Multiplicativity of the maximal output 2-norm for depolarized Werner-Holevo channels

Understand

We study the multiplicativity of the output 2-norm for depolarized Werner-Holevo channels and show that multiplicativity holds for a product of two identical channels in this class.

• Moreover, it shown that the depolarized Werner-Holevo channels do not satisfy the entrywise positivity condition introduced by C.
• King and M.B.
• Ruskai, which suggests that the main result is non-trivial.