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Conference on Precision Electromagnetic Measurements

Current-reversal technique for single-parameter electron pumps

Myung‐Ho Bae, Bum-Kyu Kim, Byeong-Sung Yu, Wan-Seop Kim, Nam Kim

Published Aug 1, 2020• 0 citations
Publisher

Abstract

We developed a current-reversal operation method for single-parameter electron pumps, based on cryo-gate switches located between the ohmic contacts and quantum dot. The current reversal mode provided an enhanced signal-to-noise ratio, resulting in a reduction of the measurement time to reach the same relative measurement uncertainty, compared to a conventional unipolar current measurement method.

DOI
10.1109/cpem49742.2020.9191893

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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 RFB. A lower RFB of 50 kΩ enables high-speed current measurement with a −3 dB cutoff frequency f−3dB = 28 MHz and noise-floor NF = 8.5 × 10−27 A2/Hz, while a larger RFB of 400 kΩ provides low-noise measurement with NF = 1.0 × 10−27 A2/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 RFB = 200 kΩ, which compares favorably with the best-reported values for the radio frequency reflectometry technique. The time resolution can be further improved at the cost of the SNR (or vice versa) by using an even smaller (larger) RFB, 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.