Quantum steering has recently been formalized in the framework of a resourcetheory of steering, and several quantifiers have already been introduced. Here,we propose an information-theoretic quantifier for steering called intrinsicsteerability, which uses conditional mutual information to measure thedeviation of a given assemblage from one having a local hidden-state model. Wethus relate conditional mutual information to quantum steering and introducemonotones that satisfy certain desirable properties. The idea behind thequantifier is to suppress the correlations that can be explained by aninaccessible quantum system and then quantify the remaining intrinsiccorrelations. A variant of the intrinsic steerability finds operational meaningas the classical communication cost of sending the measurement choice andoutcome to an eavesdropper who possesses a purifying system of the underlyingbipartite quantum state that is being measured.
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