Brandon Buonacorsi - Modeling the Exchange Interaction in Silicon Quantum Dots
Silicon metal-oxide-semiconductor field effect transistor (MOSFET) quantum dots are promising candidates for scalable quantum computing using electron spin qubits due to their long coherence times, compact size, and ease of integration into existing fabrication technologies. I will introduce how we fabricate these devices and describe the experimental characterizations we do to check the stability and tunability of our quantum dots. In a double quantum dot device, two qubit gates are realized through the Heisenberg exchange interaction. A current challenge for scaling these quantum dot devices is to have a model that allows for quantitative estimation of the exchange energy over a wide range of electrostatic potentials. Approximate methods such as Heitler-London and Hund-Milliken are often applied to GaAs dots, but break down in Silicon due to the larger effective mass of the electron. I will discuss our progress towards building a simulation toolbox for exchange energies based on configuration interaction (CI) methods commonly used in quantum chemistry. A finite-element solver simulates the potential landscape of Silicon MOSFET double quantum dots as a function of applied gate potentials, and the results are input to a CI code to calculate the two-electron eigenstates and energies.