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Classical simulation of real-space quantum dynamics is challenging due to the exponential scaling of computational cost with system dimensions. Quantum computer offers the potential to simulate quantum dynamics with polynomial complexity;…

Quantum Physics · Physics 2021-10-13 Chee-Kong Lee , Chang-Yu Hsieh , Shengyu Zhang , Liang Shi

A model subspace configuration interaction method is developed to obtain chemically accurate electron correlations by diagonalising a very compact effective Hamiltonian of realistic molecule. The construction of the effective Hamiltonian is…

Chemical Physics · Physics 2022-10-18 Jiasheng Li , Jun Yang

The complete active space self-consistent field (CASSCF) method is the principal approach employed for studying strongly correlated systems. However, exact CASSCF can only be performed on small active spaces of ~20 electrons in ~20 orbitals…

Computational Physics · Physics 2021-12-22 Daniel S. Levine , Diptarka Hait , Norm M. Tubman , Susi Lehtola , K. Birgitta Whaley , Martin Head-Gordon

This work develops and illustrates a new method of calculating "chemically accurate" electronic wavefunctions (and energies) via a truncated full configuration interaction (CI) procedure which arguably circumvents the large matrix…

Chemical Physics · Physics 2022-12-21 Stephen J. Cotton

Finding the ground-state energy of molecules is an important and challenging computational problem for which quantum computing can potentially find efficient solutions. The variational quantum eigensolver (VQE) is a quantum algorithm that…

Quantum Physics · Physics 2023-02-15 Daniel Yoffe , Amir Natan , Adi Makmal

Recent advances in selected CI, including the adaptive sampling configuration interaction (ASCI) algorithm and its heat bath extension, have made the ASCI approach competitive with the most accurate techniques available, and hence an…

We introduce the pCI software package for high-precision atomic structure calculations. The standard method of calculation is based on the configuration interaction (CI) method to describe valence correlations, but can be extended to attain…

In quantum/classical (QM/CM) partitioning methods for multi-scale modeling, one is often forced to introduce uncontrolled phenomenological effects of the environment (CM) in the quantum (QM) domain as ab initio quantum calculations are…

Chemical Physics · Physics 2007-05-23 Aditi Mallik , Carlos E. Taylor , Keith Runge , James W. Dufty

Preserving quantum coherence with the increase of a system's size and complexity is a major challenge. Molecules, with their diverse sizes and complexities and many degrees of freedom, are an excellent platform for studying the transition…

Quantum Physics · Physics 2024-09-23 Tamar Levin , Ziv Meir

Inspired by our earlier semi-stochastic work aimed at converging high-level coupled-cluster (CC) energetics [J. E. Deustua, J. Shen, and P. Piecuch, Phys. Rev. Lett. 119, 223003 (2017); J. Chem. Phys. 154, 124103 (2021)], we propose a novel…

Chemical Physics · Physics 2022-10-06 Karthik Gururangan , J. Emiliano Deustua , Jun Shen , Piotr Piecuch

The semistochastic heat-bath configuration interaction (SHCI) method is a selected configuration interaction plus perturbation theory method that has provided near-full configuration interaction (FCI) levels of accuracy for many systems…

Chemical Physics · Physics 2021-11-30 Yuan Yao , Emmanuel Giner , Tyler A. Anderson , Julien Toulouse , C. J. Umrigar

We present quantum algorithms, for Hamiltonians of linear combinations of local unitary operators, for Hamiltonian matrix-vector products and for preconditioning with the inverse of shifted reduced Hamiltonian operator that contributes to…

Quantum Physics · Physics 2020-09-09 Zhiyong Zhang

We introduce a new selected configuration interaction plus perturbation theory algorithm that is based on a deterministic analog of our recent efficient heat-bath sampling algorithm. This Heat-bath Configuration Interaction (HCI) algorithm…

Chemical Physics · Physics 2016-08-22 Adam Holmes , Norm Tubman , Cyrus Umrigar

A key goal in quantum chemistry methods, whether ab initio or otherwise, is to achieve size consistency. In this manuscript we formulate the related idea of "Casimir-Polder size consistency" that manifests in long-range dispersion…

Chemical Physics · Physics 2017-11-27 Tim Gould , Julien Toulouse , János Ángyán , John F. Dobson

Simulation of chemical reactions on quantum computing platforms using quantum classical hybrid algorithms such as the Variational Quantum Eigensolver (VQE) is challenged by the need for a reaction consistent treatment of electron…

Chemical Physics · Physics 2026-03-16 L. Roy , M. Sarkar , M. Tewari , A. Kumar , M. Paranjothy

It is crucial to reduce the resources required to run quantum algorithms and simulate physical systems on quantum computers due to coherence time limitations. With regards to Hamiltonian simulation, a significant effort has focused on…

Quantum Physics · Physics 2022-12-01 Diana B. Chamaki , Stuart Hadfield , Katherine Klymko , Bryan O'Gorman , Norm M. Tubman

We propose a configuration-interaction (CI) representation to calculate induced nuclear fission with explicit inclusion of nucleon-nucleon interactions in the Hamiltonian. The framework is designed for easy modeling of schematic…

Nuclear Theory · Physics 2021-02-16 G. F. Bertsch , K. Hagino

We give a thorough analysis of the convergence properties of the configuration-interaction method as applied to parabolic quantum dots among other systems, including \emph{a priori} error estimates. The method converges slowly in general,…

Computational Physics · Physics 2013-05-29 Simen Kvaal

Currently available noisy intermediate-scale quantum (NISQ) devices are limited by the number of qubits that can be used for quantum chemistry calculations on molecules. We show herein that the number of qubits required for simulations on a…

One approach for solving interacting many-fermion systems is the configuration-interaction method, also sometimes called the interacting shell model, where one finds eigenvalues of the Hamiltonian in a many-body basis of Slater determinants…

Nuclear Theory · Physics 2015-06-15 Calvin W. Johnson , W. Erich Ormand , Plamen G. Krastev