Showing 1–50 of 100 results for author: Satoh, T

RuleSet Generation Framework for Application Layer Integration in Quantum Internet

Authors: Rei Kawano, Shin Nishio, Hideaki Kawaguchi, Shota Nagayama, Takahiko Satoh

Abstract: Layered architectures for the Quantum Internet have been proposed, inspired by that of the classical Internet, which has demonstrated high maintainability even in large-scale systems. While lower layers in the Quantum Internet, such as entanglement generation and distribution, have been extensively studied, the application layer - responsible for translating user requests into executable quantum-n… ▽ More Layered architectures for the Quantum Internet have been proposed, inspired by that of the classical Internet, which has demonstrated high maintainability even in large-scale systems. While lower layers in the Quantum Internet, such as entanglement generation and distribution, have been extensively studied, the application layer - responsible for translating user requests into executable quantum-network operations - remains largely unexplored. A significant challenge is translating application-level requests into the concrete instructions executable at lower layers. In this work, we introduce a RuleSet-based framework that explicitly incorporates the application layer into the layered architecture of the Quantum Internet. Our framework builds on a RuleSet-based protocol, clarifying communication procedures, organizing application request information, and introducing new Rules for application execution by embedding application specifications into RuleSets. To evaluate feasibility, we constructed state machines from the generated RuleSets. This approach enables a transparent integration from the application layer down to the physical layer, thereby lowering barriers to deploying new applications on the Quantum Internet. △ Less

Submitted 8 December, 2025; originally announced December 2025.

Comments: 11 pages, 16 figures

Four-body interactions in Kerr parametric oscillator circuits

Authors: Yohei Kawakami, Tomohiro Yamaji, Aiko Yamaguchi, Yuya Kano, Takaaki Aoki, Aree Taguchi, Kiyotaka Endo, Tetsuro Satoh, Ayuka Morioka, Yuichi Igarashi, Masayuki Shirane, Tsuyoshi Yamamoto

Abstract: We theoretically present new unit circuits of Kerr parametric oscillators (KPOs) with four-body interactions, which enable the scalable embedding of all-to-all connected logical Ising spins using the Lechner-Hauke-Zoller (LHZ) scheme. These unit circuits enable four-body interactions using linear couplers, making the circuit fabrication and characterization much simpler than those of conventional… ▽ More We theoretically present new unit circuits of Kerr parametric oscillators (KPOs) with four-body interactions, which enable the scalable embedding of all-to-all connected logical Ising spins using the Lechner-Hauke-Zoller (LHZ) scheme. These unit circuits enable four-body interactions using linear couplers, making the circuit fabrication and characterization much simpler than those of conventional unit circuits with nonlinear couplers. Numerical calculations indicate that the magnitudes of the coupling constants can be comparable to those in conventional circuits. On the basis of this theory, we designed a four-KPO circuit and experimentally confirmed the four-body correlation by measuring the pump-phase dependence of the parity of the four-KPO states. We show that the choice of the pump frequencies are important not only to enable the four-body interaction, but to cancel the effects of other unwanted interactions. Using the circuit, we demonstrated the quantum annealing based on the LHZ scheme, where the strength of the interaction between the logical Ising spins is mapped to the local field and controlled by a coherent drive applied to each KPO. △ Less

Submitted 29 November, 2025; originally announced December 2025.

On the abelianization of the special derivation Lie algebras of free Lie algebras

Authors: Naoya Enomoto, Takao Satoh

Abstract: In this paper, we show that there are infinitely many linearly independent elements in the abelianization of the Lie algebra of special derivations of a free Lie algebra by using the Morita traces. Furthermore, we show that the abelianization contains non-trivial elements which are killed by the Morita traces. In this paper, we show that there are infinitely many linearly independent elements in the abelianization of the Lie algebra of special derivations of a free Lie algebra by using the Morita traces. Furthermore, we show that the abelianization contains non-trivial elements which are killed by the Morita traces. △ Less

Submitted 20 November, 2025; originally announced November 2025.

Comments: 29 pages

MSC Class: 20F36; 20F40; 17B40; 17B01; 17B56

Symbiotic causal network of seagrass-bacteria-algae-diatoms interactions

Authors: Hirokuni Miyamoto, Kenta Suzuki, Shigeharu Moriya, Makiko Matsuura, Naoko Tsuji, Teruno Nakaguma, Chitose Ishii, Takayuki Nagatsuka, Takashi Satoh, Wataru Suda, Tamotsu Kato, Chie Shindo, Atsushi Kurotani, Hiroaki Kodama, Hiroshi Masuya, Satoshi Wada, Nobuhiro Kawachi, Hisashi Miyamoto, Yukinari Tsuruda, Yohei Shimasaki, Shouzo Ogizo, Nobuo Suzuki, Tomoharu Yuge, Toshio Takahashi, Tomohito Ojima , et al. (9 additional authors not shown)

