Article
Chemistry, Physical
Xiang Li, Jia-Cheng Huang, Guang-Ze Zhang, Hao-En Li, Chang-Su Cao, Dingshun Lv, Han-Shi Hu
Summary: This article introduces a general nonstochastic optimization algorithm for neural-network quantum states (NQS) in chemical systems. The algorithm accelerates the optimization process by bypassing the need for Markov-chain Monte Carlo within the variational Monte Carlo (VMC) framework, and it offers comparable or superior accuracy and convergence compared to its stochastic counterpart.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2023)
Article
Chemistry, Physical
Brandon Eskridge, Henry Krakauer, Shiwei Zhang
Summary: Molecular magnets have great potential in quantum information and computing, but their accurate computational treatment is challenging due to the competition among different effects. Electron correlation and spin-orbit coupling play central roles, and the large size of molecular magnets adds to the complexity. The use of auxiliary-field quantum Monte Carlo allows for an ab initio treatment that accurately includes electron correlation, spin-orbit coupling, and material specificity.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Chemistry, Physical
Janus J. Eriksen
Summary: The Perspective discusses the future prospects of full configuration interaction (FCI) theory, comparing key contemporary approximations and discussing their required traits. Despite significant progress in the field over the years, there is still a need to enhance the overall applicability of electronic structure theory for systems of general composition and increasing size.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2021)
Article
Chemistry, Physical
Nick S. Blunt
Summary: This study investigates fixed- and partial-node approximations in Slater determinant basis sets using FCIQMC for sampling. While the partial-node approximation is limited due to the large walker populations required, the fixed-node approximation proves to be an accurate and practical method, particularly for CAS problems in large active spaces.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2021)
Article
Physics, Multidisciplinary
Matteo Ciardi, Tommaso Macri, Fabio Cinti
Summary: This work explores methodology for investigating interacting systems with contact interactions, introducing a class of zonal estimators for path-integral Monte Carlo methods aimed at providing physical information about limited regions of inhomogeneous systems. The usefulness of zonal estimators is demonstrated through their application to a system of trapped bosons in a quasiperiodic potential in two dimensions, focusing on finite temperature properties across a wide range of potential values. Finally, the generalization of such estimators to local fluctuations of particle numbers and magnetic ordering in multi-component systems, spin systems, and systems with nonlocal interactions is discussed.
Article
Chemistry, Physical
Jorge Alfonso Charry Martinez, Matteo Barborini, Alexandre Tkatchenko
Summary: The article introduces an accurate, efficient, and transferable variational ansatz based on a combination of electron-positron geminal orbitals and a Jastrow factor. This ansatz explicitly includes the electron-positron correlations and is optimized using variational Monte Carlo. The approach is applied to calculate binding energies for various atomic and molecular systems, showing improved accuracy compared to previous calculations.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2022)
Review
Chemistry, Physical
Yihe Xu, Yifan Cheng, Yinxuan Song, Haibo Ma
Summary: Thanks to the high compression of the matrix product state (MPS) form and the efficient site-by-site iterative sweeping optimization algorithm, the density matrix normalization group (DMRG) and its time-dependent variant (TD-DMRG) have become powerful computational tools for accurately simulating the electronic structure and quantum dynamics of strongly correlated molecules. However, to understand the quantum many-body behaviors of realistic systems, the interaction between the active subsystem and the correlated environment needs to be considered. Three new post-DMRG and TD-DMRG approaches are introduced in this paper to extend the efficacy of accurate DMRG/TD-DMRG computations to realistic strongly correlated systems coupled with large environments.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2023)
Article
Computer Science, Software Engineering
Zackary Misso, Benedikt Bitterli, Iliyan Georgiev, Wojciech Jarosz
Summary: We introduce a general framework for transforming biased estimators into unbiased and consistent estimators in the same field. We demonstrate how this framework can be applied to rendering and improve existing unbiased estimation strategies. We provide examples of novel unbiased forms of transmittance estimation, photon mapping, and finite differences that are developed using this framework.
ACM TRANSACTIONS ON GRAPHICS
(2022)
Article
Engineering, Multidisciplinary
M. Croci, K. E. Willcox, S. J. Wright
Summary: This paper extends MLBLUE method to multi-output forward UQ problems and presents new semidefinite programming formulations for their optimal setup. These formulations yield the optimal number of samples required and the optimal selection of low-fidelity models to use. The new multi-output formulations can be solved reliably and efficiently.
