Showing papers by "Mitsubishi Electric published in 2019"
University of Aizu1, Brown University2, Graduate University for Advanced Studies3, Japan Aerospace Exploration Agency4, Kwansei Gakuin University5, Tohoku University6, Chiba Institute of Technology7, University of Paris-Sud8, Planetary Science Institute9, INAF10, Tokyo City University11, Japan Atomic Energy Agency12, National Institute for Environmental Studies13, Toho University14, National Institute of Advanced Industrial Science and Technology15, Kōchi University16, University of Tokyo17, Nagoya University18, Rikkyo University19, Meiji University20, Kobe University21, National Institute of Polar Research22, Mitsubishi Electric23
TL;DR: The Hayabusa2 team's study of the near-Earth carbonaceous asteroid 162173 Ryugu, at which the spacecraft arrived in June 2018, describes Ryugu's geological features and surface colors and combined results from all three papers to constrain the asteroid's formation process.
Abstract: The near-Earth asteroid 162173 Ryugu, the target of the Hayabusa2 sample-return mission, is thought to be a primitive carbonaceous object. We report reflectance spectra of Ryugu's surface acquired with the Near-Infrared Spectrometer (NIRS3) on Hayabusa2, to provide direct measurements of the surface composition and geological context for the returned samples. A weak, narrow absorption feature centered at 2.72 micrometers was detected across the entire observed surface, indicating that hydroxyl (OH)-bearing minerals are ubiquitous there. The intensity of the OH feature and low albedo are similar to thermally and/or shock-metamorphosed carbonaceous chondrite meteorites. There are few variations in the OH-band position, which is consistent with Ryugu being a compositionally homogeneous rubble-pile object generated from impact fragments of an undifferentiated aqueously altered parent body.
244 citations
TL;DR: In this article, a deep learning-based method was proposed to improve the performance of SAGINs, where the authors analyzed several main challenges of SagINs and explained how these problems can be solved by AI.
Abstract: It is widely acknowledged that the development of traditional terrestrial communication technologies cannot provide all users with fair and high quality services due to scarce network resources and limited coverage areas. To complement the terrestrial connection, especially for users in rural, disaster-stricken, or other difficult-to-serve areas, satellites, UAVs, and balloons have been utilized to relay communication signals. On this basis, SAGINs have been proposed to improve the users' QoE. However, compared with existing networks such as ad hoc networks and cellular networks, SAGINs are much more complex due to the various characteristics of three network segments. To improve the performance of SAGINs, researchers are facing many unprecedented challenges. In this article, we propose the AI technique to optimize SAGINs, as the AI technique has shown its predominant advantages in many applications. We first analyze several main challenges of SAGINs and explain how these problems can be solved by AI. Then, we consider the satellite traffic balance as an example and propose a deep learning based method to improve traffic control performance. Simulation results evaluate that the deep learning technique can be an efficient tool to improve the performance of SAGINs.
226 citations
TL;DR: The proposed input/output architectures for convolutional neural network (CNN)-based cross-view gait recognition are used and it is confirmed that the proposed architectures outperformed the state-of-the-art benchmarks in accordance with their suitable situations of verification/identification tasks and view differences.
Abstract: In this paper, we discuss input/output architectures for convolutional neural network (CNN)-based cross-view gait recognition. For this purpose, we consider two aspects: verification versus identification and the tradeoff between spatial displacements caused by subject difference and view difference. More specifically, we use the Siamese network with a pair of inputs and contrastive loss for verification and a triplet network with a triplet of inputs and triplet ranking loss for identification. The aforementioned CNN architectures are insensitive to spatial displacement, because the difference between a matching pair is calculated at the last layer after passing through the convolution and max pooling layers; hence, they are expected to work relatively well under large view differences. By contrast, because it is better to use the spatial displacement to its best advantage because of the subject difference under small view differences, we also use CNN architectures where the difference between a matching pair is calculated at the input level to make them more sensitive to spatial displacement. We conducted experiments for cross-view gait recognition and confirmed that the proposed architectures outperformed the state-of-the-art benchmarks in accordance with their suitable situations of verification/identification tasks and view differences.
157 citations
15 Sep 2019
TL;DR: A novel system that separates the voice of a target speaker from multi-speaker signals, by making use of a reference signal from the target speaker, by training two separate neural networks.
