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

# qiskit.opflow\.converters

## Converters

`qiskit.opflow.converters`

> **Deprecated since version 0.24.0**
>
> The [`qiskit.opflow`](/docs/api/qiskit/0.46/opflow#module-qiskit.opflow "qiskit.opflow") module is deprecated and will be removed no earlier than 3 months after the release date. For code migration guidelines, visit [https://qisk.it/opflow\_migration](https://qisk.it/opflow_migration).

Converters are objects which manipulate Operators, usually traversing an Operator to change certain sub-Operators into a desired representation. Often the converted Operator is isomorphic or approximate to the original Operator in some way, but not always. For example, a converter may accept [`CircuitOp`](/docs/api/qiskit/0.46/qiskit.opflow.primitive_ops.CircuitOp "qiskit.opflow.primitive_ops.CircuitOp") and return a [`SummedOp`](/docs/api/qiskit/0.46/qiskit.opflow.list_ops.SummedOp "qiskit.opflow.list_ops.SummedOp") of [`PauliOp`](/docs/api/qiskit/0.46/qiskit.opflow.primitive_ops.PauliOp "qiskit.opflow.primitive_ops.PauliOp")’s representing the circuit unitary. Converters may not have polynomial space or time scaling in their operations. On the contrary, many converters, such as a [`MatrixExpectation`](/docs/api/qiskit/0.46/qiskit.opflow.expectations.MatrixExpectation "qiskit.opflow.expectations.MatrixExpectation") or [`MatrixEvolution`](/docs/api/qiskit/0.46/qiskit.opflow.evolutions.MatrixEvolution "qiskit.opflow.evolutions.MatrixEvolution"), which convert [`PauliOp`](/docs/api/qiskit/0.46/qiskit.opflow.primitive_ops.PauliOp "qiskit.opflow.primitive_ops.PauliOp")’s to [`MatrixOp`](/docs/api/qiskit/0.46/qiskit.opflow.primitive_ops.MatrixOp "qiskit.opflow.primitive_ops.MatrixOp")’s internally, will require time or space exponential in the number of qubits unless a clever trick is known (such as the use of sparse matrices).

> **Note**
>
> Not all converters are in this module, as [`expectations`](/docs/api/qiskit/0.46/qiskit.opflow.expectations#module-qiskit.opflow.expectations "qiskit.opflow.expectations") and [`evolutions`](/docs/api/qiskit/0.46/qiskit.opflow.evolutions#module-qiskit.opflow.evolutions "qiskit.opflow.evolutions") are also converters.

### Converter Base Class

The converter base class simply enforces the presence of a [`convert()`](/docs/api/qiskit/0.46/qiskit.opflow.converters.ConverterBase#convert "qiskit.opflow.converters.ConverterBase.convert") method.

|                                                                                                                            |                                                                                                                                                          |
| -------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------- |
| [`ConverterBase`](/docs/api/qiskit/0.46/qiskit.opflow.converters.ConverterBase "qiskit.opflow.converters.ConverterBase")() | Deprecated: Converters take an Operator and return a new Operator, generally isomorphic in some way with the first, but with certain desired properties. |

### Converters

In addition to the base class, directory holds a few miscellaneous converters which are used frequently around the Operator flow.

|                                                                                                                                                                     |                                                                                                                                                                                            |
| ------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| [`CircuitSampler`](/docs/api/qiskit/0.46/qiskit.opflow.converters.CircuitSampler "qiskit.opflow.converters.CircuitSampler")(backend\[, statevector, ...])           | Deprecated: The CircuitSampler traverses an Operator and converts any CircuitStateFns into approximations of the state function by a DictStateFn or VectorStateFn using a quantum backend. |
| [`AbelianGrouper`](/docs/api/qiskit/0.46/qiskit.opflow.converters.AbelianGrouper "qiskit.opflow.converters.AbelianGrouper")(\[traverse])                            | Deprecated: The AbelianGrouper converts SummedOps into a sum of Abelian sums.                                                                                                              |
| [`DictToCircuitSum`](/docs/api/qiskit/0.46/qiskit.opflow.converters.DictToCircuitSum "qiskit.opflow.converters.DictToCircuitSum")(\[traverse, convert\_dicts, ...]) | Deprecated: Converts `DictStateFns` or `VectorStateFns` to equivalent `CircuitStateFns` or sums thereof.                                                                                   |
| [`PauliBasisChange`](/docs/api/qiskit/0.46/qiskit.opflow.converters.PauliBasisChange "qiskit.opflow.converters.PauliBasisChange")(\[destination\_basis, ...])       | Deprecated: Converter for changing Paulis into other bases.                                                                                                                                |
| [`TwoQubitReduction`](/docs/api/qiskit/0.46/qiskit.opflow.converters.TwoQubitReduction "qiskit.opflow.converters.TwoQubitReduction")(num\_particles)                | 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.                             |