Manipulation of charge qubits in chains of quantum dots

Scalability of a qubit concept is one of the prerequisites for quantum computing. Usually one thinks that in semiconductor based qubit architectures scaling is relatively simple due to the achievements in microelectronics Nevertheless one has to work really hard and develop new concepts to control and manipulate quantum states in such systems.

In this PhD work such concepts will be developed and tested for the case of charge qubits in semiconducting quantum dots. In the figure below a typical device is shown as to be investigated in the course of the PhD work. The figure shows 4 quantum dots produced via split-gate technique in a GaAs/AlGaAs heterostructure. Also shown are the different gates used for tuning and manipulating the qubits. Such devices will be produced with the help of ebeam lithography. They will be tested at low temperatures as e.g. shown in Ref. [1] and characterized in detail by involving full counting statistics as e.g. done in Refs. [2,3]. Using modern numerical concepts of artificial intelligence the tuning of the will be simplified and initialization of qubits will be much easier.

[1] J. Bayer et al., Ann. Phys. (Berlin) 531, 1800393 (2019).
[2] T. Wagner et al., Nature Physics 15, 330 (2019).
[3] T. Wagner et al. Nature Nanotechnology 12, 218 (2017)

Figure: Split-gate structure with 4 quantum dots on top of a GaAs/AlGaAs heterostructure.