Quantum Beam Research Articles

Active Pt-Nanocoated Layer with Pt-O-Ce Bonds on a CeO x Nanowire Cathode Formed by Electron Beam Irradiation.

A Pt-nanocoated layer (thickness of approx. 10–20 nm) with Pt–O–Ce bonds was created through the water radiolysis reaction on a CeOx nanowire (NW), which was induced by electron beam irradiation to the mixed suspension of K2PtCl4 aqueous solution and the CeOx NW. In turn, when Pt-nanocoated CeOx NW/C (Pt/C ratio = 0.2) was used in the cathode layer of a membrane electrode assembly (MEA), both an improved fuel cell performance and stability were achieved. The fuel cell performance observed for the MEA using Pt-nanocoated CeOx NW/C with Pt–O–Ce bonds, which was prepared using the electron beam irradiation method, improved and maintained its performance (observed cell potential of approximately 0.8 V at 100 mW cm–2) from 30 to 140 h after the start of operation. In addition, the activation overpotential at 100 mA cm–2 (0.17 V) obtained for MEA using Pt-nanocoated CeOx NW/C was approximately half of the value at 100 mA cm–2 (0.35 V) of MEA using a standard Pt/C cathode. In contrast, the fuel cell performance (0.775 V at 100 mW cm–2 after 80 h of operation) of MEA using a nanosized Pt-loaded CeOx NW (Pt/C = 0.2), which was prepared using the conventional chemical reduction method, was lower than that of MEA using a Pt-nanocoated CeOx/C cathode and showed reduction after 80 h of operation. It is considered why the nanocoated layer having Pt–O–Ce bonds heterogeneously formed on the surface of the CeOx NW and the bare CeO2 surface consisting of Ce4+ cations would become unstable in an acidic atmosphere. Furthermore, when a conventional low-amount Pt/C cathode (Pt/C = 0.04) was used as the cathode layer of the MEA, its stable performance could not be measured after 80 h of operation as a result of flooding caused by a lowering of electrocatalytic activity on the Pt/C cathode in the MEA. In contrast, a low-amount Pt-nanocoated CeOx NW (Pt/C = 0.04) could maintain a low activation overpotential (0.22 V at 100 mA cm–2) of MEA at the same operation time. Our surface first-principles modeling indicates that the high quality and stable performance observed for the Pt-nanocoated CeOx NW cathode of MEA can be attributed to the formation of a homogeneous electric double layer on the sample. Since the MEA performance can be improved by examining a more effective method of electron beam irradiation to all surfaces of the sample, the present work result shows the usefulness of the electron beam irradiation method in preparing active surfaces. In addition, the quantum beam technology such as the electron beam irradiation method was shown to be useful for increasing both performance and stability of fuel cells.

Generating 77 T using a portable pulse magnet for single-shot quantum beam experiments

We devised a portable system that generates pulsed high magnetic fields up to 77 T with 3 μs duration. The system employs the single turn coil method, a destructive way of field generation. The system consists of a capacitor of 10.4 μF, a 30 kV charger, a mono air-gap switch, a triggering system, and a magnet clamp, which weighs less than 1.0 tons in total and is transportable. The system offers opportunities for single-shot experiments at ultrahigh magnetic fields in combinations with novel quantum beams. The single-shot x-ray diffraction experiment using a x-ray free-electron laser at 65 T is presented. We comment on the possible update of the system for the generation of 100 T.

Research Activity on Quantum Beam at Toyota Central R&D Labs, and Visualization of Water Transport Distribution in a Fuel Cell Using Synchrotron Radiation X-rays

Research Activity on Quantum Beam at Toyota Central R&D Labs, and Visualization of Water Transport Distribution in a Fuel Cell Using Synchrotron Radiation X-rays

Acknowledgment to Reviewers of Quantum Beam Science in 2021

Rigorous peer-reviews are the basis of high-quality academic publishing [...]

A study on the structure of bovine casein micelles in milk using quantum beams

A study on the structure of bovine casein micelles in milk using quantum beams

Protein large-scale motions revealed by quantum beams: A new era in understanding protein dynamics.

Protein large-scale motions revealed by quantum beams: A new era in understanding protein dynamics.

The quantum beam splitter revisited without a vacuum state

In this article we explain in a new light two fundamental concepts ofquantum optics, the quantum beam splitter and the quantum interferometer, in termsof two state quantum wave functions. This method is consistent with the concept ofentanglement, and hence the algebra needed to describe them is reduced to additionsand products of the components of the quantum states. Furthermore, under thepremises of this method it is possible to study quantum states of greater complexity,like those arising from the addition and products of single photon states.

