Bachelors Defense: Lillian Austin

Preparation and tuning of a triple dot spin qubit

The realization of a quantum computer could have huge implications for the modern world. The basic building block of such a computer would be a qubit, analogous to the classical bit. One candidate base for a qubit is electron spin, which allows for a system that can be manipulated but is still fairly decoupled from its environment. One significant obstacle to be overcome in the creation of a qubit is the problem of decoherence - information lost through interactions with the environment that limits the capacity for memory and gate fidelity. These decoherence e↵ects can be minimized by operating the qubit within a ”sweet spot”, corresponding to a spot in parameter space where the properties of the system relevant to gate fidelity and memory are minimally a↵ected by environmental changes that otherwise disturb them. It has been proposed that there exists a full sweet spot from charge noise for a triple-dot exchange-only qubit, and that gate operations can be performed without moving away from the sweet spot. For this thesis, I will discuss two such proposed sweet-spots, and AEON and the ARX qubit, and the preparation of a qubit for testing them. Additionally, obstacles in the tuning of a triple dot are discussed, and, as the device used has been cooled down before, and I will take this opportunity to compare the device’s behaviour in different cool-downs.