In this presentation, we report direct evidence of the bosonic nature of SPPs in a scattering-based beamsplitter, in one of the most simple experiments of quantum optics - done using SPPs instead of photons propagating in air. A parametric down-conversion source is used to produce two indistinguishable photons, each of which is converted into a SPP on a metal-stripe waveguide and then made to interact through a semi-transparent Bragg mirror. In this plasmonic analog of the Hong-Ou-Mandel experiment, we measure a coincidence dip with a visibility of 72%, the signature that SPPs are bosons and that quantum interference is clearly involved.
We have witnessed proliferate growth in theoretical and experimental efforts to understand and control physical systems in a
quantum level. In a quantum optics laboratory, Gaussian states, whose phase properties are described by Gaussian
probability-like functions, were generated but there was some limitation to use them for various tasks of quantum
information processing. There have been suggestions and realisations to engineer the quantum state by subtracting or adding
single photons from/to a Gaussian field. It is also possible to test fundamental quantum theories using these techniques. We
discuss various issues in subtraction and addition of single photons.