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Determining the low-energy eigenspectra of quantum many-body systems is a long-standing challenge in physics. In this work, we solve this problem by introducing two novel algorithms to determine low-energy eigenstates based on a compact…

Strongly Correlated Electrons · Physics 2023-05-26 Xuan Li , Zongsheng Zhou , Guanglei Xu , Runze Chi , Yibin Guo , Tong Liu , Haijun Liao , Tao Xiang

Quantum machine learning (QML) leverages quantum states for data encoding, with key approaches being explicit models that use parameterized quantum circuits and implicit models that use quantum kernels. Implicit models often have lower…

Quantum Physics · Physics 2025-12-08 Akimoto Nakayama , Hayata Morisaki , Kosuke Mitarai , Hiroshi Ueda , Keisuke Fujii

In this study, we propose quantum annealing-enhanced Markov Chain Monte Carlo (QAEMCMC), where QA is integrated into the MCMC subroutine. QA efficiently explores low-energy configurations and overcomes local minima, enabling the generation…

Quantum Physics · Physics 2025-02-13 Shunta Arai , Tadashi Kadowaki

Variational algorithms for strongly correlated chemical and materials systems are one of the most promising applications of near-term quantum computers. We present an extension to the variational quantum eigensolver that approximates the…

Quantum Physics · Physics 2020-08-26 William J. Huggins , Joonho Lee , Unpil Baek , Bryan O'Gorman , K. Birgitta Whaley

In this work, we propose a reduced basis method for efficient solution of parametric linear systems. The coefficient matrix is assumed to be a linear matrix-valued function that is symmetric and positive definite for admissible values of…

Numerical Analysis · Mathematics 2021-09-28 Antti Autio , Antti Hannukainen

Quantum many-body control is a central milestone en route to harnessing quantum technologies. However, the exponential growth of the Hilbert space dimension with the number of qubits makes it challenging to classically simulate quantum…

Quantum Physics · Physics 2023-07-26 Friederike Metz , Marin Bukov

Accurate state preparation is a critical bottleneck in many quantum algorithms, particularly those for ground state energy estimation. Even in fault-tolerant quantum computing, preparing a quantum state with sufficient overlap to the…

Quantum Physics · Physics 2025-10-07 Gwonhak Lee , Minhyeok Kang , Jungsoo Hong , Stepan Fomichev , Joonsuk Huh

Quantum machine learning algorithms, the extensions of machine learning to quantum regimes, are believed to be more powerful as they leverage the power of quantum properties. Quantum machine learning methods have been employed to solve…

Computational Physics · Physics 2021-06-01 Shree Hari Sureshbabu , Manas Sajjan , Sangchul Oh , Sabre Kais

Variational quantum algorithms (VQAs) represent a promising pathway toward achieving practical quantum advantage on near-term hardware. Despite this promise, for generic, expressive ans\"atze, their scalability is critically hindered by…

Quantum Physics · Physics 2026-02-26 Chenfeng Cao , Yeqing Zhou , Swamit Tannu , Nic Shannon , Robert Joynt

We propose a hybrid quantum-classical algorithm for approximating the ground state and ground state energy of a Hamiltonian. Once the Ansatz has been decided, the quantum part of the algorithm involves the calculation of two overlap…

Quantum Physics · Physics 2020-10-13 Kishor Bharti

{Many-body quantum states at thermal equilibrium are ubiquitous in nature. Investigating their dynamical properties is a formidable task due to the complexity of the Hilbert space they live in. Quantum computers may have the potential to…

Quantum Physics · Physics 2024-07-25 Mirko Consiglio , Tony J. G. Apollaro

In this work, we present a multiple-scale perturbation technique suitable for the study of open quantum systems, which is easy to implement and in few iterative steps allows us to find excellent approximate solutions. For any time-local…

Quantum Physics · Physics 2019-04-30 D. N. Bernal-García , B. A. Rodríguez , H. Vinck-Posada

Large, sparse linear systems are pervasive in modern science and engineering, and Krylov subspace solvers are an established means of solving them. Yet convergence can be slow for ill-conditioned matrices, so practical deployments usually…

This paper is an algorithmic study of quantum phase estimation with multiple eigenvalues. We present robust multiple-phase estimation (RMPE) algorithms with Heisenberg-limited scaling. The proposed algorithms improve significantly from the…

Quantum Physics · Physics 2023-10-26 Haoya Li , Hongkang Ni , Lexing Ying

Currents through quantum systems may probe non-analyticities in quantum-critical many-body ground states. For a large class of dissipative quantum critical systems we show that it is possible to obtain the reduced system dynamics in the…

Statistical Mechanics · Physics 2020-05-19 C. W. Wächtler , G. Schaller

As more practical and scalable quantum computers emerge, much attention has been focused on realizing quantum supremacy in machine learning. Existing quantum ML methods either (1) embed a classical model into a target Hamiltonian to enable…

Quantum Physics · Physics 2022-10-05 Zhihao Zhang , Zhuoming Chen , Heyang Huang , Zhihao Jia

In this paper, we focus on efficient methods to solve discretized linear systems obtained from eddy current optimal control problems in an all-at-once approach. We construct a new low-rank matrix equation method based on a special splitting…

Numerical Analysis · Mathematics 2024-03-19 Min-Li Zeng , Martin Stoll

Reinforcement Learning (RL) techniques have been increasingly applied in optimizing control systems. However, their application in quantum systems is hampered by the challenge of performing closed-loop control due to the difficulty in…

Quantum Physics · Physics 2024-02-08 Tanmay Neema , Susmit Jha , Tuhin Sahai

Quantum state preparation is vital in quantum computing and information processing. The ability to accurately and reliably prepare specific quantum states is essential for various applications. One of the promising applications of quantum…

Quantum Physics · Physics 2024-04-26 Yen-Jui Chang , Wei-Ting Wang , Hao-Yuan Chen , Shih-Wei Liao , Ching-Ray Chang

We investigate the quantum algorithm of Babbush et al. (arXiv:2303.13012v3) for simulating coupled harmonic oscillators, which promises exponential speedups over classical methods. Focusing on linearly connected oscillator chains, we bridge…