Korshakov Nikita D, Moskalev Dmitry O, Soloveva Anastasia A, Moskaleva Daria A, Lotkov Evgeniy S, Ibragimov Artem R, Androschuk Margarita V, Ryzhikov Ilya A, Panfilov Yuri V, Rodionov Ilya A
FMN Laboratory, Bauman Moscow State Technical University, Moscow, Russia, 105005.
Dukhov Automatics Research Institute, VNIIA, Moscow, Russia, 127030.
Sci Rep. 2024 Oct 30;14(1):26066. doi: 10.1038/s41598-024-74071-7.
Reproducibility of Al/AlO/Al Josephson junctions is a challenge for scaling up superconducting quantum processors. The frequency uncertainty of the transmon qubits arising from the fabrication process is attributed to deviations in the Josephson junction microstructure and electrical properties. Here, we present a solution for this problem using the post-fabrication Josephson junction thermal annealing process. The developed thermal post-exposure method allows not only to increase the junction resistance by 175%, but also to decrease by 60% with a step of 10% in R, which opens up new possibilities for tuning the frequency of qubits. The resistance is shown to be strongly temperature dependent, and is weakly dependent on the holding time. The linear dimensions of the electrodes and the sidewalls contribution to the total JJ area also have a significant impact on the final resistance after annealing. Finally, a theoretical model of the structure modification in a tunnel barrier with changes in oxygen concentration gradient is proposed. The proposed thermal annealing approach can be used to form stable and reproducible tunnel barriers and scalable frequency trimming for widely used fixed-frequency transmon qubits.
铝/氧化铝/铝约瑟夫森结的可重复性是扩大超导量子处理器规模的一项挑战。制造过程中产生的跨导量子比特的频率不确定性归因于约瑟夫森结微观结构和电学性质的偏差。在此，我们提出一种利用制造后约瑟夫森结热退火工艺解决此问题的方法。所开发的热后曝光方法不仅能使结电阻增加175%，还能以10%的步长将其降低60%，这为调整量子比特频率开辟了新的可能性。结果表明，电阻强烈依赖于温度，而对保持时间的依赖性较弱。电极的线性尺寸和侧壁对约瑟夫森结总面积的贡献对退火后的最终电阻也有显著影响。最后，提出了一个随氧浓度梯度变化的隧道势垒结构改性的理论模型。所提出的热退火方法可用于形成稳定且可重复的隧道势垒，并为广泛使用的固定频率跨导量子比特进行可扩展的频率微调。
