论文标题
改善了分子系统的地面和激发态的量子假想时间演变的算法
Improved algorithms of quantum imaginary time evolution for ground and excited states of molecular systems
论文作者
论文摘要
量子假想的时间演化（Qite）是最近提出的量子古典杂种算法，可以保证达到最低系统状态。在这项研究中，我们对QITE进行了一些改进，主要关注分子应用。我们分析了逐阶的基础方程顺序的推导，并提出了理论上建立的修改。我们的结果清楚地表明了此处衍生的方程式的合理性，从而可以更好地近似单一的假想时间传播。我们还讨论了如何准确估计假想时间进化状态的规范，并将其应用于使用量子Lanczos算法的激发状态计算。最后，我们提出了折叠光谱QITE方案，作为对一般激发态模拟的QITE的直接扩展。所有这些发展的有效性通过无声的模拟来说明，从而进一步了解了量子算法的想象时间演变。
Quantum imaginary time evolution (QITE) is a recently proposed quantum-classical hybrid algorithm that is guaranteed to reach the lowest state of system. In this study, we present several improvements on QITE, mainly focusing on molecular applications. We analyze the derivation of the underlying QITE equation order-by-order, and suggest a modification that is theoretically well founded. Our results clearly indicate the soundness of the here-derived equation, enabling a better approximation of the imaginary time propagation by a unitary. We also discuss how to accurately estimate the norm of an imaginary-time-evolved state, and applied it to excited state calculations using the quantum Lanczos algorithm. Finally, we propose the folded-spectrum QITE scheme as a straightforward extension of QITE for general excited state simulations. The effectiveness of all these developments is illustrated by noiseless simulations, offering the further insights into quantum algorithms for imaginary time evolution.
