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arXiv 2104.03409quant-phcond-mat.mtrl-sci
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量子计算机能带理论的系统变分方法

A systematic variational approach to band theory in a quantum computer

Kyle Sherbert, Frank Cerasoli, Marco Buongiorno Nardelli

摘要:

量子计算机有望彻底改变我们模拟分子的能力,而基于云的硬件越来越多地被研究人员所使用。诸如量子相位估计和变分量子本征求解器之类的算法正在被积极开发并在小型系统中得到验证。然而,极其有限的量子位数和低保真度严重限制了有用的应用,特别是在结晶阶段,其中难以开发紧凑的轨道基础。为了解决这个困难,我们提出了一个混合量子经典算法来解决能带结构的任何周期性系统所描述的一个适当的紧束缚模型。我们展示了我们的算法,通过计算一个简单的立方晶体的能带结构与一个$s$和三个$p$轨道每个网站(一个简单的模型,钋)使用模拟器越来越逼真的噪声水平,并最终在IBM量子计算机上的计算。我们的研究结果表明,该算法是可靠的,在低噪声设备,功能与当今的噪声量子计算机的精度低,并显示复杂性,规模为$Ω(M^3)$与每个单元格的紧束缚轨道的数量$M$,类似于其经典的同行。我们的模拟提供了对“量子”思维的新见解,并展示了当今正在积极开发的算法如何在特殊情况下进行优化,例如能带结构计算。

英文摘要:

Quantum computers promise to revolutionize our ability to simulate molecules, and cloud-based hardware is becoming increasingly accessible to a wide body of researchers. Algorithms such as Quantum Phase Estimation and the Variational Quantum Eigensolver are being actively developed and demonstrated in small systems. However, extremely limited qubit count and low fidelity seriously limit useful applications, especially in the crystalline phase, where compact orbital bases are difficult to develop. To address this difficulty, we present a hybrid quantum-classical algorithm to solve the band structure of any periodic system described by an adequate tight-binding model. We showcase our algorithm by computing the band structure of a simple-cubic crystal with one $s$ and three $p$ orbitals per site (a simple model for Polonium) using simulators with increasingly realistic levels of noise and culminating with calculations on IBM quantum computers. Our results show that the algorithm is reliable in a low-noise device, functional with low precision on present-day noisy quantum computers, and displays a complexity that scales as $Ω(M^3)$ with the number $M$ of tight-binding orbitals per unit-cell, similarly to its classical counterparts. Our simulations offer a new insight into the ``quantum'' mindset and demonstrate how the algorithms under active development today can be optimized in special cases, such as band structure calculations.

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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