Han, Da Bean Hu, Kang-Min Lim, Hyang-Tag Kim, Hyun Woo 2026-02-26T05:30:13Z 2026-02-26T05:30:13Z 2026-02-26 2026-02 https://pubs.kist.re.kr/handle/201004/154372 Recent advances in quantum technologies have led to the development of several quantum algorithms for computing molecular energetics. However, most existing approaches are limited to determining ground-state energies with relatively few studies addressing multilevel systems. In this work, we explore two quantum algorithms capable of addressing multilevel molecular orbital (MO) energetics: the subspace search variational quantum eigensolver (SSVQE) and iterative quantum phase estimation (IQPE). To benchmark their performance, we employed an exactly solvable Hamiltonian derived from the Huckel method. Both SSVQE and IQPE successfully reproduced the MO energies. We further discussed quantum circuit design and measurement noise using SSVQE. We found out the critical influence of quantum circuit design on computational accuracy. By examining SSVQE under noisy conditions, we could discuss its feasibility for implementation on near-term quantum hardware. English American Chemical Society Exploring Huckel Molecular Orbital Energies through Variational and Phase Estimation Quantum Algorithms Article 10.1021/acs.jpclett.5c03857 1 The Journal of Physical Chemistry Letters, v.17, no.8, pp.2205 - 2212 The Journal of Physical Chemistry Letters 17 8 2205 2212 Y scie scopus 001691760700001 Chemistry, Physical Nanoscience & Nanotechnology Materials Science, Multidisciplinary Physics, Atomic, Molecular & Chemical Chemistry Science & Technology - Other Topics Materials Science Physics Article; Early Access COMPLEX