Mixing doubly stochastic quantum channels with the completely depolarizing channel. (English) Zbl 1172.81322

Watrous, John

Quantum Inf. Comput. 9, No. 5-6, 406-413 (2009).

Summary: It is proved that every doubly stochastic quantum channel that is properly averaged with the completely depolarizing channel can be written as a convex combination of unitary channels. It follows that within the space of doubly stochastic quantum channels, there is a ball with positive radius around the completely depolarizing channel within which all channels are convex combinations of unitary channels.

MSC:

81P68	Quantum computation
94A40	Channel models (including quantum) in information and communication theory

Keywords:

doubly stochastic quantum channels; random unitary channels; mixed unitary channels; theory of quantum information