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We present ground and excited state energies obtained from Diffusion Monte Carlo (DMC) calculations, using accurate multiconfiguration wave functions, for $N$ electrons ($N\le13$) confined to a circular quantum dot. We analyze the…

Condensed Matter · Physics 2009-10-31 F. Pederiva , C. J. Umrigar , E. Lipparini

Variational approaches, such as variational Monte Carlo (VMC) or the variational quantum eigensolver (VQE), are powerful techniques to tackle the ground-state many-electron problem. Often, the family of variational states is not invariant…

Quantum Physics · Physics 2023-10-10 Javier Robledo Moreno , Jeffrey Cohn , Dries Sels , Mario Motta

Quantum computers have a potential for solving quantum chemistry problems with higher accuracy than classical computers. Quantum computing quantum Monte Carlo (QC-QMC) is a QMC with a trial state prepared in quantum circuit, which is…

Quantum Physics · Physics 2024-06-07 Shu Kanno , Hajime Nakamura , Takao Kobayashi , Shigeki Gocho , Miho Hatanaka , Naoki Yamamoto , Qi Gao

We report diffusion quantum Monte Carlo calculations of three-dimensional Wigner crystals in the density range r_s=100-150. We have tested different types of orbital for use in the approximate wave functions but none improve upon the simple…

Strongly Correlated Electrons · Physics 2008-01-03 N. D. Drummond , Z. Radnai , J. R. Trail , M. D. Towler , R. J. Needs

We study the efficiency, precision and accuracy of all-electron variational and diffusion quantum Monte Carlo calculations using Slater basis sets. Starting from wave functions generated by Hartree-Fock and density functional theory, we…

Materials Science · Physics 2010-02-11 Norbert Nemec , Michael D. Towler , R. J. Needs

The magnitude of finite-size effects and Coulomb interactions in quantum Monte Carlo simulations of van der Waals interactions between weakly bonded benzene molecules are investigated. To that extent, two trial wave functions of the…

Soft Condensed Matter · Physics 2018-05-23 S. Azadi , T. D. Kühne

We perform excited-state variational Monte Carlo and diffusion Monte Carlo calculations using a simple and efficient wave function ansatz. This ansatz follows the recent variation-after-response formalism, accurately approximating a…

Strongly Correlated Electrons · Physics 2018-12-24 Nick S. Blunt , Eric Neuscamman

Variational Monte Carlo (VMC) is an approach for computing ground-state wavefunctions that has recently become more powerful due to the introduction of neural network-based wavefunction parametrizations. However, efficiently training neural…

Machine Learning · Statistics 2023-10-03 Robert J. Webber , Michael Lindsey

The so-called phaseless quantum Monte-Carlo method currently offers one of the best performing theoretical framework to investigate interacting Fermi systems. It allows to extract an approximate ground-state wavefunction by averaging…

Strongly Correlated Electrons · Physics 2017-03-31 Olivier Juillet , Alexandre Leprévost , Jérémy Bonnard , Raymond Frésard

We propose a modification of the Variational Quantum Eigensolver algorithm for electronic structure optimization using quantum computers, named non-unitary Variational Quantum Eigensolver (nu-VQE), in which a non-unitary operator is…

We report diffusion Monte Carlo (DMC) calculations on MgO in the rock-salt and CsCl structures. The calculations are based on Hartree-Fock pseudopotentials, with the single-particle orbitals entering the correlated wave function being…

Strongly Correlated Electrons · Physics 2016-08-16 D. Alfè , M. Alfredsson , J. Brodholt , M. J. Gillan M. D. Towler , R. J. Needs

Using trial wavefunctions prepared on quantum devices to reduce the bias of auxiliary-field quantum Monte Carlo (QC-AFQMC) has established itself as a promising hybrid approach to the simulation of strongly correlated many body systems.…

Quantum Physics · Physics 2024-09-16 Matthew Kiser , Matthias Beuerle , Fedor Simkovic

We present a variational function that targets excited states directly based on their position in the energy spectrum, along with a Monte Carlo method for its evaluation and minimization whose cost scales polynomially for a wide class of…

Strongly Correlated Electrons · Physics 2016-01-22 Luning Zhao , Eric Neuscamman

We present an efficient low-rank updating algorithm for updating the trial wavefunctions used in Quantum Monte Carlo (QMC) simulations. The algorithm is based on low-rank updating of the Slater determinants. In particular, the computational…

Materials Science · Physics 2009-06-25 Phani K. V. V. Nukala , P. R. C. Kent

Variational quantum algorithms are poised to have significant impact on high-dimensional optimization, with applications in classical combinatorics, quantum chemistry, and condensed matter. Nevertheless, the optimization landscape of these…

Quantum Physics · Physics 2022-02-02 Taylor L. Patti , Omar Shehab , Khadijeh Najafi , Susanne F. Yelin

Computation of ionic forces using quantum Monte Carlo methods has long been a challenge. We introduce a simple procedure, based on known properties of physical electronic densities, to make the variance of the Hellmann-Feynman estimator…

Computational Physics · Physics 2007-05-23 Simone Chiesa , David Ceperley , Shiwei Zhang

A computational model is presented to calculate the ground state energy of neutral and charged excitons confined in semiconductor quantum dots. The model is based on the variational Quantum Monte Carlo method and effective mass…

Mesoscale and Nanoscale Physics · Physics 2021-02-03 Josep Planelles , Juan I. Climente

Treating the fermionic ground state problem as a constrained stochastic optimization problem, a formalism for fermionic quantum Monte Carlo is developed that makes no reference to a trial wavefunction. Exchange symmetry is enforced by…

Strongly Correlated Electrons · Physics 2020-10-14 Michael Hutcheon

The quantum Monte Carlo methods represent a powerful and broadly applicable computational tool for finding very accurate solutions of the stationary Schroedinger equation for atoms, molecules, solids and a variety of model systems. The…

Computational Physics · Physics 2011-01-28 Jindrich Kolorenc , Lubos Mitas

We introduce a simple generalization of the well known geminal wavefunction already applied in Quantum Chemistry to atoms and small molecules. The main feature of the proposed wavefunction is the presence of the antisymmetric geminal part…

Condensed Matter · Physics 2009-11-10 Michele Casula , Sandro Sorella