An All-van-der-Waals Qubit

  1. Sein Park,
  2. Sameia Zaman,
  3. Junghyun Kim,
  4. Junyoung An,
  5. Daniel Rodan-Legrain,
  6. Hung-Yu Tsao,
  7. Chia-Chin Tsai,
  8. Aranya Goswami,
  9. Réouven Assouly,
  10. William P. Banner,
  11. Gabriel D. Cutter,
  12. Kenji Watanabe,
  13. Takashi Taniguchi,
  14. Terry P. Orlando,
  15. Gil-Ho Lee,
  16. Kyle Serniak,
  17. Max Hays,
  18. Jeffrey A. Grover,
  19. Philip Kim,
  20. Pablo Jarillo-Herrero,
  21. Joel I.J. Wang,
  22. and William D. Oliver
Advances in solid-state physics, materials science, and device engineering have accelerated the development of superconducting qubits. Among emerging platforms, van der Waals (vdW) materials and their heterostructures are potentially attractive building blocks for quantum devices, yet their realization in qubit architectures remains largely underexplored. Here we report an all-vdW superconducting qubit based on a NbSe2-hBN-NbSe2 junction, in which a thin hBN layer simultaneously provides Josephson coupling and capacitive shunting between two NbSe2 islands, forming a „merged-element“ transmon. Temporal characterization using circuit quantum electrodynamics (cQED) techniques yields an average energy-relaxation time T1,avg=55 μs, Hahn-echo coherence time T2E,avg=21 μs, and Ramsey coherence time T2R,avg=1.9 μs. The relatively low Ramsey time is primarily attributable to an enhanced sensitivity to charge noise consistent with the realized device parameters and not a fundamental limitation. These results show that lumped-element superconducting qubits based on vdW heterostructures can achieve coherence times comparable to those of conventional Al-AlOx-Al qubits, while offering a reduced device footprint and suppressed stray capacitive coupling.
arxiv pdf

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