def _pauli_expansion_(self) -> value.LinearDict[str]:
"""Computes Pauli expansion of self from Pauli expansions of terms."""
def extend_term(pauli_names: str, qubits: Tuple['cirq.Qid', ...],
all_qubits: Tuple['cirq.Qid', ...]) -> str:
"""Extends Pauli product on qubits to product on all_qubits."""
assert len(pauli_names) == len(qubits)
qubit_to_pauli_name = dict(zip(qubits, pauli_names))
return ''.join(qubit_to_pauli_name.get(q, 'I') for q in all_qubits)
def extend(
expansion: value.LinearDict[str], qubits: Tuple['cirq.Qid',
...],
all_qubits: Tuple['cirq.Qid', ...]) -> value.LinearDict[str]:
"""Extends Pauli expansion on qubits to expansion on all_qubits."""
return value.LinearDict({
extend_term(p, qubits, all_qubits): c
for p, c in expansion.items()
})
result = value.LinearDict({}) # type: value.LinearDict[str]
for op, coefficient in self.items():
expansion = protocols.pauli_expansion(op)
extended_expansion = extend(expansion, op.qubits, self.qubits)
result += extended_expansion * coefficient
return result
def assert_pauli_expansion_is_consistent_with_unitary(val: Any) -> None:
"""Checks Pauli expansion against unitary matrix."""
# Check to see if the protocol is supported without doing a fallback
# to unitary, otherwise the test is vacuous.
method = getattr(val, '_pauli_expansion_', None)
if method is None:
return
pauli_expansion = protocols.pauli_expansion(val, default=None)
if pauli_expansion is None:
return
unitary = protocols.unitary(val, None)
if unitary is None:
return
num_qubits = protocols.num_qubits(val,
default=unitary.shape[0].bit_length() -
1)
basis = operator_spaces.kron_bases(operator_spaces.PAULI_BASIS,
repeat=num_qubits)
recovered_unitary = operator_spaces.matrix_from_basis_coefficients(
pauli_expansion, basis)
assert np.allclose(unitary, recovered_unitary, rtol=0, atol=1e-12)
def assert_pauli_expansion_is_consistent_with_unitary(val: Any) -> None:
"""Checks Pauli expansion against unitary matrix."""
pauli_expansion = protocols.pauli_expansion(val, default=None)
if pauli_expansion is None:
return
unitary = protocols.unitary(val, None)
if unitary is None:
return
num_qubits = unitary.shape[0].bit_length() - 1
basis = operator_spaces.kron_bases(operator_spaces.PAULI_BASIS,
repeat=num_qubits)
recovered_unitary = operator_spaces.matrix_from_basis_coefficients(
pauli_expansion, basis)
assert np.allclose(unitary, recovered_unitary, rtol=0, atol=1e-12)
def _pauli_expansion_(self) -> value.LinearDict[str]:
if self._is_parameterized_():
return NotImplemented
expansion = protocols.pauli_expansion(self._iswap)
assert set(expansion.keys()).issubset({'II', 'XX', 'YY', 'ZZ'})
assert np.isclose(expansion['XX'], expansion['YY'])
v = (expansion['XX'] + expansion['YY']) / 2
phase_angle = np.pi * self.phase_exponent
c, s = np.cos(2 * phase_angle), np.sin(2 * phase_angle)
return value.LinearDict({
'II': expansion['II'],
'XX': c * v,
'YY': c * v,
'XY': s * v,
'YX': -s * v,
'ZZ': expansion['ZZ'],
})
def _pauli_expansion_(self) -> value.LinearDict[str]:
return protocols.pauli_expansion(self.sub_operation)
def _pauli_expansion_(self) -> value.LinearDict[str]:
result = value.LinearDict({}) # type: value.LinearDict[str]
for gate, coefficient in self.items():
result += protocols.pauli_expansion(gate) * coefficient
return result
def _pauli_expansion_(self) -> value.LinearDict[str]:
return protocols.pauli_expansion(self.gate)
