论文标题
谷物：颗粒状铝纳米结构量量子
Gralmonium: Granular Aluminum Nano-Junction Fluxonium Qubit
论文作者
论文摘要
介质约瑟夫森连接（JJS）由由纳米薄氧化物分离的重叠的超导电极组成，为超导量子电路提供了宝贵的非线性来源，并且是最新的量子量子的核心，例如transmon and transmon and fluxonium。在这里，我们表明，在Fluxonium Qubit中，JJ的作用也可以通过印刷定义的，自我结构的颗粒铝（GRAL）纳米结构：超导体 - 绝缘体 - perconconcontotor（SIS）JJ，该jj以单层为单层，零角蒸发。我们昵称Gralmonium的测得的量子的测量光谱与标准的磁通量乘积是无法区分的。值得注意的是，缺乏介质平行板电容器会导致本质上大的gral纳米结构充电能量在$ \ mathrm {ghz} $的范围内，可与Josephson Energy $ e_ \ e_ \ mathrm {j} $相媲美。我们测量$ t_1 = 10 \，\ mathrm {μs} $的平均能量放松时间和$ t_2^\ text {echo} = 9 \，\ mathrm {μs} $。 Gralmonium对Gral Nano-Gonuntion的$ e_ \ text {J} $的指数敏感性提供了高度易感的检测器。确实，我们观察到从毫秒到几天的时标上的$ e_ \ text {j} $的自发跳跃，这为超导材料中的显微镜缺陷提供了强大的诊断工具。
Mesoscopic Josephson junctions (JJs), consisting of overlapping superconducting electrodes separated by a nanometer thin oxide layer, provide a precious source of nonlinearity for superconducting quantum circuits and are at the heart of state-of-the-art qubits, such as the transmon and fluxonium. Here, we show that in a fluxonium qubit the role of the JJ can also be played by a lithographically defined, self-structured granular aluminum (grAl) nano-junction: a superconductor-insulator-superconductor (SIS) JJ obtained in a single layer, zero-angle evaporation. The measured spectrum of the resulting qubit, which we nickname gralmonium, is indistinguishable from the one of a standard fluxonium qubit. Remarkably, the lack of a mesoscopic parallel plate capacitor gives rise to an intrinsically large grAl nano-junction charging energy in the range of tens of $\mathrm{GHz}$, comparable to its Josephson energy $E_\mathrm{J}$. We measure average energy relaxation times of $T_1=10\,\mathrm{μs}$ and Hahn echo coherence times of $T_2^\text{echo}=9\,\mathrm{μs}$. The exponential sensitivity of the gralmonium to the $E_\text{J}$ of the grAl nano-junction provides a highly susceptible detector. Indeed, we observe spontaneous jumps of the value of $E_\text{J}$ on timescales from milliseconds to days, which offer a powerful diagnostics tool for microscopic defects in superconducting materials.
