---
title: TwoQubitReduction (v0.46)
description: API reference for qiskit.opflow.converters.TwoQubitReduction in qiskit v0.46
source: https://eu-de.quantum.cloud.ibm.com/docs/en/api/qiskit/0.46/qiskit.opflow.converters.TwoQubitReduction
---

# TwoQubitReduction

*class* `qiskit.opflow.converters.TwoQubitReduction(num_particles)`

[GitHub](https://github.com/qiskit/qiskit/tree/stable/0.46/qiskit/opflow/converters/two_qubit_reduction.py)

Bases: [`ConverterBase`](/docs/api/qiskit/0.46/qiskit.opflow.converters.ConverterBase "qiskit.opflow.converters.converter_base.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 [https://qisk.it/opflow\_migration](https://qisk.it/opflow_migration).

**Parameters**

**num\_particles** ([*int*](https://docs.python.org/3/library/functions.html#int)  *|*[*List*](https://docs.python.org/3/library/typing.html#typing.List)*\[*[*int*](https://docs.python.org/3/library/functions.html#int)*] |* [*Tuple*](https://docs.python.org/3/library/typing.html#typing.Tuple)*\[*[*int*](https://docs.python.org/3/library/functions.html#int)*,* [*int*](https://docs.python.org/3/library/functions.html#int)*]*) – number of particles, if it is a list, the first number is alpha and the second number if beta.

## Methods

### convert

`convert(operator)`

Converts the Operator to tapered one by Z2 symmetries.

**Parameters**

**operator** ([*OperatorBase*](/docs/api/qiskit/0.46/qiskit.opflow.OperatorBase "qiskit.opflow.operator_base.OperatorBase")) – the operator

**Returns**

A new operator whose qubit number is reduced by 2.

**Return type**

[*OperatorBase*](/docs/api/qiskit/0.46/qiskit.opflow.OperatorBase "qiskit.opflow.operator_base.OperatorBase")