--- title: library (latest version) description: API reference for qiskit_fermions.mappers.library in the latest version of qiskit-fermions source: https://quantum.cloud.ibm.com/docs/en/api/qiskit-fermions/mappers-library --- # Mapper Library This module provides efficient implementations of commonly used operator representation mapper routines. ## Python wrappers The functions below are thin, type-agnostic convenience mappers. Each delegates to the appropriate library implementation below under the hood, based on the type of the object it is given. They do not implement any conversion logic themselves. | | | | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | [`fermion_operator`](/docs/api/qiskit-fermions/mappers-library-fermion-operator#qiskit_fermions.mappers.library.fermion_operator "qiskit_fermions.mappers.library.fermion_operator")(operator) | Converts an operator into a [`FermionOperator`](/docs/api/qiskit-fermions/operators-fermion-operator#qiskit_fermions.operators.FermionOperator "qiskit_fermions.operators.FermionOperator"). | | [`jordan_wigner`](/docs/api/qiskit-fermions/mappers-library-jordan-wigner#qiskit_fermions.mappers.library.jordan_wigner "qiskit_fermions.mappers.library.jordan_wigner")(operator, num\_qubits) | Map an operator to a `SparseObservable` under the Jordan-Wigner transformation. | | [`majorana_operator`](/docs/api/qiskit-fermions/mappers-library-majorana-operator#qiskit_fermions.mappers.library.majorana_operator "qiskit_fermions.mappers.library.majorana_operator")(operator) | Converts an operator into a [`MajoranaOperator`](/docs/api/qiskit-fermions/operators-majorana-operator#qiskit_fermions.operators.MajoranaOperator "qiskit_fermions.operators.MajoranaOperator"). | ## Library implementations The functions below are the native, efficient mapper implementations backing this module. | | | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | [`fermion_jordan_wigner`](/docs/api/qiskit-fermions/mappers-library-fermion-jordan-wigner#qiskit_fermions.mappers.library.fermion_jordan_wigner "qiskit_fermions.mappers.library.fermion_jordan_wigner")(op, num\_qubits) | Map a [`FermionOperator`](/docs/api/qiskit-fermions/operators-fermion-operator#qiskit_fermions.operators.FermionOperator "qiskit_fermions.operators.FermionOperator") to a [`SparseObservable`](/docs/api/qiskit/qiskit.quantum_info.SparseObservable) under the Jordan-Wigner transformation. | | [`fermion_to_majorana`](/docs/api/qiskit-fermions/mappers-library-fermion-to-majorana#qiskit_fermions.mappers.library.fermion_to_majorana "qiskit_fermions.mappers.library.fermion_to_majorana")(fer\_op) | Map a [`FermionOperator`](/docs/api/qiskit-fermions/operators-fermion-operator#qiskit_fermions.operators.FermionOperator "qiskit_fermions.operators.FermionOperator") to a [`MajoranaOperator`](/docs/api/qiskit-fermions/operators-majorana-operator#qiskit_fermions.operators.MajoranaOperator "qiskit_fermions.operators.MajoranaOperator"). | | [`majorana_to_fermion`](/docs/api/qiskit-fermions/mappers-library-majorana-to-fermion#qiskit_fermions.mappers.library.majorana_to_fermion "qiskit_fermions.mappers.library.majorana_to_fermion")(maj\_op) | Map a [`MajoranaOperator`](/docs/api/qiskit-fermions/operators-majorana-operator#qiskit_fermions.operators.MajoranaOperator "qiskit_fermions.operators.MajoranaOperator") to a [`FermionOperator`](/docs/api/qiskit-fermions/operators-fermion-operator#qiskit_fermions.operators.FermionOperator "qiskit_fermions.operators.FermionOperator"). | | [`edge_vertex_to_fermion`](/docs/api/qiskit-fermions/mappers-library-edge-vertex-to-fermion#qiskit_fermions.mappers.library.edge_vertex_to_fermion "qiskit_fermions.mappers.library.edge_vertex_to_fermion")(inter\_op) | Map an [`EdgeVertexOperator`](/docs/api/qiskit-fermions/operators-edge-vertex-operator#qiskit_fermions.operators.EdgeVertexOperator "qiskit_fermions.operators.EdgeVertexOperator") to a [`FermionOperator`](/docs/api/qiskit-fermions/operators-fermion-operator#qiskit_fermions.operators.FermionOperator "qiskit_fermions.operators.FermionOperator"). | | [`edge_vertex_to_majorana`](/docs/api/qiskit-fermions/mappers-library-edge-vertex-to-majorana#qiskit_fermions.mappers.library.edge_vertex_to_majorana "qiskit_fermions.mappers.library.edge_vertex_to_majorana")(inter\_op) | Map an [`EdgeVertexOperator`](/docs/api/qiskit-fermions/operators-edge-vertex-operator#qiskit_fermions.operators.EdgeVertexOperator "qiskit_fermions.operators.EdgeVertexOperator") to a [`MajoranaOperator`](/docs/api/qiskit-fermions/operators-majorana-operator#qiskit_fermions.operators.MajoranaOperator "qiskit_fermions.operators.MajoranaOperator"). | | [`transfer_vertex_to_fermion`](/docs/api/qiskit-fermions/mappers-library-transfer-vertex-to-fermion#qiskit_fermions.mappers.library.transfer_vertex_to_fermion "qiskit_fermions.mappers.library.transfer_vertex_to_fermion")(inter\_op) | Map a [`TransferVertexOperator`](/docs/api/qiskit-fermions/operators-transfer-vertex-operator#qiskit_fermions.operators.TransferVertexOperator "qiskit_fermions.operators.TransferVertexOperator") to a [`FermionOperator`](/docs/api/qiskit-fermions/operators-fermion-operator#qiskit_fermions.operators.FermionOperator "qiskit_fermions.operators.FermionOperator"). | | [`transfer_vertex_to_majorana`](/docs/api/qiskit-fermions/mappers-library-transfer-vertex-to-majorana#qiskit_fermions.mappers.library.transfer_vertex_to_majorana "qiskit_fermions.mappers.library.transfer_vertex_to_majorana")(inter\_op) | Map a [`TransferVertexOperator`](/docs/api/qiskit-fermions/operators-transfer-vertex-operator#qiskit_fermions.operators.TransferVertexOperator "qiskit_fermions.operators.TransferVertexOperator") to a [`MajoranaOperator`](/docs/api/qiskit-fermions/operators-majorana-operator#qiskit_fermions.operators.MajoranaOperator "qiskit_fermions.operators.MajoranaOperator"). | | [`transfer_vertex_to_edge_vertex`](/docs/api/qiskit-fermions/mappers-library-transfer-vertex-to-edge-vertex#qiskit_fermions.mappers.library.transfer_vertex_to_edge_vertex "qiskit_fermions.mappers.library.transfer_vertex_to_edge_vertex")(inter\_op) | Map a [`TransferVertexOperator`](/docs/api/qiskit-fermions/operators-transfer-vertex-operator#qiskit_fermions.operators.TransferVertexOperator "qiskit_fermions.operators.TransferVertexOperator") to an [`EdgeVertexOperator`](/docs/api/qiskit-fermions/operators-edge-vertex-operator#qiskit_fermions.operators.EdgeVertexOperator "qiskit_fermions.operators.EdgeVertexOperator"). |