Boosting computational power through spatial multiplexing in quantum reservoir computing

Quantum reservoir computing provides a framework for exploiting the natural dynamics of quantum systems as a computational resource. It can implement real-time signal processing and solve temporal machine learning problems in general, which requires memory and nonlinear mapping of the recent input stream using the quantum dynamics in computational supremacy region, where the classical simulation of the system is intractable. A nuclear magnetic resonance spin-ensemble system is one of the realistic candidates for such physical implementations, which is currently available in laboratories. In this paper, considering these realistic experimental constraints for implementing the framework, we introduce a scheme, which we call a spatial multiplexing technique, to effectively boost the computational power of the platform. This technique exploits disjoint dynamics, which originate from multiple different quantum systems driven by common input streams in parallel. Accordingly, unlike designing a single large quantum system to increase the number of qubits for computational nodes, it is possible to prepare a huge number of qubits from multiple but small quantum systems, which are operationally easy to handle in laboratory experiments. We numerically demonstrate the effectiveness of the technique using several benchmark tasks and quantitatively investigate its specifications, range of validity, and limitations in detail.Comment: 15 page

Continuous optimization by quantum adaptive distribution search

In this paper, we introduce the quantum adaptive distribution search (QuADS), a quantum continuous optimization algorithm that integrates Grover adaptive search (GAS) with the covariance matrix adaptation - evolution strategy (CMA-ES), a classical technique for continuous optimization. QuADS utilizes the quantum-based search capabilities of GAS and enhances them with the principles of CMA-ES for more efficient optimization. It employs a multivariate normal distribution for the initial state of the quantum search and repeatedly updates it throughout the optimization process. Our numerical experiments show that QuADS outperforms both GAS and CMA-ES. This is achieved through adaptive refinement of the initial state distribution rather than consistently using a uniform state, resulting in fewer oracle calls. This study presents an important step toward exploiting the potential of quantum computing for continuous optimization

Spin current generation from an epitaxial tungsten dioxide WO2_{2}

We report on efficient spin current generation at room temperature in rutile type WO$_{2}$ grown on Al$_{2}$O$_{3}$(0001) substrate. The optimal WO$_{2}$ film has (010)-oriented monoclinically distorted rutile structure with metallic conductivity due to 5$\it{d}$$^2$ electrons, as characterized by x-ray diffraction, electronic transport, and x-ray photoelectron spectroscopy. By conducting harmonic Hall measurement in Ni$_{81}$Fe$_{19}$/WO$_{2}$ bilayer, we estimate two symmetries of the spin-orbit torque (SOT), i.e., dampinglike (DL) and fieldlike ones to find that the former is larger than the latter. By comparison with the Ni$_{81}$Fe$_{19}$/W control sample, the observed DL SOT efficiency $\xi$$_{DL}$ of WO$_{2}$ (+0.174) is about two thirds of that of W (-0.281) in magnitude, with a striking difference in their signs. The magnitude of the $\xi$$_{DL}$ of WO$_{2}$ exhibits comparable value to those of widely reported Pt and Ta, and Ir oxide IrO$_{2}$. The positive sign of the $\xi$$_{DL}$ of WO$_{2}$ can be explained by the preceding theoretical study based on the 4$\it{d}$ oxides. These results highlight that the epitaxial WO$_{2}$ offers a great opportunity of rutile oxides with spintronic functionalities, leading to future spin-orbit torque-controlled devices.Comment: 14 pages, 4 figure

Investigation of automotive light blinking pattern conveying a driver's intention to yield

This paper proposes a method of conveying a driver’s intention to yield by blinking automotive lighting. Generally, headlight flashing indicates a driver’s intention to yield to another driver or pedestrians in Japan. However, this signaling method can have several meanings, including warning other drivers of road dangers such as crashed cars, or informing other drivers of the presence of a pedestrian. There is a possibility of a misunderstanding, increasing the risk of accidents. Therefore, we have investigated an effective method for facilitating communication in traffic. This study focuses on nonverbal communication in which blinking lights convey the driver’s intentions to others. In this study, visibility is not considered. Nine blinking patterns that changed the light colors, waveform, and blinking cycle were presented to fifteen healthy participants, and visual impressions were evaluated to identify the most suitable blinking patterns. These nine patterns indicate a driver’s intention to yield to pedestrians and other drivers. The results indicated that a blue-green blinking pattern in which luminance changes with a triangular wave pattern with a one-second cycle was best conveyed the intention to yield

A METHOD FOR ESTIMATING ELBOW VARUS TORQUE USING ONLY A BASEBALL WITH AN EMBEDDED SENSOR

Currently, to measure the elbow varus torque during baseball pitching, it is necessary to attach markers and sensors to the body. The purpose of this study is to develop the method for estimating elbow varus torque by only a baseball with an embedded sensor, and examine the accuracy. Eight baseball pitchers threw a four-seam fastball with maximum effort. The varus torque was estimated using one-link-segment model by an accelerometer and gyro sensor placed in the baseball. The Intraclass Correlation Coefficients between the maximum values of the varus torque calculated by the proposed method and the values calculated by the motion capture system was high (ICC(3,1) = 0.73).This result indicates that proof of concept by one-link model is success and warrants future research to potentially develop a system with greater accuracy

Hemodynamic Analysis of a Microanastomosis Using Computational Fluid Dynamics

[Background] Technical issues in free flap transfer, such as the selection of recipient vessels and the positioning and method of anastomosis of the vascular pedicle, have been the subject of vigorous debate. Recent developments in computational fluid dynamics (CFD) have enabled the analysis of blood flow within microvessels. In this study, CFD was used to analyze hemodynamics in a microanastomosis. [Methods] In the fluid calculation process, the fluid domain modelizes microvessels with anastomosis. The inlet flow conditions were measured as venous waveform, and the fluid is simulated as blood. Streamlines (SL), wall shear stress (WSS), and oscillatory shear index (OSI) at the anastomosis were visualized and analyzed for observing effects from the flow field. [Results] Some flow disruption was evident as the SL passed over the sutures. The maximum recorded WSS was 13.37 Pa where the peak of a suture was exposed in the lumen. The local maximum value of the OSI was 0.182, recorded at the base of the anastomosis on the outflow side. [Conclusion] In the ideal anastomosis, the SL is disrupted as little as possible by the sutures. The WSS indicated that thrombus formation is unlikely to occur at suture peaks, but more likely to occur at the base of sutures, where the OSI is high. Tight suture knots are important in microanastomosis