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Strong tunable coupling between two distant superconducting spin qubits

Nature Physics (2024)Cite this article

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Abstract

Andreev spin qubits have recently emerged as an alternative qubit platform with realizations in semiconductor–superconductor hybrid nanowires. In these qubits, the spin degree of freedom of a quasiparticle trapped in a Josephson junction is intrinsically spin–orbit coupled to the supercurrent across the junction. This interaction has previously been used to perform spin readout, but it has also been predicted to facilitate inductive multi-qubit coupling. Here we demonstrate a strong supercurrent-mediated longitudinal coupling between two distant Andreev spin qubits. We show that it is both gate- and flux-tunable into the strong coupling regime and, furthermore, that magnetic flux can be used to switch off the coupling in situ. Our results demonstrate that integrating microscopic spin states into a superconducting qubit architecture can combine the advantages of both semiconductors and superconducting circuits and pave the way to fast two-qubit gates between distant spins.

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Fig. 1: Device and readout.
Fig. 2: Individual ASQ properties.
Fig. 3: Strong longitudinal coupling between the two ASQs.
Fig. 4: Tunability of the coupling strength.

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Data availability

The data that support the findings of this study are publicly available via 4TU.ResearchData at https://doi.org/10.4121/e10185d0-026e-480f-bbaa-3448c6e1b9a2. Source data are provided with this paper.

Code availability

The analysis code that supports the findings of this study is publicly available via 4TU.ResearchData at https://doi.org/10.4121/e10185d0-026e-480f-bbaa-3448c6e1b9a2.

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Acknowledgements

We thank B. van Heck, A. Kou, G. de Lange, V. Fatemi, P. Kurilovich, S. Diamond, T. Connolly, H. Nho, C. Boettcher, V. Kurilovich and X. Xue for discussions and their feedback on this paper. We thank Y. Nazarov for insightful discussions. We thank P. Krogstrup for guidance in the material growth. This work is part of the research project ‘Scalable circuits of Majorana qubits with topological protection’ (i39, SCMQ), project number 14SCMQ02, which is (partly) financed by the Dutch Research Council. It has further been supported by the Microsoft Quantum initiative. C.K.A. acknowledges support from the Dutch Research Council.

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Author notes

  1. These authors contributed equally: Marta Pita-Vidal, Jaap J. Wesdorp.

Authors and Affiliations

  1. QuTech and Kavli Institute of Nanoscience, Delft University of Technology, Delft, the Netherlands

    Marta Pita-Vidal, Jaap J. Wesdorp, Lukas J. Splitthoff, Arno Bargerbos, Leo P. Kouwenhoven & Christian Kraglund Andersen

  2. Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark

    Yu Liu

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Contributions

J.J.W., M.P.-V. and C.K.A. conceived the experiment. Y.L. developed and provided the nanowire materials. J.J.W, M.P.-V., L.J.S. and A.B. prepared the experimental setup and data acquisition tools. L.J.S. deposited the nanowires. J.J.W, M.P.-V. and A.B designed the device. J.J.W and M.P.-V. fabricated the device, performed the measurements and analysed the data, with continuous feedback from L.J.S., A.B. and C.K.A. L.P.K. and C.K.A. supervised the work. J.J.W., M.P.-V. and C.K.A. wrote the paper with feedback from all authors.

Corresponding authors

Correspondence to Marta Pita-Vidal or Christian Kraglund Andersen.

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Nature Physics thanks Jean-Damien Pillet and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Discussion, Figs. 1–24 and Tables 1–5.

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Pita-Vidal, M., Wesdorp, J.J., Splitthoff, L.J. et al. Strong tunable coupling between two distant superconducting spin qubits. Nat. Phys. (2024). https://doi.org/10.1038/s41567-024-02497-x

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