稀释制冷机中低温设备平面上的可溯源原位微波功率测量
Traceable In Situ Microwave Power Measurement at the Cryogenic Device Plane in a Dilution Refrigerator
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中文总结 AI 辅助
研究在稀释制冷机中低温设备平面上进行微波功率测量的问题，核心方法是利用定制可变温度台，结合热射频功率传输、低温S参数校正和不确定度评估，实现可溯源微波功率校准，给出了不同功率下的不确定度范围。
中文摘要 AI 辅助
准确了解传递到低温被测设备（DUT）的微波功率对于超导量子电路的特性表征和运行至关重要。然而，由于分布式衰减、阻抗失配、开关路径重复性和温度相关的微波组件，在稀释制冷机内部很难获得此信息。本文提出了一种在低温设备平面上进行射频功率的原位测量方法。该方法使用定制的可变温度台（VTS）作为低温热传递元件。VTS由四线直流加热器和在20 dB直通衰减器中耗散的微波功率交替加热。通过拟合热瞬态并比较相应的稳态温度，通过交流/直流替代程序从直接测量的直流电功率推断出吸收的微波功率。然后基于开关辅助的短路-开路-负载-互易校准，通过低温双端口散射参数测量来考虑衰减器的有限反射和传输，从而将结果参考到DUT参考平面。该系统在稀释制冷机中得到验证，DUT输入平面的功率在-43至-58 dBm之间。所展示的相对标准不确定度范围从-43.9 dBm时的约2%到-57.6 dBm时的约40%。所提出的方法将热射频功率传输、低温S参数校正和不确定度评估结合在一个与量子器件实验兼容的测量架构中，为毫开尔文级别的可溯源微波功率校准提供了一条实用途径。
英文摘要
Accurate knowledge of the microwave power delivered to a cryogenic device under test (DUT) is essential for the characterization and operation of superconducting quantum circuits. However, this information is difficult to obtain inside dilution refrigerators because of distributed attenuation, impedance mismatch, switch-path repeatability, and temperature-dependent microwave components. This paper presents an in situ measurement method for RF power at the cryogenic device plane. The method uses a custom variable temperature stage (VTS) as a cryogenic thermal-transfer element. The TVS is alternately heated by a four-wire DC heater and by microwave power dissipated in a 20 dB pass-through attenuator. By fitting the thermal transients and comparing the corresponding steady-state temperatures, the absorbed microwave power is inferred from a directly measured DC electrical power through an AC/DC substitution procedure. The finite reflection and transmission of the attenuator are then accounted for by cryogenic two-port scattering-parameter measurements based on a switch-assisted Short--Open--Load--Reciprocal calibration, so that the result is referred to the DUT reference plane. The system is demonstrated in a dilution refrigerator with powers between -43 and -58 dBm at the DUT input plane. The demonstrated relative standard uncertainty ranges from about 2% at -43.9 dBm to about 40% at -57.6 dBm. The proposed approach combines thermal RF power transfer, cryogenic S-parameter correction, and uncertainty evaluation in a measurement architecture compatible with quantum-device experiments, providing a practical route toward traceable microwave-power calibration at millikelvin stages.
