An intrinsic order-theoretic characterization of the weak expectation property

We prove the following characterization of the weak expectation property for operator systems in terms of Wittstock’s matricial Riesz separation property: an operator system $S$ satisfies the weak expectation property if and only if $M_q(S)$ satisfies the matricial Riesz separation property for every $q\in $\mathbb{N}$$. This can be seen as the noncommutative analog of the characterization of simplex spaces among function systems in terms of the classical Riesz separation property.