Excited state calculations using variational quantum eigensolver with spin-restricted ansätze and automatically-adjusted constraints

The ground and excited state calculations at key geometries, such as the Frank-Condon (FC) and the conical intersection (CI) geometries, are essential for understanding photophysical properties. To compute these geometries on noisy intermediate-scale quantum devices, we proposed a strategy that comb...

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Bibliographic Details
Published in:arXiv.org 2022-12
Main Authors: Gocho, Shigeki, Nakamura, Hajime, Kanno, Shu, Gao, Qi, Kobayashi, Takao, Inagaki, Taichi, Hatanaka, Miho
Format: Article
Language:English
Subjects:
Accuracy
Algorithms
Constraints
Coordination compounds
Ethylene
Excitation
Optimization
Phenols
Potential energy
Quantum chemistry
Quantum computers
Quantum computing
Self consistent fields
Wave functions
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Summary:The ground and excited state calculations at key geometries, such as the Frank-Condon (FC) and the conical intersection (CI) geometries, are essential for understanding photophysical properties. To compute these geometries on noisy intermediate-scale quantum devices, we proposed a strategy that combined a chemistry-inspired spin-restricted ansatz and a new excited state calculation method called the variational quantum eigensolver under automatically-adjusted constraints (VQE/AC). Unlike the conventional excited state calculation method, called the variational quantum deflation, the VQE/AC does not require the pre-determination of constraint weights and has the potential to describe smooth potential energy surfaces. To validate this strategy, we performed the excited state calculations at the FC and CI geometries of ethylene and phenol blue at the complete active space self-consistent field (CASSCF) level of theory, and found that the energy errors were at most 2 kcal mol\(^{-1}\) even on the ibm_kawasaki device.
ISSN:2331-8422