Erik Rosendahl Kjellgren
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View article: Cost-effective scalable quantum error mitigation for tiled Ansätze
Cost-effective scalable quantum error mitigation for tiled Ansätze Open
We introduce a cost-effective quantum error mitigation technique that builds on the recent Ansatz-based gate and readout error mitigation method (M0). The technique, tiled M0, leverages the unique structure of tiled Ansätze (e.g., tUPS, QN…
View article: Hyperfine Coupling Constants on Quantum Computers: Performance, Errors, and Future Prospects
Hyperfine Coupling Constants on Quantum Computers: Performance, Errors, and Future Prospects Open
We present the first implementation and computation of electron spin resonance isotropic hyperfine coupling constants (HFCs) on a quantum hardware. As illustrative test cases, we compute the HFCs for the hydroxyl radical (OH•), …
View article: Reduced density matrix and cumulant approximations of quantum linear response
Reduced density matrix and cumulant approximations of quantum linear response Open
Linear response (LR) is an important tool in the computational chemist's toolbox. It is therefore no surprise that the emergence of quantum computers has led to a quantum version, quantum LR (qLR). However, the current quantum era of near-…
View article: Critical Limitations in Quantum-Selected Configuration Interaction Methods
Critical Limitations in Quantum-Selected Configuration Interaction Methods Open
Quantum Selected Configuration Interaction (QSCI) methods (also known as Sample-based Quantum Diagonalization, SQD) have emerged as promising near-term approaches to solving the electronic Schrödinger equation with quantum computers. In th…
View article: Exact closed-form expression for unitary spin-adapted fermionic singlet double excitation operators
Exact closed-form expression for unitary spin-adapted fermionic singlet double excitation operators Open
We derive exact closed-form expressions for the matrix exponential of the anti-Hermitian spin-adapted singlet double excitation fermionic operators. These expressions enable the efficient implementation of such operators within unitary pro…
View article: Understanding and mitigating noise in molecular quantum linear response for spectroscopic properties on quantum computers
Understanding and mitigating noise in molecular quantum linear response for spectroscopic properties on quantum computers Open
Absorption spectra of LiH obtained on a quantum computer using quantum linear response, Pauli saving, QWC, and Ansatz-based read-out and gate error mitigation.
View article: Excited-state methods based on state-averaged long-range CASSCF short-range DFT
Excited-state methods based on state-averaged long-range CASSCF short-range DFT Open
This work introduces two state-averaged methods – SA-CAS-srDFT and CI-srDFT – for excited-state CAS-srDFT calculations. Benchmarking shows that the CI-srDFT approach yields more accurate and physically consistent results than its SA counte…
View article: Self-consistent Quantum Linear Response with a Polarizable Embedding environment
Self-consistent Quantum Linear Response with a Polarizable Embedding environment Open
Quantum computing presents a promising avenue for solving complex problems, particularly in quantum chemistry, where it could accelerate the computation of molecular properties and excited states. This work focuses on hybrid quantum-classi…
View article: Multiconfigurational short-range on-top pair-density functional theory
Multiconfigurational short-range on-top pair-density functional theory Open
We present the theory and implementation of a fully variational wave function -- density functional theory (DFT) hybrid model, which is applicable to many cases of strong correlation. We denote this model the multiconfigurational self-cons…
View article: Understanding and mitigating noise in molecular quantum linear response for spectroscopic properties on quantum computers
Understanding and mitigating noise in molecular quantum linear response for spectroscopic properties on quantum computers Open
The promise of quantum computing to circumvent the exponential scaling of quantum chemistry has sparked a race to develop chemistry algorithms for quantum architecture. However, most works neglect the quantum-inherent shot noise, let alone…
View article: Reduced Density Matrix Formulation of Quantum Linear Response
Reduced Density Matrix Formulation of Quantum Linear Response Open
The prediction of spectral properties via linear response (LR) theory is an important tool in quantum chemistry for understanding photoinduced processes in molecular systems. With the advances of quantum computing, we recently adapted this…
View article: Electric Field Gradient Calculations for Ice VIII and IX Using Polarizable Embedding: A Comparative Study on Classical Computers and Quantum Simulators
Electric Field Gradient Calculations for Ice VIII and IX Using Polarizable Embedding: A Comparative Study on Classical Computers and Quantum Simulators Open
We test the performance of the polarizable embedding variational quantum eigensolver self-consistent field (PE-VQE-SCF) model for computing electric field gradients with comparisons to conventional complete active space self-consistent-fie…
View article: Divergences in classical and quantum linear response and equation of motion formulations
Divergences in classical and quantum linear response and equation of motion formulations Open
Calculating molecular properties using quantum devices can be done through the quantum linear response (qLR) or, equivalently, the quantum equation of motion (qEOM) formulations. Different parameterizations of qLR and qEOM are available, n…
View article: The variational quantum eigensolver self-consistent field method within a polarizable embedded framework
The variational quantum eigensolver self-consistent field method within a polarizable embedded framework Open
We formulate and implement the Variational Quantum Eigensolver Self Consistent Field (VQE-SCF) algorithm in combination with polarizable embedding (PE), thereby extending PE to the regime of quantum computing. We test the resulting algorit…
View article: Subspace methods for the simulation of molecular response properties on a quantum computer
Subspace methods for the simulation of molecular response properties on a quantum computer Open
We explore Davidson methods for obtaining excitation energies and other linear response properties within quantum self-consistent linear response (q-sc-LR) theory. Davidson-type methods allow for obtaining only a few selected excitation en…
View article: Which options exist for NISQ-friendly linear response formulations?
