def _setup_qpe(self):
self._operator._check_representation('paulis')
self._ret['translation'] = sum(
[abs(p[0]) for p in self._operator.paulis])
self._ret['stretch'] = 0.5 / self._ret['translation']
# translate the operator
self._operator._simplify_paulis()
translation_op = Operator([[
self._ret['translation'],
Pauli(np.zeros(self._operator.num_qubits),
np.zeros(self._operator.num_qubits))
]])
translation_op._simplify_paulis()
self._operator += translation_op
# stretch the operator
for p in self._operator._paulis:
p[0] = p[0] * self._ret['stretch']
# check for identify paulis to get its coef for applying global phase shift on ancillae later
num_identities = 0
for p in self._operator.paulis:
if np.all(p[1].v == 0) and np.all(p[1].w == 0):
num_identities += 1
if num_identities > 1:
raise RuntimeError(
'Multiple identity pauli terms are present.')
self._ancilla_phase_coef = p[0].real if isinstance(
p[0], complex) else p[0]
self._construct_qpe_evolution()
logger.info('QPE circuit qasm length is roughly {}.'.format(
len(self._circuit.qasm().split('\n'))))
def _compute_energy(self):
self._operator._check_representation('paulis')
self._ret['translation'] = sum(
[abs(p[0]) for p in self._operator.paulis])
self._ret['stretch'] = 0.5 / self._ret['translation']
# translate the operator
self._operator._simplify_paulis()
translation_op = Operator([[
self._ret['translation'],
Pauli(np.zeros(self._operator.num_qubits),
np.zeros(self._operator.num_qubits))
]])
translation_op._simplify_paulis()
self._operator += translation_op
# stretch the operator
for p in self._operator._paulis:
p[0] = p[0] * self._ret['stretch']
# check for identify paulis to get its coef for applying global phase shift on ancilla later
num_identities = 0
for p in self._operator.paulis:
if np.all(p[1].v == 0) and np.all(p[1].w == 0):
num_identities += 1
if num_identities > 1:
raise RuntimeError(
'Multiple identity pauli terms are present.')
self._ancilla_phase_coef = p[0].real if isinstance(
p[0], complex) else p[0]
self._ret['phase'] = self._estimate_phase_iteratively()
self._ret['top_measurement_decimal'] = sum([
t[0] * t[1] for t in
zip([1 / 2**p for p in range(1, self._num_iterations + 1)],
[int(n) for n in self._ret['top_measurement_label']])
])
self._ret['energy'] = self._ret['phase'] / self._ret[
'stretch'] - self._ret['translation']