发表机构
Korea Institute of Science and Technology (KIST); Korea University of Science and Technology; Kyung Hee University; Gwangju Institute of Science and Technology（韩国科学技术院; 韩国科学技术院; 庆熙大学; 光州科学技术院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
研究针对NISQ硬件VQE多局限于基态的问题，利用光子轨道角动量qudits实现SSVQE，估算HeH⁺分子和海森堡链的激发态能量，确立光子qudits是高效的激发态量子模拟途径。
AI 中文摘要
准确的激发态能量对于解释荧光和光化学过程至关重要，但噪声中等规模量子（NISQ）硬件上的变分量子本征求解器（VQE）大多局限于基态。子空间搜索 VQE（SSVQE）提供了一种适用于 NISQ 的激发态求解途径，无需基于辅助量子比特的重叠测量，但由于需要在共享变分幺正操作下相干制备和操控多个正交基态，一直缺乏实验演示。本文通过将正交 qudit 态编码在单光子的轨道角动量中并优化共享变分电路，在光子平台上实现了 SSVQE。我们估算了四维 HeH⁺分子和八维海森堡链的激发态能量，从而证明了在高维希尔伯特空间中可扩展的激发态本征求解。我们的结果确立了光子 qudits 是实现激发态量子模拟的资源高效途径。
英文摘要
Accurate excited state energies are essential for interpreting fluorescence and photochemical processes, yet variational quantum eigensolvers (VQEs) on noisy intermediate-scale quantum (NISQ) hardware have largely been confined to ground states. Subspace-search VQE (SSVQE) offers a NISQ-friendly route to excited states without ancilla-based overlap measurements, however it has lacked an experimental demonstration since it requires the coherent preparation and manipulation of multiple orthogonal basis states under a shared variational unitary. Here we realize SSVQE on a photonic platform by encoding orthogonal qudit states in the orbital angular momentum of single photons and optimizing a shared variational circuit. We estimate excited state energies for a four-dimensional $\rm{HeH^+}$ molecule and an eight-dimensional Heisenberg chain, thereby demonstrating scalable excited state eigensolving in a high-dimensional Hilbert space. Our results establish photonic qudits as a resource-efficient pathway to excited state quantum simulation.
Comments8 pages, 4 figures, Supplementary Note
Journal refnpj Quantum Information (2026)
DOI：10.1038/s41534-026-01380-2
