Ab initio molecular dynamics (AIMD) is a powerful tool to predict properties of molecular and condensed matter systems. The quality of this procedure is based on accurate electronic structure calculations. The development of quantum processors has shown great potential for the efficient evaluation of accurate ground and excited state energies of molecular systems, opening up new avenues for molecular dynamics simulations. In this work we address the use of variational quantum algorithms for the calculation of accurate atomic forces to be used in AIMD. In particular, we provide solutions for the alleviation of the statistical noise associated to the measurements of the expectation values of energies and forces, as well as schemes for the mitigation of the hardware noise sources (in particular, gate infidelities, qubit decoherence and readout errors). Despite the relative large error in the calculation of the potential energy, our results show that the proposed algorithms can provide reliable MD trajectories in the microcanonical (constant energy) ensemble. Further, exploiting the intrinsic noise arising from the quantum measurement process, we also propose a Langevin dynamics algorithm for the simulation of canonical, i.e., constant temperature, dynamics. Both algorithms (microcanonical and canonical) are applied to the simulation of simple molecular systems such as H2 and H3+. Finally, we also provide results for the dynamics of H2 obtained with IBM quantum computer ibmq_athens.
Revealing microcanonical phases and phase transitions of strongly correlated electrons via time-averaged classical shadows
量子计算机和模拟器有望使强关联量子系统的研究成为可能。然而，令人惊讶的是，他们很难计算基态。然而，它们可以有效地计算封闭量子系统的动力学。提出了一种从量子动力学出发研究强关联电子量子热力学的方法。我们定义了时间平均经典阴影（TACS），并证明了它是冯诺依曼系综的时间平均密度矩阵的经典阴影（CS）。然后，我们表明，扩散映射，一个无监督的机器学习算法，可以有效地学习相图和相变的一维横向场伊辛模型都为基态使用CS \emph{and state trajectories}使用TACS。它从状态轨迹中学习特征，这些特征似乎是沿着微正则相图中的路径拍摄的总共90，000个镜头的磁化率和熵。我们的研究结果表明，量子模拟器的少量发射可以产生具有量子优势的量子热力学数据。
Energy-filtered random-phase states as microcanonical thermal pure quantum states
提出了一种通过引入一个纯量子态--能量过滤随机相位态来计算微正则系综量子多体系统有限温度性质的方法，这也是近期量子计算机的一个潜在应用.在我们的形式主义中，微正则系综由两个参数指定，即，系统的能量及其相关的能量窗口。因此，态密度被表示为以目标能量为中心的高斯和，其扩展对应于能量窗口的宽度。然后，我们表明，热力学量，如熵和温度的计算通过评估的时间演化算子的跟踪和跟踪的时间演化算子乘以系统的哈密顿量。我们还描述了如何使用适合量子计算的随机对角酉电路来评估这些迹线。代表我们的微正则系综的纯量子态与Wall和Neuhauser为滤波器对角化方法[M. R. Wall和D. Neuhauser，J.Chem.Phys.102，8011（1995）]，因此我们将其称为能量过滤的随机相位状态。能量过滤的随机相位状态本质上是时间演化状态的傅里叶变换，其初始状态被准备为随机相位状态，并且傅里叶变换的时间积分中的截止时间设置能量窗口的宽度的倒数。所提出的方法是通过计算的热力学量的一维自旋1/2海森堡模型的小集群高达28量子比特的数值，表明该方法是最有效的目标能量周围的密集分布的能量本征态。
Quantum Simulation of Magnetic Materials: from Ab-Initio to NISQ
HQS Quantum Simulations GmbH（HQS量子模拟有限公司）；Department of High Performance Computing, Institute of Software Technology, German Aerospace Center (DLR)（德国航空航天中心软件技术研究所高性能计算部）
Fault-tolerant quantum simulation of the Pauli-Breit Hamiltonian for ab initio hybrid quantum-classical molecular design with applications to photodynamic therapy
Improved precision scaling for simulating coupled quantum-classical dynamics
University of Toronto（多伦多大学）；Pacific Northwest National Laboratory（太平洋西北国家实验室）；Canadian Institute for Advanced Studies（加拿大高级研究所）；Boehringer Ingelheim（勃林格殷格翰）；University of Innsbruck（因斯布鲁克大学）
An Ab initio Framework for Simulating Ultrafast Nonlinear Cavity Quantum Electrodynamics Spectra
School of Science, Hangzhou Dianzi University（杭州电子科技大学理学院）；Graduate School of Computer and Information Sciences, Hosei University（法政大学计算机与信息科学研究生院）；Key laboratory of colloid and interface chemistry, School of Chemistry and Chemical Engineering, Shandong University（山东大学化学与化工学院胶体与界面化学重点实验室）
Error-corrected phase estimation averaged over variable grids on a trapped-ion quantum computer: hyperacuity spectra of a CO molecule adsorbed onto $χ$-Fe$_5$C$_2$
Quemix Inc.（Quemix公司）；Department of Physics, The University of Tokyo（东京大学物理系）；Business Creation Sector R&D Center, MITSUI KINZOKU COMPANY, LIMITED（三井金属株式会社业务创造部门研发中心）；Quantum Materials and Applications Research Center, National Institutes for Quantum Science and Technology (QST)（量子科学技术研究机构量子材料与应用程序研究中心）
Shadow tomography for classical tensor network simulations
Marcus Center for Theoretical Chemistry, California Institute of Technology（加州理工学院马库斯理论化学中心）；Division of Chemistry and Chemical Engineering, California Institute of Technology（加州理工学院化学与化学工程系）
The Complexity of Thermalization in Finite Quantum Systems
National Institute of Standards & Technology（美国国家标准与技术研究院）；University of Maryland, College Park（马里兰大学帕克分校）；Joint Quantum Institute（联合量子研究所）；Department of Physics, University of Maryland, College Park（马里兰大学帕克分校物理系）；Department of Computer Science and Institute for Advanced Computer Studies, University of Maryland, College Park（马里兰大学帕克分校计算机科学与高级计算机科学研究所）
