A5042140240- Advanced Chemical Physics Studies
- Quantum Computing Algorithms and Architecture
- Physics of Superconductivity and Magnetism
- Quantum and electron transport phenomena
- Machine Learning in Materials Science
- Advanced Condensed Matter Physics
- Quantum Information and Cryptography
- Magnetism in coordination complexes
- Spectroscopy and Quantum Chemical Studies
- Quantum many-body systems
- Catalysis and Oxidation Reactions
- Magnetic and transport properties of perovskites and related materials
- Metalloenzymes and iron-sulfur proteins
- Metal-Catalyzed Oxygenation Mechanisms
- Catalytic Processes in Materials Science
- Probabilistic and Robust Engineering Design
- Photochemistry and Electron Transfer Studies
- Quantum, superfluid, helium dynamics
- Soil Geostatistics and Mapping
- Iron-based superconductors research
- Molecular spectroscopy and chirality
- Theoretical and Computational Physics
- Inorganic Fluorides and Related Compounds
- Advanced NMR Techniques and Applications
- Quantum Mechanics and Non-Hermitian Physics
Chalmers University of Technology
2022-2024
Max Planck Institute for Solid State Research
2018-2023
Max Planck Society
2021
University of Waterloo
2020
Data61
2020
University of Iowa
2020
University of Cambridge
2019-2020
Massey University
2020
King's College London
2020
Commonwealth Scientific and Industrial Research Organisation
2020
The developments of the open-source OpenMolcas chemistry software environment since spring 2020 are described, with a focus on novel functionalities accessible in stable branch package or via interfaces other packages. These span wide range topics computational and presented thematic sections: electronic structure theory, spectroscopy simulations, analytic gradients molecular optimizations, ab initio dynamics, new features. This report offers an overview chemical phenomena processes can...
We present NECI, a state-of-the-art implementation of the Full Configuration Interaction Quantum Monte Carlo (FCIQMC) algorithm, method based on stochastic application Hamiltonian matrix sparse sampling wave function. The program utilizes very powerful parallelization and scales efficiently to more than 24 000 central processing unit cores. In this paper, we describe core functionalities NECI its recent developments. This includes capabilities calculate ground excited state energies,...
Transcorrelated methods provide an efficient way of partially transferring the description electronic correlations from ground-state wave function directly into underlying Hamiltonian. In particular, Dobrautz et al. [Phys. Rev. B 99, 075119 (2019)] have demonstrated that use momentum-space representation, combined with a nonunitary similarity transformation, results in Hubbard Hamiltonian possesses significantly more ``compact'' function, dominated by single Slater determinant. This...
We provide a spin-adapted formulation of the Full Configuration Interaction Quantum Monte Carlo (FCIQMC) algorithm, based on Graphical Unitary Group Approach (GUGA), which enables exploitation SU(2) symmetry within this stochastic framework. Random excitation generation and matrix element calculation Shavitt graph GUGA can be efficiently implemented via biasing procedure branching diagram. The use spin-pure basis explicitly resolves different spin-sectors ensures that stochastically sampled...
Similarity transformation of the Hubbard Hamiltonian using a Gutzwiller correlator leads to non-Hermitian effective Hamiltonian, which can be expressed exactly in momentum-space representation, and contains three-body interactions. We apply this methodology study two-dimensional model with repulsive interactions near half-filling intermediate interaction strength regime ($U/t=4$). show that at optimal or correlator, similarity transformed has extremely compact right eigenvectors, sampled...
By expressing the electronic wavefunction in an explicitly correlated (Jastrow-factorized) form, a similarity-transformed effective Hamiltonian can be derived. The is non-Hermitian and contains three-body interactions. resulting ground-state eigenvalue problem solved projectively using stochastic configuration-interaction formalism. Our approach permits use of highly flexible Jastrow functions, which we show to achieving extremely high accuracy, even with small basis sets. Results are...
In this work, we demonstrate how to efficiently compute the one- and two-body reduced density matrices within spin-adapted full configuration interaction quantum Monte Carlo (FCIQMC) method, which is based on graphical unitary group approach (GUGA). This allows us use GUGA-FCIQMC as a spin-pure (CI) eigensolver complete active space self-consistent field (CASSCF) procedure hence stochastically treat spaces far larger than conventional CI solvers while variationally relaxing orbitals for...
Quantum computing is emerging as a new computational paradigm with the potential to transform several research fields including quantum chemistry. However, current hardware limitations (including limited coherence times, gate infidelities, and connectivity) hamper implementation of most algorithms call for more noise-resilient solutions. We propose an explicitly correlated Ansatz based on transcorrelated (TC) approach target these major roadblocks directly. This method transfers, without any...
We present a protocol based on unitary transformations of molecular orbitals to reduce the number nonvanishing coefficients spin-adapted configuration interaction expansions. Methods that exploit sparsity Hamiltonian matrix and compactness its eigensolutions, such as full quantum Monte Carlo (FCIQMC) algorithm in implementation, are well suited this protocol. The wave function compression resulting from approach is particularly attractive for antiferromagnetically coupled polynuclear spin...
Polynuclear transition-metal (PNTM) clusters owe their catalytic activity to numerous energetically low-lying spin states and stable oxidation states. The characterization of electronic structure represents one the greatest challenges modern chemistry. We propose a theoretical framework that enables resolution targeted with ease apply it two [Fe(III)4S4] cubanes. Through direct access many-body wave functions, we identify important correlation mechanisms interplay geometrical distortions...