Abstract: Seagrass meadows contribute to the conservation of marine ecosystems, reduction in global warming impacts and pathogen controls. However, the decline in seagrass habitats due to environmental loads has become an urgent global issue. One way to address this issue is to better understand healthy seagrass habitats. Here, we estimate the structural characteristics of symbiotic and metabolic systems in… ▽ More Seagrass meadows contribute to the conservation of marine ecosystems, reduction in global warming impacts and pathogen controls. However, the decline in seagrass habitats due to environmental loads has become an urgent global issue. One way to address this issue is to better understand healthy seagrass habitats. Here, we estimate the structural characteristics of symbiotic and metabolic systems in sediments from eight coastal regions of Japan, with each region containing both seagrass-covered areas and adjacent unvegetated areas. Notably, seagrasses commonly maintain a balanced symbiotic relationship characterized by a positive association with cable bacteria (Desulfobulbaceae), nitrogen-cycling bacteria (Hyphomonadaceae), and coral algae (Corallinophycidae) and a negative association with diatoms (Diatomea). Furthermore, seagrass growth conditions influence metabolic pathways by activating nitrogen-related metabolism while attenuating methanogenesis. Our findings highlight the crucial roles of marine plants and their symbiotic systems in ensuring environmental conservation within the context of blue carbon storage across environmental gradients. △ Less

Submitted 24 November, 2025; v1 submitted 17 November, 2025; originally announced November 2025.

Comments: 11 pages, 6 main figures, and supplementary information (21 figures and 7 tables)

Dense packing of the surface code: code deformation procedures and hook-error-avoiding gate scheduling

Authors: Kohei Fujiu, Shota Nagayama, Shin Nishio, Hideaki Kawaguchi, Takahiko Satoh

Abstract: The surface code is one of the leading quantum error correction codes for realizing large-scale fault-tolerant quantum computing (FTQC). One major challenge in realizing surface-code-based FTQC is the extremely large number of qubits required. To mitigate this problem, fusing multiple codewords of the surface code into a densely packed configuration has been proposed. It is known that by using den… ▽ More The surface code is one of the leading quantum error correction codes for realizing large-scale fault-tolerant quantum computing (FTQC). One major challenge in realizing surface-code-based FTQC is the extremely large number of qubits required. To mitigate this problem, fusing multiple codewords of the surface code into a densely packed configuration has been proposed. It is known that by using dense packing, the number of physical qubits required per logical qubit can be reduced to approximately three-fourths compared to simply placing surface-code patches side by side. Despite its potential, concrete deformation procedures and quantitative error-rate analyses have remained largely unexplored. In this work, we present a detailed code-deformation procedure that transforms multiple standard surface code patches into a densely packed, connected configuration, along with a conceptual microarchitecture to utilize this dense packing. We also propose a CNOT gate-scheduling for stabilizer measurement circuits that suppresses hook errors in the densely packed surface code. We performed circuit-level Monte Carlo noise simulation of densely packed surface codes using this gate scheduling. The numerical results demonstrate that as the code distance of the densely packed surface code increases and the physical error rate decreases, the logical error rate of the densely packed surface code becomes lower than that of the standard surface code. Furthermore, we find that only when employing hook-error-avoiding syndrome extraction can the densely packed surface code achieve a lower logical error rate than the standard surface code, while simultaneously reducing the space overhead. △ Less

Submitted 10 November, 2025; originally announced November 2025.

Comments: 17 pages, 18 figures

Quantum annealing in capacitively coupled Kerr parametric oscillators using frequency-chirped drives

Authors: T. Yamaji, S. Masuda, Y. Kano, Y. Kawakami, A. Yamaguchi, T. Satoh, A. Morioka, Y. Igarashi, M. Shirane, T. Yamamoto

Abstract: We study parametric oscillations of two capacitively coupled Kerr parametric oscillators (KPOs) with frequency-chirped two- and one-photon drives. The two-KPO system adiabatically evolves from the initial vacuum state to an oscillation state corresponding to a solution state in quantum-annealing applications. Frequency chirping dynamically changes the detuning between resonance and oscillation fre… ▽ More We study parametric oscillations of two capacitively coupled Kerr parametric oscillators (KPOs) with frequency-chirped two- and one-photon drives. The two-KPO system adiabatically evolves from the initial vacuum state to an oscillation state corresponding to a solution state in quantum-annealing applications. Frequency chirping dynamically changes the detuning between resonance and oscillation frequencies during parametric modulation and reduces unwanted population transfer to excited states caused by pure dephasing and photon loss. We observe that frequency chirping increases the success probability to obtain the solution state and that simulations taking into account pure dephasing reproduce experiments with and without frequency chirping. This study demonstrates the effectiveness and applicability of frequency chirping to a KPO-based quantum annealer. △ Less

Submitted 28 November, 2025; v1 submitted 30 June, 2025; originally announced June 2025.

