ONLINE PhD Defense: Federico Fedele

Spin interactions within a two-dimensional array of GaAs double dots

Spin qubits are widely studied as a candidate platform for building a quantum processor. Milestones in the field include reliable device fabrication, tuning and operation of spin qubits in one- and two-dimensional arrays. I present the results of experiments performed towards these objectives by fabricating, measuring, and manipulating two-dimensional spin-qubit arrays encoded in electrostatically defined quantum dots. These involve experiments exploring the manipulation of multiple spin qubits. In particular, I present an experimental protocol to measure the synchronization between two singlet-triplet qubits’ exchange control operations with sub-nanosecond resolution. Then, I show the simultaneous control of four singlet-triplet qubits by performing simultaneous exchange-controlled operations and T2* measurements across the array. Finally, I investigate the coupling of distant qubits using the long-range exchange interaction via a quantum mediator, realized as a multielectron dot embedded in our device architecture. In particular, we show that we can bias the device in a configuration in which one of the qubits can be coherently coupled with the quantum mediator.