Cutting-edge Technologies

Transcription

1 Technologies in fields such as optical devices, material science, and information science, at the true cutting-edge of a new era. Contents H-CT-1 H-CT-2 H-CT-3 H-CT-4 H-CT-5 H-CT-6 H-CT-7 H-CT-8 Wave Field Synthesis for Realtime Sound Field Transmission Millimeter-Wave Scanner: Precise Imaging Technique for Nondestructive Inspection Monolithically Integrated Light Source for Future 100 GbE Transceiver Phase-Sensitive Amplifier Capable for Ultra-Low-Noise Amplification Optic Flow Facilitates Smooth Handwriting Formal Verification Method of Anonymity and Privacy Quantum Memory: Storing Superconducting Qubit Information Unraveling Exotic Electronic States for Error-Free Quantum Computing

2 Wave Field Synthesis for Realtime Sound Field Transmission Super-realistic sensation, Audio signal processing We are interested in creating an extremely realistic audio system that gives a sense of sharing a space, and we have developed a system for recording wave fronts and physically reconstructing them. By applying a new algorithm for preserving the physical properties of sound waves to large-scale microphone and loudspeaker arrays, we have made possible realtime recording and reproduction of a sound space. Spatially recording and reproducing the wave fronts using large-scale arrays enables listeners in the reproduction room to sense the reality of the location of the recorded sound. Conventional stereo panning techniques give a sense of left and right to the sound waves; ours gives not only a sense of right and left but also back and front. It is possible to reproduce sound images that pop-up from the sound wall (loudspeaker array), so listeners in the reproduction room can share the perceived space with people in the recording room. It is possible to record and reproduce a sound space in realtime by using our new transformation algorithm. A telepresence system that gives a sense of sharing space that is close to face-to-face communication. A super-realistic audio system that is almost the same as listening to a live source. Realtime transmission of sound space Recording room How s it going? Realtime signal transform Loudspeaker array Microphone array Pop-up sound image Reproduces sense of distance NTT Cyber Space Laboratories Reproduction room How s it going? Large sweet spot Realtime signal transform based on physical properties We derived digital filter to transform microphone signals into loudspeaker signals based on physical properties. : Kirchhoff-Helmholtz integral equation Achieved as digital signal processing H-CT-1

3 Millimeter-wave, Imaging, Nondestructive inspection Millimeter-Wave Scanner: Precise Imaging Technique for Nondestructive Inspection A millimeter-wave scanner is a precise imaging technique using millimeter-wave near-field back-scattering detection. It can be used to detect tiny objects that are ten times smaller than the spatial resolution determined by the diffraction limit. Linearly arrayed antennas pick up a two-dimensional image as they are scanned across a surface. The scanner would be useful for nondestructive inspection of fine cracks on the surfaces of concrete telephone poles that are covered with sheets preventing the posting of bills. Imaging objects covered with a dielectric material and inside wooden structures Outstanding spatial resolution: ten times finer than the diffraction limit in quasi-optics Safe and license free Realtime imaging while scanning Millimeter-wave scanner Radiation antenna Detection arrayed antennas Crack NTT Microsystem Integration Laboratories Application image CP * Bill-posting preventing sheet Scanner Detection of concealed surface cracks on concrete poles Detection of concealed surface cracks on concrete structures reinforced with aramid sheets Detection of concealed surface cracks on concrete walls of buildings decorated with wallpaper, ceramic tiles, and so on System setup PC Battery Results PC Battery Imaging of borings by insects and growth rings in wooden houses and cultural properties Crack Defect inspection during factory production of food-stuffs and plastic products Scanner Crack * CP: Concrete Pole H-CT-2

4 100 Gigabit Ethernet, Monolithic integration, Electroabsorption modulator Monolithically Integrated Light Source for Future 100 GbE Transceiver This is an optical transmitter module for future 100 GbE *1 transceivers. By monolithically integrating four 25-Gbit/s light sources and their optical multiplexer (MUX) on one chip, we have created a very compact 100 G transmitter chip. Furthermore, we have developed a 100 GbE TOSA *2 using three-dimensional (3-D) wiring and an FPC *3 electrical interface, whose volume is 94 % less than that of the conventional one. Ultrafast 100-Gbit/s optical signals can be generated with the module. Broadband 25-Gbit/s EA-DFB laser *4 for monolithic integration Compact optical semiconductor chip with four monolithically integrated 25 G light sources and their MUXes Specially designed TOSA, using 3-D wiring for high-speed modulation and low electrical crosstalk and FPC electrical interface 94 % volume reduction in comparison with a conventional transmitter unit Error-free operation in single-mode fiber transmission of up to 40 km Conventional transmitter module for 100 GbE MUX Volume: 31.5 cc Four 25 G light sources - Compact 100 G optical chip (2 mm x 2.6 mm), in which four 25 G light sources and their MUX are monolithically integrated - 94 % volume reduction due to use of very compact TOSA using 3-D wiring and FPC electrical interface NTT Photonics Laboratories Compact transmitter module developed in this work Laser (1) Laser (2) Laser (3) Laser (4) Volume: 1.82 cc MUX Faster, and higher capacity of client-side networks Middle and long- distance LANs, such as used by inter-data center networks Green optical devices (low power consumption, compact) Next step: Large-scale integration and capacity increase 0 km 10 km Eye diagrams of 25 Gbit/s x 4 optical signal Laser (1) Laser (2) Laser (3) Laser (4) *1 100 GbE: 100 Gigabit Ethernet *2 TOSA: Transmitter Optical SubAssembly *3 FPC: Flexible Printed Circuit *4 EA-DFB laser: ElectroAbsorption modulator integrated with DFB laser 40 km H-CT-3

