class qiskit.opflow.converters.TwoQubitReduction(num_particles)[source]#

Bases: ConverterBase

Deprecated: Two qubit reduction converter which eliminates the central and last qubit in a list of Pauli that has diagonal operators (Z,I) at those positions.

Chemistry specific method: It can be used to taper two qubits in parity and binary-tree mapped fermionic Hamiltonians when the spin orbitals are ordered in two spin sectors, (block spin order) according to the number of particles in the system.

Deprecated since version 0.24.0: The class qiskit.opflow.converters.two_qubit_reduction.TwoQubitReduction is deprecated as of qiskit-terra 0.24.0. It will be removed no earlier than 3 months after the release date. For code migration guidelines, visit


num_particles (int | List[int] | Tuple[int, int]) -- number of particles, if it is a list, the first number is alpha and the second number if beta.



Converts the Operator to tapered one by Z2 symmetries.


operator (OperatorBase) -- the operator


A new operator whose qubit number is reduced by 2.

Return type: