Showing papers by "NEC published in 2011"

Field test of quantum key distribution in the Tokyo QKD Network

Abstract: A secure communication network with quantum key distribution in a metropolitan area is reported. Six different QKD systems are integrated into a mesh-type network. GHz-clocked QKD links enable us to demonstrate the world-first secure TV conferencing over a distance of 45km. The network includes a commercial QKD product for long-term stable operation, and application interface to secure mobile phones. Detection of an eavesdropper, rerouting into a secure path, and key relay via trusted nodes are demonstrated in this network.

Noise spectroscopy through dynamical decoupling with a superconducting flux qubit

Abstract: Quantum coherence in natural and artificial spin systems is fundamental to applications ranging from quantum information science to magnetic-resonance imaging and identification. Several multipulse control sequences targeting generalized noise models have been developed to extend coherence by dynamically decoupling a spin system from its noisy environment. In any particular implementation, however, the efficacy of these methods is sensitive to the specific frequency distribution of the noise, suggesting that these same pulse sequences could also be used to probe the noise spectrum directly. Here we demonstrate noise spectroscopy by means of dynamical decoupling using a superconducting qubit with energy-relaxation time T1 =12 μs. We first demonstrate that dynamical decoupling improves the coherence time T 2 in this system up to the T2 =2 T1 limit (pure dephasing times exceeding 100 μs), and then leverage its filtering properties to probe the environmental noise over a frequency (f) range 0.2-20 MHz, observing a 1/fα distribution with α < 1. The characterization of environmental noise has broad utility for spin-resonance applications, enabling the design of optimized coherent-control methods, promoting device and materials engineering, and generally improving coherence. © 2011 Macmillan Publishers Limited. All rights reserved.

Electrical control of the ferromagnetic phase transition in cobalt at room temperature

Abstract: Electrical control of magnetic properties is crucial for device applications in the field of spintronics. Although the magnetic coercivity or anisotropy has been successfully controlled electrically in metals as well as in semiconductors, the electrical control of Curie temperature has been realized only in semiconductors at low temperature. Here, we demonstrate the room-temperature electrical control of the ferromagnetic phase transition in cobalt, one of the most representative transition-metal ferromagnets. Solid-state field effect devices consisting of a ultrathin cobalt film covered by a dielectric layer and a gate electrode were fabricated. We prove that the Curie temperature of cobalt can be changed by up to 12 K by applying a gate electric field of about ±2 MV cm(-1). The two-dimensionality of the cobalt film may be relevant to our observations. The demonstrated electric field effect in the ferromagnetic metal at room temperature is a significant step towards realizing future low-power magnetic applications.

Observation of the intrinsic pinning of a magnetic domain wall in a ferromagnetic nanowire

Abstract: The spin transfer torque is essential for electrical magnetization switching. When a magnetic domain wall is driven by an electric current through an adiabatic spin torque, the theory predicts a threshold current even for a perfect wire without any extrinsic pinning. The experimental confirmation of this 'intrinsic pinning', however, has long been missing. Here, we give evidence that this intrinsic pinning determines the threshold, and thus that the adiabatic spin torque dominates the domain wall motion in a perpendicularly magnetized Co/Ni nanowire. The intrinsic nature manifests itself both in the field-independent threshold current and in the presence of its minimum on tuning the wire width. The demonstrated domain wall motion purely due to the adiabatic spin torque will serve to achieve robust operation and low energy consumption in spintronic devices.

Implementing the Quantum von Neumann Architecture with Superconducting Circuits

Abstract: The von Neumann architecture for a classical computer comprises a central processing unit and a memory holding instructions and data. We demonstrate a quantum central processing unit that exchanges data with a quantum random-access memory integrated on a chip, with instructions stored on a classical computer. We test our quantum machine by executing codes that involve seven quantum elements: Two superconducting qubits coupled through a quantum bus, two quantum memories, and two zeroing registers. Two vital algorithms for quantum computing are demonstrated, the quantum Fourier transform, with 66% process fidelity, and the three-qubit Toffoli-class OR phase gate, with 98% phase fidelity. Our results, in combination especially with longer qubit coherence, illustrate a potentially viable approach to factoring numbers and implementing simple quantum error correction codes.

Albatross: lightweight elasticity in shared storage databases for the cloud using live data migration

Abstract: Database systems serving cloud platforms must serve large numbers of applications (or tenants). In addition to managing tenants with small data footprints, different schemas, and variable load patterns, such multitenant data platforms must minimize their operating costs by efficient resource sharing. When deployed over a pay-per-use infrastructure, elastic scaling and load balancing, enabled by low cost live migration of tenant databases, is critical to tolerate load variations while minimizing operating cost. However, existing databases---relational databases and Key-Value stores alike---lack low cost live migration techniques, thus resulting in heavy performance impact during elastic scaling. We present Albatross, a technique for live migration in a multitenant database serving OLTP style workloads where the persistent database image is stored in a network attached storage. Albatross migrates the database cache and the state of active transactions to ensure minimal impact on transaction execution while allowing transactions active during migration to continue execution. It also guarantees serializability while ensuring correctness during failures. Our evaluation using two OLTP benchmarks shows that Albatross can migrate a live tenant database with no aborted transactions, negligible impact on transaction latency and throughput both during and after migration, and an unavailability window as low as 300 ms.

Organic Radical Battery Approaching Practical Use

Abstract: The electrochemical redox reactions of organic polymers bearing robust unpaired electrons were investigated to determine the applicability of these polymers to rechargeable batteries. Such an “orga...

MD-HBase: A Scalable Multi-dimensional Data Infrastructure for Location Aware Services

Abstract: The ubiquity of location enabled devices has resulted in a wide proliferation of location based applications and services. To handle the growing scale, database management systems driving such location based services (LBS) must cope with high insert rates for location updates of millions of devices, while supporting efficient real-time analysis on latest location. Traditional DBMSs, equipped with multi-dimensional index structures, can efficiently handle spatio-temporal data. However, popular open source relational database systems are overwhelmed by the high insertion rates, real-time querying requirements, and terabytes of data that these systems must handle. On the other hand, Key-value stores can effectively support large scale operation, but do not natively support multi-attribute accesses needed to support the rich querying functionality essential for the LBSs. We present MD-HBase, a scalable data management system for LBSs that bridges this gap between scale and functionality. Our approach leverages a multi-dimensional index structure layered over a Key-value store. The underlying Key-value store allows the system to sustain high insert throughput and large data volumes, while ensuring fault-tolerance, and high availability. On the other hand, the index layer allows efficient multi-dimensional query processing. We present the design of MD-HBase that builds two standard index structuresâ€"the K-d tree and the Quad treeâ€"over a range partitioned Key-value store. Our prototype implementation using HBase, a standard open-source Key-value store, can handle hundreds of thousands of inserts per second using a modest 16 node cluster, while efficiently processing multidimensional range queries and nearest neighbor queries in real-time with response times as low as hundreds of milliseconds.

Nonvolatile semiconductor memory device

Abstract: A nonvolatile semiconductor memory device includes a memory cell array in which a plurality of nonvolatile memory cells are arrayed, and a program voltage generator that switches current supply amount based on the number of memory cells that are programmed at the same time, among the plurality of memory cells. The nonvolatile semiconductor memory device further includes a selection circuit that selects, among the plurality of memory cells, one or more memory cells that are programmed, to flow a current outputted by the program voltage generator.

Compact Circularly-Polarized Patch Antenna Loaded With Metamaterial Structures

Abstract: A metamaterial-inspired low-profile patch antenna is proposed and studied for circularly-polarized (CP) radiation. The present antenna, which has a single-fed configuration, is loaded with the composite right/left-handed (CRLH) mushroom-like structures and a reactive impedance surface (RIS) for miniaturization purpose. The CP radiation is realized by exciting two orthogonally-polarized modes simultaneously which are located in the left-handed (LH) region. The detailed antenna radiation characteristics are examined and illustrated with both simulated and experimental results. The CP performance can be controlled in several different ways. This antenna exhibits an overall size of 0.177λ0 × 0.181λ0 × 0.025λ0 at 2.58 GHz and a radiation efficiency around 72%. Finally, based on the proposed CP patch antenna, a compact dual-band dual linearly-polarized patch antenna has also been designed and fabricated. Promising experimental results are observed.

Image processing apparatus, image processing method, and program

Abstract: A job generation unit generates, from a source program, a job to be executed by any of a plurality of processing resources The job generation unit calculates job characteristic information that allows estimation of an index value capable of indicating the amount of heat generated in the processing resources due to execution of the job, and appends the job characteristic information to the job This makes it possible to estimate a temperature rise in a processing resource to which the job is allocated, by using a method that facilitates implementation in a system in which a scheduler allocates a job to a plurality of processing resources

Deterministic entanglement of photons in two superconducting microwave resonators.