A novel combined unitary and symmetric group approach is used to study the spin-$\frac{1}{2}$ Heisenberg model related Fermionic systems in a total spin-adapted representation, using linearly-parameterised Ansatz for many-body wave function. We show that more compact ground-state function representation---indicated by larger leading coefficient---is obtained when combining ${\mathcal{S}}_{n}$, form of permutations underlying lattice site ordering, with cumulative spin coupling based on...
Decoherence and gate errors severely limit the capabilities of state-of-the-art quantum computers. This work introduces a strategy for reference-state error mitigation (REM) chemistry that can be straightforwardly implemented on current near-term devices. REM applied alongside existing procedures, while requiring minimal postprocessing only one or no additional measurements. The approach is agnostic to underlying mechanical ansatz designed variational eigensolver. Up two orders-of-magnitude...
We investigate the optimization of flexible tailored real-space Jastrow factors for use in transcorrelated (TC) method combination with highly accurate quantum chemistry methods, such as initiator full configuration interaction Monte Carlo (FCIQMC). obtained by minimizing variance TC reference energy are found to yield better, more consistent results than those variational energy. compute all-electron atomization energies challenging first-row molecules C2, CN, N2, and O2 find that yields...
Variational quantum algorithms (VQAs) represent a promising approach to utilizing current computing infrastructures. VQAs are based on parameterized circuit optimized in closed loop via classical algorithm. This hybrid reduces the processing unit load but comes at cost of optimization that can feature flat energy landscape. Existing techniques, including either imaginary time-propagation, natural gradient, or momentum-based approaches, candidates place significant burden device suffer...
In this article the recent developments of open-source OpenMolcas chemistry software environment, since spring 2020, are described, with main focus on novel functionalities that accessible in stable branch package and/or via interfaces other packages. These community span a wide range topics computational chemistry, and presented thematic sections associated electronic structure theory, spectroscopy simulations, analytic gradients molecular optimizations, ab initio dynamics, new features....
In this work, we investigate the performance of a recently proposed transcorrelated (TC) approach based on single-parameter correlation factor [E. Giner, J. Chem. Phys. 154, 084119 (2021)] for systems involving more than two electrons. The benefit such an relies its simplicity as efficient numerical-analytical schemes can be set up to compute two- and three-body integrals occurring in effective TC Hamiltonian. To obtain accurate ground state energies within given basis set, present scheme is...
Quantum computing is emerging as a new computational paradigm with the potential to transform several research fields, including quantum chemistry. However, current hardware limitations (including limited coherence times, gate infidelities, and connectivity) hamper straightforward implementation of most algorithms call for more noise-resilient solutions. In chemistry, number available qubits operations particularly restrictive since, each molecular orbital, one needs, in general, two qubits....
The near-term utility of quantum computers is hindered by hardware constraints in the form noise. One path to achieving noise resilience hybrid algorithms decrease required circuit depth - number applied gates solve a given problem. This work demonstrates how reduce combining transcorrelated (TC) approach with adaptive ansätze and their implementations context variational imaginary time evolution (AVQITE). combined TC-AVQITE method used calculate ground state energies across potential energy...
We investigate Nagaoka ferromagnetism in the two-dimensional Hubbard model with one hole using spin-adapted [$\text{SU}(2)$ conserving] full configuration interaction quantum Monte Carlo method. This methodology gives us access to ground-state energies of all possible spin states $S$ finite lattices, here obtained for lattices up 26 sites various strengths ($U$). The critical strength, ${U}_{c}$, at which transition occurs is determined each lattice and found be proportional size larger...
We present a stochastic method for solving the time-dependent Schrödinger equation, generalizing ground state full configuration interaction quantum Monte Carlo method. By performing time integration in complex plane close to real-time axis, numerical effort is kept manageable and analytic continuation real frequencies efficient. This allows us perform ab initio calculation of electron spectra strongly correlated systems. The can be used as cluster solver embedding schemes.
The near-term utility of quantum computers is hindered by hardware constraints in the form noise. One path to achieving noise resilience hybrid algorithms decrease required circuit depth -- number applied gates solve a given problem. This work demonstrates how reduce combining transcorrelated (TC) approach with adaptive ans\"atze and their implementations context variational imaginary time evolution (AVQITE). combined TC-AVQITE method used calculate ground state energies across potential...
Two-dimensional Hubbard lattices with two or three holes are investigated as a function of $U$ in the large-$U$ limit. In so-called Nagaoka limit (one-hole system at infinite $U$), it is known that model exhibits ferromagnetic ground state. Here, by means exact full configuration interaction quantum Monte Carlo simulations applied to periodic up 24 sites, we compute spin-spin correlation functions increasing $U$. The clearly demonstrate onset domains, centered on individual holes. overall...
Transcorrelated methods provide an efficient way of partially transferring the description electronic correlations from ground state wavefunction directly into underlying Hamiltonian. In particular, Dobrautz et al. [Phys. Rev. B, 99(7), 075119, (2019)] have demonstrated that use momentum-space representation, combined with a non-unitary similarity transformation, results in Hubbard Hamiltonian possesses significantly more compact wavefunction, dominated by single Slater determinant. This...
<p>Polynuclear transition-metal (PNTM) clusters, ubiquitous in biological systems, owe their catalytic activity to the presence of a large manifold low-lying spin states, and number stable oxidation states. The ab initio description such systems - starting from electronic Schrodinger equation represents one greatest challenges modern quantum chemistry, requiring highly multiconfigurational treatments. We propose theoretical framework simple physically motivated molecular-orbital...