Transfer function approach to quantum control systems

The paper gives an approach to feedback control for quantum systems described by noncummutative operators. We investigate the dynamics of a quantum system interacting with an optical field through which the output of the system is fed back. This process corresponds to quantum feedback via local operations and quantum channels. Based on an input/output description, the dynamics of the feedback system is translated in terms of control theory. This establishes a link between quantum optics and control theory, and the concept and tools of control theory contribute not only to understand quantum control, but enable to solve some of the fundamental problems in quantum mechanics.