7 papers
Orbital-Optimized Unitary Coupled Cluster for Indirect Nuclear Spin-Spin Coupling Constants within a Quantum Linear Response Framework
Juliane H. Fuglsbjerg, Peter Reinholdt, Erik Kjellgren +4
We present a quantum linear response (qLR) approach within an active-space framework for computing indirect nuclear spin-spin coupling constants, a key ingredient in NMR spectra pr…
Reduced density matrix and cumulant approximations of quantum linear response
Theo Juncker von Buchwald, Erik Rosendahl Kjellgren, Jacob Kongsted +3
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,…
Redundant parameter dependencies in truncated classic and quantum Linear Response and Equation of Motion theory
Erik Rosendahl Kjellgren, Peter Reinholdt, Karl Michael Ziems +3
Extracting molecular properties from a wave function can be done through the linear response (LR) formalism or, equivalently, the equation of motion (EOM) formalism. For a simple m…
Exact closed-form expression for unitary spin-adapted fermionic singlet double excitation operators
Erik Rosendahl Kjellgren, Karl Michael Ziems, Peter Reinholdt +3
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 ef…
Hyperfine Coupling Constants on Quantum Computers: Performance, Errors, and Future Prospects
Phillip W. K. Jensen, Gustav Stausbøll Hedemark, Karl Michael Ziems +6
We present the first implementation and computation of electron spin resonance isotropic hyperfine coupling constants (HFCs) on quantum hardware. As illustrative test cases, we com…
Critical Limitations in Quantum-Selected Configuration Interaction Methods
Peter Reinholdt, Karl Michael Ziems, Erik Rosendahl Kjellgren +3
Quantum Selected Configuration Interaction (QSCI) methods (also known as Sample-based Quantum Diagonalization, SQD) have emerged as promising near-term approaches to solving the el…