Fix README chemistry sample
@@ -120,6 +120,7 @@ Now that Qiskit Aqua is installed, it's time to begin working with it. We are r
```python
from qiskit.chemistry import FermionicOperator
from qiskit.chemistry.drivers import PySCFDriver, UnitsType
+from qiskit.aqua.operators import Z2Symmetries
# Use PySCF, a classical computational chemistry software
# package, to compute the one-body and two-body integrals in
@@ -135,7 +136,7 @@ num_spin_orbitals = molecule.num_orbitals * 2
ferOp = FermionicOperator(h1=molecule.one_body_integrals, h2=molecule.two_body_integrals)
map_type = 'PARITY'
qubitOp = ferOp.mapping(map_type)
-qubitOp = qubitOp.two_qubit_reduced_operator(num_particles)
+qubitOp = Z2Symmetries.two_qubit_reduction(qubitOp, num_particles)
num_qubits = qubitOp.num_qubits
# set the backend for the quantum computation