149 citations
TL;DR: Detailed analyses on the double-lattice structure indicate that the resonators have the potential to realize a brightness of up to 10 GW cm−2 sr−1, suggesting that compact, affordable semiconductor lasers will be able to rival existing gas and fibre/disk lasers.
Abstract: Achieving high brightness (where brightness is defined as optical power per unit area per unit solid angle) in semiconductor lasers is important for various applications, including direct-laser processing and light detection and ranging for next-generation smart production and mobility. Although the brightness of semiconductor lasers has been increased by the use of edge-emitting-type resonators, their brightness is still one order of magnitude smaller than that of gas and solid-state/fibre lasers, and they often suffer from large beam divergence with strong asymmetry and astigmatism. Here, we develop a so-called ‘double-lattice photonic crystal’, where we superimpose two photonic lattice groups separated by one-quarter wavelength in the x and y directions. Using this resonator, an output power of 10 W with a very narrow-divergence-angle (<0.3°) symmetric surface-emitted beam is achieved from a circular emission area of 500 μm diameter under pulsed conditions, which corresponds to a brightness of over 300 MW cm−2 sr−1. In addition, an output power up to ~7 W is obtained under continuous-wave conditions. Detailed analyses on the double-lattice structure indicate that the resonators have the potential to realize a brightness of up to 10 GW cm−2 sr−1, suggesting that compact, affordable semiconductor lasers will be able to rival existing gas and fibre/disk lasers. An optimized design for a broad-area surface-emitting photonic-crystal laser leads to high brightness of over 300 MW cm–2 sr–1 and an output power of 10 W under pulsed excitation.
127 citations
TL;DR: In this paper, a guard ring (GR) was employed to improve the breakdown voltage (V) of vertical Ga2O3 Schottky barrier diodes (SBDs) with or without a field-plate (FP) by eliminating electric field concentration at the edges of anode and FP electrodes.
Abstract: A guard ring (GR) was employed to improve the breakdown voltage ( ${V}_{\text {br}}$ ) of vertical Ga2O3 Schottky barrier diodes (SBDs) with or without a field-plate (FP) by eliminating electric field concentration at the edges of anode and FP electrodes. The GR structure was formed by nitrogen (N)-ion implantation. Four types of vertical SBD structures with: 1) neither a GR nor a FP; 2) a GR; 3) a FP; and 4) both a GR and a FP were fabricated on the same substrate. The SBDs with a GR [structures 2) and 4)] showed larger ${V}_{\text {br}}$ values than their GR-free counterparts [structures 1) and 3)]. Considering the trade-off relationship between ${V}_{\text {br}}$ and specific on-resistance ( ${R}_{\text {on}}$ ), a ${V}_{\text {br}}/{R}_{\text {on}}$ combination of 1.43 kV/ $4.7~\text {m}\Omega \cdot \text {cm}^{2}$ for the GR/FP-SBD corresponds to one of the best balanced data for Ga2O3 SBDs.
116 citations
TL;DR: In this paper, a joint bidding and pricing problem is formulated as a Markov decision process (MDP) with continuous state and action spaces in which the energy bid and the energy price are two actions that share a common objective.
Abstract: In this paper, we address the problem of jointly determining the energy bid submitted to the wholesale electricity market (WEM) and the energy price charged in the retailed electricity market (REM) for a load serving entity (LSE). The joint bidding and pricing problem is formulated as a Markov decision process (MDP) with continuous state and action spaces in which the energy bid and the energy price are two actions that share a common objective. We apply the deep deterministic policy gradient (DDPG) algorithm to solve this MDP for the optimal bidding and pricing policies. Yet, the DDPG algorithm typically requires a significant number of state transition samples, which are costly in this application. To this end, we apply neural networks to learn dynamical bid and price response functions from historical data to model the WEM and the collective behavior of the end use customers (EUCs), respectively. These response functions explicitly capture the inter-temporal correlations of the WEM clearing results and the EUC responses and can be utilized to generate state transition samples without any cost. More importantly, the response functions also inform the choice of states in the MDP formulation. Numerical simulations illustrated the effectiveness of the proposed methodology.
