We give an affirmative answer to the question posed by Yang et al. on the existence of indecomposable 2-positive linear maps from M₃ (C) to M₄ (C). In this study, we construct an explicit class of linear maps in B (M₃ (C), M₄ (C) ) that are positive, yet fail to be completely positive or completely copositive. Furthermore, we demonstrate that the associated Choi matrices of these maps serve as entanglement witnesses.
C. A. Winda (Sat,) studied this question.