Kim Yongbin, Krylov Anna I
Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States.
J Phys Chem A. 2023 Aug 10;127(31):6552-6566. doi: 10.1021/acs.jpca.3c02480. Epub 2023 Jul 28.
Near-term quantum devices promise to revolutionize quantum chemistry, but simulations using the current noisy intermediate-scale quantum (NISQ) devices are not practical due to their high susceptibility to errors. This motivated the design of NISQ algorithms leveraging classical and quantum resources. While several developments have shown promising results for ground-state simulations, extending the algorithms to excited states remains challenging. This paper presents two cost-efficient excited-state algorithms inspired by the classical Davidson algorithm. We implemented the Davidson method into the quantum self-consistent equation-of-motion unitary coupled-cluster (q-sc-EOM-UCC) excited-state method adapted for quantum hardware. The circuit strategies for generating desired excited states are discussed, implemented, and tested. We demonstrate the performance and accuracy of the proposed algorithms (q-sc-EOM-UCC/Davidson and its variational variant) by simulations of H, H, LiH, and HO molecules. Similar to the classical Davidson scheme, q-sc-EOM-UCC/Davidson algorithms are capable of targeting a small number of excited states of the desired character.
近期的量子设备有望彻底改变量子化学，但使用当前有噪声的中等规模量子（NISQ）设备进行模拟由于其对错误高度敏感而不实用。这促使了利用经典和量子资源的NISQ算法的设计。虽然一些进展已在基态模拟中显示出有希望的结果，但将算法扩展到激发态仍然具有挑战性。本文提出了两种受经典戴维森算法启发的具有成本效益的激发态算法。我们将戴维森方法应用于适用于量子硬件的量子自洽运动方程酉耦合簇（q-sc-EOM-UCC）激发态方法中。讨论、实现并测试了用于生成所需激发态的电路策略。我们通过对H、H₂、LiH和H₂O分子的模拟展示了所提出算法（q-sc-EOM-UCC/戴维森及其变分变体）的性能和准确性。与经典戴维森方案类似，q-sc-EOM-UCC/戴维森算法能够针对少量具有所需特征的激发态。
