimulator
 from qiskit import ClassicalRegister, QuantumCircuit, QuantumRegister, transpile
-from qiskit.circuit import Parameter
+from qiskit.circuit import Parameter, ParameterVector
 from qiskit.circuit.library import PauliEvolutionGate
 from qiskit.circuit.library import standard_gates as qiskit_gates
 from qiskit.providers.basicaer import BasicAer
@@ -466,6 +465,45 @@ def test_verbatim(self):
             Circuit().h(0).cnot(0, 1)
         )
 
+    def test_parameter_vector(self):
+        """Tests ParameterExpression translation."""
+        qiskit_circuit = QuantumCircuit(1)
+        v = ParameterVector("v", 2)
+        qiskit_circuit.rx(v[0], 0)
+        qiskit_circuit.ry(v[1], 0)
+        braket_circuit = to_braket(qiskit_circuit)
+
+        expected_braket_circuit = (
+            Circuit().rx(0, FreeParameter("v_0")).ry(0, FreeParameter("v_1"))
+        )
+        assert braket_circuit == expected_braket_circuit
+
+    def test_parameter_expression(self):
+        """Tests ParameterExpression translation."""
+        qiskit_circuit = QuantumCircuit(1)
+        v = ParameterVector("v", 2)
+        qiskit_circuit.rx(Parameter("a") + 2 * Parameter("b"), 0)
+        qiskit_circuit.ry(v[0] - 2 * v[1], 0)
+        braket_circuit = to_braket(qiskit_circuit)
+
+        expected_braket_circuit = (
+            Circuit()
+            .rx(0, FreeParameter("a") + 2 * FreeParameter("b"))
+            .ry(0, FreeParameter("v_0") - 2 * FreeParameter("v_1"))
+        )
+        assert braket_circuit == expected_braket_circuit
+
+    def test_name_conflict_with_parameter_vector(self):
+        """Tests ParameterExpression translation."""
+        qiskit_circuit = QuantumCircuit(1)
+        v = ParameterVector("v", 1)
+        v0 = Parameter("v_0")
+        qiskit_circuit.rx(v0, 0)
+        qiskit_circuit.ry(v[0], 0)
+
+        with pytest.raises(ValueError, match="Please rename your parameters."):
+            to_braket(qiskit_circuit)
+
     @patch("qiskit_braket_provider.providers.adapter.transpile")
     def test_invalid_ctrl_state(self, mock_transpile):
         """Tests that control states other than all 1s are rejected."""