Optimizing fermionic Hamiltonians with classical interactions

Fuente: arXiv
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Autores principales: Stroeks, Maarten, Terhal, Barbara M., Herasymenko, Yaroslav
Formato: Preprint
Publicado: 2025
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author Stroeks, Maarten
Terhal, Barbara M.
Herasymenko, Yaroslav
author_facet Stroeks, Maarten
Terhal, Barbara M.
Herasymenko, Yaroslav
contents We consider the optimization problem (ground energy search) for fermionic Hamiltonians with classical interactions. This QMA-hard problem is motivated by the Coulomb electron-electron interaction being diagonal in the position basis, a fundamental fact that underpins electronic-structure Hamiltonians in quantum chemistry and condensed matter. We prove that fermionic Gaussian states achieve an approximation ratio of at least 1/3 for such Hamiltonians, independent of sparsity. This shows that classical interactions are sufficient to prevent the vanishing Gaussian approximation ratio observed in SYK-type models. We also give efficient semi-definite programming algorithms for Gaussian approximations to several families of traceless and positive-semidefinite classically interacting Hamiltonians, with the ability to enforce a fixed particle number. The technical core of our results is the concept of a Gaussian blend, a construction for Gaussian states via mixtures of covariance matrices.
format Preprint
id arxiv_https___arxiv_org_abs_2510_02122
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Optimizing fermionic Hamiltonians with classical interactions
Stroeks, Maarten
Terhal, Barbara M.
Herasymenko, Yaroslav
Quantum Physics
We consider the optimization problem (ground energy search) for fermionic Hamiltonians with classical interactions. This QMA-hard problem is motivated by the Coulomb electron-electron interaction being diagonal in the position basis, a fundamental fact that underpins electronic-structure Hamiltonians in quantum chemistry and condensed matter. We prove that fermionic Gaussian states achieve an approximation ratio of at least 1/3 for such Hamiltonians, independent of sparsity. This shows that classical interactions are sufficient to prevent the vanishing Gaussian approximation ratio observed in SYK-type models. We also give efficient semi-definite programming algorithms for Gaussian approximations to several families of traceless and positive-semidefinite classically interacting Hamiltonians, with the ability to enforce a fixed particle number. The technical core of our results is the concept of a Gaussian blend, a construction for Gaussian states via mixtures of covariance matrices.
title Optimizing fermionic Hamiltonians with classical interactions
topic Quantum Physics
url https://arxiv.org/abs/2510.02122