Modifications of Metallic and Inorganic Materials by Using Ion/Electron Beams

Welcome to the Special Issue of Quantum Beam Science entitled “Modifications of Metallic and Inorganic Materials by Using Ion/Electron Beams” [...]

Creation of intense quantum beam via interaction of ultra-intense laser light with porous structure materials

Creation of intense quantum beam via interaction of ultra-intense laser light with porous structure materials

Generation of Intense Short Electron Pulses Using High‐Intensity Lasers

The great potential of high‐intensity lasers to generate quantum beams for material analysis is highlighted by introducing some representative examples, including laser electron acceleration for ultrafast electron diffraction/deflectometry and laser terahertz surface wave generation. We have demonstrated that short electron pulses can be generated by intense femtosecond laser pulses. The pulse duration is as short as 100 fs, which is superior to that obtained using conventional accelerators. These short electron pulses are applicable to not only to the study of materials but also the observation of laser–matter interaction phenomena. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

(Invited) Synchrotron X-Ray and Pulsed Neutron Imaging of Water Transport Distribution in Fuel Cells

In order to realize a sustainable energy society, it is necessary to optimize energy and effectively utilize it by combining an electric grid and a hydrogen grid instead of the conventional fossil fuel-dependent type. Hydrogen has a high affinity with renewable energy and can be produced from various primary energies, so it is positioned as a promising energy in the future. We position fuel cell vehicles (FCVs) powered by hydrogen as the ultimate eco-friendly car, and are making vigorous efforts to develop high performance/reliability and low cost FCVs.Polymer electrolyte fuel cells (PEFCs) convert the chemical energy stored in hydrogen into electricity, with water as the only by-product. The inherent advantages of a PEFC include high electric energy efficiency and power density, low operating temperature and fast start-up, along with reduced environmental impact. PEFCs are regarded as a clean and efficient powertrain technology for automotive applications, serving as replacements for conventional internal combustion engines.PEFCs consist of an electrolyte membrane sandwiched between an anode and a cathode, and both the anode and cathode have laminated structures composed of a catalyst layer (CL) and gas channels in contact with a gas diffusion layer (GDL). When hydrogen and oxygen flow through the gas channels, an electrochemical reaction occurs in the CL, producing a by-product of water in addition to electrical power. The water generated by power generation then passes through the cathode GDL to the gas channel, and is finally discharged to the outside of the vehicle.The performance of fuel cells is greatly affected both by materials such as catalysts and electrolytes, and by how efficiently water generated by power generation is discharged, that is the essential role in water management function. To achieve a high-power density, it is really important to design sophisticated water management from water generation on the catalyst of FC to drainage outside the vehicle. Regarding the water management in PEFCs, it is necessary to manage it on a very wide scale from nanometer to millimeter. Based on the viewpoint that FC multiscale analysis linking materials, devices and vehicles is essential to achieve high performance by water management, we are currently constructing our original multiscale analysis combining quantum beam analysis using X-ray and neutron which enables liquid water visualization, as shown in Figure.In this presentation, I will exhibit two topics. First, I report improving water management in GDL through microporous layer (MPL) modifications [1]. Advanced 4D operando X-ray imaging (3D structure plus time) was employed to analyse the water content in GDLs, and demonstrated that the superior performance of cells with large MPL pores is due to the efficient formation of water pathways. The second is pulsed neutron imaging for differentiation of ice and liquid water distribution [2]. Energy-resolved neutron imaging is a methodology capable of distinguishing between liquid water and ice, and is effective for investigating ice formation in PEFCs operating in a subfreezing environment. We have enabled the observation of liquid water/ice distributions in a large field of view (300 mm × 300 mm) by manufacturing a sub-zero environment chamber that can be cooled down to -30 oC, as a step towards in situ visualition of full-size fuel cells.We hope that these studies will lead to the development of next generation FCVs. Figure 1

Scheme for sub-shot-noise transmission measurement using a time-multiplexed single-photon source

Sub-shot-noise performance in transmission measurements can be achieved in optical quantum metrology owing to significantly lower uncertainty in light intensity of quantum beams compared to their classical counterparts. In this work, we simulate the outcome of an experiment that uses a multiplexed single-photon source, considering several types of experimental losses, where we show that the sub-Poissonian statistics of the output is key for achieving sub-shot-noise performance. We compare the numerical results with the shot-noise limit attained using coherent sources and the quantum limit, obtained with an ideal photon-number Fock state. We also investigate conditions in which threshold detectors can be used, as well as the effect of input light fluctuations. Our results show that sub-shot-noise performance can be achieved with improvement factors ranging from 1.5 to 2, even without using number-resolving detectors.

