The control, manipulation and detection of surface plasmons and cold atoms.
Dlamini, Sanele Goodenough.
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Cold atoms and surface plasmons are now widely recognised as having a vast potential as sources for future quantum information technologies, including in quantum simulations, quantum computing and quantum-enhanced metrology. In the first part of this Thesis an experimental investigation of the decoherence of single surface plasmon polaritons in plasmonic waveguides is carried out. In the study, a Mach-Zehnder configuration previously considered for measuring decoherence in atomic, electronic and photonic systems, is used. By placing waveguides of di erent lengths in one arm measurements of the amplitude damping time, pure phase damping time and total phase damping time were achieved. Decoherence was found to be mainly due to amplitude damping and thus losses arising from inelastic electron and photon scattering play the most important role in the decoherence of plasmonic waveguides in the quantum regime. However, pure phase damping is not completely negligible. In the second part of the Thesis the properties of light in the fundamental mode of a subwavelengthdiameter plasmonic nanowire are also investigated. One of the applications of the light is the trapping of atoms by the optical force of the evanescent field and the subsequent guiding of the emitted light from the atoms. The quantum correlation functions of the emitted light from di erent numbers of atoms into the wave guided mode of the nanowire are investigated analytically. It is found that the nanowire provides an efficient method of generating quantum states of light - it gives a faster time scale for the dynamics and improved coupling e ciency compared to an equivalent dielectric nanofiber. The results of this Thesis will be useful for the design of plasmonic waveguide systems for carrying out phase-sensitive quantum applications, such as quantum sensing, and for the generation of novel quantum states of light for quantum computing and quantum communication. The probing techniques developed for the plasmonic waveguides may also be applied to other types of plasmonic nanostructures, such as those used as nanoantennas, as unit cells in metamaterials and as nanotraps for cold atoms.