When does noise increase the quantum capacity?

Abstract

Superactivation is the property that two channels with zero quantum capacity can be used together to yield positive capacity. Here we demonstrate that this effect exists for a wide class of inequivalent channels, none of which can simulate each other. We also consider the case where one of two zero capacity channels are applied, but the sender is ignorant of which one is applied. We find examples where the greater the entropy of mixing of the channels, the greater the lower bound for the capacity. Finally, we show that the effect of superactivation is rather generic by providing example of superactivation using the depolarizing channel.

Corrected minor typos

References in corpus (4)

• Quantum Communication With Zero-Capacity Channels
• The structure of degradable quantum channels
• Extensive nonadditivity of privacy
• For quantum information, two wrongs can make a right

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• Algorithmic Superactivation of Asymptotic Quantum Capacity of Zero-Capacity Quantum Channels
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• Quasi-Superactivation of Classical Capacity of Zero-Capacity Quantum Channels
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• Noise is resource-contextual in quantum communication
• Superactivation of Quantum Channels is Limited by the Quantum Relative Entropy Function
• Simultaneous superadditivity of the direct and complementary channel capacities