87 citations
TL;DR: A hierarchical DM (HiDM) scheme, having fully parallelized input–output interfaces and a pipelined architecture that can efficiently perform the DM/invDM without the complex operations of previously proposed methods such as constant composition DM is proposed.
Abstract: The implementation difficulties of combining distribution matching (DM) and dematching (invDM) for probabilistic shaping (PS) with soft-decision forward error correction (FEC) coding can be relaxed by reverse concatenation, for which the FEC coding and decoding lies inside the shaping algorithms. PS can seemingly achieve performance close to the Shannon limit, although there are practical implementation challenges that need to be carefully addressed. We propose a hierarchical DM (HiDM) scheme, having fully parallelized input–output interfaces and a pipelined architecture that can efficiently perform the DM/invDM without the complex operations of previously proposed methods such as constant composition DM. Furthermore, HiDM can operate at a significantly larger post-FEC bit error rate (BER) for the same post-invDM BER performance, which facilitates simulations. These benefits come at the cost of a slightly larger rate loss and required signal-to-noise ratio at a given post-FEC BER.
75 citations
TL;DR: In this paper, the authors proposed a significantly more resource-efficient verification protocol for graph states that only requires O(n5 log n) copies, where n is the size of the graph state.
Abstract: Verifying quantum states is central to certifying the correct operation of various quantum information processing tasks. In particular, in measurement-based quantum computing, checking whether correct graph states are generated is essential for reliable quantum computing. Several verification protocols for graph states have been proposed, but none of these are particularly resource efficient: multiple copies are required to extract a single state that is guaranteed to be close to the ideal one. The best protocol currently known requires O(n15) copies of the state, where n is the size of the graph state. In this paper, we construct a significantly more resource-efficient verification protocol for graph states that only requires O(n5 log n) copies. The key idea is to employ Serfling’s bound, which is a probability inequality in classical statistics. Utilizing Serfling’s bound also enables us to generalize our protocol for qudit and continuous-variable graph states. Constructing a resource-efficient verification protocol for them is non-trivial. For example, the previous verification protocols for qubit graph states that use the quantum de Finetti theorem cannot be generalized to qudit and continuous-variable graph states without tremendously increasing the resource overhead. This is because the overhead caused by the quantum de Finetti theorem depends on the local dimension. On the other hand, in our protocol, the resource overhead is independent of the local dimension, and therefore generalizing to qudit or continuous-variable graph states does not increase the overhead. The flexibility of Serfling’s bound also makes our protocol robust: our protocol accepts slightly noisy but still useful graph states.
55 citations
Patent•
01 Jan 2019TL;DR: In this paper, a parallax-barrier shutter panel including a plurality of sub-pixels arranged widthwise, the subpixels each being changeable between a light transmittance state and a light block state by driving a liquid crystal layer held between a first transparent substrate and a second transparent substrate with a first opaque electrode extending lengthwise.
Abstract: An image display apparatus includes a parallax-barrier shutter panel including a plurality of sub-pixels arranged widthwise, the sub-pixels each being changeable between a light transmittance state and a light block state by driving a liquid crystal layer held between a first transparent substrate and a second transparent substrate with a first transparent electrode extending lengthwise. The first transparent substrate includes in a display area, a lower-layer first transparent electrode disposed under an interlayer insulating film and an upper-layer first transparent electrode disposed on the interlayer insulating film, the lower-layer first transparent electrode and the upper-layer first transparent electrode being the first transparent electrode. The first transparent substrate includes in an area adjacent to the display area, a lower-layer metal wire disposed under the interlayer insulating film and an upper-layer metal wire disposed on the interlayer insulating film. A lower-layer transparent electrode is connected to the lower-layer metal wire.
51 citations
TL;DR: The results show that pilot-based DSP combined with overhead optimization can increase the robustness and performance of systems using advanced modulation formats while still maintaining state-of-the-art spectral efficiency and multi-Tb/s throughput.
