Nonclassical steering in quantum optics

Abstract

Optical nonclassicality is considered as the impossibility to represent quantum states as statistical mixtures of coherent states. Furthermore, it is considered as an important example of quantum resources needed, e.g., for the generation of entanglement with passive linear optics, as well as for tasks in quantum metrology and non-universal quantum computing. We consider a scenario where the informational incompleteness of quantum measurements is insufficient to reveal optical nonclassicality [1]. It turns out that even in such a scenario for the case of states conditionally prepared on one mode of optical radiation by a measurement on another mode, we can still extract some information about nonclassicality. This task can be performed by a proper analysis of nonclassical steering---a class of quantum correlations beyond quantum entanglement and discord for which we introduce a rigorous description [2].