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A quantum channel is conjugate degradable if the channel's environment can be simulated up to complex conjugation using the channel's output. For all such channels, the quantum capacity can be evaluated using a single-letter formula. In this article we introduce conjugate degradability and establish a number of its basic properties. We then use it to calculate the quantum capacity of N to N +1 and 1 to M universal quantum cloning machines as well as the quantum capacity of a channel that arises naturally when data are being transmitted to an accelerating receiver. All the channels considered turn out to have strictly positive quantum capacity, meaning they could be used as part of a communication system to send quantum states reliably.

We consider coverage problems in robot sensor networks with minimal sensing capabilities. In particular, we demonstrate that a "blind" swarm of robots with no localization and only a weak form of distance estimation can rigorously determine coverage in a bounded planar domain of unknown size and shape. The methods we introduce come from algebraic topology.

Abstract-In this paper, we present an approach towards the computation of certain topological invariants in real sensor networks. As shown by many researchers, these invariants are relevant for modeling certain properties of the network such as coverage and routing. What has been lacking so far is a concrete decentralized method to compute these invariants for proper implementation. In this paper, we give an approach towards such an implementation. The main tools being used here are the the so-called higher order Laplacian operators and distributed methods for their spectral analysis that resemble gossip algorithms.