Analytical Nonadiabatic Couplings and Gradients within the State-Averaged Orbital-Optimized Variational Quantum Eigensolver

Saad Yalouz*, Emiel Koridon, Bruno Senjean, Benjamin Lasorne, Francesco Buda, Lucas Visscher

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

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Abstract

We introduce several technical and analytical extensions to our recent state-averaged orbital-optimized variational quantum eigensolver (SA-OO-VQE) algorithm (see Yalouz et al. Quantum Sci. Technol. 2021, 6, 024004). Motivated by the limitations of current quantum computers, the first extension consists of an efficient state-resolution procedure to find the SA-OO-VQE eigenstates, and not just the subspace spanned by them, while remaining in the equi-ensemble framework. This approach avoids expensive intermediate resolutions of the eigenstates by postponing this problem to the very end of the full algorithm. The second extension allows for the estimation of analytical gradients and nonadiabatic couplings, which are crucial in many practical situations ranging from the search of conical intersections to the simulation of quantum dynamics, in, for example, photoisomerization reactions. The accuracy of our new implementations is demonstrated on the formaldimine molecule CH2NH (a minimal Schiff base model relevant for the study of photoisomerization in larger biomolecules), for which we also perform a geometry optimization to locate a conical intersection between the ground and first-excited electronic states of the molecule.

Original languageEnglish
Pages (from-to)776-794
Number of pages19
JournalJournal of chemical theory and computation
Volume18
Issue number2
Early online date14 Jan 2022
DOIs
Publication statusPublished - 8 Feb 2022

Bibliographical note

Funding Information:
S.Y. acknowledges support from The Netherlands Organization for Scientific Research (NWO/OCW), and the Interdisciplinary Thematic Institute ITI-CSC via the IdEx Unistra (ANR-10-IDEX-0002) within the program Investissement d’Avenir. E.K. acknowledges support from Shell Global Solutions BV.

Publisher Copyright:
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Funding

S.Y. acknowledges support from The Netherlands Organization for Scientific Research (NWO/OCW), and the Interdisciplinary Thematic Institute ITI-CSC via the IdEx Unistra (ANR-10-IDEX-0002) within the program Investissement d’Avenir. E.K. acknowledges support from Shell Global Solutions BV.

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