A scalable demonstrator for trapped-ion quantum computing using modules connected by electric fields

This thesis describes the development of a modular demonstrator device for scalable quantum computing using ion traps connected by electric fields. The experiment was configured to control the positions of two independent surface-electrode ion trap modules, whose electrodes when aligned create a potential suitable for ion transport between the modules. In principle this method can be used to construct a modular ion-trap processor of arbitrary size. An analysis of the requirements for reliable, low-loss transfer of ion qubits between the modules is presented. The experiment was used to trap 174Yb ions and to transport ions between modules as a proof-of-principle quantum link. The ion trap geometry incorporates a junction to enable reordering and transport of ions between spatially separated zones, and the experiment is designed for operating microwave-driven quantum logic gates using a magnetic field gradient. To increase the maximum attainable current for on-chip magnetic gradient coils, a scalable cryogenic cooling system was developed with high cooling power and an extensible design. The cooling system was connected to the demonstrator experiment and two additional ion trap experiments to prove its capability to scale in size. The minimum temperature achieved was 40 K under no active heat load, and 70 K for a heat load of 111W. This permits large gradients for high-fidelity logic gates, an order of magnitude reduction in ion heating rate, and lowers vacuum chamber pressure for increased ion lifetimes. The demonstrator experiment is a step towards the realisation of a large-scale quantum computer based on trapped ions.