diff --git a/qiskit_dynamics/backend/backend_utils.py b/qiskit_dynamics/backend/backend_utils.py
index 3d153e7e2..e762f2d72 100644
--- a/qiskit_dynamics/backend/backend_utils.py
+++ b/qiskit_dynamics/backend/backend_utils.py
@@ -136,7 +136,7 @@ def _get_memory_slot_probabilities(
                 level = str(max_outcome_value)
             memory_slot_result[-(idx + 1)] = level
 
-        memory_slot_result = "".join(memory_slot_result)
+        memory_slot_result = hex(int("".join(memory_slot_result), 2))
         if memory_slot_result in memory_slot_probs:
             memory_slot_probs[memory_slot_result] += prob
         else:
diff --git a/qiskit_dynamics/backend/dynamics_backend.py b/qiskit_dynamics/backend/dynamics_backend.py
index e87f5b574..79df9424e 100644
--- a/qiskit_dynamics/backend/dynamics_backend.py
+++ b/qiskit_dynamics/backend/dynamics_backend.py
@@ -882,7 +882,7 @@ def default_experiment_result_function(
 
         # construct results object
         exp_data = ExperimentResultData(
-            counts=counts, memory=memory_samples if backend.options.memory else None
+            counts=counts, memory=memory_samples.tolist() if backend.options.memory else None
         )
         return ExperimentResult(
             shots=backend.options.shots,