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Accurate computation of multiple eigenvalues of quantum Hamiltonians is essential in quantum chemistry, materials science, and molecular spectroscopy. Estimating excited-state energies is challenging for classical algorithms due to…

Quantum Physics · Physics 2026-05-22 Grzegorz Rajchel-Mieldzioć , Szymon Pliś , Emil Zak

Harrow-Hassidim-Lloyd algorithm (HHL) allows for the exponentially faster solution of a system of linear equations. However, this algorithm requires the postselection of an ancilla qubit to obtain the solution. This postselection makes the…

Quantum Physics · Physics 2023-11-10 D. V. Babukhin

Estimating the eigenstate properties of quantum systems is a long-standing, challenging problem for both classical and quantum computing. Existing universal quantum algorithms typically rely on ideal and efficient query models (e.g. time…

Quantum Physics · Physics 2026-01-21 Jinzhao Sun , Pei Zeng , Tom Gur , M. S. Kim

Recent advancements in quantum algorithms have reached a state where we can consider how to capitalize on quantum and classical computational resources to accelerate molecular resonance state identification. Here we identify molecular…

Quantum Physics · Physics 2026-03-26 Jingcheng Dai , Atharva Vidwans , Eric H. Wan , Alexander X. Miller , Micheline B. Soley

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

Large-scale eigenvalue problems pose a significant challenge to classical computers. While there are efficient quantum algorithms for unitary or Hermitian matrices, eigenvalue problems for non-normal matrices remain open in quantum…

Quantum Physics · Physics 2026-03-25 Honghong Lin , Yun Shang

We describe a quantum algorithm for preparing states that encode solutions of non-homogeneous linear partial differential equations. The algorithm is a continuous-variable version of matrix inversion: it efficiently inverts differential…

Quantum Physics · Physics 2019-09-11 Juan Miguel Arrazola , Timjan Kalajdzievski , Christian Weedbrook , Seth Lloyd

Quantum algorithms with a proven theoretical speedup over classical computation are rare. Among the most prominent is the Harrow-Hassidim-Lloyd (HHL) algorithm for solving sparse linear systems. Here, HHL is applied to encode melodic…

Quantum Physics · Physics 2026-04-24 Alexis Kirke

We propose a quantum inverse iteration algorithm which can be used to estimate the ground state properties of a programmable quantum device. The method relies on the inverse power iteration technique, where the sequential application of the…

Quantum Physics · Physics 2020-01-22 Oleksandr Kyriienko

We present a hybrid classical/quantum algorithm for efficiently solving the eigenvalue problem of many-particle Hamiltonians on quantum computers with limited resources by splitting the workload between classical and quantum processors.…

Quantum Physics · Physics 2022-03-01 John P. T. Stenger , Daniel Gunlycke , C. Stephen Hellberg

Solving linear systems and computing eigenvalues are two fundamental problems in linear algebra. For solving linear systems, many efficient quantum algorithms have been discovered. For computing eigenvalues, currently, we have efficient…

Quantum Physics · Physics 2020-09-22 Changpeng Shao

In this paper, we investigate a new extragradient algorithm for solving pseudomonotone equilibrium problems on Hadamard manifolds. The algorithm uses a variable stepsize which is updated at each iteration and based on some previous…

Optimization and Control · Mathematics 2021-07-27 Jingjing Fan , Bing Tan , Songxiao Li

Superconducting quantum circuits are promising candidate for building scalable quantum computers. Here, we use a four-qubit superconducting quantum processor to solve a two-dimensional system of linear equations based on a quantum algorithm…

This is a series of studies devoted to modeling and solving heat and mass transfer problems occurring in electric contacts where we employ and develop mathematical apparatus along with quantum algorithms for solving moving boundary value…

Computational Physics · Physics 2020-10-13 Merey M. Sarsengeldin , Zuhair M. Nashed

The procedure for simulating the nuclear magnetic resonance spectrum linked to the spin system of a molecule for a certain nucleus entails diagonalizing the associated Hamiltonian matrix. As the dimensions of said matrix grow exponentially…

Quantum Physics · Physics 2024-10-29 Joaquín Ossorio-Castillo , Alexandre Rodríguez-Coello

Quantum resonances described by non-Hermitian tridiagonal-matrix Hamiltonians $H$ with complex energy eigenvalues are considered. The method of evaluation of quantities $\sigma_n$ known as the singular values of $H$ is proposed. Its basic…

Mathematical Physics · Physics 2025-05-12 Miloslav Znojil

We propose a novel numerical algorithm for computing the electronic structure related eigenvalue problem of incommensurate systems. Unlike the conventional practice that approximates the system by a large commensurate supercell, our…

Numerical Analysis · Mathematics 2019-03-27 Yuzhi Zhou , Huajie Chen , Aihui Zhou

In this chapter we are examining several iterative methods for solving nonlinear eigenvalue problems. These arise in variational image-processing, graph partition and classification, nonlinear physics and more. The canonical eigenproblem we…

Numerical Analysis · Mathematics 2020-10-07 Guy Gilboa

Many eigenvalue problems arising in practice are often of the generalized form $A\x=\lambda B\x$. One particularly important case is symmetric, namely $A, B$ are Hermitian and $B$ is positive definite. The standard algorithm for solving…

Quantum Physics · Physics 2021-10-20 Changpeng Shao , Jin-Peng Liu

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