Modelling Exchange in Silicon Quantum Dots

Mr Brandon Buonacorsi
Institute for Quantum Computing at the University of Waterloo, Canada
2pm Friday 17 November 2017
CQC2T Conference Room, Level 2, Newton Building J12, UNSW Kensington Campus

A challenge for modelling quantum dot spin qubits in silicon is the quantitative estimation of the exchange energy J 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. While the present calculations assume a single valley state, the CI methods can be extended to properly account for multiple valley states. I will also give a brief overview of our group’s experimental program, including quantum transport in nanowires, carbon nanotubes, and silicon quantum dots.