Towards hole spin qubits and Majorana fermions in Germanium (START-Programm)

The self-assembled growth of crystalline Ge islands on Si was reported for the first time in 1990. This created great expectations that such nanostructures could provide a valid route towards innovative, scalable and CMOS-compatible nanodevices. Two decades later the PI was able to realize the first devices based on such structures, and to investigate for the first time their electronic properties. His results indicate that Ge self-assembled quantum dots display a rather unique combination of properties, i.e. low hyperfine interaction, strong and tunable spin-orbit coupling and spin selective tunneling. In 2012, the PI's group went a step further and realized for the first time ultra-small self-assembled Ge nanowires monolithically integrated on standard Si substrates, which will allow thus the PI's group to move towards double quantum dots and Majorana fermions. In view of their exceptionally small and self-defined cross section, these Ge wires hold promise for the realization of hole systems with exotic properties and provide a new development route for silicon-based nanoelectronics. Within this project, the PI aims to explore these newly developed Ge self-assembled nanowires, both for spin based as well as for topological (Majorana fermions) quantum computation. His long term vision is to couple these two types of "quantum hardware" in one "technological platform" enabling thus the coherent transfer of quantum information between them.