Kalra Rachpon, Laucht Arne, Dehollain Juan Pablo, Bar Daniel, Freer Solomon, Simmons Stephanie, Muhonen Juha T, Morello Andrea
Centre for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, UNSW Australia, Sydney NSW 2052, Australia.
Rev Sci Instrum. 2016 Jul;87(7):073905. doi: 10.1063/1.4959153.
Cryogen-free low-temperature setups are becoming more prominent in experimental science due to their convenience and reliability, and concern about the increasing scarcity of helium as a natural resource. Despite not having any moving parts at the cold end, pulse tube cryocoolers introduce vibrations that can be detrimental to the experiments. We characterize the coupling of these vibrations to the electrical signal observed on cables installed in a cryogen-free dilution refrigerator. The dominant electrical noise is in the 5-10 kHz range and its magnitude is found to be strongly temperature dependent. We test the performance of different cables designed to diagnose and tackle the noise, and find triboelectrics to be the dominant mechanism coupling the vibrations to the electrical signal. Flattening a semi-rigid cable or jacketing a flexible cable in order to restrict movement within the cable, successfully reduces the noise level by over an order of magnitude. Furthermore, we characterize the effect of the pulse tube vibrations on an electron spin qubit device in this setup. Coherence measurements are used to map out the spectrum of the noise experienced by the qubit, revealing spectral components matching the spectral signature of the pulse tube.
由于其便利性和可靠性，以及对作为自然资源的氦日益稀缺的担忧，无低温恒温器的低温装置在实验科学中越来越突出。尽管在冷端没有任何运动部件，但脉冲管制冷机引入的振动可能对实验有害。我们表征了这些振动与在无低温恒温器稀释制冷机中安装的电缆上观察到的电信号之间的耦合。主要的电噪声在5 - 10 kHz范围内，并且发现其幅度强烈依赖于温度。我们测试了旨在诊断和解决噪声的不同电缆的性能，发现摩擦电是将振动与电信号耦合的主要机制。将半刚性电缆弄平或在柔性电缆上套上护套以限制电缆内的移动，成功地将噪声水平降低了一个数量级以上。此外，我们表征了此装置中脉冲管振动对电子自旋量子比特器件的影响。相干测量用于绘制量子比特所经历噪声的频谱，揭示与脉冲管频谱特征相匹配的频谱成分。