Which options exist for NISQ-friendly linear response formulations? Open
Linear response (LR) theory is a powerful tool in classic quantum chemistry crucial to understanding photo-induced processes in chemistry and biology. However, performing simulations for large systems and in the case of strong electron cor…
View article: Quantum Equation of Motion with Orbital Optimization for Computing Molecular Properties in Near-Term Quantum Computing
Quantum Equation of Motion with Orbital Optimization for Computing Molecular Properties in Near-Term Quantum Computing Open
Determining the properties of molecules and materials is one of the premier applications of quantum computing. A major question in the field is how to use imperfect near-term quantum computers to solve problems of practical value. Inspired…
View article: PE-VQESCF calculation data
PE-VQESCF calculation data Open
View article: PE-VQESCF calculation data
PE-VQESCF calculation data Open
View article: The variational quantum eigensolver self-consistent field method within a polarizable embedded framework
The variational quantum eigensolver self-consistent field method within a polarizable embedded framework Open
We formulate and implement the Variational Quantum Eigensolver Self Consistent Field (VQE-SCF) algorithm in combination with polarizable embedding (PE), thereby extending PE to the regime of quantum computing. We test the resulting algorit…
View article: Multiconfigurational short-range density functional theory for nuclear magnetic resonance shielding constants with gauge-including atomic orbitals
Multiconfigurational short-range density functional theory for nuclear magnetic resonance shielding constants with gauge-including atomic orbitals Open
In this paper, we present the theory and implementation of nuclear magnetic resonance shielding constants with gauge-including atomic orbitals for the hybrid multiconfigurational short-range density functional theory model. As a special ca…
View article: Multi-configurational short-range density functional theory can describe spin–spin coupling constants of transition metal complexes
Multi-configurational short-range density functional theory can describe spin–spin coupling constants of transition metal complexes Open
The multi-configurational short-range (sr) density functional theory has been extended to the calculation of indirect spin–spin coupling constants (SSCCs) for nuclear magnetic resonance spectroscopy. The performance of the new method is co…
View article: MC--srDFT spin-spin coupling constants input files for Dalton
MC--srDFT spin-spin coupling constants input files for Dalton Open
Input files used to run CAS--srDFT calculations for spin-spin couplings constant calculations with the Dalton program.
View article: MC--srDFT spin-spin coupling constants input files for Dalton
MC--srDFT spin-spin coupling constants input files for Dalton Open
Input files used to run CAS--srDFT calculations for spin-spin couplings constant calculations with the Dalton program.
View article: Dalton Project: A Python platform for molecular- and electronic-structure simulations of complex systems
Dalton Project: A Python platform for molecular- and electronic-structure simulations of complex systems Open
The Dalton Project provides a uniform platform access to the underlying full-fledged quantum chemistry codes Dalton and LSDalton as well as the PyFraME package for automatized fragmentation and parameterization of complex molecular environ…
View article: Dataset for the article "Dalton Project: A Python platform for molecular- and electronic-structure simulations of complex systems"
Dataset for the article "Dalton Project: A Python platform for molecular- and electronic-structure simulations of complex systems" Open
This dataset contains additional material related to the article "Dalton Project: A Python platform for molecular- and electronic-structure simulations of complex systems". The article is available at https://doi.org/10.1063/1.5144298 (ope…
View article: Dataset for the article "Dalton Project: A Python platform for molecular- and electronic-structure simulations of complex systems"
Dataset for the article "Dalton Project: A Python platform for molecular- and electronic-structure simulations of complex systems" Open
This dataset contains additional material related to the article "Dalton Project: A Python platform for molecular- and electronic-structure simulations of complex systems". The article is available at https://doi.org/10.1063/1.5144298 (ope…
View article: Cost-Effective Potential for Accurate Polarizable Embedding Calculations in Protein Environments
Cost-Effective Potential for Accurate Polarizable Embedding Calculations in Protein Environments Open
The fragment-based polarizable embedding (PE) model combined with an appropriate electronic structure method constitutes a highly efficient and accurate multiscale approach for computing spectroscopic properties of a central moiety includi…
View article: CPPE: An Open-Source C++ and Python Library for Polarizable Embedding
CPPE: An Open-Source C++ and Python Library for Polarizable Embedding Open
We present a modular open-source library for polarizable embedding (PE) named CPPE. The library is implemented in C++, and it additionally provides a Python interface for rapid prototyping and experimentation in a high-level scripting lang…
View article: Triplet excitation energies from multiconfigurational short-range density-functional theory response calculations
Triplet excitation energies from multiconfigurational short-range density-functional theory response calculations Open
Linear response theory for the multiconfigurational short-range density functional theory (MC–srDFT) model is extended to triplet response with a singlet reference wave function. The triplet linear response equations for MC–srDFT are deriv…