Coherent observer engineering for protecting quantum information

Abstract : In this paper, we extend the applicability of coherent quantum observers to enable the generation of decoherence free subsystem which can be used for quantum information storage. In particular, a general quantum linear passive system can be equipped with a decoherence free subsystem by placing some of its poles on the imaginary axis via engineered observer-based controller. The controller design for the case of optical cavity systems is illustrated in the context of examples.