Overview of Research in Laboratories

Materials Science Laboratory
Hideki Yamamoto
    The aim of the Materials Science Laboratory is to contribute to progress in materials science and to revolutionize information communication technology by creating novel materials and functions through materials design at the atomic and molecular levels.
  The laboratory consists of three research groups investigating a wide range of materials including typical compound semiconductors such as GaAs and GaN, two-dimensional materials such as graphene, high-Tc oxide superconductors, and biological molecules. We are conducting innovative materials research based on advanced thin-film growth technologies and high-precision and high-resolution measurements of structures and properties along with theoretical studies.
  This year, we succeeded in controlling the surface morphologies of non-polar AlN heteroepitaxial layers, which points toward the realization of high-performance light emitting devices operating in the deep ultraviolet spectral region. We also prepared millimeter-scale single-crystalline graphene. Our high-quality samples allowed us to observe quantum oscillations for the first time using high-temperature superconductor thin films. Furthermore, we fabricated conductive and highly biocompatible silk gel films with which we have developed a new method for cell manipulation and the electrical stimulation of specific cells. Last but certainly not least, electrodes and electrical leads made of a functional sensing fabric “hitoe”, which we developed in collaboration with Toray Industries Inc., have been officially registered as general medical devices and offer a broad scope for medical use.
Physical Science Laboratory
Akira Fujiwara
   The aim of the Physical Science Laboratory is to develop semiconductor- and superconductor-based devices and hybrid-type devices, which will have a revolutionary impact on future ICT society. Utilizing the high-quality crystal growth techniques and nanolithography techniques that we have developed, research groups in our laboratory are exploring novel properties that could lead to nanodevices for ultimate electronics and sensors and novel information processing devices based on new degrees of freedom such as single electrons, mechanical oscillations, quantum coherent states, electron correlation, and spins.
   This year we achieved the world’s most accurate gigahertz single-electron transfer using a silicon nanotransistor, and we performed an experimental test on the macroscopic realism problem using a superconducting flux qubit. We also studied the quasi-Ising coupling of electromechanical resonators and coherent coupling between thousands of superconducting qubits and a superconducting resonator to explore functional physical coupled systems. Moreover, we developed novel material and device technology including band-engineered two-dimensional topological insulators in InAs/InxGa1-xSb heterostructures and graphene-based electron emitters and liquid-gated transistors.
Optical Science Laboratory
Hideki Gotoh
   The aims of the Optical Science Laboratory is to develop innovative core technologies for optical communications and optical signal processing, and to make fundamental scientific progress.
   The groups in our laboratory are working to achieve quantum state control and quantum information processing by using very weak light, to discover intriguing phenomena by using very intense short pulse light, to control optical properties by using photonic crystals and ultrasonic techniques, and to characterize the unique properties of semiconductor nanostructures such as quantum dots and nanowires.
   This year, one of our achievements as regards quantum computers has been the demonstration of a new computing scheme with a laser cavity composed of an optical fiber and a phase sensitive amplifier. This scheme, known as a “quantum neural network”, has been employed to solve a max-cut problem, which is a combinatorial optimization problem, and has realized a 50 times faster computation time than conventional computers. Moreover, we have achieved the electronic oscillation of the 1 PHz regime with attosecond optical technologies and suppressed the noises of microwave sources by employing optical-comb technologies.
Nanophotonics Center
Masaya Notomi
   The Nanophotonics Center (NPC) was established in April 2012, and is now composed of several groups involved in nanophotonics research and based in NTT’s Basic Research Laboratories and Device Technology Laboratories. Our aim is to develop a full-fledged large-scale photonic integration technology that will allow the dense integration of a large number of nano-scale photonic devices with various functions in a single chip. Furthermore, we are targeting a huge reduction in energy consumption for photonic information processing by taking advantage of nanophotonics technology.
   This year, we achieved super-efficient optical-to-electrical energy conversion by using ultrasmall-capacitance nano-photodetectors integrated with resistors. We have also demonstrated the high-speed modulation of sub-wavelength nanowire photonic-crystal lasers. Furthermore, we have achieved various nanophotonic devices (deep sub-wavelength plasmonic waveguides, superconducting single-photon detectors, and photonic-crystal lasers) efficiently coupled to Si waveguides.