Quantum Equation-of-Motion Method with Single, Double, and Triple Excitations

2024/06/15 by Yuhan Zheng, Zheng, Yuhan, Jie Liu +5 · 1 citation
Computer Science · Physics and Astronomy · #FOS: Physical sciences #Quantum Information and Cryptography #Quantum Physics (quant-ph) #Quantum optics and atomic interactions #Spectroscopy and Quantum Chemical Studies

paper · pdf · doi:10.48550/arxiv.2406.10680

openalex publication_date 2024/06/15 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

The quantum equation-of-motion (qEOM) method with singles and doubles has been suggested to study electronically excited states while it fails to predict the excitation energies dominated by double excitations. In this work, we present an efficient implementation of the qEOM method with single, double and triple excitations. In order to reduce the computational complexity, we utilize the point group symmetry and perturbation theory to screen triple excitation operators, and the scaling is reduced from N_o⁶N_v⁶ to N_o⁵N_v⁵. Furthermore, we introduce a perturbation correction to the excitation energy to account for the effect of ignored triple excitation operators. We apply this method to study challenging cases, for which the qEOM-SD method exhibits large errors, such as the 2 ¹Δ excited state of \rmCH⁺ and the 2 ¹Σ state of \rmH₈ molecule. Our new method yields the energy errors less than 0.18 eV.

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• Quantum Simulations of Battery Electrolytes with VQE-qEOM and SQD: Active-Space Design, Dissociation, and Excited States of LiPF₆, NaPF₆, and FSI Salts

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