The performance of superconducting circuits for quantum computing is limited by materials losses. In particular, coherence times are typically bounded by two-level system (TLS) losses at single photon powers and millikelvin temperatures. The identification of low loss fabrication techniques, materials, and thin film dielectrics is critical to achieving scalable architectures for superconducting quantum computing. Superconducting microwave resonators provide a convenient qubit proxy for assessing performance and studying TLS loss and other mechanisms relevant to superconducting circuits such as non-equilibrium quasiparticles and magnetic flux vortices. In this review article, we provide an overview of considerations for designing accurate resonator experiments to characterize loss, including applicable types of losses, cryogenic setup, device design, and methods for extracting material and interface losses, summarizing techniques that have been evolving for over two decades. Results from measurements of a wide variety of materials and processes are also summarized. Finally, we present recommendations for the reporting of loss data from superconducting microwave resonators to facilitate materials comparisons across the field.

中文翻译：

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使用超导微波谐振器进行材料损耗测量

用于量子计算的超导电路的性能受到材料损耗的限制。特别是，相干时间通常受单光子功率和毫开尔文温度下的两级系统 (TLS) 损失的限制。低损耗制造技术、材料和薄膜电介质的识别对于实现超导量子计算的可扩展架构至关重要。超导微波谐振器为评估性能和研究 TLS 损耗以及与超导电路相关的其他机制（如非平衡准粒子和磁通涡流）提供了方便的量子位代理。在这篇评论文章中，我们概述了设计精确谐振器实验以表征损耗的注意事项，包括适用的损耗类型、低温设置、设备设计，以及提取材料和界面损耗的方法，总结了二十多年来不断发展的技术。还总结了各种材料和过程的测量结果。最后，我们提出了报告超导微波谐振器损耗数据的建议，以促进整个领域的材料比较。