Abstract: Quantum entanglement, one of the defining features of quantum mechanics, has been demonstrated in a variety of nonlinear spinlike systems. Quantum entanglement in linear systems has proven significantly more challenging, as the intrinsic energy level degeneracy associated with linearity makes quantum control more difficult. Here we demonstrate the quantum entanglement of photon states in two independent linear microwave resonators, creating $N$-photon NOON states (entangled states $|N0⟩+|0N⟩$) as a benchmark demonstration. We use a superconducting quantum circuit that includes Josephson qubits to control and measure the two resonators, and we completely characterize the entangled states with bipartite Wigner tomography. These results demonstrate a significant advance in the quantum control of linear resonators in superconducting circuits.

Radio communication apparatus and current reducing method

Abstract: A radio communication apparatus includes: a first casing; a second casing; a connection section that connects the first and second casings to each other to be movable; and an antenna device that operates at a predetermined communication frequency. In the radio communication apparatus, first and second states are switched between by relatively moving the first and second casings. The first state is a state in which the first and second casings are opened or closed with respect to one another, and a first conductor ( 122 ) installed from the connection section to the first casing and a second conductor ( 240 ) installed from the connection section to the second casing are separated and faced each other. In the first state, the first conductor ( 122 ) and the second conductor ( 240 ) are electrically connected to each other at the communication frequency. The second state is a state in which the first and second casings are closed or opened with respect to one another.

Fast optical channel recovery in field demonstration of 100-Gbit/s Ethernet over OTN using real-time DSP.

Abstract: A field trial of 100-Gbit/s Ethernet over an optical transport network (OTN) is conducted using a real-time digital coherent signal processor. Error free operation with the Q-margin of 3.2 dB is confirmed at a 100 Gbit/s Ethernet analyzer by concatenating a low-density parity-check code with a OTN framer forward error correction, after 80-ch WDM transmission through 6 spans x 70 km of dispersion shifted fiber without inline-dispersion compensation. Also, the recovery time of 12 msec is observed in an optical route switching experiment, which is achieved through fast chromatic dispersion estimation functionality.

Current-induced domain wall motion in perpendicularly magnetized CoFeB nanowire

Abstract: Current-induced domain wall motion in perpendicularly magnetized CoFeB nanowires with a stack structure of Ta(1.0 nm)/CoFeB(1.2 nm)/MgO(2.0 nm)/Ta(1.0 nm) was investigated. Domain wall motion driven by adiabatic spin-transfer torque was observed at a current of about 74 μA, corresponding to a current density of 6.2×107 A/cm2. The obtained results were compared with those of a micromagnetic simulation and the spin polarization of the CoFeB was estimated to be 0.72.

Current-induced effective field in perpendicularly magnetized Ta/CoFeB/MgO wire

Abstract: The current-induced effective field in perpendicularly magnetized Ta/CoFeB/MgO wire was investigated. A threshold field decrease of 6.4 kOe/mA was observed by measuring the threshold field of Hall resistance versus the magnetic field curve with various bias currents. The decrease was probably caused by the in-plane effective field, mainly due to the Rashba effect. The effective field of the Ta/CoFeB/MgO wire was smaller and opposite in direction compared to that of Pt/Co/AlOx previously reported.

Photon shell game in three-resonator circuit quantum electrodynamics

Abstract: The ability to coherently switch a state between two systems is a key requirement for quantum information processing. Such control is now demonstrated by shifting the quantum state of a microwave photon between any one of three superconducting-circuit resonators: in analogy to the classic three cups and a ball game.

Low core losses and magnetic properties of Fe85-86Si1-2B8P4Cu1 nanocrystalline alloys with high B for power applications (invited)

Abstract: Recently, the energy crisis and the continued growth in electrical power generation strongly demand minimization of wasteful energy dissipation. Magnetic core loss (W) is the main source of energy dissipation in motors and transformers. This requires the development of soft magnetic materials with low coercivity (Hc) and high magnetic flux density (B). Fe-rich Fe85-86Si1-2B8P4Cu1 (at. %) alloy ribbons made from industrial raw materials (containing some impurities) with 6 mm in width have a heteroamorphous structure containing a large number of extremely small Fe grains (less than 3 nm), resulting from the unique effects of P and Cu addition in proper amounts. Crystallization of these alloys by annealing shows a uniform precipitation of α-Fe, leading to a uniform nanocrystallized structure of α-Fe grains, 16–19 nm in size, accompanied by an intergranular amorphous layer about 1 nm in width. The wide ribbons exhibit high B of 1.82–1.85 T (at 800 A/m), almost comparable to commercial oriented Fe–3 mass% Si a...

