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quant-ph2026

Second-Order Magnetic Properties in Paramagnetic Molecules From a Current Density Formulation Including Scalar Relativistic Effects

Francesco Ferdinando Summa, Sonia Coriani, Andre Severo Pereira Gomes

This work presents the theoretical background for the computation of nuclear magnetic shielding, nuclear hyperfine and magnetizability tensors of paramagnetic molecules, using a ma…

quant-ph2026

Resource-efficient energy-based operator selection in fermionic ADAPT-VQE via exact Hamiltonian transformation

Emanuele Rossi, Erik Rosendahl Kjellgren, Artur F. Izmaylov +3

The energy-based approach to operator selection in ADAPT-VQE relies on reconstructing the one-parameter energy landscape for each operator in the pool. In fermionic implementations…

quant-ph2026

Orbital-optimized spin-adapted multistate contracted VQE for excited states and properties on quantum hardware

Erik Rosendahl Kjellgren, Karl Michael Ziems, Peter Reinholdt +3

We introduce the orbital-optimized multistate contracted variational quantum eigensolver (oo-MC-VQE) method with spin-adapted operators for the computation of ground and excited st…

quant-ph2026

Quantum error mitigation using energy sampling and extrapolation enhanced Clifford data regression

Zhongqi Zhao, Erik Rosendahl Kjellgren, Sonia Coriani +3

Error mitigation is essential for the practical implementation of quantum algorithms on noisy intermediate-scale quantum (NISQ) devices. This work explores and extends Clifford Dat…

quant-ph2025

Cost-effective scalable quantum error mitigation for tiled Ansätze

Oskar Graulund Lentz Rasmussen, Erik Kjellgren, Peter Reinholdt +4

We introduce a cost-effective quantum error mitigation technique that builds upon the recent Ansatz-based gate and readout error mitigation method (M0). The technique, tiled M0, le…

quant-ph2025

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…