qdk_chemistry.plugins.qiskit.qubit_mapper module

Qiskit-based qubit mappers to map electronic structure Hamiltonians to qubit operators.

This module provides a QiskitQubitMapper class to convert Hamiltonians to QubitOperators using different mapping strategies (“jordan-wigner”, “bravyi-kitaev”, and “parity”).

class qdk_chemistry.plugins.qiskit.qubit_mapper.QiskitQubitMapper

Bases: QubitMapper

Map an electronic structure Hamiltonian to a QubitOperator using Qiskit.

This is a third-party backend: it reads mapping.base_encoding to select the corresponding Qiskit Nature mapper class and ignores mapping.table. The qubit operator is built from scratch using Qiskit Nature’s own fermion-to-qubit pipeline.

Warning

Because this backend chooses its transform by encoding name rather than from the Pauli table, it relies on the mapping’s base_encoding string being consistent with its table. This is guaranteed for factory-produced mappings (MajoranaMapping.jordan_wigner(), .bravyi_kitaev(), etc.) and is verified by cross-backend eigenvalue tests in the test suite. Manually built mappings with mismatched names will produce silently incorrect results.

Tapering-based encodings (e.g. parity two-qubit reduction) are supported — each backend handles tapering in its own _run_impl() via the QubitMapper._taper_result() helper.

Both restricted (RHF) and unrestricted (UHF) Hamiltonians are supported. For unrestricted systems, separate alpha and beta one-body and two-body integrals are forwarded to Qiskit Nature’s ElectronicEnergy.

Supported base encodings:

• "jordan-wigner" → qiskit_nature.second_q.mappers.JordanWignerMapper

• "bravyi-kitaev" → qiskit_nature.second_q.mappers.BravyiKitaevMapper

• "parity" → qiskit_nature.second_q.mappers.ParityMapper

Examples

>>> from qdk_chemistry.algorithms import create
>>> from qdk_chemistry.data import MajoranaMapping
>>> mapper = create("qubit_mapper", "qiskit")
>>> mapping = MajoranaMapping.jordan_wigner(num_modes=n_spin_orbitals)
>>> qh = mapper.run(hamiltonian, mapping)

QubitMappers: ClassVar = {'bravyi-kitaev': qiskit_nature.second_q.mappers.BravyiKitaevMapper, 'jordan-wigner': qiskit_nature.second_q.mappers.JordanWignerMapper, 'parity': qiskit_nature.second_q.mappers.ParityMapper}

__init__()

Initialize QiskitQubitMapper.

name()

Return the algorithm name qiskit.

Return type:

str

class qdk_chemistry.plugins.qiskit.qubit_mapper.QiskitQubitMapperSettings

Bases: QubitMapperSettings

Settings configuration for a QiskitQubitMapper.

__init__()

Initialize QiskitQubitMapperSettings.