Numerical Optimization Strategies for the Variational Hamiltonian Ansatz in Noisy Quantum Environments

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Hauptverfasser: Illésová, S., Novák, V., Bezděk, T., Possel, C., Beseda, M.
Format: Preprint
Veröffentlicht: 2025
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author Illésová, S.
Novák, V.
Bezděk, T.
Possel, C.
Beseda, M.
author_facet Illésová, S.
Novák, V.
Bezděk, T.
Possel, C.
Beseda, M.
contents The prevalence of variational methods in near-term quantum computing makes optimizer choice critical, yet selection is frequently intuition-based. We therefore present a systematic benchmark of eight classical optimization algorithms for variational quantum chemistry using the truncated Variational Hamiltonian Ansatz. Performance is evaluated on H$_2$, H$_4$, and LiH in both full and active-space representations under noiseless and finite-shot sampling noise. Sampling noise substantially reshapes cost landscapes, induces wandering near minima, and flips optimizer rankings: gradient-based methods perform best in noiseless simulations, whereas population-based optimizers, particularly CMA-ES, show greater robustness under finite-shot noise. Optimizer performance is strongly problem dependent: Hartree-Fock initialization aids small systems, but its advantage diminishes with system size. Also, we observe that finite shot sampling frequently violates the lower bound given by the variational principle, a principle that cannot be strictly held in the presence of noise. By exploiting the guaranteed convergence of Evolution Strategies to a steady state distribution defined by the noise floor, we utilize the symmetry of these violations to achieve energy estimation precision beyond the intrinsic sampling limit.
format Preprint
id arxiv_https___arxiv_org_abs_2505_22398
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Numerical Optimization Strategies for the Variational Hamiltonian Ansatz in Noisy Quantum Environments
Illésová, S.
Novák, V.
Bezděk, T.
Possel, C.
Beseda, M.
Quantum Physics
Numerical Analysis
81P68, 90C56
G.1.6; J.2
The prevalence of variational methods in near-term quantum computing makes optimizer choice critical, yet selection is frequently intuition-based. We therefore present a systematic benchmark of eight classical optimization algorithms for variational quantum chemistry using the truncated Variational Hamiltonian Ansatz. Performance is evaluated on H$_2$, H$_4$, and LiH in both full and active-space representations under noiseless and finite-shot sampling noise. Sampling noise substantially reshapes cost landscapes, induces wandering near minima, and flips optimizer rankings: gradient-based methods perform best in noiseless simulations, whereas population-based optimizers, particularly CMA-ES, show greater robustness under finite-shot noise. Optimizer performance is strongly problem dependent: Hartree-Fock initialization aids small systems, but its advantage diminishes with system size. Also, we observe that finite shot sampling frequently violates the lower bound given by the variational principle, a principle that cannot be strictly held in the presence of noise. By exploiting the guaranteed convergence of Evolution Strategies to a steady state distribution defined by the noise floor, we utilize the symmetry of these violations to achieve energy estimation precision beyond the intrinsic sampling limit.
title Numerical Optimization Strategies for the Variational Hamiltonian Ansatz in Noisy Quantum Environments
topic Quantum Physics
Numerical Analysis
81P68, 90C56
G.1.6; J.2
url https://arxiv.org/abs/2505.22398