Abstract
Molecular spin qudits based on lanthanide complexes offer a promising platform for quantum technologies, combining chemical tunability with multi-level encoding. However, experimental demonstrations of their envisaged capabilities remain scarce, posing the difficulty of achieving precise control over coherences between qudit states in long pulse sequences. Here, we implement in a 173Yb(trensal) qudit the Quantum Fourier Transform (QFT), a core component of numerous quantum algorithms, storing quantum information in the phases of coherences. QFT provides an ideal benchmark for coherence manipulation and a challenge for molecular spin qudits. We address this challenge by embedding a full-refocusing protocol for spin qudits in our algorithm, mitigating inhomogeneous broadening and enabling a high-fidelity recovery of the state. Complete state tomography demonstrates the performance of the algorithm, while simulations provide insight into the physical mechanisms behind inhomogeneous broadening. This work shows the feasibility of quantum logic on molecular spin qudits and highlights their potential.
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Acknowledgements
The Authors acknowledge financial support by the European Union through the Horizon Europe Program within the ERC-Synergy project CASTLE (grant no. 101071533, S. Carretta), through NextGenerationEU Mission 4 Component 2 within the PNRR MUR project NQSTI (National Quantum Science and Technology Institute), CUP D93C2200094000 (grant no. PE0000023, R.D.R. and S. Carretta), and through NextGenerationEU Mission 4 Component 1 within the PRIN 2022 program project CROQUET, CUP D53D23010400006 (grant no. 2022L57S28, E.G.). The work was also funded by the Novo Nordisk Foundation under the Exploratory Interdisciplinary Synergy Program 2021 call (grant no. NNF21OC0070832, S.P. and S. Carretta).
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Rubín-Osanz, M., Bersani, L., Chicco, S. et al. Implementing the Quantum Fourier Transform on a molecular qudit with full refocusing and state tomography. Nat Commun (2026). https://doi.org/10.1038/s41467-026-72390-z
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DOI: https://doi.org/10.1038/s41467-026-72390-z
