def measure_single_paulistring(
pauli_observable: pauli_string.PauliString,
key: Optional[Union[str, 'cirq.MeasurementKey']] = None,
) -> raw_types.Operation:
"""Returns a single PauliMeasurementGate which measures the pauli observable
Args:
pauli_observable: The `cirq.PauliString` observable to measure.
key: Optional `str` or `cirq.MeasurementKey` that gate should use.
If none provided, it defaults to a comma-separated list of
`str(qubit)` for each of the target qubits.
Returns:
An operation measuring the pauli observable.
Raises:
ValueError: if the observable is not an instance of PauliString or if the coefficient
is not +1.
"""
if not isinstance(pauli_observable, pauli_string.PauliString):
raise ValueError(
f'Pauli observable {pauli_observable} should be an instance of cirq.PauliString.'
)
if pauli_observable.coefficient != 1:
raise ValueError(f"Pauli observable {pauli_observable} must have a coefficient of +1.")
if key is None:
key = _default_measurement_key(pauli_observable)
return PauliMeasurementGate(pauli_observable.values(), key).on(*pauli_observable.keys())
def measure_paulistring_terms(
pauli_basis: pauli_string.PauliString,
key_func: Callable[[raw_types.Qid],
str] = str) -> List[raw_types.Operation]:
"""Returns a list of operations individually measuring qubits in the pauli basis.
Args:
pauli_basis: The `cirq.PauliString` basis in which each qubit should
be measured.
key_func: Determines the key of the measurements of each qubit. Takes
the qubit and returns the key for that qubit. Defaults to str.
Returns:
A list of operations individually measuring the given qubits in the
specified pauli basis.
Raises:
ValueError: if `pauli_basis` is not an instance of `cirq.PauliString`.
"""
if not isinstance(pauli_basis, pauli_string.PauliString):
raise ValueError(
f'Pauli observable {pauli_basis} should be an instance of cirq.PauliString.'
)
return [
PauliMeasurementGate([pauli_basis[q]], key=key_func(q)).on(q)
for q in pauli_basis
]