A generalised framework for non-classicality of states

Abstract

Non-classical probability (along with its underlying logic) is a defining feature of quantum mechanics. A formulation that incorporates them, inherently and directly, would promise a unified description of seemingly different prescriptions of non-classicality of states that have been proposed so far. This paper sets up such a formalism. It is based on elementary considerations, free of ad-hoc definitions, and is completely operational. It permits a systematic construction of non-classicality conditions on states and also to quantify the non-classicality, at the same time. This quantification, as shown for the example of two level systems, can serve as a measure of coherence and can be furthermore, harnessed to obtain a measure for pure state entanglement for coupled two level systems.