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

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
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