A quantum search decoder for natural language processing

Probabilistic language models, e.g. those based on recurrent neural networks such as long short-term memory models (LSTMs), often face the problem of finding a high probability prediction from a sequence of random variables over a set of tokens. This is commonly addressed using a form of greedy decoding such as beam search, where a limited number of highest-likelihood paths (the beam width) of the decoder are kept, and at the end the maximum-likelihood path is chosen. In this work, we construct a quantum algorithm to find the globally optimal parse (i.e. for infinite beam width) with high constant success probability. When the input to the decoder follows a power law with exponent k > 0, our algorithm has runtime Rnf(R, k), where R is the alphabet size, n the input length; here f < 1/2, and frightarrow 0 exponentially fast with increasing k, hence making our algorithm always more than quadratically faster than its classical counterpart. We further modify our procedure to recover a finite beam width variant, which enables an even stronger empirical speedup while still retaining higher accuracy than possible classically. Finally, we apply this quantum beam search decoder to Mozilla’s implementation of Baidu’s DeepSpeech neural net, which we show to exhibit such a power law word rank frequency.

Frustration-driven magnetic fluctuations as the origin of the low-temperature skyrmion phase in Co7Zn7Mn6

In chiral cubic helimagnets, phases of magnetic skyrmions—topologically protected spin whirls—are stabilized by thermal fluctuations over a narrow region directly below the magnetic ordering temperature Tc. Due to often being touted for use in applications, there is a high demand to identify new ways to stabilize equilibrium skyrmion phases far below Tc where they may display an enhanced robustness against external perturbation due to a larger magnetic order parameter. Here, from quantum beam experiments on the chiral magnet Co7Zn7Mn6, we unveil a direct correlation between the stability of its second skyrmion phase-stable far from Tc, and a concomitant enhancement of an underlying magnetic fluctuation rate that is driven by geometric magnetic frustration. The influences of other leading skyrmion stability mechanisms, such as those derived from thermal fluctuations and low T cubic anisotropies, are shown to be weak in this system. We therefore advance the existence of a fundamental mechanism for stabilizing topological skyrmions in Co7Zn7Mn6 chiral magnet that draws upon magnetic frustration as the key ingredient.

Report on the 3rd Meeting of Quantum Beam Measurement Club

Report on the 3rd Meeting of Quantum Beam Measurement Club

Atom-Light Hybrid Quantum Gyroscope

A new type of atom-light hybrid quantum gyroscope (ALHQG) is proposed due to its high rotation sensitivity. It consists of an optical Sagnac loop to couple rotation rate and an atomic ensemble as quantum beam splitter/recombiner (QBS/C) based on atomic Raman amplification process to realize the splitting and recombination of the optical wave and the atomic spin wave. The rotation sensitivity can be enhanced by the quantum correlation between Sagnac loop and QBS/C. The optimal working condition is investigated to achieve the best sensitivity. The numerical results show that the rotation sensitivity can beat the standard quantum limit (SQL) in ideal condition. Even in the presence of the attenuation under practical condition, the best sensitivity of the ALHQG can still beat the SQL and is better than that of a fiber optic gyroscope (FOG). Such an ALHQG could be practically applied for modern inertial navigation system.

Matrix representations for classical and quantum beam splitters

Matrices provide a practical and elegant tool for describing the transformation properties of beam splitters and waveguide couplers acting on single-mode optical fields. Using a systematic approach, we show how the application of various physical constraints determines the form of the matrix for both classical fields and quantum number states. The goal is to provide a clear explanation of the conditions under which various matrix forms are appropriate to represent four-port couplers and beam splitters. Examples of calculations using the matrices are provided.

Synthesis, Battery Characteristics and Crystal and Electronic Structure of Cathode Material Spinel Mg(Co, Ni, Mn)2O4 for Mg Secondary Battery

