def _build_commutator_routine(
params: List, operator: PauliSumOp, z2_symmetries: Z2Symmetries
) -> Tuple[int, int, PauliSumOp, PauliSumOp, PauliSumOp, PauliSumOp]:
"""Numerically computes the commutator / double commutator between operators.
Args:
params: list containing the indices of matrix element and the corresponding
excitation operators
operator: the hamiltonian
z2_symmetries: z2_symmetries in case of tapering
Returns:
The indices of the matrix element and the corresponding qubit
operator for each of the EOM matrices
"""
m_u, n_u, left_op, right_op_1, right_op_2 = params
if left_op is None or right_op_1 is None and right_op_2 is None:
q_mat_op = None
w_mat_op = None
m_mat_op = None
v_mat_op = None
else:
if right_op_1 is not None:
# The sign which we use in the case of the double commutator is arbitrary. In
# theory, one would choose this according to the nature of the problem (i.e.
# whether it is fermionic or bosonic), but in practice, always choosing the
# anti-commutator has proven to be more robust.
q_mat_op = double_commutator(left_op,
operator,
right_op_1,
sign=False)
# In the case of the single commutator, we are always interested in the energy
# difference of two states. Thus, regardless of the problem's nature, we will
# always use the commutator.
w_mat_op = commutator(left_op, right_op_1)
q_mat_op = None if len(q_mat_op) == 0 else q_mat_op
w_mat_op = None if len(w_mat_op) == 0 else w_mat_op
else:
q_mat_op = None
w_mat_op = None
if right_op_2 is not None:
# For explanations on the choice of commutation relation, please refer to the
# comments above.
m_mat_op = double_commutator(left_op,
operator,
right_op_2,
sign=False)
v_mat_op = commutator(left_op, right_op_2)
m_mat_op = None if len(m_mat_op) == 0 else m_mat_op
v_mat_op = None if len(v_mat_op) == 0 else v_mat_op
else:
m_mat_op = None
v_mat_op = None
if not z2_symmetries.is_empty():
if q_mat_op is not None and len(q_mat_op) > 0:
q_mat_op = z2_symmetries.taper(q_mat_op)
if w_mat_op is not None and len(w_mat_op) > 0:
w_mat_op = z2_symmetries.taper(w_mat_op)
if m_mat_op is not None and len(m_mat_op) > 0:
m_mat_op = z2_symmetries.taper(m_mat_op)
if v_mat_op is not None and len(v_mat_op) > 0:
v_mat_op = z2_symmetries.taper(v_mat_op)
return m_u, n_u, q_mat_op, w_mat_op, m_mat_op, v_mat_op
def _build_commutator_routine(
params: List, operator: PauliSumOp, z2_symmetries: Z2Symmetries,
sign: bool
) -> Tuple[int, int, PauliSumOp, PauliSumOp, PauliSumOp, PauliSumOp]:
"""Numerically computes the commutator / double commutator between operators.
Args:
params: list containing the indices of matrix element and the corresponding
excitation operators
operator: the hamiltonian
z2_symmetries: z2_symmetries in case of tapering
sign: commute or anticommute
Returns:
The indices of the matrix element and the corresponding qubit
operator for each of the EOM matrices
"""
m_u, n_u, left_op, right_op_1, right_op_2 = params
if left_op is None:
q_mat_op = None
w_mat_op = None
m_mat_op = None
v_mat_op = None
else:
if right_op_1 is None and right_op_2 is None:
q_mat_op = None
w_mat_op = None
m_mat_op = None
v_mat_op = None
else:
if right_op_1 is not None:
q_mat_op = double_commutator(left_op,
operator,
right_op_1,
sign=sign)
w_mat_op = commutator(left_op, right_op_1) \
if sign else anti_commutator(left_op, right_op_1)
q_mat_op = None if len(q_mat_op) == 0 else q_mat_op
w_mat_op = None if len(w_mat_op) == 0 else w_mat_op
else:
q_mat_op = None
w_mat_op = None
if right_op_2 is not None:
m_mat_op = double_commutator(left_op,
operator,
right_op_2,
sign=sign)
v_mat_op = commutator(left_op, right_op_2) \
if sign else anti_commutator(left_op, right_op_2)
m_mat_op = None if len(m_mat_op) == 0 else m_mat_op
v_mat_op = None if len(v_mat_op) == 0 else v_mat_op
else:
m_mat_op = None
v_mat_op = None
if not z2_symmetries.is_empty():
if q_mat_op is not None and len(q_mat_op) > 0:
q_mat_op = z2_symmetries.taper(q_mat_op)
if w_mat_op is not None and len(w_mat_op) > 0:
w_mat_op = z2_symmetries.taper(w_mat_op)
if m_mat_op is not None and len(m_mat_op) > 0:
m_mat_op = z2_symmetries.taper(m_mat_op)
if v_mat_op is not None and len(v_mat_op) > 0:
v_mat_op = z2_symmetries.taper(v_mat_op)
return m_u, n_u, q_mat_op, w_mat_op, m_mat_op, v_mat_op