Abstract
The dissertation reports a series of electron transport experiments on semiconductor nanowires towards realizing the hypothesized topological quantum computation. A topological quantum computer manipulates information that is stored nonlocally in the topology of a physical system. Such an operation possesses advantages over the current quantum computation platforms due to its robustness against local sources of decoherence, offering a natural fault-tolerance. Among various candidate platforms to realize topological quantum computation, semiconductor nanowires with strong spin-orbit coupling attached to conventional superconductors have emerged as a prime contender. The predicted topological properties of such a system is associated with the emergence of Majorana modes.

The presence of disorder has been considered to be the main obstacle towards the realization of a topological quantum computer based on semiconductor nanowires. Disorder can mimic the experimentally measurable properties of Majoranas, or can render the promise of fault-tolerance ineffective. The experiments in the dissertation aim for eliminating the disorder on the surface of the nanowire, and in the interface between the nanowire and the superconductor. Following a series of investigations demonstrating materials improvements, ballistic Majorana nanowire devices are realized.