00485nas a2200145 4500008003900000245008100039210006900120260001600189300001100205490000700216100001900223700002900242700002000271856004800291 2018 d00aAll phase-space linear bosonic channels are approximately Gaussian dilatable0 aAll phasespace linear bosonic channels are approximately Gaussia cJan-11-2018 a1130120 v201 aLami, Ludovico1 aSabapathy, Krishna Kumar1 aWinter, Andreas uhttps://grupsderecerca.uab.cat/giq/node/91301928nas a2200133 4500008003900000245009200039210006900131300001100200490000700211520147100218100002901689700002001718856005601738 2017 d00aNon-{Gaussian} operations on bosonic modes of light: {Photon}-added {Gaussian} channels0 aNon Gaussian operations on bosonic modes of light Photon added G a0623090 v953 aWe present a framework for studying bosonic non-Gaussian channels of continuous-variable systems. Our emphasis is on a class of channels that we call photon-added Gaussian channels, which are experimentally viable with current quantum-optical technologies. A strong motivation for considering these channels is the fact that it is compulsory to go beyond the Gaussian domain for numerous tasks in continuous-variable quantum information processing such as entanglement distillation from Gaussian states and universal quantum computation. The single-mode photon-added channels we consider are obtained by using two-mode beam splitters and squeezing operators with photon addition applied to the ancilla ports giving rise to families of non-Gaussian channels. For each such channel, we derive its operator-sum representation, indispensable in the present context. We observe that these channels are Fock preserving (coherence nongenerating). We then report two examples of activation using our scheme of photon addition, that of quantum-optical nonclassicality at outputs of channels that would otherwise output only classical states and of both the quantum and private communication capacities, hinting at far-reaching applications for quantum-optical communication. Further, we see that noisy Gaussian channels can be expressed as a convex mixture of these non-Gaussian channels. We also present other physical and information-theoretic properties of these channels.1 aSabapathy, Krishna Kumar1 aWinter, Andreas uhttps://link.aps.org/doi/10.1103/PhysRevA.95.06230901758nas a2200157 4500008003900000022001400039245009500053210006900148260000800217490000700225520125900232100001801491700002901509700001401538856004801552 2017 d a2469-992600aScaling maps of s-ordered quasiprobabilities are either nonpositive or completely positive0 aScaling maps of sordered quasiprobabilities are either nonpositi caug0 v963 aContinuous-variable systems in quantum theory can be fully described through any one of the s-ordered family of quasiprobabilities Lambda(s) (a), s is an element of [-1,1]. We ask forwhat values of (s,a) is the scalingmap Lambda(s) (alpha) -{\textgreater} a(-2) Lambda(s) (a(-1)alpha) a positive map? Our analysis based on a duality we establish settles this issue: (i) the scaling map generically fails to be positive, showing that there is no useful entanglement witness of the scaling type beyond the transpose map, and (ii) in the two particular cases (s = 1,{\textbar}a{\textbar} {\textless}= 1) and (s = -1,{\textbar}a{\textbar} {\textgreater}= 1), and only in these two nontrivial cases, the map is not only positive but also completely positive as seen through the noiseless attenuator and amplifier channels. We also present a “phase diagram” for the behavior of the scaling maps in the s-a parameter space with regard to its positivity, obtained from the viewpoint of symmetric-ordered characteristic functions. This also sheds light on similar diagrams for the practically relevant attenuation and amplification maps with respect to the noise parameter, especially in the range below the complete-positivity (or quantum-limited) threshold.1 aIvan, Solomon1 aSabapathy, Krishna Kumar1 aSimon, R. uhttps://grupsderecerca.uab.cat/giq/node/84500514nas a2200121 4500008003900000022001400039245008900053210006900142260001100211490000700222100002900229856013400258 2016 d a2469-993400aProcess output nonclassicality and nonclassicality depth of quantum-optical channels0 aProcess output nonclassicality and nonclassicality depth of quan c4/20160 v931 aSabapathy, Krishna Kumar uhttps://grupsderecerca.uab.cat/giq/publications/process-output-nonclassicality-and-nonclassicality-depth-quantum-optical-channels00454nas a2200121 4500008003900000022001400039245006300053210006200116260001200178490000700190100002900197856010600226 2015 d a1094-162200aQuantum-optical channels that output only classical states0 aQuantumoptical channels that output only classical states c11/20150 v921 aSabapathy, Krishna Kumar uhttps://grupsderecerca.uab.cat/giq/publications/quantum-optical-channels-output-only-classical-states