Nuclear magnetic resonance 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 nuclear magnetic resonance signals at low magnetic field, sensitivity down to the single-molecule level and full access to atomically precise molecular architectures for quantum technologies. Here we report the optical read-out of coherently controlled nuclear spins in a europium-based molecular crystal. By harnessing ultranarrow optical transitions, we achieve the 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 nuclear magnetic resonance and underscore the promise of molecular nuclear spins for quantum information processing. Optical initialization and read-out of nuclear spins with a spin coherence time of 2 ms in a Eu3+ molecular crystal is demonstrated with radio-frequency control, providing coherent nuclear spin manipulation for quantum information technologies.

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Nature

Researchers demonstrate optical initialization and read-out of coherently controlled nuclear spins in a europium-based molecular crystal ([Eu(BA)4(pip)]). Using ultranarrow optical transitions of Eu3+, they achieve direct optical access to nuclear spin states without relying on electron spin intermediaries. Radio-frequency driving addresses two nuclear quadrupole resonances with narrow inhomogeneous linewidths. The team implements Rabi oscillations, Hahn-echo sequences, and CPMG dynamical decoupling, achieving nuclear spin coherence times up to 2 ms. These results establish molecular nuclear spins as a viable platform for quantum information processing, with potential for single-molecule quantum registers integrated into nanophotonic cavities.

Optically detected nuclear magnetic resonance of coherent spins in a molecular complex