Measurement of charge configurations in few-electron quantum dots is a vital technique for spin-based quantum information processing. While fast and high-fidelity measurement is possible by using proximal quantum dot charge sensors, their operating range is limited and prone to electrical disturbances. Here we demonstrate realtime operation of a charge sensor in a feedback loop to maintain its sensitivity suitable for fast charge sensing in a Si/SiGe double quantum dot. Disturbances to the charge sensitivity, due to variation of gate voltages for operating the quantum dot and 1/f charge fluctuation, are compensated by a digital PID controller with the bandwidth of ≈100kHz. The rapid automated tuning of a charge sensor enables unobstructed charge stability diagram measurement facilitating realtime quantum dot tuning and submicrosecond single-shot spin readout without compromising the performance of a charge sensor in time-consuming experiments for quantum information processing.
@article{arxiv.2103.15258,
title = {Real-Time Feedback Control of Charge Sensing for Quantum Dot Qubits},
author = {Takashi Nakajima and Yohei Kojima and Yoshihiro Uehara and Akito Noiri and Kenta Takeda and Takashi Kobayashi and Seigo Tarucha},
journal= {arXiv preprint arXiv:2103.15258},
year = {2021}
}