fix: Raise exception for probs with observable

src/braket/pennylane_plugin/translation.py

@@ -18,6 +18,7 @@
 import numpy as onp
 import pennylane as qp
 from pennylane import numpy as np
+from pennylane.exceptions import DeviceError
 from pennylane.measurements import MeasurementProcess
 from pennylane.operation import Operation, Operator
 from pennylane.pulse import ParametrizedEvolution
@@ -567,6 +568,8 @@ def translate_result_type(
     observable = measurement.obs
 
     if isinstance(measurement, qp.measurements.ProbabilityMP):
+        if observable and observable.diagonalizing_gates():
+            raise DeviceError("Probability result type not supported for observables")
         return Probability(targets)
 
     if isinstance(measurement, qp.measurements.StateMP):

test/unit_tests/test_translation.py

@@ -47,6 +47,7 @@
 )
 from pennylane import measurements
 from pennylane import numpy as pnp
+from pennylane.exceptions import DeviceError
 from pennylane.pulse import ParametrizedEvolution, transmon_drive
 from pennylane.wires import Wires
 
@@ -841,6 +842,17 @@ def test_translate_result_type_unsupported_obs():
         translate_result_type(tape.measurements[0], [0], frozenset())
 
 
+def test_translate_result_type_probs_observable():
+    """Tests if a DeviceError is raised by translate_result_type for a Probability return type
+    with an observable attached"""
+    mp = qp.probs(op=qp.X(wires=0))
+
+    with pytest.raises(
+        DeviceError, match="Probability result type not supported for observables"
+    ):
+        translate_result_type(mp, [0], frozenset())
+
+
 def test_translate_result():
     result_dict = _result_meta()
     result_dict["resultTypes"] = [