Real-Time Feedback Control of Charge Sensing for Quantum Dot Qubits

TL;DR

This paper presents a real-time feedback control system for charge sensors in quantum dot qubits, enabling fast, stable, and high-fidelity charge detection crucial for quantum computing applications.

Contribution

It introduces a digital PID controller-based feedback loop that maintains charge sensor sensitivity in real-time, improving measurement speed and stability in quantum dot systems.

Findings

Achieved charge sensor operation bandwidth of approximately 100 kHz.

Enabled real-time charge stability diagram measurement and rapid quantum dot tuning.

Facilitated submicrosecond single-shot spin readout without sensor performance loss.

Abstract

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 $\approx 100\,{\rm kHz}$. 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.