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
(2023)
Article
Chemistry, Physical
Giovani L. Rech, Andre L. Martinotto, Janete E. Zorzi, Claudio A. Perottoni
Summary: The relative stability between the crystal structure of alpha-F-2, space group C2/c, and a hypothesized high-pressure phase, space group Cmce, was investigated using Density Functional Theory and Quantum Monte Carlo calculations. The analysis of the phonon dispersion spectra showed that the Cmce phase exhibits dynamical instability near the Gamma-point at ambient pressure, which disappears under increasing pressure. This instability is attributed to the absence of sigma-holes in the fluorine molecule, resulting in repulsive head-to-head interactions between molecules.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2023)
Article
Chemistry, Physical
Oliver A. Bramley, Timothy J. H. Hele, Dmitrii Shalashilin
Summary: Zombie states are a formalism that describes coupled coherent fermionic states in a computationally tractable manner. This study extends the previous work on Zombie states and develops efficient algorithms for evaluating operators and addressing normalization. It also presents techniques for improving accuracy and calculating low-lying excited states.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Computer Science, Interdisciplinary Applications
Shuang Zhao, Jerome Spanier
Summary: This paper introduces a new family of hybrid estimators aimed at controlling the efficiency of Monte Carlo computations in particle transport problems. By combining transport-constrained unbiased radiance estimators with conventional terminal estimation, the efficiency of the resulting hybrid estimator can be moderated without introducing bias. The gains in efficiency are illustrated by comparing the hybrid strategy with more conventional estimation methods in a series of multi-layer numerical examples.
JOURNAL OF COMPUTATIONAL PHYSICS
(2021)
Article
Quantum Science & Technology
Steven Herbert
Summary: This paper proposes a novel method for quantum Monte Carlo integration that utilizes Fourier series decomposition and quantum amplitude estimation to retain the full quadratic quantum advantage. The method is theoretically proven to have asymptotic advantage and is supported by numerical results showcasing its practical benefits.
Article
Chemistry, Physical
Jonas Feldt, Antoine Bienvenu, Roland Assaraf
Summary: In this paper, a new estimator in the variational Monte Carlo framework is proposed, which utilizes numerically cheap single-core subsamplings to improve the estimation of molecular properties. Furthermore, a spin-dependent core definition is introduced to simplify the algorithm and enhance its efficiency.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2022)
Article
Materials Science, Multidisciplinary
Tommaso Morresi, Rodolphe Vuilleumier, Michele Casula
Summary: A new method for computing phonons in molecular crystals under strong quantum anharmonicity is proposed and successfully applied to solid hydrogen at high pressure. The method, based on path integral molecular dynamics simulations, shows remarkably low variance and accuracy in predicting phonon frequencies. Experimental validation of the results for different phases is also provided.
Article
Chemistry, Physical
Nick S. Blunt
Summary: This study investigates fixed- and partial-node approximations in Slater determinant basis sets using FCIQMC for sampling. While the partial-node approximation is limited due to the large walker populations required, the fixed-node approximation proves to be an accurate and practical method, particularly for CAS problems in large active spaces.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2021)
Article
Chemistry, Physical
Nicholas Lee, Alex J. W. Thom
Summary: In this article, a method of applying spin rotation on symmetry broken unrestricted Hartree-Fock (sb-UHF) states to generate a basis for nonorthogonal configuration interaction (NOCI) is proposed. The dissociation of ethene was examined using this method and spin-pure states were obtained. The method was also shown to restore spin symmetry for molecules of various sizes, improving upon existing NOCI methods.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2022)
Article
Multidisciplinary Sciences
T. M. Graham, Y. Song, J. Scott, C. Poole, L. Phuttitarn, K. Jooya, P. Eichler, X. Jiang, A. Marra, B. Grinkemeyer, M. Kwon, M. Ebert, J. Cherek, M. T. Lichtman, M. Gillette, J. Gilbert, D. Bowman, T. Ballance, C. Campbell, E. D. Dahl, O. Crawford, N. S. Blunt, B. Rogers, T. Noel, M. Saffman
Summary: Gate-model quantum computers promise to solve computational problems by utilizing neutral-atom hyperfine qubits and strong entangling interactions provided by Rydberg states. Several quantum algorithms have been successfully demonstrated on a programmable neutral-atom quantum computer.
Correction
Chemistry, Physical
Maria-Andreea Filip, Alex J. W. Thom
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Chemistry, Multidisciplinary
Robert Izsak, Christoph Riplinger, Nick S. Blunt, Bernardo de Souza, Nicole Holzmann, Ophelia Crawford, Joan Camps, Frank Neese, Patrick Schopf
Summary: Quantum computers are expected to be useful in simulating strongly correlated chemical systems, but careful selection of orbital spaces is crucial. This study presents a scheme for automatically selecting an active space and combines quantum phase estimation and variational quantum eigensolver algorithms to accurately describe the environment. The protocol outlined here can be applied to chemical systems of any size, including those beyond the capabilities of classical computation.
JOURNAL OF COMPUTATIONAL CHEMISTRY
(2023)
Article
Chemistry, Physical
Anna T. Bui, Niamh A. Hartley, Alex J. W. Thom, Alexander C. Forse
Summary: Electrochemical carbon dioxide capture is seen as a promising alternative to conventional energy-intensive methods. This approach uses redox-active molecules like quinones to capture CO2. However, there is a risk of side-reactions with oxygen. This study investigates the trade-off between the redox potential and CO2 capture strength in different quinone derivatives, providing insights for the design of improved redox-active molecules.