Fast Tunable Coupler for Superconducting Qubits

Abstract: A major challenge in the field of quantum computing is the construction of scalable qubit coupling architectures. Here, we demonstrate a novel tunable coupling circuit that allows superconducting qubits to be coupled over long distances. We show that the interqubit coupling strength can be arbitrarily tuned over nanosecond time scales within a sequence that mimics actual use in an algorithm. The coupler has a measured on/off ratio of 1000. The design is self-contained and physically separate from the qubits, allowing the coupler to be used as a module to connect a variety of elements such as qubits, resonators, amplifiers, and readout circuitry over distances much larger than nearest-neighbor. Such design flexibility is likely to be useful for a scalable quantum computer.

Communication control system, control server, forwarding node, communication control method, and communication control program

Abstract: A communication control system includes a control server for controlling a process rule held in a forwarding node. The control server includes a network information storage unit for storing a logical network identifier which is an identifier of a logical network defined by setting of the forwarding node, and a correspondence relation between a device connected to the forwarding node and the logical network; and an address resolution unit for, upon receiving from the forwarding node an address resolution request for a destination communication device which is a destination of the packet or a communication device for forwarding the packet received from a source communication device which is a source of the packet to another device, performing interlayer address resolution for the destination communication device or the communication device, and setting the logical network identifier of the logical network to which the source communication device belongs.

Ambivalent Effect of Oxygen Vacancies on Li2MnO3: A First-Principles Study

Abstract: First-principles calculations were done to examine the effect of oxygen vacancies in Li2MnO3 on the lithium extraction from the crystal As the ratio of O-vacancy increases, the redox potential associated with the lithium extraction decreases and the Mn contribution in the charge compensation for the lithium extraction increases These findings indicate that the introduction of O-vacancy activates the Mn sites as the redox center in the lithium extraction process However, the lithium extraction from Li2MnO3 tends to cause successive O2 evolution from the crystal This results in a high O-vacancy density in the crystal, which in turn triggers a drastic volume reduction during the lithium extraction process

Input support system, method, and program

Abstract: Disclosed is an input support system (1) provided with: a database (10) for accumulating data in relation to a plurality of items; an extraction unit (104) for comparing input data obtained as the result of performing voice recognition processing on voice data (D0), and data in relation to the items in the database (10), and for extracting data similar to the input data from the database; and a presentation unit (106) for presenting the extracted data as candidates to be registered in the database (10).

Oxygen-Enhanced Dissolution of Platinum in Acidic Electrochemical Environments

Abstract: We investigated the influence of oxygen on the dissolution of platinum in acidic electrochemical environments, which is closely related to the degradation of the cathodes in operating polymer electrolyte fuel cells (PEFCs), by using carbon-supported platinum nanoparticles (Pt/C), bulk polycrystalline Pt electrodes, and Pt(111) single crystals. We found that the platinum dissolution under potential cycling was significantly enhanced by the presence of oxygen even in the lower potential regions (OH adsorption potentials under inert atmospheres): the amount of dissolved platinum increased by factors of 1.2, 18, and 19 on the Pt/C, polycrystalline Pt, and Pt(111) surfaces, respectively, when the potential of the electrodes was cycled under O2. The results of electrochemical and electrochemical scanning tunneling microscopy measurements revealed that a few monolayers of the platinum surface were oxidized, and the surface was roughened by the exposure to oxygen, even in the low potential regions, where no surfa...

RSOsPR10 Expression in Response to Environmental Stresses is Regulated Antagonistically by Jasmonate/Ethylene and Salicylic Acid Signaling Pathways in Rice Roots

