A discrete invitation to quantum filtering and feedback control. (English) Zbl 1167.93028
Summary: The engineering and control of devices at the quantum mechanical level – such as those consisting of small numbers of atoms and photons – is a delicate business. The fundamental uncertainty that is inherently present at this scale manifests itself in the unavoidable presence of noise, making this a novel field of application for stochastic estimation and control theory. In this expository paper we demonstrate estimation and feedback control of quantum mechanical systems in what is essentially a noncommutative version of the binomial model that is popular in mathematical finance. The model is extremely rich and allows a full development of the theory while remaining completely within the setting of finite-dimensional Hilbert spaces (thus avoiding the technical complications of the continuous theory). We introduce discretized models of an atom in interaction with the electromagnetic field, obtain filtering equations for photon counting and homodyne detection, and solve a stochastic control problem using dynamic programming and Lyapunov function methods.
MSC:
93E11 | Filtering in stochastic control theory |
93E15 | Stochastic stability in control theory |
93E20 | Optimal stochastic control |
81P15 | Quantum measurement theory, state operations, state preparations |
81S25 | Quantum stochastic calculus |
34F05 | Ordinary differential equations and systems with randomness |
49L20 | Dynamic programming in optimal control and differential games |