Publications by authors named "Takahiro Inagaki"

SPring-8-II is a major upgrade project of SPring-8 that was inaugurated in October 1997 as a third-generation synchrotron radiation light source. This upgrade project aims to achieve three goals simultaneously: achievement of excellent light source performance, refurbishment of aged systems, and significant reduction in power consumption for the entire facility. A small emittance of 50 pm rad will be achieved by (1) replacing the existing double-bend lattice structure with a five-bend achromat one, (2) lowering the stored beam energy from 8 to 6 GeV, (3) increasing the horizontal damping partition number from 1 to 1.

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A coherent XY machine (CXYM) is a physical spin simulator that can simulate the XY model by mapping XY spins onto the continuous phases of non-degenerate optical parametric oscillators (NOPOs). Here, we demonstrated a large-scale CXYM with >47,000 spins by generating 10-GHz-clock time-multiplexed NOPO pulses via four-wave mixing in a highly nonlinear fiber inside a fiber ring cavity. By implementing a unidirectional coupling from the ith pulse to the (i + 1)th pulse with a variable 1-pulse delay planar lightwave circuit interferometer, we successfully controlled the effective temperature of a one-dimensional XY spin network within two orders of magnitude.

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A machine-learning-based beam optimizer has been implemented to maximize the spectral brightness of the X-ray free-electron laser (XFEL) pulses of SACLA. A new high-resolution single-shot inline spectrometer capable of resolving features of the order of a few electronvolts was employed to measure and evaluate XFEL pulse spectra. Compared with a simple pulse-energy-based optimization, the spectral width was narrowed by half and the spectral brightness was improved by a factor of 1.

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Article Synopsis
  • Obturator hernia is a rare but serious condition that typically affects older women with health issues.
  • A 54-year-old woman experienced pain due to a herniated small intestine through the left obturator foramen, discovered via CT scans after her previous health complications.
  • Emergency surgery was required to remove the necrotic part of her intestine, emphasizing the need for prompt diagnosis and treatment to prevent life-threatening situations.
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A 64-year-old man visited the outpatient department of our hospital for the first time due to bilateral lower limb edema, which he noticed 1 week before the visit. Pain suddenly developed in the left lower limb while the patient was in the waiting room. Nephrotic syndrome was suspected based on blood and urine test results.

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Article Synopsis
  • Increasing interest in physical system-based computers aims to overcome digital computer performance limits, highlighting the coherent Ising machine (CIM) as a promising solution for combinatorial optimization.* -
  • The CIM utilizes over 100,000 optical parametric oscillator pulses as Ising spins, achieving faster and more effective solutions to complex maximum cut problems compared to traditional methods like simulated annealing.* -
  • Operating near a phase transition point, the CIM demonstrates the ability to generate high-quality solutions and offers a wide range of results, which is particularly beneficial for fast random sampling in machine learning applications.*
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Nonlinear dynamics of spiking neural networks have recently attracted much interest as an approach to understand possible information processing in the brain and apply it to artificial intelligence. Since information can be processed by collective spiking dynamics of neurons, the fine control of spiking dynamics is desirable for neuromorphic devices. Here we show that photonic spiking neurons implemented with paired nonlinear optical oscillators can be controlled to generate two modes of bio-realistic spiking dynamics by changing optical-pump amplitude.

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The minimum requirements for an optical reservoir computer, a recent paradigm for computation using simple algorithms, are nonlinearity and internal interactions. A promising optical system satisfying these requirements is a platform based on coupled degenerate optical parametric oscillators (DOPOs) in a fiber ring cavity. We can expect advantages using DOPOs for reservoir computing with respect to scalability and reduction of excess noise; however, the continuous stabilization required for reservoir computing has not yet been demonstrated.

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We generated time-multiplexed degenerate optical parametric oscillator (DOPO) pulses using a nonlinear fiber Sagnac loop as a phase-sensitive amplifier (PSA), where the pump and amplified light in pump-signal-idler degenerate four-wave mixing can be spatially separated. By placing the PSA in a fiber cavity, we successfully generated more than 5000 time-multiplexed DOPO pulses. We confirmed the bifurcation of pulse phases to 0 or relative to the pump phase, which makes them useful for representing Ising spins in an Ising model solver based on coherent optical oscillator networks.

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A high-repetition linear accelerator with multibeamline operation for X-rays allows users to perform multiple simultaneous experiments with an X-ray free-electron laser (XFEL) at lower actual cost per user while maintaining the availability of the laser. As the first step toward a higher pulse repetition rate (PRR), we developed radio frequency (RF) components at 5712 MHz and tested them for their feasibility at an RF PRR of 120 pulses per second (pps). To increase the RF PRR from the present value of 60 pps-at the SPring-8 Angstrom compact free-electron laser-to 120 pps, we re-examined the thermal designs of the present RF components for the XFEL.

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Physical annealing systems provide heuristic approaches to solving combinatorial optimization problems. Here, we benchmark two types of annealing machines-a quantum annealer built by D-Wave Systems and measurement-feedback coherent Ising machines (CIMs) based on optical parametric oscillators-on two problem classes, the Sherrington-Kirkpatrick (SK) model and MAX-CUT. The D-Wave quantum annealer outperforms the CIMs on MAX-CUT on cubic graphs.

