Irreducibly $SU(2)$-covariant quantum channels of low rank

Abstract

We investigate information theoretic properties of low rank (less than or equal to 3) quantum channels with $SU(2)$-symmetry, where we have a complete description. We prove that PPT property coincides with entanglement-breaking property and that degradability seldomly holds in this class. In connection with these results we will demonstrate how we can compute Holevo and coherent information of those channels. In particular, we exhibit a strong form of additivity violation of coherent information, which resembles the superactivation of coherent information of depolarizing channels.

24 pages

References in corpus (3)

• Degenerate Quantum Codes for Pauli Channels
• The structure of degradable quantum channels
• New lower bounds on the non-zero capacity of Pauli Channels