The preparation, controlled evolution, and measurement of specific quantum states are fundamental activities in physics. The study of new states of matter and the new perspectives on quantum physics that are provided by processing the information are but two of the important reasons for pursuing such research. The numerous potential applications range from performing precision measurements to manipulating molecular nanoscale devices. Optimally designing the control and measurement strategies is important for extracting the most information about the state of the system from a given set of measurements. Tools based on control theory have been developed for such purposes for systems that obey the laws of classical physics. But for quantum systems, redirecting those tools—and possibly introducing new ones as needed—is a challenge.
That control concepts may be useful for robustly creating particular quantum states has long been recognized. The development of complex pulse sequences in nuclear magnetic resonance is a...
