全范德华量子比特
An All-van-der-Waals Qubit
- Massachusetts Institute of Technology（麻省理工学院）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究报道了基于 NbSe2-hBN-NbSe2 结的全范德华超导量子比特，实现了与传统铝基量子比特相当的相干时间，并具有更小尺寸和低杂散电容优势。
AI中文摘要：
固态物理、材料科学和器件工程的进步加速了超导量子比特的发展。在新兴平台中，范德华（vdW）材料及其异质结构是量子器件潜在的有吸引力的构建模块，但它们在量子比特架构中的实现仍 largely 未被探索。在此，我们报告了一种基于 NbSe$_2$-hBN-NbSe$_2$ 结的全 vdW 超导量子比特，其中薄 hBN 层同时提供两个 NbSe$_2$ 岛之间的约瑟夫森耦合和电容分流，形成“合并元件”transmon。使用电路量子电动力学（cQED）技术进行的时间表征得到平均能量弛豫时间 $T_{1,\mathrm{avg}} = 55 ~\mu s$，Hahn 回波相干时间 $T_{2\mathrm{E},\mathrm{avg}} = 21 ~\mu s$，以及 Ramsey 相干时间 $T_{2\mathrm{R},\mathrm{avg}} = 1.9~\mu s$。相对较低的 Ramsey 时间主要归因于对电荷噪声的增强敏感性，这与实现的器件参数一致，并非根本限制。这些结果表明，基于 vdW 异质结构的集总元件超导量子比特可以实现与传统 Al-AlO$_\mathrm{x}$-Al 量子比特相当的相干时间，同时提供更小的器件尺寸和抑制的杂散电容耦合。
英文摘要：
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 $T_{1,\mathrm{avg}} = 55 ~μs$, Hahn-echo coherence time $T_{2\mathrm{E},\mathrm{avg}} = 21 ~μs$, and Ramsey coherence time $T_{2\mathrm{R},\mathrm{avg}} = 1.9~μs$. 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-AlO$_\mathrm{x}$-Al qubits, while offering a reduced device footprint and suppressed stray capacitive coupling.
