NbN-based flux qubit with ferromagnetic π-junction.

ORAL

Abstract

We report a superconducting flux qubit operating at zero magnetic field by utilizing a ferromagnetic Josephson p-junction [1]. Using the fabrication technology for niobium nitride (NbN)-based quantum circuits [2-4], we fabricated a NbN-based flux qubit with NbN/AlN/NbN Josephson junctions and a NbN/PdNi/NbN π-junction. By embedding this flux qubit with p-junction in a 3D cavity-QED architecture for characterization [5], we confirmed the optimal operation at zero magnetic field through microwave spectroscopy and time-domain coherence measurements. The qubit lifetime is in the microsecond range, which we argue is limited by quasiparticle excitations in the metallic ferromagnet layer. We will discuss the impact of the NbN/PdNi/NbN p-junction on the qubit coherence time, providing valuable insight into the coherence properties of the superconducting flux qubits.

(S.K and L. V. A. contributed equally to this work.)

* This work was supported by Japan Science and Technology Agency Core Research for Evolutionary Science and Technology (Grant No. JPMJCR1775), JSPS KAKENHI (JP19H05615), JST ERATO (JPMJER1601), and partially by MEXT Quantum Leap Flagship Programs (JPMXS0120319794 and JPMXS0118068682).

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Publication: [1] T. Yamashita et al., Phys. Rev. Lett. 95, 097001 (2005).
[2] W. Qiu and H. Terai, Appl. Phys. Exp. 13, 126501 (2020).
[3] S. Kim et al, Commun. Mater. 2, 98 (2021).
[4] D. Pham et al, Sci. Rep. 12, 6863 (2022).
[5] L. Abdurakhimov et al., Appl. Phys. Lett. 115, 262601 (2019).

Presenters

  • Sunmi Kim

    NICT

Authors

  • Sunmi Kim

    NICT

  • Leonid V Abdurakhimov

    NTT Basic Research Laboratories, IQM Finland Oy

  • Duong Pham

    Tohoku University

  • Wei Qiu

    NICT, IQM Finland Oy

  • Hirotaka Terai

    NICT, National Institute of Information and Communications Technology

  • Sahel Ashhab

    NICT, National Institute of Information and Communications Technol, National Institute of Information and Communications Technology (NICT)

  • Shiro Saito

    NTT Basic Research Laboratories

  • Taro Yamashita

    Tohoku University

  • Kouichi Semba

    NICT, National Institute of Information and Communications technology (NICT)