def validate_args(self, qubits: Sequence[Qid]) -> None:
"""Checks if this gate can be applied to the given qubits.
By default checks if input is of type Qid and qubit count.
Child classes can override.
Args:
qubits: The collection of qubits to potentially apply the gate to.
Throws:
ValueError: The gate can't be applied to the qubits.
"""
if len(qubits) != qid_shape_protocol.num_qubits(self):
raise ValueError('Wrong number of qubits for <{!r}>. '
'Expected {} qubits but got <{!r}>.'.format(
self, qid_shape_protocol.num_qubits(self),
qubits))
if any([not isinstance(qubit, Qid) for qubit in qubits]):
raise ValueError('Gate was called with type different than Qid.')
def __pow__(self, power):
if power == 1:
return self
if power == -1:
# HACK: break cycle
from cirq.devices import line_qubit
decomposed = decompose.decompose_once_with_qubits(
self,
qubits=line_qubit.LineQubit.range(
qid_shape_protocol.num_qubits(self)),
default=None)
if decomposed is None:
return NotImplemented
inverse_decomposed = inverse.inverse(decomposed, None)
if inverse_decomposed is None:
return NotImplemented
return _InverseCompositeGate(self)
return NotImplemented
def _num_qubits_(self):
return qid_shape_protocol.num_qubits(self._original)
def _backwards_compatibility_num_qubits(self) -> int:
return qid_shape_protocol.num_qubits(self)
