论文标题
简化的Josephson-Gonuntion制造过程,用于重复性高性能超导量子位
Simplified Josephson-junction fabrication process for reproducibly high-performance superconducting qubits
论文作者
论文摘要
我们引入了一种简化的针对约瑟夫森连接的制造技术,并用$ T_1 $放松时间平均50美元$ 〜μ $ S($ Q> $ 1.5 $ \ times $ 10 $^6 $)。基于铝制的约瑟夫森连接的当前阴影蒸发技术需要一个单独的光刻步骤,以放置一个贴片,从而使连接电极和电路接线层之间的电动,超导连接。斑块连接消除了寄生交界,否则会对介电损失产生重大贡献。在我们的斑块集成跨型(PICT)连接技术中,我们使用一个光刻步骤和一个真空循环来蒸发连接电极和斑块。在一项3600多个连接的研究中,我们在晶圆上显示的平均电阻变化为3.7 $ \%$,其中包含40 $ 0.5 $ \ tims $ 0.5厘米$^2 $芯片,交界处面积在0.01至0.16 $ $ $ m $ m $ m $^2 $之间。电阻的平均芯片差异为2.7 $ \%$,20芯片在1.4至2 $ \%$之间变化。对于用于Transmon Qubits的结量尺寸,我们推断出1.7-2.5 $ \%$的晶圆级过渡频率变化。我们表明,这种变化的60-70 $ \%$归因于交界处的区域波动,而其余的是由隧道结构不均匀引起的。这种高频率可预测性是扩大量子计算机中量子数数量的要求。
We introduce a simplified fabrication technique for Josephson junctions and demonstrate superconducting Xmon qubits with $T_1$ relaxation times averaging above 50$~μ$s ($Q>$1.5$\times$ 10$^6$). Current shadow-evaporation techniques for aluminum-based Josephson junctions require a separate lithography step to deposit a patch that makes a galvanic, superconducting connection between the junction electrodes and the circuit wiring layer. The patch connection eliminates parasitic junctions, which otherwise contribute significantly to dielectric loss. In our patch-integrated cross-type (PICT) junction technique, we use one lithography step and one vacuum cycle to evaporate both the junction electrodes and the patch. In a study of more than 3600 junctions, we show an average resistance variation of 3.7$\%$ on a wafer that contains forty 0.5$\times$0.5-cm$^2$ chips, with junction areas ranging between 0.01 and 0.16 $μ$m$^2$. The average on-chip spread in resistance is 2.7$\%$, with 20 chips varying between 1.4 and 2$\%$. For the junction sizes used for transmon qubits, we deduce a wafer-level transition-frequency variation of 1.7-2.5$\%$. We show that 60-70$\%$ of this variation is attributed to junction-area fluctuations, while the rest is caused by tunnel-junction inhomogeneity. Such high frequency predictability is a requirement for scaling-up the number of qubits in a quantum computer.