Doubling the size of quantum selected configuration interaction based on seniority-zero space and its application to QC-QSCI-AFQMC

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Auteurs principaux: Yoshida, Yuichiro, Murokoshi, Takuma, Nakagawa, Rika, Mori, Chihiro, Katayama, Yuta, Kuroda, Naoya, Furukawa, Shigeki, Tagami, Hanae, Mizukami, Wataru
Format: Preprint
Publié: 2026
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author Yoshida, Yuichiro
Murokoshi, Takuma
Nakagawa, Rika
Mori, Chihiro
Katayama, Yuta
Kuroda, Naoya
Furukawa, Shigeki
Tagami, Hanae
Mizukami, Wataru
author_facet Yoshida, Yuichiro
Murokoshi, Takuma
Nakagawa, Rika
Mori, Chihiro
Katayama, Yuta
Kuroda, Naoya
Furukawa, Shigeki
Tagami, Hanae
Mizukami, Wataru
contents We propose doubly occupied configuration interaction-quantum selected configuration interaction (DOCI-QSCI), which samples from the seniority-zero space. While the use of this space effectively doubles the qubit budget, equaling the number of spatial orbitals, this sector restriction can compromise quantitative accuracy. To compensate for this, we expand sampled bitstrings via their Cartesian product into a larger space that includes seniority-breaking determinants. The resulting wave function is also proposed using the trial state in phaseless auxiliary-field quantum Monte Carlo (ph-AFQMC) to recover dynamical correlations across the full orbital space (DOCI-QSCI-AFQMC). We evaluate the proposed methods on the H6 chain, N2 dissociation, and the addition of singlet O2 to a BODIPY dye. For the H6 chain, DOCI-QSCI-AFQMC reproduces the accuracy of the level of the complete-active-space counterpart with the quantum device ibm kobe. For N2 and BODIPY-O2, with (14e, 28o) and up to (20e, 20o) active spaces, it yields reasonable results, whereas single-reference CCSD(T) fails qualitatively. These results demonstrate that the DOCI-QSCI doubles the orbital space accessible to conventional QSCI and subsequent ph-AFQMC post-processing delivers reasonably high accuracy.
format Preprint
id arxiv_https___arxiv_org_abs_2602_07912
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Doubling the size of quantum selected configuration interaction based on seniority-zero space and its application to QC-QSCI-AFQMC
Yoshida, Yuichiro
Murokoshi, Takuma
Nakagawa, Rika
Mori, Chihiro
Katayama, Yuta
Kuroda, Naoya
Furukawa, Shigeki
Tagami, Hanae
Mizukami, Wataru
Quantum Physics
Chemical Physics
We propose doubly occupied configuration interaction-quantum selected configuration interaction (DOCI-QSCI), which samples from the seniority-zero space. While the use of this space effectively doubles the qubit budget, equaling the number of spatial orbitals, this sector restriction can compromise quantitative accuracy. To compensate for this, we expand sampled bitstrings via their Cartesian product into a larger space that includes seniority-breaking determinants. The resulting wave function is also proposed using the trial state in phaseless auxiliary-field quantum Monte Carlo (ph-AFQMC) to recover dynamical correlations across the full orbital space (DOCI-QSCI-AFQMC). We evaluate the proposed methods on the H6 chain, N2 dissociation, and the addition of singlet O2 to a BODIPY dye. For the H6 chain, DOCI-QSCI-AFQMC reproduces the accuracy of the level of the complete-active-space counterpart with the quantum device ibm kobe. For N2 and BODIPY-O2, with (14e, 28o) and up to (20e, 20o) active spaces, it yields reasonable results, whereas single-reference CCSD(T) fails qualitatively. These results demonstrate that the DOCI-QSCI doubles the orbital space accessible to conventional QSCI and subsequent ph-AFQMC post-processing delivers reasonably high accuracy.
title Doubling the size of quantum selected configuration interaction based on seniority-zero space and its application to QC-QSCI-AFQMC
topic Quantum Physics
Chemical Physics
url https://arxiv.org/abs/2602.07912