Abstract: We present a low-complexity fully pilot-based digital signal processing (DSP) chain designed for high spectral efficiency optical transmission systems. We study the performance of the individual pilot algorithms in simulations before demonstrating transmission of a 51×24 Gbaud PM-64QAM superchannel over distances reaching 1000 km. We present an overhead optimization technique using the system achievable information rate to find the optimal balance between increased performance and throughput reduction from adding additional DSP pilots. Using the optimal overhead of 2.4%, we report 9.3 (8.3) bits/s/Hz spectral efficiency, or equivalently 11.9 (10.6) Tb/s superchannel throughput, after 480 (960) km of transmission over 80 km spans with EDFA-only amplification. Moreover, we show that the optimum overhead depends only weakly on transmission distance, concluding that back-to-back optimization is sufficient for all studied distances. Our results show that pilot-based DSP combined with overhead optimization can increase the robustness and performance of systems using advanced modulation formats while still maintaining state-of-the-art spectral efficiency and multi-Tb/s throughput.
TL;DR: This paper proposes a set of performance metrics selected in terms of actual field use as a solution to clarify the important technologies in bin picking and uses the selected metrics to compare the four original robot systems, which achieved the best performance in the Stow task of the Amazon Robotics Challenge 2017.
Abstract: Bin picking is still a challenge in robotics, as patent in recent robot competitions. These competitions are an excellent platform for technology comparisons since some participants may use state-o...
Patent•
11 Apr 2019TL;DR: A stator coil accommodated in a slot of a rotary electric machine includes a coil conductor, a main insulating layer, a low resistance corona shield layer, and a stator coils extending outside the slot.
Abstract: A stator coil accommodated in a slot of a rotary electric machine includes a coil conductor, a main insulating layer, a low resistance corona shield layer, and a stator coil extending outside the slot is provided with a first stator coil at the end of the low resistance corona shield layer has a first nonlinear resistance layer and a second nonlinear resistance layer partially overlapping with an end of the first nonlinear resistance layer, and a lower limit value of an electric resistivity of the second nonlinear resistance layer in a predetermined electric field is larger than an upper limit value of an electric resistivity of the first nonlinear resistance layer by one order of magnitude or more.
TL;DR: The authors negatively answer the question by showing oscillators without a combinatorial loop, and show how to detect and reject the proposed oscillators by a design rule check.
Abstract: Virtual field-programmable gate array (FPGA) is an emerging technology to put multiple users in the same FPGA fabric with logical isolation. Security researchers have studied new threats in virtual FPGA and proposed attacks on the logical isolation by exploiting analogue natures of FPGA. These attacks use an oscillator comprising a combinatorial loop to have access to the analogue domain using digital components only. Interestingly, the system in the field prohibits a combinatorial loop by a design rule check. In this Letter, the authors study if prohibiting a combinatorial loop is sufficient to thwart the conventional attacks. They negatively answer the question by showing oscillators without a combinatorial loop. They also show how to detect and reject the proposed oscillators by a design rule check.
TL;DR: In this paper, high-responsivity, long-wavelength infrared graphene photodetectors operating at room temperature are described, which are based on the photogating effect, enhanced by a pyroelectric effect in the LiNbO3 substrate due to heat generation as a result of radiation absorption by a SiN layer on the substrate.
Abstract: This report describes high-responsivity, long-wavelength infrared graphene photodetectors operating at room temperature, that are based on the photogating effect. Photogating is enhanced by a pyroelectric effect in the lithium niobium oxide (LiNbO3) substrate due to heat generation as a result of radiation absorption by a SiN layer on the substrate. This significantly modulates the back-gate voltage, and increases the photoresponse by a factor of approximately 600. Switching of the charge carrier type in the graphene is observed in response to higher light intensities. The pronounced modulation of the photogating voltage changes the carrier type of graphene.
TL;DR: In this paper, a lifetime model for bond wire contacts of insulated gate bipolar transistors (IGBT) power modules is reported, based on power cycling tests obtained under accelerated conditions, and a finite-element model taking into account the electrical, thermal, and mechanical coupling.
