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class qiskit.opflow.converters.TwoQubitReduction(num_particles)

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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 in the Qiskit 1.0 release. For code migration guidelines, visit in a new tab).


num_particles (int(opens in a new tab) |List(opens in a new tab)[int(opens in a new tab)] | Tuple(opens in a new tab)[int(opens in a new tab), int(opens in a new tab)]) – 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


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