5 Low-noise amplification, Phase sensitive amplification, PPLN Phase-Sensitive Amplifier Capable for Ultra-Low-Noise Amplification Future high-capacity photonic network systems will need higher SNRs *1 because their capacity is limited by nonlinear impairments in optical fiber and noise from optical amplifiers. When amplifying optical signals, a deterioration in signal quality is unavoidable if conventional laser amplifiers such as EDFAs *2 are used. NTT Laboratories demonstrated a phase sensitive amplifier (PSA) based on a PPLN *3 waveguide device allowing for highly efficient nonlinear effects and achieved low noise amplification beyond the theoretical limit of conventional laser amplifiers. The PSA can theoretically have zero additional noise and is thus promising for the key technologies in future photonic networks. Optical signals can be amplified without additional noise. A low noise figure of 2.2 db, below the quantum limit (3 db) of a laser amplifier, was experimentally confirmed. The PSA amplifies only the in-phase component and deamplifies the quadrature one. Deamplification of the quadrature phase component can reduce the phase noise of the optical signal. Low-noise amplifiers in future high-speed, high-capacity photonic network systems Optical transmitters with chirp-reducing capability exploiting the phase squeezing property of the PSA. Conceptual gain/phase characteristics of PSA π Gain Output phase Amplify in-phase only Q phase component deamplified Phase difference Conventional amplifier PSA Phase difference Configuration of PSA using PPLN Phase modulator π 2 Reduced chirping Local oscillator (for generating pump) Signal 0.77-μm EDFA BPF * pump Module 0.77-μm pump Signal NTT Photonics Laboratories Pump OPA module PPLN waveguide PSA out *1 SNR: Signal-to-Noise Ratio *2 EDFA: Erbium-Doped Fiber Amplifier *3 PPLN: Periodically Poled Lithium Niobate PLL PZT PPLN waveguide SHG module * BPF: Band-Pass Filter H-CT-4

6 NTT Research and Development 2012 Review of Activities Interactive interface, Visualfeedback delay, Brain science Optic Flow Facilitates Smooth Handwriting NTT Communication Science Laboratories Effects of the method Optic flow reduces the resistance caused by the delay. Can write with ease Sluggish A. No delay In the implementation example shown in the right figure, a specific color pattern, which does not disturb the operation, is overlaid on the background of the display. Disturbed writing B. Delayed Smooth writing An optic flow is defined as moving that pattern, and by making the flow respond to the operator s hand movements, the resistive sensation caused by the delay can be alleviated. Our method exploits implicit motor-control functions in the human brain that tend to accelerate hand movement in the direction of the optic flow. C. Delay + Flow Mechanism Relative resistance [%] Transmission and digital encoding/decoding delays in telecommunication seriously impair the quality of interactive network services. For instance, when cursor motion is delayed during writing, the user feels a resistive/sluggish sensation (see B in the top-left figure). However, efforts to reduce these delays are obstructed by theoretical and economical limits. To circumvent these limits, we have developed a new technology that uses implicit human brain functions to improve the user experience of controlling delayed systems. 100 Reduced resistance No flow With flow Delay of the cursor [ms] Applications Screen 3. Acceleration The method can be used in the following interactive network services having transmission or digital encoding/decoding delays in order to reduce resistive and sluggish sensations that make it harder to perform tasks and induce mental fatigue. - Robotic remote-controlled operation with realtime visual feedback 2. Acceleration 1. Flow - Network games requiring realtime manual operation with visual feedback - Interactive window operation of remote computers Digitizing tablet - Handwriting on the remote computer through a telecommunication network We use an implicit motor control function which accelerates the hand to the direction of the optic flow. H-CT-5 The method improves interactive feeling for various network services.