Abstract: In this paper, a lifetime model for bond wire contacts of insulated gate bipolar transistors (IGBT) power modules is reported. This model is based on power cycling tests obtained under accelerated conditions, and a finite-element model taking into account the electrical, thermal, and mechanical coupling. It allows us to estimate the bond wire lifetime for a large scale of junction temperature swing amplitudes ( $ {\Delta }T_{j}$ ) and stress durations ( $t_{\mathrm{\scriptscriptstyle ON}}$ ). To build it, a numerical design of experiment was performed in both high and low stress values ( $\Delta T_{j}$ ). Then, a strain-life curve has been constructed where the average strain values on a defined volume around the contact areas between top-metallization and the most exposed bond wires to fatigue and lift-off have been used. As a result, it has been shown that the total strain is linearly dependent with $\Delta T_{j}$ and power law dependent with $t_{\mathrm{\scriptscriptstyle ON}}$ . The combination of the strain-life relation and the strain dependency with stress parameters leads to the lifetime relationship. The obtained lifetime model has been satisfactorily validated with some additional experimental points obtained from literature and with a large range of values for $t_{\mathrm{\scriptscriptstyle ON}}$ . This methodology can be easily replicated to other structures and is quite generic.
TL;DR: A new high resolution low-energy X-ray camera that is promising for imaging secondary electron bremsstrahlung X-rays during irradiation of carbon-ions even near clinical conditions is developed and compared with a Monte Carlo simulation.
Abstract: Low-energy x-ray imaging of the secondary electron bremsstrahlung (SEB) x-ray emitted during carbon-ion irradiation is a promising method for range estimation. However, it remains unclear whether the method can be used for imaging with the clinical dose levels of carbon-ion and whether the bremsstrahlung x-ray can be detected from the deeper part of the body. To clarify these points, we developed a new high resolution low-energy x-ray camera and conducted imaging of the SEB x-ray during the irradiation of carbon-ions of different energies and intensities. Imaging was also tried with an x-ray camera using a human-head-sized, 17 cm diameter cylindrical phantom. To develop a high resolution imaging detector for a low-energy x-ray, we used a 20 × 20 × 0.5 mm thick cerium-doped yttrium aluminum perovskite, YA1O3 (YAP(Ce)) scintillator plate, which was optically coupled to a 25 mm square high quantum efficiency (HQE) type position sensitive photomultiplier tube (PSPMT). The imaging detector was encased in a 2 cm thick tungsten container and a pinhole collimator was attached to its camera head. After evaluating the camera's performance, SEB x-ray imaging was tried during irradiation of the carbon-ion and compared the results with a Monte Carlo simulation. We imaged the beam tracks by the SEB x-ray in real-time during irradiation of the carbon-ion and imaging and range estimation were possible even with near clinical dose level of 7.5 × 108 particles of carbon-ion. Clear images of a SEB x-ray were also obtained for a 17 cm diameter cylindrical phantom. The measured images were good agreement with the Monte Carlo simulation. We confirmed that our developed YAP(Ce) camera is promising for imaging SEB x-rays during irradiation of carbon-ions even near clinical conditions.
TL;DR: In this paper, a flux weakening strategy for deadbeat-direct torque and flux control (DB-DTFC) was proposed to achieve the maximum feasible torque over the entire operating range.
Abstract: Flux weakening techniques have been developed for field-oriented control (FOC) drives to achieve the maximum torque capability above the base speed. Deadbeat-direct torque and flux control (DB-DTFC) has the advantages of precise torque and flux control and reduced parameter sensitivity compared to FOC, thus it has the benefit of more consistently achieving the maximum torque capability in the flux weakening region more accurately. This paper introduces a flux weakening strategy for DB-DTFC. Considering voltage and current limits, a simple solution to the optimal trajectory for the stator flux magnitude is derived to achieve the maximum feasible torque over the entire operating range. Results show that the speed control is extended to a significantly higher range beyond the base speed. Torque control is less sensitive to machine parameters and has better dynamics in the flux weakening region compared with the traditional FOC drives. Self-sensing is also investigated in the flux weakening region. Challenges of self-sensing are addressed to significantly extend the high-speed operating range.
Patent•
01 Mar 2019TL;DR: In this article, an electric power steering device including a DC power supply; a motor; an inverter circuit configured to convert DC power output from the DC power input to an AC power and output the AC power after the conversion to the motor; and a filter circuit, which is provided between the DC Power supply and the inverter, and includes a choke coil.
Abstract: Provided is an electric power steering device including: a DC power supply; a motor; an inverter circuit configured to convert a DC power output from the DC power supply to an AC power and output the AC power after the conversion to the motor; and a filter circuit, which is provided between the DC power supply and the inverter circuit, and includes a choke coil. The choke coil includes: a core; and one or more conductor sets each including two conductors wound in parallel on the core. A tip on one side of each of the two conductors included in each of the conductor sets is connected to the DC power supply side, and a tip on another side of each of the two conductors is connected to the inverter circuit side.
