tmp = pauli_group(number_of_qubits, case="tensor")
# sort on the weight of the Pauli operator
return sorted(tmp,
key=lambda x: -np.count_nonzero(
np.array(x.to_label(), "c") == b"I"))
elif case == "tensor":
# the Pauli set is in tensor order II IX IY IZ XI ...
for k in range(4**number_of_qubits):
z = np.zeros(number_of_qubits, dtype=bool)
x = np.zeros(number_of_qubits, dtype=bool)
# looping over all the qubits
for j in range(number_of_qubits):
# making the Pauli for each j fill it in from the
# end first
element = (k // (4**j)) % 4
if element == 1:
x[j] = True
elif element == 2:
z[j] = True
x[j] = True
elif element == 3:
z[j] = True
temp_set.append(Pauli(z, x))
return temp_set
else:
raise QiskitError(
f"Only support 'weight' or 'tensor' cases but you have {case}."
)
raise QiskitError("Only support number of qubits is less than 5")