Abstract: Plant roots play important roles not only in the absorption of water and nutrients, but also in stress tolerance. Previously, we identified RSOsPR10 as a root-specific pathogenesis-related (PR) protein induced by drought and salt treatments in rice. Transcripts and proteins of RSOsPR10 were strongly induced by jasmonate (JA) and the ethylene (ET) precursor 1-aminocyclopropane-1-carboxylic acid (ACC), while salicylic acid (SA) almost completely suppressed these inductions. Immunohistochemical analyses showed that RSOsPR10 strongly accumulated in cortex cells surrounding the vascular system of roots, and this accumulation was also suppressed when SA was applied simultaneously with stress or hormone treatments. In the JA-deficient mutant hebiba, RSOsPR10 expression was up-regulated by NaCl, wounding, drought and exogenous application of JA. This suggested the involvement of a signal transduction pathway that integrates JA and ET signals in plant defense responses. Expression of OsERF1, a transcription factor in the JA/ET pathway, was induced earlier than that of RSOsPR10 after salt, JA and ACC treatments. Simultaneous SA treatment strongly inhibited the induction of RSOsPR10 expression and, to a lesser extent, induction of OsERF1 expression. These results suggest that JA/ET and SA pathways function in the stress-responsive induction of RSOsPR10, and that OsERF1 may be one of the transcriptional factors in the JA/ET pathway.

Name-database server, name-resolution system, entry-search method, and entry-search program

Abstract: A node information storage means stores an entry of node information in which at least an address and a record type are associated with a host name A search target record deciding means decides a record type of an entry of a search target from a received virtual record type based on a search rule that is a rule specifying a record type of a search target according to a virtual record type An entry searching means searches the node information storage means, and specifies an entry that corresponds to the entry specifying information received from the terminal device and has the record type decided by the search target record deciding means A search result transmitting means transmits node information included in the entry specified by the entry searching means to the terminal device

Interface control system and interface control method

Abstract: An interface control system of network equipment, includes: a logical interface which is an interface of a logical group; physical ports which belong to the logical group; and an interface control section configured to incorporate the logical interface and the physical ports as management objects into a management interface when validation of a predetermined function has been performed to each of the logical interface and the physical ports.

Dynamic quantum Kerr effect in circuit quantum electrodynamics

Abstract: A superconducting qubit coupled to a microwave resonator provides a controllable system that enables fundamental studies of light-matter interactions. In the dispersive regime, photons in the resonator exhibit induced frequency and phase shifts which are revealed in the resonator transmission spectrum measured with fixed qubit-resonator detuning. In this static detuning scheme, the phase shift is measured in the far-detuned, linear dispersion regime to avoid measurement-induced demolition of the qubit quantum state. Here we explore the qubit-resonator dispersive interaction over a much broader range of detunings, by using a dynamic procedure where the qubit transition is driven adiabatically. We use resonator Wigner tomography to monitor the interaction, revealing exotic non-linear effects on different photon states, e.g., Fock states, coherent states, and Schrodinger cat states, thereby demonstrating a quantum Kerr effect in the dynamic framework.

Measurement of energy decay in superconducting qubits from nonequilibrium quasiparticles

Abstract: Quasiparticles are an important decoherence mechanism in superconducting qubits, and can be described with a complex admittance that is a generalization of the Mattis-Bardeen theory. By injecting nonequilibrium quasiparticles with a tunnel junction, we verify qualitatively the expected change of the decay rate and transition frequency in a phase qubit. With their relative change in agreement to within 4 % of prediction, the theory can be reliably used to infer quasiparticle density. We describe how settling of the decay rate may allow determination of whether qubit energy relaxation is limited by nonequilibrium quasiparticles.

Hyperspectral Imager Suite (HISUI) -Japanese hyper-multi spectral radiometer

Abstract: Hyperspectral Imager Suite (HISUI) is a next-generation Japanese optical sensor that is composed of a hyperspectral imager and a multispectral imager, which will be launched on Advanced Land Observation Satellite 3 (ALOS-3). Combination of hyperspectral and multispectral imagers contributes land remote sensing with high spectral and spatial resolution. Calibration of the HISUI functionalequivalent model has been carried out to meet the science requirements on the sensor. A center wavelength and spectral response of each band of the hyperspectral sensor is obtained, from which distortions in a spectrometer in terms of smile and keystone properties are investigated. The results of the calibration activity for the functionalequivalent model show appropriate performance of the sensors.

Network system, control method thereof and controller

Abstract: A network system includes a server which accommodates a plurality of tenants, at least one network appliance which has a resource shared by the plurality of tenants, a plurality of switches arranged between the at least one network appliance and a network; and a controller which controls the switches Each switch has a flow table indicating an association of an input source with a transfer destination of packets for each flow, and transfers packets received from the input source to the transfer destination by referring to the flow table The controller includes an assignment control block which dynamically assigns each of a plurality of tenants to any of the at least one network appliance; a route design block which designs a flow route for each of the tenants; and a switch setting block which sets the flow table for each of switches along the designed route