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arXiv 2206.04494quant-phcond-mat.str-elphysics.chem-ph
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通过模型空间量子虚时演化进行多态量子模拟

Multi-state quantum simulations via model-space quantum imaginary time evolution

Takashi Tsuchimochi, Yoohee Ryo, Siu Chung Tsang, Seiichiro L. Ten-no

AI总结:

提出模型空间量子虚时演化 MSQITE,并结合扩展 QLanczos 与虚时传播子平移,实现多基态、激发态及特定自旋态的稳定量子模拟。

摘要:

我们将模型空间框架引入量子虚时演化(QITE),以便利用量子计算机稳定估计基态和激发态。模型空间 QITE(MSQITE)通过保持模型空间的正交性,将其传播至精确空间,因此能够同时描述多个状态。量子 Lanczos(QLanczos)算法被扩展到 MSQITE,以加速收敛。研究发现,在模拟激发态时,本方案优于标准 QLanczos 以及近期提出的折叠谱 QITE。此外,我们证明,通过平移虚时传播子,可以有效消除自旋污染,从而高效捕获具有特定自旋量子数的激发态,而不会落入能量更低的不同自旋态。我们还研究了 MSQITE 中采用的不同等级酉近似如何影响结果。通过对 H4 模型系统进行含噪模拟,证明了该算法相对于 QITE 的有效性。

英文摘要:

We introduce the framework of model space into quantum imaginary time evolution (QITE) to enable stable estimation of ground and excited states using a quantum computer. Model-space QITE (MSQITE) propagates a model space to the exact one by retaining its orthogonality, and hence is able to describe multiple states simultaneously. The quantum Lanczos (QLanczos) algorithm is extended to MSQITE to accelerate the convergence. The present scheme is found to outperform both the standard QLanczos and the recently proposed folded-spectrum QITE in simulating excited states. Moreover, we demonstrate that spin contamination can be effectively removed by shifting the imaginary time propagator, and thus excited states with a particular spin quantum number are efficiently captured without falling into the different spin states that have lower energies. We also investigate how different levels of the unitary approximation employed in MSQITE can affect the results. The effectiveness of the algorithm over QITE is demonstrated by noise simulations for the H4 model system.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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