On the structure of positive maps between matrix algebras
Volume 78 / 2007
Banach Center Publications 78 (2007), 249-263
MSC: Primary 47B65; Secondary 47L07.
DOI: 10.4064/bc78-0-18
Abstract
The structure of the set of positive unital maps between $M_2(\mathbb C)$ and $M_n(\mathbb C)$ (${n\geq 3}$) is investigated. We proceed with the study of the “quantized” Choi matrix thus extending the methods of our previous paper [MM2]. In particular, we examine the quantized version of Størmer's extremality condition. Maps fulfilling this condition are characterized. To illustrate our approach, a careful analysis of Tang's maps is given.
