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arXiv 2305.04783quant-phphysics.chem-ph
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折叠谱 VQE:一种用于计算分子激发态的量子计算方法

Folded Spectrum VQE : A quantum computing method for the calculation of molecular excited states

Lila Cadi Tazi, Alex J. W. Thom

AI总结:

本文提出 FS-VQE,通过折叠谱与泡利分组扩展 VQE,以较低成本直接计算目标能量附近的分子激发态,并在 H₂ 和 LiH 上达到化学精度。

摘要:

量子计算的最新发展为量子化学提供了潜在的新途径,因为量子计算机增强的计算能力可被用于自然地编码并求解电子结构问题。理论上精确的化学量子算法已经被提出(例如 Quantum Phase Estimation,量子相位估计),但当前含噪声中等规模量子设备(NISQ)能力有限,这推动了对资源需求较低的混合算法的发展。在此背景下,Variational Quantum Eigensolver(VQE,变分量子本征求解器)算法已被成功引入,作为计算小分子基态能量的有效方法。本研究考察 Folded Spectrum(FS,折叠谱)方法,将其作为 VQE 算法的扩展,用于计算分子激发态。该方法使得直接计算所选目标能量附近的激发态成为可能,并使用与基态计算相同的 ansatz(拟设)。受 Quantum Monte Carlo(量子蒙特卡洛)文献中基于方差的方法启发,FS 方法最小化能量方差,因此需要计算上代价高昂的平方哈密顿量。我们通过采用 Pauli grouping(泡利分组)过程来缓解这种可能较差的标度性,该过程识别可同时求值的相互对易泡利字符串集合。这使得计算成本显著降低。我们将 FS-VQE 方法应用于小分子(H₂、LiH),在理想量子模拟器上获得了全部具有化学精度的电子激发态。

英文摘要:

The recent developments of quantum computing present potential novel pathways for quantum chemistry, as the increased computational power of quantum computers could be harnessed to naturally encode and solve electronic structure problems. Theoretically exact quantum algorithms for chemistry have been proposed (e.g. Quantum Phase Estimation) but the limited capabilities of current noisy intermediate scale quantum devices (NISQ) motivated the development of less demanding hybrid algorithms. In this context, the Variational Quantum Eigensolver (VQE) algorithm was successfully introduced as an effective method to compute the ground state energy of small molecules. The current study investigates the Folded Spectrum (FS) method as an extension to the VQE algorithm for the computation of molecular excited states. It provides the possibility of directly computing excited states around a selected target energy, using the same ansatz as for the ground state calculation. Inspired by the variance-based methods from the Quantum Monte Carlo literature, the FS method minimizes the energy variance, thus requiring a computationally expensive squared Hamiltonian. We alleviate this potentially poor scaling by employing a Pauli grouping procedure, identifying sets of commuting Pauli strings that can be evaluated simultaneously. This allows for a significant reduction of the computational cost. We apply the FS-VQE method to small molecules (H$_2$,LiH), obtaining all electronic excited states with chemical accuracy on ideal quantum simulators.

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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