JOURNAL OF PHYSICAL CHEMISTRY C
(2022)
Article
Chemistry, Physical
Nick S. Blunt, Joan Camps, Ophelia Crawford, Robert Izsak, Sebastian Leontica, Arjun Mirani, Alexandra E. Moylett, Sam A. Scivier, Christoph Sunderhauf, Patrick Schopf, Jacob M. Taylor, Nicole Holzmann
Summary: Computational chemistry is crucial for the pharmaceutical industry, and quantum computing is a rapidly advancing technology that promises to revolutionize computational capabilities in chemical research. This article explores the potential applications of quantum computation in pharmaceutical problems, specifically in simulating molecules. The authors provide estimates of the quantum computational cost for simulating a protein-drug complex and highlight recent advancements in quantum algorithms that significantly reduce the required resources.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2022)
Article
Chemistry, Physical
Charles J. C. Scott, Oliver J. Backhouse, George H. Booth
Summary: We demonstrate a method to construct an effective Hamiltonian for GW calculations with linear scaling and accurate excitation energy approximations. By expanding the self-energy to conserve frequency-independent moments, we can build and solve the Hamiltonian with an O[N4] approach that can potentially be reduced to O[N3]. This method allows for exact frequency integration and solution to the Dyson equation without approximation, providing accurate GW spectra and avoiding discontinuities.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Chemistry, Physical
Maria-Andreea Filip, Alex J. W. Thom
Summary: The development of multireference coupled cluster (MRCC) techniques in electronic structure theory has been challenging due to the complexity in expressing a multiconfigurational wavefunction within the single-reference coupled cluster framework. The multireference-coupled cluster Monte Carlo (mrCCMC) technique, based on the Monte Carlo approach, offers a simpler alternative but needs improvement in accuracy and computational cost. This paper explores incorporating ideas from conventional MRCC to the mrCCMC framework, resulting in methods with increased relaxation of the reference space and a better understanding of solutions to the mrCCMC equations.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Chemistry, Physical
Robert Izsak, Aleksei V. Ivanov, Nick S. Blunt, Nicole Holzmann, Frank Neese
Summary: In this article, the different measures of electron correlation in wave function theory, density functional theory, and quantum information theory are briefly reviewed. The focus is then placed on a more traditional metric based on dominant weights in the full configuration solution and its behavior regarding the choice of N-electron and one-electron basis. The impact of symmetry is discussed, and the usefulness of distinguishing between determinants, configuration state functions, and configurations as reference functions is emphasized.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2023)
Article
Chemistry, Physical
Daniel Graf, Alex J. W. Thom
Summary: We introduced an efficient methodology, called DC(HF)-DFT, for density-corrected Hartree-Fock density functional theory calculations, and its extension called corrected HF DFT (C(HF)-DFT). In this study, we further combined C(HF)-DFT with the random phase approximation (RPA) and referred to it as corrected HF RPA (C(HF)-RPA). We evaluated the proposed methodology using various RPA methods and found that C(HF)-dRPA showed promising performance, while over-corrections were often observed in RPA with exchange methods.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Chemistry, Physical
Nicholas Lee, Alex J. W. Thom
Summary: We investigate the use of a transcorrelated Hamiltonian to describe electron correlation. A method for obtaining transcorrelated wavefunctions is developed based on the bi-variational principle. The optimized Hamiltonian provides highly accurate energies for closed-shell atoms and helium-like ions, and the effects of certain correlator terms on electron-electron and electron-nuclear cusps are examined.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2023)
Article
Chemistry, Physical
Daniel Graf, Alex J. W. Thom
Summary: The crucial step in DC(HF)-DFT is to determine whether the density produced by the density functional is erroneous and should be replaced by the HF density. An indicator, based on the difference in noninteracting kinetic energies between DFT and HF calculations, is introduced to make this decision. The kinetic energy indicator directly compares the self-consistent density of the analyzed functional with the HF density, and it is size-intensive, reliable, and highly efficient. Additionally, a procedure called C(HF)-DFT is presented, which not only corrects the density but also the functional itself by evaluating a related hybrid functional.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2023)
Article
Materials Science, Multidisciplinary
Robert J. Anderson, Charles J. C. Scott, George H. Booth
Summary: The scope of full configuration interaction quantum Monte Carlo (FCIQMC) has been extended to coupled fermion-boson Hamiltonians, providing a solution that avoids truncation in boson occupation. By introducing algorithmic changes to generate efficient excitations, FCIQMC is applied in two contrasting settings, demonstrating its efficacy in simulating local electron-phonon interactions and quantum embedding schemes.
Article
Physics, Multidisciplinary
Maria-Andreea Filip, Nathan Fitzpatrick, David Munoz Ramo, Alex J. W. Thom
Summary: The Unitary Coupled Cluster (UCC) approach offers a way to utilize quantum hardware for quantum chemistry calculations, with a combined classical-quantum method proposed to reduce quantum resources by selecting important excitations in advance.
PHYSICAL REVIEW RESEARCH
(2022)
