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It is difficult to calculate the energy levels and eigenstates of a large physical system on a classical computer because of the exponentially growing size of the Hilbert space. In this work, we experimentally demonstrate a quantum…

Quantum Physics · Physics 2019-03-12 Zhaokai Li , Xiaomei Liu , Hefeng Wang , Sahel Ashhab , Jiangyu Cui , Hongwei Chen , Xinhua Peng , Jiangfeng Du

The eigenvalue density of a matrix plays an important role in various types of scientific computing such as electronic-structure calculations. In this paper, we propose a quantum algorithm for computing the eigenvalue density in a given…

Quantum Physics · Physics 2021-12-13 Yasunori Futamura , Xiucai Ye , Tetsuya Sakurai

The logarithm-determinant is an widely-present operation in many areas of physics and computer science. Derivatives of the logarithm-determinant compute physically relevant quantities in statistical physics models, quantum field theories,…

Quantum Physics · Physics 2025-09-23 Thomas E. Baker , Jaimie A. Greasley

This article reviews the 2008 quantum algorithm for linear systems of equations due to Harrow, Hassidim and Lloyd, as well as some of the followup and related work. It was submitted to the Springer Encyclopedia of Algorithms.

Quantum Physics · Physics 2017-05-17 Aram W. Harrow

Solving a quadratic nonlinear system of equations (QNSE) is a fundamental, but important, task in nonlinear science. We propose an efficient quantum algorithm for solving $n$-dimensional QNSE. Our algorithm embeds QNSE into a…

Quantum Physics · Physics 2022-10-11 Cheng Xue , Xiao-Fan Xu , Yu-Chun Wu , Guo-Ping Guo

The complex-scaling method can be used to calculate molecular resonances within the Born-Oppenheimer approximation, assuming the electronic coordinates are dilated independently of the nuclear coordinates. With this method, one will…

Quantum Physics · Physics 2021-06-16 Teng Bian , Sabre Kais

We propose a quantum algorithm for finding eigenvalues of non-unitary matrices. We show how to construct, through interactions in a quantum system and projective measurements, a non-Hermitian or non-unitary matrix and obtain its eigenvalues…

Quantum Physics · Physics 2010-12-07 Hefeng Wang , Lian-Ao Wu , Yu-xi Liu , Franco Nori

We study the problem of estimating frequency response functions of systems of coupled, classical harmonic oscillators using a quantum computer. The functional form of these response functions can be mapped to a corresponding eigenproblem of…

Quantum Physics · Physics 2025-11-14 Sven Danz , Mario Berta , Stefan Schröder , Pascal Kienast , Frank K. Wilhelm , Alessandro Ciani

Modeling composite systems of spins or electrons coupled to bosonic modes is of significant interest for many fields of applied quantum physics and chemistry. A quantum simulation can allow for the solution of quantum problems beyond…

To approximate solutions of complex nonlinear partial differential equations remains a computational challenge, especially for sets of equations relevant in industry, such as Euler or Navier-Stokes equations. Even the most sophisticated…

Quantum Physics · Physics 2026-03-25 Maximilian Mandelt Buxadé , Stefan Langer , Philipp Bekemeyer

Quantum algorithms for diverse problems, including search and optimization problems, require the implementation of a reflection operator over a target state. Commonly, such reflections are approximately implemented using phase estimation.…

Quantum Physics · Physics 2018-03-08 Anirban Narayan Chowdhury , Yigit Subasi , Rolando D. Somma

We propose a quantum algorithm for projecting a quantum system to eigenstates of any Hermitian operator, provided one can access the associated control-unitary evolution for the ancilla and the system, as well as the measurement of the…

Quantum Physics · Physics 2020-03-24 Yanzhu Chen , Tzu-Chieh Wei

Quantum tomography is a crucial tool for characterizing quantum states and devices and estimating nonlinear properties of the systems. Performing full quantum state tomography on an $N_\mathrm{q}$ qubit system requires an exponentially…

Quantum Physics · Physics 2025-09-09 Zhixin Song , Hang Ren , Melody Lee , Bryan Gard , Nicolas Renaud , Spencer H. Bryngelson

We present a quantum algorithm for systems of (possibly inhomogeneous) linear ordinary differential equations with constant coefficients. The algorithm produces a quantum state that is proportional to the solution at a desired final time.…

Quantum Physics · Physics 2017-11-07 Dominic W. Berry , Andrew M. Childs , Aaron Ostrander , Guoming Wang

Climate change is becoming one of the greatest challenges to the sustainable development of modern society. Renewable energies with low density greatly complicate the online optimization and control processes, where modern advanced…

Quantum Physics · Physics 2024-09-09 Junyu Liu , Han Zheng , Masanori Hanada , Kanav Setia , Dan Wu

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

In this paper, we explore accelerating Hamiltonian ground state energy calculation on NISQ devices. We suggest using search-based methods together with machine learning to accelerate quantum algorithms, exemplified in the Quantum…

Quantum Physics · Physics 2026-05-11 Avner Bensoussan , Elena Chachkarova , Karine Even-Mendoza , Sophie Fortz , Connor Lenihan

The rapid integration of renewable energy resources presents formidable challenges in managing power grids. While advanced computing and machine learning techniques offer some solutions for accelerating grid modeling and simulation, there…

Quantum Physics · Physics 2024-12-12 Muqing Zheng , Yousu Chen , Xiu Yang , Ang Li

State-of-the-art noisy intermediate-scale quantum devices (NISQ), although imperfect, enable computational tasks that are manifestly beyond the capabilities of modern classical supercomputers. However, present quantum computations are…

Despite the successful enhancement to the Harrow-Hassidim-Lloyd algorithm by Childs et al., who introduced the Fourier approach leveraging linear combinations of unitary operators, our research has identified non-trivial redundancies within…

Quantum Physics · Physics 2024-05-13 Rui-Bin Xu , Zhu-Jun Zheng , Zheng Zheng
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