The extreme points of SU(2)-irreducibly covariant channels

In this paper, we introduce EPOSIC channels, a class of SU(2)-covariant quantum channels. For each of them, we give a Kraus representation, its Choi matrix, a complementary channel, and its dual map. We show that they are the extreme points of all SU(2)-irreducibly covariant channels. As an application of these channels, we get an example of a positive map that is not completely positive.

EFFECTIVE METHODS IN INVESTIGATION OF IRREDUCIBLE QUANTUM OPERATIONS

In this paper we discuss some constructive procedures which can be used in characterization of irreducible quantum operations and quantum channels. Our method makes use of an explicit form of a fixed operation in its Kraus representation. A generalization of the Shemesh criterion is discussed.