1.IntroductionA magnesium secondary battery based on two-electron reaction is expected as a next-generation battery. In this study, we focused on Mg(Co, Ni, Mn)2O4 with spinel structure as a new cathode material. In the previous work, since the energy density of the Li-ion battery tended to increase when Ni is substituted for Co in their cathode materials, a Ni-substituted MgCo2O4 system[1] have been studied. It was also clarified that the discharge capacity increased by substituting Mn for Co in the MgCo2O4[2]. In this study, we adopted the advantages of Ni and Mn to the synthesized new cathode materials of MgCo2-x-yNixMnyO4 in which Co were replaced with Ni and Mn. The purpose of this study was to clarify the relationship between the battery characteristics and the crystal structure by using the three-electrode cell and quantum beam, synchrotron X-ray and neutron, analyses.2.ExperimentalAll samples were synthesized via the reverse coprecipitation method. The respective metal nitrates were mixed in the secondary distilled water at a predetermined ratio, further made up to 200 mL and added dropwise to the aqueous sodium carbonate solution at 70 °C, the precipitate was dried, pulverized with a ball mill and then calcined at 400°C. The phase of the obtained sample was identified by powder X-ray diffraction and ICP-AES. The charge/discharge test for synthesized sample was performed using a three-electrode cell (Toyo System Co., Ltd.) (90 ℃, Reference electrode: Ag, Negative electrode: AZ31, Electrolyte: 0.3 M [Mg(G4)][TFSA]2/P13TFSA, Separator: glass fiber filter). Crystal structures of the samples were analyzed by Rietveld method for the results obtained by synchrotron X-ray diffraction (BL19B2, SPring-8) and neutron diffraction (BL20, J-PARC). Furthermore, the valence of the transition metals was estimated by XAFS measurement (BL14B2, SPring-8).3.Results and DiscussionSamples were synthesized in the different metal ratios of Co, Ni and Mn in MgCo2-x-yNixMnyO4. As a result of powder X-ray diffraction, all samples were assigned to a spinel structure (Fd-3m). From the ICP-AES, although most of the composition ratios could be controlled, the Mg content in all samples tended to be slightly less than 1.0. The lattice constant increased with increasing Ni and Mn substitution. This is considered to be due to the divalent Ni on the hexacoordinated site with a larger ionic radius than those of Co and Mn. From the results of charge and discharge tests, it was found that the Ni-substituted sample showed an increase in the discharge potential, and the both Ni- and Mn-substituted samples showed an increase in the discharge capacity. As a result of Rietveld analysis of the Ni substituted samples, it was found that the substituted Ni also occupied at 8a site of the Mg diffusion path. Therefore, it is considered that the Mg diffusion was hindered and the discharge capacity became lower than that of the non-substituted product [1]. The electrochemical tests using [Mg(G4)][TFSA]2/P13TFSA electrolyte with high oxidation resistance showed the increased charge / discharge capacities after 2 cycles. The Rietveld analysis using neutron diffraction patterns clarified cation mixing and refined the mixing amounts of Co, Ni, and Mn into the 8a site. The overall tendency was that Ni was substituted at the 16d site and Mn was substituted at the 8a site. The valences of each transition metals estimated in the charge / discharge process by XAFS, all the transition metals contributed to the charge / discharge because the valences of Co, Ni, and Mn increased or decreased after the initial charge or discharge. The main feature was that Mn showed a large valence change from 4+ to 3+ [2], and it was found that it greatly contributes to the Mg insertion. Although viewpoint of deterioration needed further improvement, it was concluded that MgCo0.8Ni0.4Mn0.8O4 and MgCo0.5Ni0.5MnO4 showed the discharge capacity of 200mAh/g and were the optimum composition in this samples.This work was supported by JST ALCA-SPRING Grant Number JPMJAC1301, Japan.References1) Okamoto, T. Ichitsubo, T. Kawaguchi, Y. Kumagai, F. Oba and S. Yagi, K. Shimokawa, N. Goto, T. Doi, E. Matsubara, Adv. Sci., 2, 1500072 (2015).2) Y. Idemoto, Y. Mizutani, C. Ishibashi, N. Ishida, N. Kitamura, Electrochemistry, 87, 220 (2019). Figure 1

Quantum Beams Applying to Innovative Industrial Materials

Welcome to this Special Issue of Quantum Beam Science entitled “Quantum Beams Applying to Innovative Industrial Materials” [...]

Determining the crystal and electronic structures of the magnesium secondary battery cathode material MgCo2−xMnxO4 using first-principles calculations and a quantum beam during discharge

The stable structures of the spinel compounds MgCo2O4 and MgCo1.5Mn0.5O4 following the insertion of Mg atoms into vacant 16c sites during discharge were investigated using first-principles calculations. During this insertion, Mg atoms at 8a sites were found to migrate to other vacant 16c sites, such that the spinel form transitioned to a rock salt structure. The structural change from the standard spinel phase to a rock salt form was minimal in the case of MgCo2O4, since this change required the insertion of numerous Mg atoms. In contrast, a more pronounced structural change from the normal spinel to a rock salt form occurred in the MgCo1.5Mn0.5O4, as this change required fewer Mg atom insertions. The data suggest that the electron density and bond length between Mg atoms at 8a sites and O atoms in MgCo1.5Mn0.5O4 are both reduced compared to that in MgCo2O4. The Mg atoms in MgCo1.5Mn0.5O4 were determined to readily undergo intercalation as a result of the substitution of Mn atoms.