Lower and upper bounds on nonunital qubit channel capacities. (arXiv:1802.00646v1 [quant-ph])

Classical capacity of unital qubit channels is well known, whereas that of
nonunital qubit channels is not. We find lower and upper bounds on classical
capacity of nonunital qubit channels by using a recently developed
decomposition technique relating nonunital and unital positive qubit maps.

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