15 Sep 2019
TL;DR: This paper investigates efficient beam search techniques for end-to-end automatic speech recognition (ASR) with attentionbased encoder-decoder architecture by vectorizing multiple hypotheses during the beam search, which allows it to take advantage of the parallel computing capabilities of multi-core CPUs and GPUs.
Abstract: This paper investigates efficient beam search techniques for end-to-end automatic speech recognition (ASR) with attentionbased encoder-decoder architecture. We accelerate the decoding process by vectorizing multiple hypotheses during the beam search, where we replace the score accumulation steps for each hypothesis with vector-matrix operations for the vectorized hypotheses. This modification allows us to take advantage of the parallel computing capabilities of multi-core CPUs and GPUs, resulting in significant speedups and also enabling us to process multiple utterances in a batch simultaneously. Moreover, we extend the decoding method to incorporate a recurrent neural network language model (RNNLM) and connectionist temporal classification (CTC) scores, which typically improve ASR accuracy but have not been investigated for the use of such parallelized decoding algorithms. Experiments with LibriSpeech and Corpus of Spontaneous Japanese datasets have demonstrated that the vectorized beam search achieves 1.8× speedup on a CPU and 33× speedup on a GPU compared with the original CPU implementation. When using joint CTC/attention decoding with an RNNLM, we also achieved 11× speedup on a GPU while maintaining the benefits of CTC and RNNLM. With these benefits, we achieved almost real-time processing with a small latency of 0.1× real-time without streaming search process.
TL;DR: In this article, the carrier transport properties in the inversion layer of Si-face 4H-SiC MOSFETs with nitrided oxide were investigated, and it was revealed that the intrinsic phonon-limited mobility (μ phonon) of the SiC-based MOS-FET is a quarter or less than the conventionally presumed values.
Abstract: We propose a method to evaluate the carrier transport properties in the inversion layer of 4H–SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) experimentally. Our approach differs from conventional methods, which have adjusted the parameters in conventional mobility models. Intrinsic phonon-limited mobility (μ phonon) in the SiC MOSFET was observed by suppressing the severe impact of Coulomb scattering on the SiC MOS inversion layer by lowering the acceptor concentration (N A) of the p-type well region to the order of 1014 cm−3. In this study, we investigated the carrier transport properties in the inversion layer of Si-face 4H–SiC MOSFETs with nitrided oxide. It is revealed that the μ phonon of the SiC MOSFET is a quarter or less than the conventionally presumed values. Additionally, surface roughness scattering is found not to be the most dominant mobility-limiting factor even at high effective normal field (E eff) for the SiC MOSFET. These results demonstrate that conventional understanding of carrier scattering in the SiC MOS inversion layer should be modified, especially in the high E eff region.
TL;DR: A high-gain, high-peak-power laser amplifier at an eye-safe 1.55 μm wavelength using an Er,Yb:glass planar waveguide for wind sensing coherent Doppler lidars (CDLs) is developed and realizes high gain thanks to its multi-bounce optical-path configuration.
Abstract: We have developed a high-gain, high-peak-power laser amplifier at an eye-safe 1.55 μm wavelength using an Er,Yb:glass planar waveguide for wind sensing coherent Doppler lidars (CDLs). Our planar waveguide is free from stimulated Brillouin scattering and realizes high gain thanks to its multi-bounce optical-path configuration. A peak power of 5.5 kW with a pulse energy of 3.2 mJ is achieved at the repetition frequency of 4 kHz, which leads to an average power of 12.8 W. The gain is more than 23 dB. The wind sensing at more than 30 km is demonstrated with a CDL using the developed amplifier.
TL;DR: In this article, high-responsivity graphene photodetectors were fabricated using turbostratic stacked graphene, which provided enhanced photogating, and the photoresponse of these devices at a wavelength of 642 nm was approximately twice that obtained for a conventional monolayer graphene photoder.
