Microwave quantum optics with tunable cavity resonators and superconducting qubits

在这项工作中，我们开发了一个通用的cad辅助电路设计平台和性能评估工具，用于设计不同变体的jtwpa，它可以重现文献中实现的jtwpa的结果。在制造中，我们一直在寻找最合适的约瑟夫森结设计，以实现约瑟夫森结参数的高均匀性。从工作的开始到结束，我们已经将结电阻的标准偏差（stdev）从20%以上降低到最后测量样品的4%，覆盖了足以实现JTWPAs的芯片面积。我们将在下一批JTWPA样品中使用的最新结设计将进一步将stdev降低到1%左右，同时也大大提高了以前设计的结良率。从我们的样品测量中，我们成功地制造了一个低损耗的非线性传输线，可以作为jtwpa的基础。通过与文献中的jtwpa相当的电长度和单位电池数量（我们的样本中有1413个电池，而文献中有1000-2000个电池），我们实现了< 1dB的插入损耗，而在类似频率范围内，大多数其他实现通常为3-6 dB。我们样品的初步测量结果表明，在6 GHz的带宽上，增益平均高达7.5 dB。我们期望未来的设备在增益方面能够赶上更优化的结和电路设计。

Throughout this work, we have developed a versatile CAD-assisted circuit design platform and performance estimation tools for designing JTWPAs in different variants, which can reproduce the results of implemented JTWPAs in literatures.In fabrication, we have been searching for the most suitable Josephson junction design to achieve a high homogeneity in Josephson junction parameters. From the beginning to end of the work, we have reduced the standard deviation (stdev) in junction resistance from over 20% down to 4% in our last measured sample, covering a chip area sufficient for implementing JTWPAs. Our latest junction design to be used in the next batch of JTWPA samples will further reduce the stdev to around 1%, while also greatly improving the junction yield over the previous designs.From our sample measurements, we have successfully fabricated a low-loss nonlinear transmission line which could act as the basis for JTWPAs. With a comparable electrical length and number of unit cells to JTWPAs in literatures (1413 cells in our sample, comparing to 1000-2000 cells in literatures), we have achieved < 1dB insertion loss comparing to typically 3-6 dB in most other implementations over a similar frequency range. The preliminary measurement results of our samples demonstrated a gain up to an average of 7.5 dB, over a wide bandwidth of 6 GHz. We expect future devices to catch up in terms of gain with more optimized junction and circuit designs.