The techniques of ion trapping have been indispensable for the study of single particles and have greatly increased our understanding of the physical world. With a high degree of control over single quantum systems made possible by recent technical developments, trapped ion researchers are now looking to observe increasingly complex quantum dynamics. There is nothing fundamentally limiting the size such systems can scale to, if the remaining engineering challenges can be overcome, and there is consequently enormous potential for our understanding of physical processes on the boundary between simple quantum and large scale classical effects. The transition between quantum and classical dynamics is characterised by decoherence, which reduces the purity of quantum states as they couple to the environment. Investigation into the mechanisms of decoherence requires the development of novel tools for its classification, which motivates the experiments presented in this work. These show that multi-level coherence in the motional state of a trapped ion can be verified from interference patterns which extend the Ramsey technique. The metric uses simple operations and is shown not to be able to produce false positives, making it of interest in the study of coherence in noisy intermediate scale systems. The motional state of a trapped ion cannot be directly measured, and the scheme shows it is possible to extract information about a quantum system coupled to the measurement basis. Coherence between quantum states can enhance information processing and sensing, which is driving the development of techniques for preserving coherence in the presence of noise. This motivates the project begun in this thesis, which is to design and implement control fields for robust ion trap quantum logic. The rapid progress in the scale of ion trap devices expected in the coming years means new leaps in our understanding of the physical world could happen at any moment.