Abstract: High-responsivity graphene photodetectors were fabricated using turbostratic stacked graphene, which provided enhanced photogating. Photogating is a promising means of increasing the responsivity of graphene photodetectors, and this effect is proportional to carrier mobility. Turbostratic stacked graphene exhibits higher carrier mobility than conventional monolayer graphene because it has the same band structure as monolayer graphene while preventing scattering by the underlying SiO2 layer. The photoresponse of these devices at a wavelength of 642 nm was approximately twice that obtained for a conventional monolayer graphene photodetector. The results reported show the feasibility of producing high-responsivity graphene-based photodetectors using a simple fabrication technique.
TL;DR: This work introduces a simple yet general method to prove the security of QKD with arbitrarily long-range pulse correlations, which is compatible with those security proofs that accommodate all the other typical device imperfections, thus paving the way toward achieving implementation security in QkD with arbitrary flawed devices.
Abstract: Implementation security is a critical problem in quantum key distribution (QKD). With the advent of measurement-device-independent QKD, all security loopholes of the measurement unit have been closed. Securing the source, however, remains an elusive issue. Despite the tremendous progress made by developing security proofs that accommodate most typical source imperfections, such proofs usually disregard the effect of pulse correlations. That is, they disregard the fact that the state of an emitted signal can depend on the signals selected previously. Here, we close this gap by introducing a simple yet general method to prove the security of QKD with arbitrary pulse correlations. Our method is compatible with those security proofs that accommodate all the other source imperfections, thus paving the way towards achieving implementation security in QKD with arbitrary flawed devices. Moreover, we introduce a new security proof, which we call the reference technique, that provides high performance in the presence of source imperfections.
19 May 2019
TL;DR: In this article, SiC-MOSFET embedding SBD enables a suppression of recovery charge during turn-on process, which results in a reduction of turnon loss.
Abstract: Superior switching characteristics of SiC-MOSFET embedding SBD is demonstrated compared with conventional MOSFET and MOSFET with external SBD. Inactivation of parasitic body diode by embedding SBD enables a suppression of recovery charge during turn-on process, which results in a reduction of turn-on loss. Furthermore, elimination of external SBD reduces total chip size, or output capacitance charge, which results in a reduction of output capacitance loss.
TL;DR: Two types of simplified adaptive equalization (AEQ) are introduced, one which sacrifices differential group delay compensation (DGDC), and another which sacrifices some chromatic dispersion compensation but does provide DGDC, which showed the same performance as the conventional DSP in both experiment and simulation.
Abstract: Future passive optical network (PON) systems supporting more than 50 Gb/s/λ present a challenge for the use of intensity modulation direct detection (IM-DD). Since coherent technology improves the receiver sensitivity over that of IM-DD, it is a promising candidate for 100 Gb/s or higher PON systems. Introducing hardware-efficient signal processing technologies tailored to PON systems will help render coherent technology suitable for PON systems. We here review hardware-efficient signal processing technologies suitable for PON systems. We introduce two types of simplified adaptive equalization (AEQ), one which sacrifices differential group delay compensation (DGDC), and another which sacrifices some chromatic dispersion compensation but does provide DGDC. Transmission experiments on a 100 Gb/s/λ-based coherent wavelength division multiplexing (WDM) PON system showed that simplified AEQ without DGDC and with DGDC exhibited only 0.2 and 1.4 dB penalty, respectively, compared with conventional DSP. The additional penalty due to the maximum possible cumulative DGD was evaluated by numerical simulation. Conventional AEQ and the simplified AEQ with DGDC showed negligible penalty, but the simplified AEQ without DGDC showed a 1.4 dB penalty. We also introduce simplified carrier phase recovery (CPR) with interpolarization phase offset estimation, and this showed the same performance as the conventional DSP, in both experiment and simulation. Taking these results into account, 100 Gb/s/λ-based coherent WDM PON systems with the simplified AEQs in combination with the simplified CPR were shown to be able to support the loss budget required for eight ONU splits over an 80 km span of single mode fiber.
TL;DR: Mizutani et al. as mentioned in this paper considered a setting-choice-independent correlation (SCIC) framework in which the sending pulses can present arbitrary correlations but they are independent of the previous setting choices such as the bit, the basis and the intensity settings.
