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In this work, a scalable algorithm for the approximate quantum state preparation problem is proposed, facing a challenge of fundamental importance in many topic areas of quantum computing. The algorithm uses a variational quantum circuit…

Quantum Physics · Physics 2025-03-19 Giacomo Belli , Marco Mordacci , Michele Amoretti

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

We study the use of Krylov subspace recycling for the solution of a sequence of slowly-changing families of linear systems, where each family consists of shifted linear systems that differ in the coefficient matrix only by multiples of the…

Numerical Analysis · Mathematics 2014-10-01 Kirk M. Soodhalter , Daniel B. Szyld , Fei Xue

In this paper, by introducing a class of relaxed filtered Krylov subspaces, we propose the relaxed filtered Krylov subspace method for computing the eigenvalues with the largest real parts and the corresponding eigenvectors of non-symmetric…

Numerical Analysis · Mathematics 2020-11-17 Cun-Qiang Miao , Wen-Ting Wu

Quantum approximate optimization is one of the promising candidates for useful quantum computation, particularly in the context of finding approximate solutions to Quadratic Unconstrained Binary Optimization (QUBO) problems. However, the…

Quantum state preparation (QSP) is a fundamental task in quantum computing and quantum information processing. It is critical to the execution of many quantum algorithms, including those in quantum machine learning. In this paper, we…

Data Structures and Algorithms · Computer Science 2025-08-01 Xin Hong , Aochu Dai , Chenjian Li , Sanjiang Li , Shenggang Ying , Mingsheng Ying

In this paper, a novel and generic multi-objective design paradigm is proposed which utilizes quantum-behaved PSO(QPSO) for deciding the optimal configuration of the LQR controller for a given problem considering a set of competing…

Neural and Evolutionary Computing · Computer Science 2016-07-05 Kaveh Hassani , Won-Sook Lee

Quantum Phase Estimation (QPE) routines are known to fail probabilistically even with perfect gates and input states. This effect stems from an incompatibility of finite-sized quantum registers to capture a phase within QPE with phase…

Quantum Physics · Physics 2025-08-12 Harriet Apel , Cristian L. Cortes , Jessica Lemieux , Mark Steudtner

A milestone in the field of quantum computing will be solving problems in quantum chemistry and materials faster than state-of-the-art classical methods. The current understanding is that achieving quantum advantage in this area will…

Quantum Physics · Physics 2023-11-08 Guoming Wang , Daniel Stilck França , Ruizhe Zhang , Shuchen Zhu , Peter D. Johnson

Estimating the eigenvalues of a unitary transformation U by standard phase estimation requires the implementation of controlled-U-gates which are not available if U is only given as a black box. We show that a simple trick allows to measure…

Quantum Physics · Physics 2007-05-23 Dominik Janzing , Thomas Beth

Quadratic Unconstrained Binary Optimization (QUBO) is a general-purpose modeling framework for combinatorial optimization problems and is a requirement for quantum annealers. This paper utilizes the eigenvalue decomposition of the…

Optimization and Control · Mathematics 2021-06-22 Amit Verma , Mark Lewis

A novel linear-algebraic algorithm, multiple Arnoldi method, was developed in an interdisciplinary study between physics and applied mathematics and realized one-hundred-million-atom (100-nm-scale) electronic state calculations on the K…

Materials Science · Physics 2013-07-12 Takeo Hoshi , Keita Yamazaki , Yohei Akiyama

We propose an algorithm to obtain Green's functions as a continued fraction on quantum computers, which is based on the construction of the Krylov basis using variational quantum algorithms, and included in a Lanczos iterative scheme. This…

Quantum Physics · Physics 2021-08-27 Francois Jamet , Abhishek Agarwal , Carla Lupo , Dan E. Browne , Cedric Weber , Ivan Rungger

Effectively encoding inequality constraints is a primary obstacle in applying quantum algorithms to financial optimization. A quantum model for Markowitz portfolio optimization is presented that resolves this by embedding slack variables…

Optimization and Control · Mathematics 2026-01-08 Pablo Thomassin , Guillaume Guerard , Sonia Djebali , Vincent Marc Lambert

Near-term quantum computers will be limited in the number of qubits on which they can process information as well as the depth of the circuits that they can coherently carry out. To-date, experimental demonstrations of algorithms such as…

Chemical Physics · Physics 2023-10-18 Joel Bierman , Yingzhou Li , Jianfeng Lu

We develop a distributed Block Chebyshev-Davidson algorithm to solve large-scale leading eigenvalue problems for spectral analysis in spectral clustering. First, the efficiency of the Chebyshev-Davidson algorithm relies on the prior…

Machine Learning · Computer Science 2024-01-08 Qiyuan Pang , Haizhao Yang

Reinforcement learning (RL) provides a principled framework for decision-making in partially observable environments, which can be modeled as Markov decision processes and compactly represented through dynamic decision Bayesian networks.…

Quantum Physics · Physics 2025-07-25 Gilberto Cunha , Alexandra Ramôa , André Sequeira , Michael de Oliveira , Luís Barbosa

The calculation of excited state energies of electronic structure Hamiltonians has many important applications, such as the calculation of optical spectra and reaction rates. While low-depth quantum algorithms, such as the variational…

Quantum Physics · Physics 2019-07-03 Oscar Higgott , Daochen Wang , Stephen Brierley

We conducted quantum simulations of strongly correlated systems using the quantum flow (QFlow) approach, which enables sampling large sub-spaces of the Hilbert space through coupled eigenvalue problems in reduced dimensionality active…

Quantum Physics · Physics 2023-08-09 Karol Kowalski , Nicholas P. Bauman

Quantum phase estimation plays a central role in quantum simulation as it enables the study of spectral properties of many-body quantum systems. Most variants of the phase estimation algorithm require the application of the global unitary…