Add a no_analytic transform

doc/releases/changelog-dev.md

@@ -111,6 +111,10 @@
   (np.float64(1.0), np.float64(0.58))
   ```
 
+* A new device preprocess transform, `~.devices.preprocess.no_analytic`, is available for hardware devices and hardware-like simulators.
+  It validates that all executions are shot-based.
+  [(#8037)](https://github.com/PennyLaneAI/pennylane/pull/8037)
+
 <h4>OpenQASM-PennyLane interoperability</h4>
 
 * The :func:`qml.from_qasm3` function can now convert OpenQASM 3.0 circuits that contain
@@ -551,6 +555,7 @@ Joey Carter,
 Yushao Chen,
 Diksha Dhawan,
 Marcus Edwards,
+Lillian Frederiksen,
 Pietropaolo Frisoni,
 Simone Gasperini,
 David Ittah,

pennylane/devices/preprocess.py

@@ -107,6 +107,27 @@ def no_sampling(
     return (tape,), null_postprocessing
 
 
+@transform
+def no_analytic(
+    tape: QuantumScript, name: str = "device"
+) -> tuple[QuantumScriptBatch, PostprocessingFn]:
+    """Raises an error if the tape does not have finite shots.
+    Args:
+        tape (QuantumTape or .QNode or Callable): a quantum circuit
+        name (str): name to use in error message.
+    Returns:
+        qnode (QNode) or quantum function (Callable) or tuple[List[.QuantumTape], function]:
+        The unaltered input circuit. The output type is explained in :func:`qml.transform <pennylane.transform>`.
+
+
+    This transform can be added to forbid analytic results. This is relevant for devices
+    that can only return samples and/or counts based results.
+    """
+    if not tape.shots:
+        raise DeviceError(f"Analytic execution is not supported with {name}")
+    return (tape,), null_postprocessing
+
+
 @transform
 def validate_device_wires(
     tape: QuantumScript, wires: qml.wires.Wires | None = None, name: str = "device"

tests/devices/test_preprocess.py

@@ -25,6 +25,7 @@
     measurements_from_counts,
     measurements_from_samples,
     mid_circuit_measurements,
+    no_analytic,
     no_sampling,
     null_postprocessing,
     validate_adjoint_trainable_params,
@@ -149,6 +150,18 @@ def test_no_sampling():
         no_sampling(tape2, name="abc")
 
 
+def test_no_analytic():
+    """Test for the no_anayltic transform"""
+
+    tape1 = qml.tape.QuantumScript(shots=2)
+    batch, _ = no_analytic(tape1)
+    assert batch[0] is tape1
+
+    tape2 = qml.tape.QuantumScript(shots=None)
+    with pytest.raises(DeviceError, match="Analytic execution is not supported with abc"):
+        no_analytic(tape2, name="abc")
+
+
 def test_validate_adjoint_trainable_params_obs_warning():
     """Tests warning raised for validate_adjoint_trainable_params with trainable observables."""