Hochfrequenzgesteuerte Quanteninformationsverarbeitung in einer mikrostrukturierten Paul-Falle mit integrierten Solenoidstrukturen

A quantum computer offers both the potential to solve certain problems more efficiently than any classical computer and to contribute to questions across practically the entire spectrum of physical research, as well as beyond, through quantum simulations. One of the most advanced approaches to realizing a quantum computer to date is based on ultracold ions trapped in a Paul trap. The main challenge here, as with all other physical implementation methods, lies in the development of a complete system that can be scaled into a quantum computer capable of solving problems of practical relevance.
This dissertation contributes to the efforts to develop technologies for the realization of a scalable ion-based quantum computer. An optical method for the precise determination of the position of trapped ions based on fluorescence light is presented, which allows localization in all three spatial dimensions with an accuracy well below the wavelength of the ion fluorescence. This method enables the development of a novel approach to minimizing undesired micromotion of trapped ions. The approach is based on the analysis of ion trajectories generated by deliberate manipulation of the trapping potential of an ion trap and is particularly suitable for use with extended, planar trap chips, as it is independent of the propagation direction of the laser light used. Furthermore, a method is developed to use a trapped ion as a highly sensitive force sensor, capable of detecting forces in the yoctonewton range. This method is also based on optical position determination and requires only knowledge of the trapping potential in addition. It is highly compatible with miniaturized and highly integrated ion traps, making it suitable for applications in precision metrology. The use of magnetic field gradients enables the manipulation of individual qubits and the realization of multi-qubit gates solely through radiofrequency signals. Due to their high integrability, this represents a potential key technology for scaling ion-based quantum computers. Thiswork extends the functionality of a microstructured ion trap with integrated solenoid structures to include a dynamically controllable magnetic field gradient. The generated gradients can be static or oscillating and can be varied on timescales in the microsecond range. Oscillating magnetic field gradients enable the acceleration of multiqubit gates as well as the creation of customized, temporary coupling patterns between qubits.
The newly created degree of freedom provided by dynamic gradient control is used to demonstrate optimized qubit addressing in the frequency domain.