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Many problems in mathematics, statistical mechanics, and computer science are computationally hard but can often be mapped onto a ground-state-search problem of the Ising model and approximately solved by artificial spin-networks of coupled degenerate optical parametric oscillators (DOPOs) in coherent Ising machines. To better understand their working principle and optimize their performance, we analyze the dynamics during the ground state search of 2D Ising models with up to 1936 mutually coupled DOPOs. For regular as well as frustrated and disordered 2D lattices, the machine finds the correct solution within just a few milliseconds.

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Since an X-ray Free Electron Laser (XFEL) facility is a linac-based single-user machine, a multi-beamline mode of operation, which improves the efficiency of user experiments, is critical for accommodating users' rapidly increasing demand for beamtime. A key supporting technology is a highly stable pulsed power supply (PS), which enables stable XFEL operations by precisely switching the beam route. We developed a high-power pulsed PS to drive a kicker magnet installed in a SACLA's beam switching system.

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Article Synopsis
  • The text describes the soft X-ray free-electron laser (FEL) beamline of the SPring-8 Compact free-electron LAser (SACLA), detailing its design and performance.* -
  • A prototype machine, the SPring-8 Compact SASE Source test accelerator, was moved to the SACLA undulator hall to specifically support this soft X-ray beamline.* -
  • The system can generate both soft and hard X-ray FELs simultaneously, achieving a pulse energy of 110 µJ at a 12.4 nm wavelength with an electron beam energy of 780 MeV.*
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Unconventional, special-purpose machines may aid in accelerating the solution of some of the hardest problems in computing, such as large-scale combinatorial optimizations, by exploiting different operating mechanisms than those of standard digital computers. We present a scalable optical processor with electronic feedback that can be realized at large scale with room-temperature technology. Our prototype machine is able to find exact solutions of, or sample good approximate solutions to, a variety of hard instances of Ising problems with up to 100 spins and 10,000 spin-spin connections.

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The analysis and optimization of complex systems can be reduced to mathematical problems collectively known as combinatorial optimization. Many such problems can be mapped onto ground-state search problems of the Ising model, and various artificial spin systems are now emerging as promising approaches. However, physical Ising machines have suffered from limited numbers of spin-spin couplings because of implementations based on localized spins, resulting in severe scalability problems.

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A coherent Ising machine based on degenerate optical parametric oscillators (DOPOs) is drawing attention as a way to find a solution to the ground-state search problem of the Ising model. Here we report the generation of time-multiplexed DOPOs at a 10 GHz clock frequency. We successfully generated >50,000 DOPOs using dual-pump four-wave mixing in a highly nonlinear fiber that formed a 1 km cavity, and observed phase bifurcation of the DOPOs, which suggests that the DOPOs can be used as stable artificial spins.

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We report the distribution of time-bin entangled photon pairs over 300 km of optical fiber. We realized this by using a high-speed and high signal-to-noise ratio entanglement generation/evaluation setup that consists of periodically poled lithium niobate waveguides and superconducting single photon detectors. The observed two-photon interference fringes exhibited a visibility of 84%.

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We fabricated a polarization-independent varifocal lens using KTa(1-x)Nb(x)O3 (KTN) crystals. The polarization dependence of the KTN crystal is effectively compensated for by combining a pair of KTN lenses and a half-wave plate. This compensation is achieved by a total electro-optic effect, which consists of the Kerr effect and the elasto-optic effects via the electrostrictive and elastic strains in the KTN crystal.

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Spin is a fundamental property of electrons, with an important role in information storage. For spin-based quantum information technology, preparation and read-out of the electron spin state are essential functions. Coherence of the spin state is a manifestation of its quantum nature, so both the preparation and read-out should be spin-coherent.

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Kamisyoyosan (KSS) and Tokisyakuyakusan (TSS) are widely used herbal formulas in Japanese traditional kampo medicine to relieve the symptoms occurred in climacteric disturbance. Since Japanese physicians frequently prescribe these formulas combined with etizolam, one of benzodiazepine anxiolytics, we evaluated the pharmacokinetic interaction between KSS or TSS and etizolam, and in vitro inhibitory effect of KSS and TSS on rat cytochrome P450 (CYP) 3A activity in rat microsomes, to obtain drug information to prevent from disadvantage or adverse effects by their combined therapy. In in vitro experiment, KSS and TSS inhibited CYP3A activity comparable to grapefruit juice.

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Sho-seiryu-to (SST) is widely used herbal formula in Japanese traditional medicine (kampo) to treat allergic diseases. Since Japanese physicians frequently prescribe this formula combined with azelastine hydrochloride, one of anti-histamine and anti-allergic medicines, we evaluated the pharmacokinetic interactions between SST and azelastine hydrochloride in rats to obtain the drug information for the prevention from disadvantage or adverse effects by their combined therapy. Oral administration of SST did not influence the plasma concentration profile of azelastine after its intravaneous injection, suggesting that SST would not change the activities of metabolic enzymes such as cytochrome P450s.

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