# Hartree-Fock reference state for VQE using Bravy-Kitaev mapping and tapering

**URL:** <https://discuss.pennylane.ai/t/hartree-fock-reference-state-for-vqe-using-bravy-kitaev-mapping-and-tapering/9214>\
**Category:** PennyLane Help\
**Created:** [January 22, 2026, 8:51pm UTC](https://discuss.pennylane.ai/t/hartree-fock-reference-state-for-vqe-using-bravy-kitaev-mapping-and-tapering/9214 "2026-01-22T20:51:03Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![alima](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/alima/32/4190_2.png) [@alima](https://discuss.pennylane.ai/u/alima)\
**Post date:** [January 22, 2026, 8:51pm UTC](https://discuss.pennylane.ai/t/hartree-fock-reference-state-for-vqe-using-bravy-kitaev-mapping-and-tapering/9214/1 "2026-01-22T20:51:03Z")

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I would like to know how I can construct a Hartree-Fock reference state for VQE using Bravy-Kitaev mapping and tapering. I know it’s possible to achieve it using Jordan-Wigner, but is there any possibility of achieving it with Bravy-Kitaev?

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**Author:** ![CatalinaAlbornoz](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/catalinaalbornoz/32/1196_2.png) [@CatalinaAlbornoz](https://discuss.pennylane.ai/u/CatalinaAlbornoz)\
**Post date:** [January 22, 2026, 9:24pm UTC](https://discuss.pennylane.ai/t/hartree-fock-reference-state-for-vqe-using-bravy-kitaev-mapping-and-tapering/9214/2 "2026-01-22T21:24:46Z")

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Hi @alima , welcome to the Forum!

We have a [`qml.bravyi_kitaev`](https://docs.pennylane.ai/en/stable/code/api/pennylane.bravyi_kitaev.html) feature that allows you to convert a fermionic operator to a qubit operator using the Bravyi-Kitaev mapping. It works similar to the [`qml.jordan_wigner()`](https://docs.pennylane.ai/en/stable/code/api/pennylane.jordan_wigner.html) feature.

I think the PennyLane demo on [mapping Fermionic Hamiltonians to qubit Hamiltonians](https://pennylane.ai/qml/demos/tutorial_mapping) has exactly what you’re looking for, including a section on [energy calculation](https://pennylane.ai/qml/demos/tutorial_mapping#energy-calculation).

I hope this helps, and let us know if you have any follow up questions!