7 Privacy, Verification, Formal method Formal Verification Method of Anonymity and Privacy NTT Communication Science Laboratories The anonymity and privacy of users are important issues in information system design. We developed a method for formalizing and verifying anonymity and privacy based on the view that they are information hiding properties concerning the link between people and actions. In this view, anonymity and privacy are symmetric to each other, which can be considered a kind of duality in mathematics. This symmetry gives us a clear perspective for requirement formulation and is beneficial for verification efficiency. Mathematical formalization and rigorous verification of anonymity and privacy Flexibility in describing anonymity and privacy requirements through the use of Epistemic logic Verification flow of our method Formal behavior description State transition Formal specification (anonymity, privacy) Epistemic formula Proving that the behavior satisfies the specification Simulation of state transition Yes/No Efficient verification exploiting the symmetry (duality) between anonymity and privacy Formal anonymity and privacy verification of the FOO (Fujioka-Okamoto-Ohta) electronic voting protocol Safe and secure e-commerce and e-government systems - Flexible requirement descriptions of individual systems using Epistemic logic Meets the ISO Evaluation Criteria for Information Technology Security - Formal methods are needed for evaluation assurance levels higher than EAL 4 Clarifying the correspondence between legal and engineering requirements concerning privacy invasion - Bridging legal and engineering arguments by using a logical representation Formalizing privacy as the dual of anonymity Anonymity: concealing the agent I Alice Bob donated 2 million dollars to the nursing institution. Privacy: concealing the action withdrew $10. At the withdrew $10,000. bank, I withdrew $1,000,000. General formulation in Epistemic logic Anyone in I can perform action a. Dual (exchanging I and A) i can perform any action in A. Verification via role interchangeability Anonymity Dual Privacy Derive Derive Additional cond. Role interchangeability Identical Role interchangeability Additional cond. Duality enables share of the verification process between anonymity and privacy. H-CT-6

8 Quantum Memory: Storing Superconducting Qubit Information Quantum computer, Quantum memory, Diamond NV center We have experimentally demonstrated a quantum memory operation in a superconductordiamond hybrid system. Quantum information manipulated in a superconducting flux qubit *1 can be stored to and retrieved from an ensemble of nitrogen-vacancy (NV) centers *2 in diamond. This technique holds the promise for a future implementation of an ultra-fast quantum processor equipped with a quantum memory that can maintain quantum states over a long time. Diamond NV centers capable of long-term storage of quantum states (quantum memory). Superconducting flux qubits can be applied to quantum computation (quantum computing device). Gap-tunable superconducting flux qubits whose coupling to NV centers can be turned on and off. Quantum hybrid system that takes advantages of both systems. NV centers have transitions in both the microwave and optical bands. Basic elements in the configuration of a quantum computer. Integration of a quantum computing device and a quantum memory for large-scale quantum computing. Quantum frequency conversion between the microwave and optical regimes. Quantum repeaters for long range quantum communication. *1 Superconducting flux qubit: A quantum bit for which the direction of current flow in a superconducting loop represents a 0 or 1 state. *2 Nitrogen-vacancy (NV) center: A complex defect in a diamond lattice formed by a vacancy (V) and by its neighboring nitrogen (N) replacing a carbon atom. The spin state of electrons captured by an NV center stores quantum information. H-CT-7 Quantum processor 5 μm Superconducting flux qubit (supercurrent) 1 mm Diamond substrate Gap tunable superconducting flux qubit - ΔTunable + Sapphire substrate Superconductor-diamond hybrid quantum system Quantum data write Quantum data read Switching probability NTT Basic Research Laboratories [001] z m s = ± GHz Flux quibt Spin ensemble Quantum memory Time (ns) Oscillation that indicates quantum memory operation V y m s = 0 x Diamond NV center (electron spin) N Flux qubit Spin ensemble

9 Quantum computer, Semiconductor device, Electronic properties Unraveling Exotic Electronic States for Error-Free Quantum Computing NTT Basic Research Laboratories A challenge facing the development of quantum computers, which are expected to possess computational capabilities far exceeding those of conventional computers, is the correction of errors caused by environmental disturbances and/or inaccurate logic gate operations. By exploiting quasiparticles *1 that behave differently from fundamental particles in nature, a totally new architecture for quantum computation with exceedingly low error rate might be possible. Our highly sensitive nuclear magnetic resonance *2 measurements have unraveled the electronic states in a semiconductor device expected to host such exotic quasiparticles. Opens the possibility of a totally new architecture for quantum computing (topological quantum computing *3 ) with exceedingly low error rate. Exploits quasiparticles that behave differently from fundamental particles in nature. Exotic electronic state realized by virtue of pristine-crystal growth technique. Direct and non-distructive probing of correlated electronic states using a highly sensitive nuclear magnetic resonance technique. Quantum computing (cryptanalysis, database searching, and simulation). *1 Quasiparticle: Exchange of two fundamental particles such as electrons leaves the state indistinguishable from the original one. For quasiparticles a group of many particles collectively behaving as if they were one, theory predicts those (non-abelian quasiparticles) with exceedingly unusual properties; their exchange would transform the state into one distinct from the original. *2 Nuclear magnetic resonance: spectroscopic technique exploiting the resonant absorption of electromagnetic waves by nuclei placed in a strong magnetic field. *3 Topological quantum computing: a new method of quantum computing performed by rearranging quasiparticles. The result of the calculation depends solely on the order of the quasiparticle exchanges and does not depend on the details of the quasiparticles' trajectories. This unique property of topological quantum computing is believed to make the error rate exceedingly low. - Our findings were made through joint research with the Japan Science and Technology Agency. H-CT-8 Schematic diagram of highly sensitive nuclear magnetic resonance measurements Frequency (MHz) Nuclear magnetic resonance spectra for different electronic states (ν is a parameter designating the electronic state). The size of the peak shift reflects the spin state of the electrons (inset: electronic configuration of each state). Quasiparticle pair Position Resistance change Time Image of topological quantum computing