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Quantum Interfaces Using Nanoscale Surface Plasmons

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 Added by Fang-Yu Hong
 Publication date 2008
  fields Physics
and research's language is English




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The strong coupling between individual optical emitters and propagating surface plasmons confined to a conducting nanotip make this system act as an ideal interface for quantum networks, through which a stationary qubit and a flying photon (surface plasmon) qubit can be interconverted via a Raman process. This quantum interface paves the way for many essential functions of a quantum network, including sending, receiving, transferring, swapping, and entangling qubits at distributed quantum nodes as well as a deterministic source and an efficient detector of a single-photon. Numerical simulation shows that this scheme is robust against experimental imperfections and has high fidelity. Furthermore, being smaller this interface would significantly facilitate the scalability of quantum computers.

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We demonstrate the coherent transduction of quantum noise reduction, or squeezed light, by Ag localized surface plasmons (LSPs). Squeezed light, generated through four-wave-mixing in Rb vapor, is coupled to a Ag nanohole array designed to exhibit LSP-mediated extraordinary-optical transmission (EOT) spectrally coincident with the squeezed light source at 795 nm. We demonstrate that quantum noise reduction as a function of transmission is found to match closely with linear attenuation models, thus demonstrating that the photon-LSP-photon transduction process is coherent near the LSP resonance.
Surface plasmons (SP) in a semi-bounded quantum plasma with degenerate electrons (e.g., a metal) is considered, and some interesting consequences of electron Pauli blocking for the SP dispersion and temporal attenuation are discussed. In particular, it is demonstrated that a semi-bounded degenerate plasma with a sharp boundary supports two types of SP with distinct frequencies and qualitatively different temporal attenuation, in contrast to a non-degenerate plasma that only supports one type of SP citep{Guernsey_1969}.
We investigate a system consisting of a single, as well as two emitters strongly coupled to surface plasmon modes of a nano-wire using a Green function approach. Explicit expressions are derived for the spontaneous decay rate into the plasmon modes and for the atom-plasmon coupling as well as a plasmon-mediated atom-atom coupling. Phenomena due to the presence of losses in the metal are discussed. In case of two atoms, we observe Dicke sub- and superradiance resulting from their plasmon-mediated interaction. Based on this phenomenon, we propose a scheme for a deterministic two-qubit quantum gate. We also discuss a possible realization of interesting many-body Hamiltonians, such as the spin-boson model, using strong emitter-plasmon coupling.
Nanoscale quantum optics explores quantum phenomena in nanophotonics systems for advancing fundamental knowledge in nano and quantum optics and for harnessing the laws of quantum physics in the development of new photonics-based technologies. Here, we review recent progress in the field with emphasis on four main research areas: Generation, detection, manipulation and storage of quantum states of light at the nanoscale, Nonlinearities and ultrafast processes in nanostructured media, Nanoscale quantum coherence, Cooperative effects, correlations and many-body physics tailored by strongly confined optical fields. The focus is both on basic developments and technological implications, especially for what concerns information and communication technology, sensing and metrology, and energy efficiency.
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