Dynamical decoupling in quantum control: A system theoretic approach

Suppressing decoherence is one of the most challenging problems in the control of quantum dynamical systems. Dynamical decoupling is an open-loop decoherence control technique based on high-frequency and high-amplitude periodic controls. Here, we reformulate the effects of the basic strategy in terms of linear, symmetric matrix equations. Such a reformulation proves to be useful both in the analysis and in the synthesis of the needed unitary control actions. A general framework is provided, and simple, but significant, particular cases are studied in detail.