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Resource-efficient, low-depth implementations of quantum circuits remain a promising strategy for achieving reliable and scalable computation on quantum hardware, as they reduce gate resources and limit the accumulation of noisy operations.…

A quantum thermodynamic system is described by a Hamiltonian and a list of conserved, non-commuting charges, and a fundamental goal is to determine the minimum energy of the system subject to constraints on the charges. Recently, [Liu et…

Quantum computing holds immense promise for simulating quantum systems, a critical task for advancing our understanding of complex quantum phenomena. One of the primary goals in this domain is to accurately approximate the ground state of…

Quantum Physics · Physics 2024-11-28 Thilo R. Müller , Manuel Geiger , Christian B. Mendl

The opportunities afforded by near-term quantum computers to calculate the ground-state properties of small molecules depend on the structure of the computational ansatz as well as the errors induced by device noise. Here we investigate the…

Gate model quantum computers with too many qubits to be simulated by available classical computers are about to arrive. We present a strategy for programming these devices without error correction or compilation. This means that the number…

Quantum Physics · Physics 2017-03-21 E. Farhi , J. Goldstone , S. Gutmann , H. Neven

We introduce an algorithm that is simultaneously memory-efficient and low-scaling for applying ab initio molecular Hamiltonians to matrix-product states (MPS) via the tensor-hypercontraction (THC) format. These gains carry over to Krylov…

Strongly Correlated Electrons · Physics 2025-11-19 Yu Wang , Maxine Luo , Matthias Reumann , Christian B. Mendl

In the context of Noisy Intermediate-Scale Quantum (NISQ) computing, parameterized quantum circuits (PQCs) represent a promising paradigm for tackling challenges in quantum sensing, optimal control, optimization, and machine learning on…

Quantum Physics · Physics 2024-08-13 Dantong Li , Dikshant Dulal , Mykhailo Ohorodnikov , Hanrui Wang , Yongshan Ding

Gradient estimation is a central challenge in training parameterized quantum circuits (PQCs) for hybrid quantum-classical optimization and learning problems. This difficulty arises from several factors, including the exponential…

Quantum Physics · Physics 2026-05-25 Mohsen Heidari , Masih Mozakka , Wojciech Szpankowski

Recently, feedback-based quantum algorithms have been introduced to calculate the ground states of Hamiltonians, inspired by quantum Lyapunov control theory. This paper aims to generalize these algorithms to the problem of calculating an…

Quantum Physics · Physics 2026-01-21 Salahuddin Abdul Rahman , Özkan Karabacak , Rafal Wisniewski

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

Key properties of physical systems can be described by the eigenvalues of matrices that represent the system. Computational algorithms that determine the eigenvalues of these matrices exist, but they generally suffer from a loss of…

Quantum Physics · Physics 2023-10-31 T. Powers , R. M. Rajapakse

We explore the usefulness of mid-circuit measurements to enhance quantum algorithmics. Specifically, we assess how quantum phase estimation (QPE) and mid-circuit measurements can improve the performance of variational quantum algorithms.…

Quantum Physics · Physics 2025-09-03 Antoine Lemelin , Christophe Pere , Olivier Landon-Cardinal , Camille Coti

We present a quantum-classical hybrid algorithm that simulates electronic structures of periodic systems such as ground states and quasiparticle band structures. By extending the unitary coupled cluster (UCC) theory to describe crystals in…

Quantum Physics · Physics 2022-02-16 Nobuyuki Yoshioka , Takeshi Sato , Yuya O. Nakagawa , Yu-ya Ohnishi , Wataru Mizukami

Solving systems of linear equations is a key subroutine in many quantum algorithms. In the last 15 years, many quantum linear solvers (QLS) have been developed, competing to achieve the best asymptotic worst-case complexity. Most QLS assume…

Various Hamiltonian simulation algorithms have been proposed to efficiently study the dynamics of quantum systems on a quantum computer. The existing algorithms generally approximate the time evolution operators, which may need a deep…

Quantum Physics · Physics 2024-03-14 Zi-Jian Zhang , Jinzhao Sun , Xiao Yuan , Man-Hong Yung

Computing vacuum states of lattice gauge theories (LGTs) containing fermionic degrees of freedom can present significant challenges for classical computation using Monte-Carlo methods. Quantum algorithms may offer a pathway towards more…

Quantum Physics · Physics 2025-03-26 Lewis W. Anderson , Martin Kiffner , Tom O'Leary , Jason Crain , Dieter Jaksch

This work is on a user-friendly reduced basis method for solving a family of parametric PDEs by preconditioned Krylov subspace methods including the conjugate gradient method, generalized minimum residual method, and bi-conjugate gradient…

Numerical Analysis · Mathematics 2026-02-24 Yuwen Li , Ludmil T. Zikatanov , Cheng Zuo

Over the past three decades significant reductions have been made to the cost of estimating ground-state energies of molecular Hamiltonians with quantum computers. However, comparatively little attention has been paid to estimating the…

Block Krylov subspace methods (KSMs) comprise building blocks in many state-of-the-art solvers for large-scale matrix equations as they arise, e.g., from the discretization of partial differential equations. While extended and rational…

Numerical Analysis · Mathematics 2020-02-06 Daniel Kressner , Kathryn Lund , Stefano Massei , Davide Palitta

The quantum circuit model is the de-facto way of designing quantum algorithms. Yet any level of abstraction away from the underlying hardware incurs overhead. In the era of near-term, noisy, intermediate-scale quantum (NISQ) hardware with…

Quantum Physics · Physics 2021-08-27 Laura Clinton , Johannes Bausch , Toby Cubitt