Abstract: Despite the enormous theoretical and experimental progress made so far in quantum key distribution (QKD), the security of most existing practical QKD systems is not rigorously established yet. A critical obstacle is that almost all existing security proofs make ideal assumptions on the QKD devices. Problematically, such assumptions are hard to satisfy in the experiments, and therefore it is not obvious how to apply such security proofs to practical QKD systems. Fortunately, any imperfections and security-loopholes in the measurement devices can be perfectly closed by measurement-device-independent QKD (MDI-QKD), and thus we only need to consider how to secure the source devices. Among imperfections in the source devices, correlations between the sending pulses and modulation fluctuations are one of the principal problems, which unfortunately most of the existing security proofs do not consider. In this paper, we take into account these imperfections and enhance the implementation security of QKD. Specifically, we consider a setting-choice-independent correlation (SCIC) framework in which the sending pulses can present arbitrary correlations but they are independent of the previous setting choices such as the bit, the basis and the intensity settings. Within the framework of SCIC, we consider the dominant fluctuations of the sending states, such as the relative phases and the intensities, and provide a self-contained information-theoretic security proof for the loss-tolerant QKD protocol in the finite-key regime. We demonstrate the feasibility of secure quantum communication, and thus our work constitutes a crucial step towards guaranteeing the security of practical QKD systems. A rigorous study on source device security brings practical quantum key distribution (QKD) a step closer to information theoretic security. Existing studies on the security of QKD focus on potential security breaches from imperfect measurement devices, but have overlooked loopholes associated to source imperfections. To tackle this problem, Akihiro Mizutani and co-workers in Japan, Spain and Canada consider the security of an imperfect quantum source that sends pulses with arbitrary correlations, and fluctuations in phase and intensity. They numerically prove that secure quantum communications is feasible provided that these correlations are independent of the choices made for bit, basis and intensity. Their information theoretic security proof with setting-choice-independent correlations in the source is based on practically viable, loss-tolerant QKD in the finite-key regime. The team is confident that their findings will help realize secure quantum communication with practical source devices.
01 Nov 2019
TL;DR: A reinforcement learning-based algorithm for trajectory optimization for constrained dynamical systems, trained with a reference path and parameterize the policies with goal locations, so that the agent can be trained for multiple goals simultaneously.
Abstract: In this paper, we propose a reinforcement learning-based algorithm for trajectory optimization for constrained dynamical systems. This problem is motivated by the fact that for most robotic systems, the dynamics may not always be known. Generating smooth, dynamically feasible trajectories could be difficult for such systems. Using sampling-based algorithms for motion planning may result in trajectories that are prone to undesirable control jumps. However, they can usually provide a good reference trajectory which a model-free reinforcement learning algorithm can then exploit by limiting the search domain and quickly finding a dynamically smooth trajectory. We use this idea to train a reinforcement learning agent to learn a dynamically smooth trajectory in a curriculum learning setting. Furthermore, for generalization, we parameterize the policies with goal locations, so that the agent can be trained for multiple goals simultaneously. We show result in both simulated environments as well as real experiments, for a 6-DoF manipulator arm operated in position-controlled mode to validate the proposed idea. We compare the proposed ideas against a PID controller which is used to track a designed trajectory in configuration space. Our experiments show that our RL agent trained with a reference path outperformed a model-free PID controller of the type commonly used on many robotic platforms for trajectory tracking.
TL;DR: This paper addresses remote sensing satellite network and proposes novel beam control technique to coexist with the terrestrial networks in Q band and controls satellite's transmitting antenna boresight adaptively to maximize signal to noise power ratio of satellite ground station and minimize interference to terrestrial networks.
Abstract: The earth observation missions have been improved its sensor performance which results in a huge amount of data to be stored in remote sensing satellite and transmitted to a ground station. Although, satellite to ground transmitter had been usually used X band, several mitigation techniques for rain attenuation have been studied in recent years to migrate to Ka band for broadband transmission. Furthermore, Q band is expected to achieve higher data rate because of its broader bandwidth. However, Q band is shared with terrestrial networks, remote sensing satellite has to take into account potential constrains to them. Therefore, this paper addresses remote sensing satellite network and proposes novel beam control technique to coexist with the terrestrial networks in Q band. The proposed method controls satellite's transmitting antenna boresight adaptively to maximize signal to noise power ratio of satellite ground station and minimize interference to terrestrial networks. The effectiveness of our proposal is verified through simulation results.