The spin state of electrons or holes confined in quantum dots has been shown in many experiments to form a very promising qubit. It has long coherence times, can be manipulated on very short time scales, and has due to its small form-factor great potential for scaling. In this project we investigate the use of hole spin qubits defined in 1D Germanium- and Silicon-based nanodevices, such as Ge/Si core-shell nanowires. In particular, we aim to make use of its very unique type of strong and highly tunable spin-orbit interaction.
The overall goal of this project is to build a fast, controllable, and scalable platform to study the physics of multiple coupled qubits. For this, we intend to use the strong and electrically tunable spin-orbit interaction of these hole spin qubits, to combine unprecedented spin qubit operation speeds with long qubit lifetimes.
The strong spin-orbit interaction in the valence band of germanium and silicon nanostructures enables ultrafast all-electrical qubit control and coupling to microwave photons, potentially enabling quantum operation clock rates in the gigahertz regime. A very interesting aspect of the specific spin-orbit interaction targeted here is its large electrical tunability, in effect providing an ON/OFF switch of the interaction of the spin qubit to its environment. Investigation of this spin-orbit interaction is furthermore of fundamental interest for studies of helical hole states and Majorana fermions. We will leverage this unique feature to construct a novel type of spin qubit, which could enter the strong driving regime of qubit manipulation, while still remaining highly coherent.
In a next step, we will investigate how to efficiently generate entanglement between qubits separated by macroscopic distances, study multi-qubit physics and complete the basic toolbox of fast universal quantum computation. Finally, we will explore strategies of creating spin qubit arrays with high degrees of connectivity.