## Projects 1 & 2

### Project 1: ARC Centre of Excellence in Future Low-Energy Electronics Technologies

**Project ID: 144**

**Supervisor(s): Dimi Culcer**

My research is fully integrated into the ARC Centre of Excellence in Future Low-Energy Electronics Technologies (http://www.fleet.org.au) and is focused on two areas.

##### Quantum transport in topological materials

Topological materials, such as topological insulators, Weyl semimetals, and strongly spin-orbit coupled semiconductors, have attracted considerable attention due to their potential in spin electronics and quantum computation. Recent work has revealed the presence of topological terms in their electrical response, which are generally associated with the Berry phase and lead to quantized values of e.g. certain components of the conductivity, which can be measured experimentally. However, the interplay of topological effects with unavoidable disorder and electron-electron interactions is not well understood and the subject of much controversy. It manifests itself in the charge and spin response of these materials to external electric and magnetic fields. Our group has recently developed a theory capturing these effects on the same footing, and is actively engaged in studying this interplay in a series of hotly researched materials such as Weyl semimetals, topological insulators, and spin-3/2 hole systems.

##### Architectures for low-energy, long-lived quantum computation

Electrical control of quantum bits could pave the way for scalable quantum computation. The spin-orbit interaction provides a pathway towards this goal: an electric field changes the electron's momentum and, through the spin-orbit interaction, it rotates its spin as well. Our recent work has found that certain quantum bits based on spin-3/2 holes in semiconductors can be effectively controlled by electrical means using a gate electrode, which offers fast one- and two-qubit rotations. However, the spin-orbit interaction also brings with it sensitivity to random electric fields, such as those due to phonons and noise, and can result in a decrease in coherence. The grand aim of our research is to determine what the trade-off is between fast electrical control and decoherence: can we make electrical spin qubits fast enough that we do not need to worry about loss of quantum information?