qml.devices.preprocess.validate_observables

validate_observables(tape, stopping_condition, stopping_condition_shots=None, name='device')

Validates the observables and measurements for a circuit.

Parameters

• tape (QuantumTape or QNode or Callable) – a quantum circuit.

• stopping_condition (callable) – a function that specifies whether an observable is accepted.

• stopping_condition_shots (callable) – a function that specifies whether an observable is accepted in finite-shots mode. This replaces stopping_condition if and only if the tape has shots.

• name (str) – the name of the device to use in error messages.

Returns

The unaltered input circuit. The output type is explained in qml.transform.

Return type

qnode (QNode) or quantum function (Callable) or tuple[List[QuantumTape], function]

Raises

DeviceError – if an observable is not supported

Example:

>>> def accepted_observable(obj):
...    return obj.name in {"PauliX", "PauliY", "PauliZ"}
>>> tape = qml.tape.QuantumScript([], [qml.expval(qml.Z(0) + qml.Y(0))])
>>> validate_observables(tape, accepted_observable)
qml.DeviceError: Observable Z(0) + Y(0) not supported on device

code/api/pennylane.devices.preprocess.validate_observables

 

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