An All-van-der-Waals Qubit

arXiv:2609.14230v1 Announce Type: new Abstract: 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 NbSe$_2$-hBN-NbSe$_2$ junction, in which a thin hBN layer simultaneously provides Josephson coupling and capacitive shunting between two NbSe$_2$ islands, forming a "merged-element" transmon. Temporal characterization using circuit quantum electrodynamics (cQED) techniques yields an average energy-relaxation time $T_{1,\mathrm{avg}} = 55 ~\mu s$, Hahn-echo coherence time $T_{2\mathrm{E},\mathrm{avg}} = 21 ~\mu s$, and Ramsey coherence time $T_{2\mathrm{R},\mathrm{avg}} = 1.9~\mu s$. 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-AlO$_\mathrm{x}$-Al qubits, while offering a reduced device footprint and suppressed stray capacitive coupling.

Authors:Sein Park, Sameia Zaman, Junghyun Kim, Junyoung An, Daniel Rodan-Legrain, Hung-Yu Tsao, Chia-Chin Tsai, Aranya Goswami, Réouven Assouly, William P. Banner, Gabriel D. Cutter, Kenji Watanabe, Takashi Taniguchi, Terry P. Orlando, Gil-Ho Lee, Kyle Serniak, Max Hays, Jeffrey A. Grover, Philip Kim, Pablo Jarillo-Herrero, Joel Î-j. Wang, William D. Oliver

Abstract: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 NbSe$_2$-hBN-NbSe$_2$ junction, in which a thin hBN layer simultaneously provides Josephson coupling and capacitive shunting between two NbSe$_2$ islands, forming a "merged-element" transmon. Temporal characterization using circuit quantum electrodynamics (cQED) techniques yields an average energy-relaxation time $T_{1,\mathrm{avg}} = 55 ~\mu s$, Hahn-echo coherence time $T_{2\mathrm{E},\mathrm{avg}} = 21 ~\mu s$, and Ramsey coherence time $T_{2\mathrm{R},\mathrm{avg}} = 1.9~\mu s$. 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-AlO$_\mathrm{x}$-Al qubits, while offering a reduced device footprint and suppressed stray capacitive coupling.

Quantum Physics (quant-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Superconductivity (cond-mat.supr-con)

arXiv:2609.14230 [quant-ph]

(or arXiv:2609.14230v1 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2609.14230 arXiv-issued DOI via DataCite (pending registration)

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An All-van-der-Waals Qubit

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