A two-module trapped-ion quantum computer prototype

Quantum information technology has the potential to revolutionise a wide range of research fields and to have a profound impact on society. Today, work towards a universal quantum computer is benefiting from recent breakthroughs in quantum hardware engineering. One of the most promising approaches is based on quantum computing modules that are networked via ion shuttling. The modules make use of microfabricated electrodes that create electric fields to confine ensembles of ion qubits. Combining this modular approach with strong magnetic field gradients and long-wavelength radiation quantum gate technology can significantly improve system scalability. Nevertheless, the realisation and simultaneous integration of all the core characteristics of such modules remains an intrinsically challenging task. This doctoral thesis investigates novel techniques and components critical to the engineering of this architecture. A prototype ion trapping system is constructed for the operation of two microfabricated ion-trap modules, which will enable the execution of key operations for networked quantum logic, i.e. high-fidelity one- and two-qubit gates, and shuttling of ion qubits between both modules to realise a matter-based quantum link. In this scheme, high-fidelity quantum gates require a large magnetic field gradient to be generated at the ion position. To achieve this, novel current-carrying wire structures directly embedded within the ion-trap module were developed. These offer a scalable solution to this challenge. The operation of ion traps at cryogenic temperatures is also desirable to further enhance quantum gate fidelities. A thermal model of the ion trap is presented and a cryogenic cooling system capable of meeting the requirements of a large-scale ion-trap architecture is demonstrated. Finally, the constructed two-module ion-trap apparatus is presented. This provides a viable set-up for the execution of these key operations, paving the way towards the realisation of a universal quantum computer