Nuclear magnetic resonance (NMR) is a powerful tool for applications ranging from chemical analysis to quantum information processing. Achieving optical initialization and detection of molecular nuclear spins promises new opportunities - including improved NMR signals at low magnetic field, sensitivity down to the single-molecule level, and full access to atomically precise molecular architectures for quantum technologies. In this study, we report optical readout of coherently controlled nuclear spins in a europium-based molecular crystal. By harnessing ultra-narrow optical transitions, we achieve optical initialization and detection of nuclear spin states. Through radio-frequency driving, we address two nuclear quadrupole resonances, characterized by narrow inhomogeneous linewidths and a distinct correlation with the optical transition frequency. We implement Rabi oscillations, spin echo and dynamical decoupling techniques, achieving nuclear spin quantum coherence with a lifetime of up to 2 ms. These results highlight the capabilities of optically detected NMR (ODNMR) and underscore the potential of molecular nuclear spins for quantum information processing.
@article{arxiv.2509.01467,
title = {Optically detected nuclear magnetic resonance of coherent spins in a molecular complex},
author = {Evgenij Vasilenko and Vishnu Unni Chorakkunnath and Jeremias Resch and Nicholas Jobbitt and Diana Serrano and Philippe Goldner and Senthil Kumar Kuppusamy and Mario Ruben and David Hunger},
journal= {arXiv preprint arXiv:2509.01467},
year = {2025}
}