使用自制低温跨阻放大器实现量子点电荷传感的快速时域电流测量
Fast time-domain current measurement for quantum dot charge sensing using a homemade cryogenic transimpedance amplifier
AI总结：
本文提出基于自制 GaAs HEMT 低温 TIA 的高速低噪声时域电流测量方案，通过反馈电阻权衡带宽与噪声，实现量子点电荷传感及自旋量子比特读出所需的高时间分辨率。
摘要：
我们利用自制的、基于 GaAs 高电子迁移率晶体管的低温跨阻放大器（TIA），开发了一种高速、低噪声的时域电流测量方案。由于该 TIA 具有可与商用室温 TIA 相媲美的低输入阻抗，该方案可广泛适用于包括半导体自旋量子比特读出在内的多种低温电流测量。TIA 具有宽频率带宽和低噪声底，二者之间的权衡由反馈电阻 $R_{FB}$ 决定。较低的 $R_{FB}$ 为 50 k$Ω$ 时可实现高速电流测量，其 -3 dB 截止频率 $f_{-3dB}$ = 28 MHz，噪声底 $NF = 8.5 \ imes 10^{-27}$ A$^{2}$/Hz；而较大的 $R_{FB}$ 为 400 k$Ω$ 时可提供低噪声测量，$NF = 1.0 \ imes 10^{-27}$ A$^{2}$/Hz，$f_{-3dB}$ = 4.5 MHz。对峰峰值为 2 nA 的方波进行时域测量（该方波模拟了通过电荷传感实现标准自旋量子比特读出技术的输出），结果表明在 $R_{FB}$ = 200 k$Ω$ 时信噪比（SNR）为 12.7，时间分辨率为 48 ns，与射频（RF）反射测量技术已报道的最佳值相比具有优势。通过使用更小（更大）的 $R_{FB}$，可以以牺牲 SNR 为代价进一步提高时间分辨率（反之亦然）；同时，通过低通滤波器限制频带，还可以进一步降低噪声系数。我们的方案最适合用于需要高时间分辨率和电流灵敏度的低温传感器读出电子器件，从而为各类基础研究和工业应用提供了解决方案。
英文摘要：
We developed a high-speed and low-noise time-domain current measurement scheme using a homemade GaAs high-electron-mobility-transistor-based cryogenic transimpedance amplifier (TIA). The scheme is versatile for broad cryogenic current measurements, including semiconductor spin-qubit readout, owing to the TIA's having low input impedance comparable to that of commercial room-temperature TIAs. The TIA has a broad frequency bandwidth and a low noise floor, with a trade-off between them governed by the feedback resistance $R_{FB}$. A lower $R_{FB}$ of 50 k$Ω$ enables high-speed current measurement with a -3dB cutoff frequency $f_{-3dB}$ = 28 MHz and noise-floor $NF = 8.5 \times 10^{-27}$ A$^{2}$/Hz, while a larger $R_{FB}$ of 400 k$Ω$ provides low-noise measurement with $NF = 1.0 \times 10^{-27}$ A$^{2}$/Hz and $f_{-3dB}$ = 4.5 MHz. Time-domain measurement of a 2-nA peak-to-peak square wave, which mimics the output of the standard spin-qubit readout technique via charge sensing, demonstrates a signal-to-noise ratio (SNR) of 12.7, with the time resolution of 48 ns, for $R_{FB}$ = 200 k$Ω$, which compares favorably with the best-reported values for the radio-frequency (RF) reflectometry technique. The time resolution can be further improved at the cost of the SNR (or vice versa) by using an even smaller (larger) $R_{FB}$, with a further reduction in the noise figure possible by limiting the frequency band with a low-pass filter. Our scheme is best suited for readout electronics for cryogenic sensors that require a high time resolution and current sensitivity and thus provides a solution for various fundamental research and industrial applications.
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