Abstract
Tunable electron spins in solid media are among the most promising candidates for qubits1. In this context, molecular nanomagnets have been proposed as hardware for quantum computation2. The flexibility in their synthesis represents a distinct advantage over other spin systems, enabling the systematic production of samples with desirable properties, for example, with a view to implementing quantum logic gates3,4. Here, we report the observation of quantum interference associated with tunnelling trajectories between states of different total spin length in a dimeric molecular nanomagnet. We argue that the interference is a consequence of the unique characteristics of a molecular Mn12 wheel, which behaves as a molecular dimer with weak ferromagnetic exchange coupling: each half of the molecule acts as a single-molecule magnet, whereas the weak coupling between the two halves gives rise to an extra internal spin degree of freedom within the molecule—that is, its total spin may fluctuate. More importantly, the observation of quantum interference provides clear evidence for quantum-mechanical superpositions involving entangled states shared between both halves of the wheel.
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Acknowledgements
We gratefully acknowledge fruitful discussions with Eduardo Mucciolo and Michael Leuenberger. E.d.B., S.H. and D.N.H. acknowledge support from the US National Science Foundation (DMR0706183 and DMR0747587), (DMR0506946 and DMR0239481) and (CHE0350615), respectively.
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C.M.R. and E.d.B. planned and carried out the experiments. S.H. helped in the interpretation of the results. S.J.S., C.C.B. and D.N.H. synthesized the compound. All authors discussed the results and contributed to their interpretation.
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Ramsey, C., del Barco, E., Hill, S. et al. Quantum interference of tunnel trajectories between states of different spin length in a dimeric molecular nanomagnet. Nature Phys 4, 277–281 (2008). https://doi.org/10.1038/nphys886
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DOI: https://doi.org/10.1038/nphys886
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