Many physical and chemical processes in the condensed phase environment exhibit non-Markovian quantum dynamics. As such simulations are challenging on classical computers, we developed a variational quantum algorithm that is capable of simulating non-Markovian dynamics on NISQ devices. We used a quantum system linearly coupled to its harmonic bath as the model Hamiltonian. The non-Markovianity is captured by introducing auxiliary variables from the bath trajectories. With Monte Carlo sampling of the bath degrees of freedom, finite temperature dynamics is produced. We validated the algorithm on the simulator and demonstrated its performance on the IBM quantum device. The framework developed is naturally adapted to any anharmonic bath with non-linear coupling to the system, and is also well suited for simulating spin chain dynamics in a dissipative environment.
Error Propagation Theory for Variational Non-Markovian Open Quantum Dynamics
Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China（中国科学技术大学微尺度物质科学国家研究中心）；State Key Laboratory of Porous Materials for Separation and Conversion & MOE Key Laboratory of Computational Physical Sciences & Department of Chemistry, Fudan University（复旦大学化学系多孔材料分离转化国家重点实验室及计算物理科学教育部重点实验室）；Hefei National Laboratory（合肥国家实验室）
Simulating non-Markovian open quantum dynamics by exploiting physics-informed neural network
Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China（中国科学技术大学微尺度物质科学国家研究中心）；State Key Laboratory of Porous Materials for Separation and Conversion & MOE Key Laboratory of Computational Physical Sciences & Department of Chemistry, Fudan University（复旦大学化学系多孔材料分离转化国家重点实验室及计算物理教育部重点实验室）；Hefei National Laboratory（合肥国家实验室）
How an Equi-ensemble Description Systematically Outperforms the Weighted-ensemble Variational Quantum Eigensolver
ICGM, Université de Montpellier, CNRS, ENSCM（蒙彼利埃大学，法国国家科学研究中心，国立高等化学学校）；Dipartimento di Ingegneria e Scienze dell’Informazione e Matematica, Università dell’Aquila（阿奎拉大学）
Post-Markovian quantum master equations from classical environment fluctuations
在本文中，我们证明了两个常用的唯象后马尔可夫量子主方程可以推导出没有使用任何微扰近似。一个系统耦合到一个环境的特点是自经典的组态波动，后者服从马尔可夫动力学，定义了底层的物理模型。Shabani-Lidar方程[A. Shabani和D. A. Lidar，Phys.Rev.A71，020101（R）（2005）]及其相关的近似积分-微分核主方程是通过追踪两个不同的二分马尔可夫Lindblad动力学得到的，其中环境波动由附属系统考虑。此外，我们还找到了非马尔可夫系统动力学可以用测量轨迹系综来解释的条件，并给出了一种非马尔可夫量子跳跃方法。与最近的分析相反[L。Mazzola，E. M. Laine，H. P. Breuer，S. Maniscalco和J. Piilo，Phys.Rev.A81，062120（2010）]，我们还证明了这些主方程，即使具有指数记忆函数，也可能导致非马尔可夫效应，例如如果哈密顿系统不与耗散动力学耦合，则信息的环境到系统回流。
Open system dynamics with non-Markovian quantum jumps
我们详细讨论了如何用量子跳跃来描述非马尔可夫开放系统动力学[J. Piilo et al.，物理修订信函100，180402（2008）]。我们的结果表明，它是可能的有一个跳跃的描述包含在物理希尔伯特空间的约化系统。发展的非马尔可夫量子跳跃（NMQJ）方法是马尔可夫蒙特卡罗波函数（MCWF）方法到非马尔可夫制度的推广。该方法不仅精确地保持了密度矩阵中的概率和状态向量的范数，而且对非马尔可夫动力学有了新的认识。纯态系综的动力学说明了时间局域主方程如何描述记忆效应，以及系统的当前状态如何携带其早期状态的信息。我们的方法解决了马尔可夫MCWF方法在非马尔可夫制度的负跳概率的问题，通过定义相应的跳跃过程的正概率。结果表明，在非马尔可夫开放系统的理论描述中，由于记忆的存在，会发生量子跳跃，从而重新产生看似丢失的叠加态。
Ensemble-learning error mitigation for variational quantum shallow-circuit classifiers
Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China（电子科技大学基础与前沿研究院）；The Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology（香港科技大学电子与计算机工程学系）；Graduate School of China Academy of Engineering Physics（中国工程物理研究院研究生院）
Classical Ensembles of Single-Qubit Quantum Variational Circuits for Classification
University of KwaZulu-Natal（夸祖鲁-纳塔尔大学）；National Institute for Theoretical and Computational Science (NITheCS)（理论与计算科学国家研究所）；Centre for Artificial Intelligence Research (CAIR)（人工智能研究中心）；Stellenbosch University（斯坦伦布什大学）
Analysis of Superradiance-Based Quantum Metrology under Independent Markovian Pure Dephasing
School of Fundamental Science and Technology, Keio University（庆应义塾大学基础理工学部）；Department of Electrical, Electronic, and Communication Engineering, Faculty of Advanced Science and Engineering, Chuo University（中央大学理工学府电气电子通信工程系）；Department of Physics, Simon Fraser University（西蒙菲莎大学物理系）；Center for Spintronics Research Network, Keio University（庆应义塾大学自旋电子学研究网络中心）
Nonequilibrium thermometry via an ensemble of initially correlated qubits
Istituto Nazionale di Ottica del Consiglio Nazionale delle Ricerche (CNR-INO)（意大利国家光学研究所）；Department of Physics and Astronomy, Università di Firenze（佛罗伦萨大学物理与天文学系）；European Laboratory for Non-linear Spectroscopy, Università di Firenze（佛罗伦萨大学欧洲非线性光谱学实验室）
