标题： 用于电路量子电动力学的内部品质因数超过15亿的铌同轴腔 显示英文标题

标题： Niobium coaxial cavities with internal quality factors exceeding 1.5 billion for circuit quantum electrodynamics

摘要： V族材料如铌和钽已成为扩展电路量子电动力学(cQED)平台性能的热门选择，使具有更低错误率和更多模式的量子处理器和存储器成为可能。 然而，铌复杂的表面化学性质使得在毫开尔文温度和单光子功率下识别退相干的主要机制变得困难。 我们使用铌同轴四分之一波长腔研究了蚀刻化学、长时间的大气暴露以及冷却前后的腔体条件（特别是铌氢化物的演化）对单光子相干性的影响。 我们在单光子条件下展示了品质因数\(Q_\{int\}>1.4 \times 10^9\)的腔体，比相同几何形状的铝腔体提高了15倍。 我们严格量化了我们的制造工艺对各种损耗机制的敏感性，并展示了两能级系统(TLS)损耗正切值减少2-4倍以及残余电阻相比传统BCP蚀刻技术提高3-5倍的结果。 最后，我们在保持腔体相干性11.3毫秒的同时实现了transmon集成和相干腔控制。 我们的方法易于在学术实验室环境中复制，其性能展示标志着三维cQED领域的一项进步。 显示英文摘要

摘要： Group-V materials such as niobium and tantalum have become popular choices for extending the performance of circuit quantum electrodynamics (cQED) platforms allowing for quantum processors and memories with reduced error rates and more modes. The complex surface chemistry of niobium however makes identifying the main modes of decoherence difficult at millikelvin temperatures and single-photon powers. We use niobium coaxial quarter-wave cavities to study the impact of etch chemistry, prolonged atmospheric exposure, and the significance of cavity conditions prior to and during cooldown, in particular niobium hydride evolution, on single-photon coherence. We demonstrate cavities with quality factors of Q_int>1.4X10^9 in the single-photon regime, a 15 fold improvement over aluminum cavities of the same geometry. We rigorously quantify the sensitivity of our fabrication process to various loss mechanisms and demonstrate a 2-4X reduction in the two-level system (TLS) loss tangent and a 3-5X improvement in the residual resistance over traditional BCP etching techniques. Finally, we demonstrate transmon integration and coherent cavity control while maintaining a cavity coherence of 11.3ms. The accessibility of our method, which can easily be replicated in academic-lab settings, and the demonstration of its performance mark an advancement in 3D cQED.