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This paper presents a nonperturbative treatment of strong-coupling induced effects in atom-field systems which cannot be seen in traditional perturbative treatments invoking compromising assumptions such as the Born-Markov, rotating wave or…

Quantum Physics · Physics 2020-02-25 Jen-Tsung Hsiang , Bei-Lok Hu

We combine recent advances in excited state variational principles, fast multi-Slater Jastrow methods, and selective configuration interaction to create multi-Slater Jastrow wave function approximations that are optimized for individual…

Strongly Correlated Electrons · Physics 2019-06-19 Sergio D. Pineda Flores , Eric Neuscamman

We present our computational implementation of the equation-of-motion (EOM) coupled-cluster (CC) singles, doubles, and triples (SDT) method for computing doubly ionized (DIP) and two-electron attached (DEA) states within Q-CHEM. These…

Chemical Physics · Physics 2025-01-14 Manisha , Prashant Uday Manohar , Anna I Krylov

The variational quantum eigensolver (VQE) algorithm, designed to calculate the energy of molecular ground states on near-term quantum computers, requires specification of symmetries that describe the system, e.g. spin state and number of…

Quantum Physics · Physics 2020-06-18 Gabriel Greene-Diniz , David Muñoz Ramo

In this work we describe the rank-reduced variant of the equation-of-motion coupled cluster theory with complete inclusion of single, double, and triple excitations. The advantage of the proposed formalism in comparison with the canonical…

Chemical Physics · Physics 2026-05-15 Piotr Michalak , Michał Lesiuk

The mean-field solutions of electronic excited states are much less accessible than ground state (e.g.\ Hartree-Fock) solutions. Energy-based optimization methods for excited states, like $\Delta$-scf, tend to fall into the lowest solution…

Chemical Physics · Physics 2022-10-11 Hong-Zhou Ye , Matthew Wellborn , Nathan D. Ricke , Troy Van Voorhis

The nuclear-electronic orbital (NEO) approach incorporates nuclear quantum effects into quantum chemistry calculations by treating specified nuclei quantum mechanically, equivalently to the electrons. Within the NEO framework, excited…

Chemical Physics · Physics 2025-03-19 Christopher L. Malbon , Sharon Hammes-Schiffer

Due to their diverse nature, the faithful description of excited states within electronic structure theory methods remains one of the grand challenges of modern theoretical chemistry. Quantum Monte Carlo (QMC) methods have been applied very…

Chemical Physics · Physics 2020-06-05 Anthony Scemama , Michel Caffarel , Anouar Benali , Denis Jacquemin , Pierre-François Loos

We present unrestricted Hartree Fock method coupled with configuration interaction (CI) method (URHF-CI) suitable for the calculation of ground and excited states of large number of electrons localized by complex gate potentials in…

Mesoscale and Nanoscale Physics · Physics 2009-11-11 Ramin M. Abolfath , Pawel Hawrylak

Elucidation of the mechanism for optical spin initialization of point defects in solids in the context of quantum applications requires an accurate description of the excited electronic states involved. While variational density functional…

Materials Science · Physics 2023-07-14 Aleksei V. Ivanov , Yorick L. A. Schmerwitz , Gianluca Levi , Hannes Jónsson

The choice of molecular orbitals is decisive in configuration interaction calculations. In this letter, a democratic description of the ground and excited states follows an orthogonally constrained orbitals optimization to produce…

Quantum Physics · Physics 2023-02-16 Saad Yalouz , Vincent Robert

The quantum equation-of-motion (qEOM) method with singles and doubles has been suggested to study electronically excited states while it fails to predict the excitation energies dominated by double excitations. In this work, we present an…

Quantum Physics · Physics 2024-06-18 Yuhan Zheng , Jie Liu , Zhenyu Li , Jinlong Yang

We present the coupled-cluster singles and doubles method formulated in terms of truncated pair-natural orbitals (PNO) that are optimized to minimize the effect of truncation. Compared to the standard ground-state PNO coupled-cluster…

Chemical Physics · Physics 2020-06-09 Marjory C. Clement , Jinmei Zhang , Cannada A. Lewis , Chao Yang , Edward F. Valeev

We employ quantum Monte Carlo to obtain chemically accurate vertical and adiabatic excitation energies, and equilibrium excited-state structures for the small, yet challenging, formaldehyde and thioformaldehyde molecules. A key ingredient…

Computational Physics · Physics 2019-08-02 Monika Dash , Jonas Feldt , Saverio Moroni , Anthony Scemama , Claudia Filippi

We present the application of the recently developed one-body M{\o}ller--Plesset perturbation theory (OBMP2) to the prediction of K-edge excited states. OBMP2 is a self-consistent perturbation theory in which a canonical transformation…

Chemical Physics · Physics 2026-03-13 Lan Nguyen Tran

Energy spectra, spin configurations, and entanglement characteristics of a system of four electrons in lateral double quantum dots are investigated using exact diagonalization (EXD), as a function of interdot separation, applied magnetic…

Mesoscale and Nanoscale Physics · Physics 2009-02-12 Ying Li , Constantine Yannouleas , Uzi Landman

The effect of core excitation in the elastic scattering and breakup of a two-body halo nucleus on a stable target nucleus is studied. The structure of the weakly-bound projectile is described in the weak-coupling limit, assuming a…

Nuclear Theory · Physics 2014-06-30 R. de Diego , J. M. Arias , J. A. Lay , A. M. Moro

We present a new linked cluster expansion for calculating properties of multiparticle excitation spectra to high orders. We use it to obtain the two-particle spectra for systems of coupled spin-half dimers. We find that even for weakly…

Strongly Correlated Electrons · Physics 2008-03-26 S. Trebst , H. Monien , C. J. Hamer , Z. Weihong , R. R. P. Singh

State-specific complete active space self-consistent field (SS-CASSCF) theory has emerged as a promising route to accurately predict electronically excited energy surfaces away from molecular equilibria. However, its accuracy and…

Chemical Physics · Physics 2024-02-21 Sandra Saade , Hugh G. A. Burton

We propose a state-averaged orbital optimization scheme for improving the accuracy of excited states of the electronic structure Hamiltonian for use on near-term quantum computers. Instead of parameterizing the orbital rotation operator in…

Chemical Physics · Physics 2024-04-09 Joel Bierman , Yingzhou Li , Jianfeng Lu