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With the advent and development of quantum computers, various quantum algorithms that can solve linear equations and eigenvalues faster than classical computers have been developed. The Harrow-Hassidim-Lloyd algorithm is an algorithm that…

Quantum Physics · Physics 2025-06-23 Hyunju Lee , Kyungtaek Jun

With the advent of quantum computers, many quantum computing algorithms are being developed. Solving linear systems is one of the most fundamental problems in almost all science and engineering. The Harrow-Hassidim-Lloyd algorithm, a…

Quantum Physics · Physics 2022-01-25 Kyungtaek Jun

Quantum state preparation is a critical task in quantum computing, particularly in fields such as quantum machine learning, Hamiltonian simulation, and quantum algorithm design. The depth of preparation circuit for the most general state…

Quantum Physics · Physics 2025-08-21 Yu Li , Guojing Tian , Xiaoyu He , Xiaoming Sun

Efficiently solving large-scale sparse linear systems poses a significant challenge in computational science, especially in fields such as physics, engineering, machine learning, and finance. Traditional classical algorithms face…

Quantum Physics · Physics 2024-10-04 Hakikat Singh

Quantum algorithms for probing ground-state properties of quantum systems require good initial states. Projection-based methods such as eigenvalue filtering rely on inputs that have a significant overlap with the low-energy subspace, which…

Quantum Physics · Physics 2024-04-10 Danial Motlagh , Modjtaba Shokrian Zini , Juan Miguel Arrazola , Nathan Wiebe

The quantum state discrimination problem is to distinguish between non-orthogonal quantum states. This problem has many applications in quantum information theory, quantum communication and quantum cryptography. In this paper a quantum…

Quantum Physics · Physics 2021-02-25 Doha A. Rizk , Ahmed Younes

Harrow, Hassidim, and Lloyd showed that for a suitably specified $N \times N$ matrix $A$ and $N$-dimensional vector $\vec{b}$, there is a quantum algorithm that outputs a quantum state proportional to the solution of the linear system of…

Quantum Physics · Physics 2017-12-27 Andrew M. Childs , Robin Kothari , Rolando D. Somma

We propose a natural application of Quantum Linear Systems Problem (QLSP) solvers such as the HHL algorithm to efficiently prepare highly excited interior eigenstates of physical Hamiltonians in a variational and targeted manner. This is…

Quantum Physics · Physics 2023-10-13 Shao-Hen Chiew , Leong-Chuan Kwek

Quantum state preparation is a fundamental component of quantum algorithms, particularly in quantum machine learning and data processing, where classical data must be encoded efficiently into quantum states. Existing amplitude encoding…

Quantum Physics · Physics 2026-02-11 Carsten Blank , Israel F. Araujo

Solving linear systems of equations plays a fundamental role in numerous computational problems from different fields of science. The widespread use of numerical methods to solve these systems motivates investigating the feasibility of…

A hybrid quantum-classical algorithm is a computational scheme in which quantum circuits are used to extract information that is then processed by a classical routine to guide subsequent quantum operations. These algorithms are especially…

Quantum Physics · Physics 2025-09-03 Alon Levi , Ziv Ossi , Eliahu Cohen , Amit Te'eni

We give a classical algorithm for linear regression analogous to the quantum matrix inversion algorithm [Harrow, Hassidim, and Lloyd, Physical Review Letters'09, arXiv:0811.3171] for low-rank matrices [Wossnig, Zhao, and Prakash, Physical…

Data Structures and Algorithms · Computer Science 2022-07-06 András Gilyén , Zhao Song , Ewin Tang

In stochastic optimization problems using noisy zeroth-order (ZO) oracles only, the randomized counterpart of the Kiefer-Wolfowitz-type method is widely used to estimate the gradient. Existing algorithms generate randomized perturbation…

Optimization and Control · Mathematics 2020-11-30 Jingyi Zhu

The Harrow, Hassidim, Lloyd (HHL) algorithm is a quantum algorithm expected to accelerate solving large-scale linear ordinary differential equations (ODEs). To apply the HHL to non-linear problems such as chemical reactions, the system must…

Numerical Analysis · Mathematics 2022-07-06 Takaki Akiba , Youhi Morii , Kaoru Maruta

State preparation is a cornerstone of quantum technologies, underpinning applications in computation, communication, and sensing. Its importance becomes even more pronounced in non-Markovian open quantum systems, where environmental memory…

Quantum Physics · Physics 2026-05-29 Ritik Sareen , Akram Youssry , Alberto Peruzzo

We present a classical enhancement to improve the accuracy of the Hybrid variant (Hybrid HHL) of the quantum algorithm for solving linear systems of equations proposed by Harrow, Hassidim, and Lloyd (HHL). We achieve this by using higher…

Quantum Physics · Physics 2024-11-12 Jack Morgan , Eric Ghysels , Hamed Mohammadbagherpoor

In this paper, we model and solve a fundamental power system problem, i.e., DC power flow, using a practical quantum computer. The Harrow-Hassidim-Lloyd (HHL) quantum algorithm is used to solve the DC power flow problem. The HHL algorithm…

Quantum Physics · Physics 2020-10-07 Rozhin Eskandarpour , Kumar Ghosh , Amin Khodaei , Liuxi Zhang , Aleksi Paaso , Shay Bahramirad

Preparing the ground state of a system is an important task in physics. We propose a quantum algorithm for preparing the ground state of a physical system that can be simulated on a quantum computer. The system is coupled to an ancillary…

Quantum Physics · Physics 2018-05-14 Hefeng Wang

Computational Fluid Dynamics simulations are crucial in industrial applications but require extensive computational resources, particularly for extreme turbulent regimes. While classical digital approaches remain the standard, quantum…

Quantum Physics · Physics 2025-04-18 Francesco Turro , Alessandra Lignarolo , Daniele Dragoni

By using the quantum computing the properties of hypernuclei ${}^5_{\Lambda}$He, ${}^{\ 6}_{{\Lambda\Lambda}}$He and ${}^9_{\Lambda}$Be can be investigated within microscopic cluster model. Our approach combines quantum neural network (QNN)…

Quantum Physics · Physics 2025-07-02 Hantao Zhang , Dong Bai , Zhongzhou Ren