Controlling quantum phenomena: Why does it appear easy to achieve?

The introduction of optimal control theory and associated optimal control experiments have produced many successful results for manipulating quantum systems including those of high complexity. These findings may appear surprising as hundreds of control variables are simultaneously searched to optimize a typical objective. This paper discusses the reason for this attractive behaviour, revealing that the origin lies in the quantum system simply being controllable and undergoing unitary evolution. Under satisfaction of these conditions, the search space landscape for maximizing the probability of making a quantum transition is shown to have no false extrema. Although real systems may not be fully controllable, this result provides the basis to explain the generally successful findings from quantum optimal control simulations and experiments, as well as provides a very positive projection of the future for the field.