Problem 19: Continuous-measurement based feedback control is highly complex because modifying the measurement as part of the feedback can increase the performance. Optimal protocols are still not known even for a single qubit, and progress is hampered by the size of the search space. Explore more complex protocols for small quantum systems than those that have been tried to date to see if they enhance performance, guided by known results to-date. For protocols that do enhance performance, consider whether this enhancement has a bearing on coherent feedback.