Accurate detection of quantum states is a vital step in the development of quantum computing. Image-charge detection of quantum states of electrons on liquid helium can potentially be used for the readout of a single-electron qubit; however, low sensitivity due to added noise hinders its usage in high fidelity and bandwidth (BW) applications. One method to improve the readout accuracy and bandwidth is to use cryogenic amplifications near the signal source to minimize the effects of stray capacitance. We experimentally demonstrate a two-stage amplification scheme with a low power dissipation of 90 {\mu}W at the first stage located at the still plate of the dilution refrigerator and a high gain of 40 dB at the second stage located at the 4 K plate. The good impedance matching between different stages and output devices ensure high BW and constant gain in a wide frequency range. The detected image-charge signals are compared for one-stage and two-stage amplification schemes.

中文翻译：

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用于读出液氦上电子量子态的图像电荷检测的低温放大

准确检测量子态是量子计算发展的关键一步。液氦上电子量子态的图像电荷检测可潜在地用于单电子量子位的读出；然而，由于增加的噪声导致的低灵敏度阻碍了其在高保真度和带宽 (BW) 应用中的使用。提高读出精度和带宽的一种方法是在信号源附近使用低温放大来最小化杂散电容的影响。我们通过实验证明了一种两级放大方案，在位于稀释制冷机静止板的第一级具有 90 {\mu}W 的低功耗，在位于 4 K 的第二级具有 40 dB 的高增益盘子。不同级和输出设备之间良好的阻抗匹配确保了宽频率范围内的高带宽和恒定增益。针对一级和二级放大方案比较检测到的图像电荷信号。