---
title: transfer_vertex_to_fermion (latest version)
description: API reference for qiskit_fermions.mappers.library.transfer_vertex_to_fermion in the latest version of qiskit-fermions
source: https://quantum.cloud.ibm.com/docs/en/api/qiskit-fermions/mappers-library-transfer-vertex-to-fermion
---

# transfer\_vertex\_to\_fermion

`transfer_vertex_to_fermion(inter_op)`

Map a [`TransferVertexOperator`](/docs/api/qiskit-fermions/operators-transfer-vertex-operator "qiskit_fermions.operators.TransferVertexOperator") to a [`FermionOperator`](/docs/api/qiskit-fermions/operators-fermion-operator "qiskit_fermions.operators.FermionOperator").

**Parameters**

**inter\_op** – the transfer-vertex operator to map.

**Returns**

The mapped fermionic operator.

## Definition

This function decomposes the transfer-vertex operators in terms of the fermionic action operators as defined [here](/docs/api/qiskit-fermions/operators-transfer-vertex-operator#transfervertexoperator-definition).

## Usage

```pycon
>>> from qiskit_fermions.mappers.library import transfer_vertex_to_fermion
>>> from qiskit_fermions.operators import TransferVertexOperator
>>> inter_op = TransferVertexOperator.from_dict({((0, 0),): 1, ((1, 2),): 2, ((2, 1),): -2})
>>> fer_op = transfer_vertex_to_fermion(inter_op)
>>> print(format(fer_op.normal_ordered().simplify()))
  1.000000e0 +0.000000e0j * ()
 -2.000000e0 +0.000000e0j * (-2 -1)
 -2.000000e0 +0.000000e0j * (+0 -0)
  2.000000e0 -0.000000e0j * (+2 +1)
```