Add __pos__ for Parameter

qiskit/circuit/parameterexpression.py

@@ -327,8 +327,11 @@ def __rsub__(self, other):
     def __mul__(self, other):
         return self._apply_operation(operator.mul, other)
 
+    def __pos__(self):
+        return self._apply_operation(operator.mul, 1)
+
     def __neg__(self):
-        return self._apply_operation(operator.mul, -1.0)
+        return self._apply_operation(operator.mul, -1)
 
     def __rmul__(self, other):
         return self._apply_operation(operator.mul, other, reflected=True)

releasenotes/notes/unary_pos_for_parameterexpression-6421421b6dc20fbb.yaml

@@ -0,0 +1,4 @@
+---
+features_circuits:
+  - |
+    :class:`.ParameterExpression` now supports the unary ``+`` operator.

test/python/circuit/test_parameters.py

@@ -1755,6 +1755,13 @@ def test_negated_expression(self):
 
         self.assertEqual(float(bound_expr2), 3)
 
+    def test_positive_expression(self):
+        """This tests parameter unary plus."""
+        x = Parameter("x")
+        y = +x
+        self.assertEqual(float(y.bind({x: 1})), 1.0)
+        self.assertIsInstance(+x, type(-x))
+
     def test_standard_cu3(self):
         """This tests parameter negation in standard extension gate cu3."""
         from qiskit.circuit.library import CU3Gate