We present a framework for studying bosonic non-Gaussian channels ofcontinuous-variable systems. Our emphasis is on a class of channels that wecall photon-added Gaussian channels, which are experimentally viable withcurrent quantum-optical technologies. A strong motivation for considering thesechannels is the fact that it is compulsory to go beyond the Gaussian domain fornumerous tasks in continuous-variable quantum information processing such asentanglement distillation from Gaussian states and universal quantumcomputation. The single-mode photon-added channels we consider are obtained byusing two-mode beam splitters and squeezing operators with photon additionapplied to the ancilla ports giving rise to families of non-Gaussian channels.For each such channel, we derive its operator-sum representation, indispensablein the present context. We observe that these channels are Fock preserving(coherence nongenerating). We then report two examples of activation using ourscheme of photon addition, that of quantum-optical nonclassicality at outputsof channels that would otherwise output only classical states and of both thequantum and private communication capacities, hinting at far-reachingapplications for quantum-optical communication. Further, we see that noisyGaussian channels can be expressed as a convex mixture of these non-Gaussianchannels. We also present other physical and information-theoretic propertiesof these channels.
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