Semiconductor Quantum Dot Fabrication
Electronic noise affects measuring the physical phenomena of various systems, particularly those regarding the precise measurement of quantum states. For example, the signal originating from a spin qubit within a semiconductor quantum dot device hinges on a small charge difference (a charge quanta in most cases), rendering it highly susceptible to electronic noise. Moreover, electrical line noise can induce decoherence by interacting with the quantum states of the system. In some cases, extremely low temperatures, often in the millikelvin range, are required to mitigate these challenges. Achieving such conditions necessitates the use of dilution refrigerators along with meticulously designed DC and RF lines.
While commercial dilution refrigerators are readily available, customization of electrical lines is often needed to tailor them to specific physical systems. In our case, we had to customize both RF and DC lines to suppress the decoherence induced by electrical noise and ensure high signal-to-noise ratio (SNR) readouts of qubit states. Throughout the project, my contributions included configuring RF reflectometry setups with attenuators and directional couplers, developing and installing DC filters and bias-tees, and constructing various passive component devices like breakout boxes.
In addition to customizing the dilution refrigerator, I also participated in selecting and installing various electronic measurement instruments such as the ultrahigh lock-in amplifier (UHFLI), low-noise stable DC voltage source, and arbitrary waveform generator. These measures collectively contributed to achieving the stringent noise suppression required for our experiments.