Recently, polymer nanocomposites reinforced with lower volume fraction of nanoceramics and carbon nanotubes have attracted steadily growing interest due to their peculiar and fascinating properties as well as their unique applications in commercial sectors. The incorporation of nanoceramics such as layered silicate clays, calcium carbonate or silica nanoparticles arranged on the nanometer scale with a high aspect ratio and/or an extremely large surface area into polymers improves their mechanical performances significantly. The properties of nanocomposites depend greatly on the chemistry of polymer matrices, nature of nanofillers, and the way in which they are prepared. The uniform dispersion of nanofillers in the polymer matrices is a general prerequisite for achieving desired mechanical and physical characteristics. In this review article, current development on the processing, structure, and mechanical properties of polymer nanocomposites reinforced with respective layered silicates, ceramic nanoparticles and carbon nanotubes will be addressed. Particular attention is paid on the structure–property relationship of such novel high-performance polymer nanocomposites.

Structural and mechanical properties of polymer nanocomposites

We review the current status of single-photon-source and single-photon-detector technologies operating at wavelengths from the ultraviolet to the infrared. We discuss applications of these technologies to quantum communication, a field currently driving much of the development of single-photon sources and detectors.

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Invited review article: Single-photon sources and detectors

I. Introduction (Preface, Nanostructures in Si Inversion Layers, Nanostructures in GaAs-AlGaAs Heterostructures, Basic Properties). 
II. Diffusive and Quasi-Ballistic Transport (Classical Size Effects, Weak Localization, Conductance Fluctuations, Aharonov-Bohm Effect, Electron-Electron Interactions, Quantum Size Effects, Periodic Potential). 
III. Ballistic Transport (Conduction as a Transmission Problem, Quantum Point Contacts, Coherent Electron Focusing, Collimation, Junction Scattering, Tunneling). 
IV. Adiabatic Transport (Edge Channels and the Quantum Hall Effect, Selective Population and Detection of Edge Channels, Fractional Quantum Hall Effect, Aharonov-Bohm Effect in Strong Magnetic Fields, Magnetically Induced Band Structure).

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Quantum Transport in Semiconductor Nanostructures

▪ Abstract This account reviews the discovery, synthesis, properties, and the latest research advances of carbon nanotubes developed over the past 12 years. Because of their remarkable electronic and mechanical properties, carbon nanotubes are unique and exciting. The field has been developed rapidly, and the number of publications per year is increasing almost exponentially. Various technological applications are likely to arise using nanotubes for fabrication of flat panel displays, gas storage devices, toxic gas sensors, Li+ batteries, robust and lightweight composites, conducting paints, electronic nanodevices, etc. Further experimental and theoretical research is still necessary so that novel technologies will become a reality in the early twenty-first century.

Science and Technology of the Twenty-First Century: Synthesis, Properties, and Applications of Carbon Nanotubes

Publisher Summary Quantum transport is conveniently studied in a two-dimensional electron gas (2DEG) because of the combination of a large Fermi wavelength and large mean free path. Semiconductor nanostructures are unique in offering the possibility of studying quantum transport in an artificial potential landscape. This is the regime of ballistic transport in which scattering with impurities are neglected. The chapter presents a self-contained account of these three novel transport regimes in semiconductor nanostructures. The study of quantum transport in semiconductor nanostructures is motivated by more than scientific interest. The fabrication of nanostructures relies on sophisticated crystal growth and lithographic techniques that exist because of the industrial effort toward the miniaturization of transistors. Conventional transistors operate in the regime of classical diffusive transport, which breaks down on short length scales. The discovery of novel transport regimes in semiconductor nanostructures provides options for the development of innovative future devices.

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A photon detector combining the two avalanche photon diodes (APD) has been demonstrated for qubit discrimination in 1550 nm. Spikes accompanied with the signals in gated-mode were canceled by balanced output from the two APDs. The spike cancellation enabled one to reduce the threshold in the discriminators, and thus the gate pulse voltage. The dark count probability and afterpulse probability were reduced to 7x10^-7 and 10^-4, respectively, without affecting the detection efficiency (11 %) at 178 K.

https://arxiv.org/pdf/quant-ph/0206150.pdf

A balanced gated-mode photon detector for qubit discrimination in 1550 nm

We report the observation of large-amplitude oscillations in the magnetoresistance of a two-dimensional electron gas in a GaAs-${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As heterostructure with an artificially imposed antidot lattice potential. The period of the oscillations is about h/2e as a function of the magnetic flux threading through the unit cell of the antidot lattice. The oscillations are definitely visible in the antidot array with a hexagonal lattice configuration, the amplitude reaching 20% of the sample resistance, but almost invisible with a square lattice configuration. We believe that the hexagonal lattice potential is suitable for electrons to return to their starting points and to contribute to coherent backscattering. We also show the oscillations cannot be described by the theory for the diffusive regime estalished by Al'tshuler, Aronov, and Spivak.

Observation of large h/2e oscillations in semiconductor antidot lattices.

We have observed the Aharonov-Bohm (AB) effect in magnetoresistance of a two-dimensional electron gas with a two-dimensional array of depleted circular regions, called antidots. Fine oscillations with a period of about h/ea2 (a = period of the array) are found in the magnetoresistance peak which originates from the formation of the localized orbits encircling a single antidot. These oscillations are a manifestation of the AB effect accompanied by quantization of the localized orbits.

Aharonov-Bohm effect in antidot structures

Electron focusing effect is observed in a two‐dimensional electron gas using samples with simple multiparallel one‐dimensional channels made by a Be focused ion beam (FIB). Subharmonics and harmonics are resolved; their strengths allow a direct determination of the elastic scattering length le =1.8 μm and the specularity coefficient p=0.35 for electron reflection at the boundary defined by the FIB. The temperature dependence of the focusing effect is much weaker than the Shubnikov–de Haas effect.

Electron focusing with multiparallel one-dimensional channels made by focused ion beam

Abstract Ultrafine gold particles with a diameter of 20 nm were dispersed in carbonaceous soot containing single-wall carbon nanotubes (SWNTs). These gold particles catalyzed the oxidation of carbonaceous impurities at about 350°C. This selective oxidation enabled us to purify SWNTs.

Kazuo Nakamura

Papers

A balanced gated-mode photon detector for qubit discrimination in 1550 nm

Observation of large h/2e oscillations in semiconductor antidot lattices.

Aharonov-Bohm effect in antidot structures

Electron focusing with multiparallel one-dimensional channels made by focused ion beam

Purification of single-wall carbon nanotubes by using ultrafine gold particles