Partially Coherent Direct Sum Channels

  title={Partially Coherent Direct Sum Channels},
  author={Stefano Chessa and Vittorio Giovannetti},
We introduce Partially Coherent Direct Sum (PCDS) quantum channels, as a generalization of the already known Direct Sum quantum channels. We derive necessary and sufficient conditions to identify the subset of those maps which are degradable, and provide a simplified expression for their quantum capacities. Interestingly, the special structure of PCDS allows us to extend the computation of the quantum capacity formula also for quantum channels which are explicitly not degradable (nor… 

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