Study of Nb and NbN Resonators at 0.1 K for Low-Noise Microwave SQUID Multiplexers
Study of Nb and NbN Resonators at 0.1 K for Low-Noise Microwave SQUID Multiplexers
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用于低噪声微波 SQUID 多路复用器的 Nb 和 NbN 谐振器 0.1 K 的研究
DOI：
10.1109/tasc.2016.2637865
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发表时间：
2017
影响因子：
1.8
通讯作者：
H. Takahashi
中科院分区：
文献类型：
--
作者：
T. Irimatsugawa;F. Hirayama;H. Yamamori;S. Kohjiro;A. Sato;S. Nagasawa;D. Fukuda;M. Hidaka;Y. Sato;M. Ohno;H. Takahashi
超导谐振器的品质因数和噪声性能在微波SQUID复用器(MW-MUX)中起着重要的作用。由于我们研制了用于过渡边缘传感器阵列的微波SQUID复用器，其工作温度约为100mK，其中二能级系统(TLS)的影响是显著的。在本文中，我们通过对四种类型的谐振器的表征，研究了电极材料或晶片对MW-MUX噪声性能的影响。虽然谐振频率的温度依赖关系和QU的功率依赖关系在不同材料之间表现出明显的差异，但构成MW-MUX读出噪声的频率噪声是相似的。理论模型预测，在适合我国MW-MUX低噪声运行的功率范围内，不是TLS而是其他损耗占主导地位。此外，根据测量的频率噪声和从频率到磁通的换算√系数计算的估计磁通噪声为1-5(μΦ0/√Hz)@1赫兹，0.2-0.8(μΦ0/√赫兹)@3千赫。这些结果表明，我们的MW-MUX的噪声对材料的依赖性很小，并且与典型的DC SQUID兼容的低噪声工作是可能的。因此，采用我们的材料的MW-MUX不会受到TLS带来的低频噪声的影响。
The quality factors and noise performances of superconducting resonators play an important role in microwave SQUID multiplexer (MW-MUX). Since we develop microwave SQUID multiplexer for transition edge sensor arrays, the operation temperature is around 100 mK where the effects of two level system (TLS) can be significant. In this paper, we have investigated the electrode-material or wafer dependence of noise performance of MW-MUX by characterizing four types of resonators. Although the temperature dependence of resonance frequency and the power dependence of Qu show clear difference among the materials, frequency noises which contribute the readout noise of MW-MUX are similar. Theoretical model predicts that not TLS but other loss dominates Qu in the power region suitable for the low-noise operation of our MW-MUX. Further, the estimated flux noise calculated from the measured frequency noise and the conversion √ coefficient from frequency to flux were 1-5 (μΦ0/√Hz) @ 1 Hz, 0.2-0.8 (μΦ0/√Hz) @ 3 kHz. These results indicate the noise of our MW-MUX has small material dependence and the compatible low noise operation to typical dc SQUIDs would be possible. Therefore, the MW-MUX with our materials would not suffer from the low frequency noise due to TLS.