Comments: 11 pages, 11 figures

Journal ref: Phys. Rev. Applied 24, 064052 (2025)

Symmetry analysis of cross-circular and parallel-circular Raman optical activity

Authors: Hikaru Watanabe, Rikuto Oiwa, Gakuto Kusuno, Takuya Satoh, Ryotaro Arita

Abstract: The Raman scattering regarding the circularly-polarized incident and scattered lights is closely related to the circular activity of a given system. We investigate the symmetry of its activity, called the cross-circular and parallel-circular Raman optical activity. The analysis is systematically performed with the magnetic point groups and indicates that the response allows for a useful diagnosis… ▽ More The Raman scattering regarding the circularly-polarized incident and scattered lights is closely related to the circular activity of a given system. We investigate the symmetry of its activity, called the cross-circular and parallel-circular Raman optical activity. The analysis is systematically performed with the magnetic point groups and indicates that the response allows for a useful diagnosis of the symmetry of materials like chirality and (magneto-)axiality. It is also shown that the Stokes and anti-Stokes processes are related to each other by the conserved antiunitary symmetry for the time-reversal operation and that combined with the mirror reflection. △ Less

Submitted 2 September, 2025; v1 submitted 26 June, 2025; originally announced June 2025.

Comments: 13 pages, 2 figures, 3 tables

Improved sampling bounds and scalable partitioning for quantum circuit cutting beyond bipartitions

Authors: Junya Nakamura, Takahiko Satoh, Shinichiro Sanji

Abstract: We propose a new method for identifying cutting locations for quantum circuit cutting, with a primary focus on partitioning circuits into three or more parts. Under the assumption that the classical postprocessing function is decomposable, we derive a new upper bound on the sampling overhead resulting from both time-like and space-like cuts. We show that this bound improves upon the previously kno… ▽ More We propose a new method for identifying cutting locations for quantum circuit cutting, with a primary focus on partitioning circuits into three or more parts. Under the assumption that the classical postprocessing function is decomposable, we derive a new upper bound on the sampling overhead resulting from both time-like and space-like cuts. We show that this bound improves upon the previously known bound by orders of magnitude in cases of three or more partitions. Based on this bound, we formulate an objective function, $L_Q^{}$, and present a method to determine cutting locations that minimize it. Our method is shown to outperform a previous approach in terms of computation time. Moreover, the quality of the obtained partitioning is found to be comparable to or better than that of the baseline in all but a few cases, as measured by $L_Q^{}$. These results are obtained by identifying cutting locations in a number of benchmark circuits of the size and type expected in quantum computations that outperform classical computers. △ Less

Submitted 1 July, 2025; v1 submitted 22 June, 2025; originally announced June 2025.

Comments: 24 pages, 5 figures; v2: reference added

Raman Optical Activity Induced by Ferroaxial Order in $\textrm{NiTiO}_3$

Authors: Gakuto Kusuno, Takeshi Hayashida, Takayuki Nagai, Hikaru Watanabe, Rikuto Oiwa, Tsuyoshi Kimura, Takuya Satoh

Abstract: Raman optical activity (ROA) -- the dependence of Raman scattered light intensity on the circular polarization of incident and scattered light -- has traditionally been associated with chiral molecules and magnetic materials. In this study, we demonstrate that ROA can also arise in ferroaxial materials that possess spatial inversion and time-reversal symmetries. Using circularly polarized Raman sp… ▽ More Raman optical activity (ROA) -- the dependence of Raman scattered light intensity on the circular polarization of incident and scattered light -- has traditionally been associated with chiral molecules and magnetic materials. In this study, we demonstrate that ROA can also arise in ferroaxial materials that possess spatial inversion and time-reversal symmetries. Using circularly polarized Raman spectroscopy on single-crystalline $\textrm{NiTiO}_3$, we observed a pronounced ROA signal in the cross-circular polarization configuration, which correlates with the ferroaxial domain structure. Our symmetry analysis and tight-binding model calculations reveal that the natural ROA (NROA) originates from the ferroaxial order and persists even within the electric dipole approximation. These results establish ROA as a powerful probe of ferroaxial order in centrosymmetric systems. △ Less

Submitted 28 May, 2025; originally announced May 2025.

Comments: 16 pages and 4 figures

Enhancing the Dynamic Range of Quantum Sensing via Quantum Circuit Learning

Authors: Hideaki Kawaguchi, Yuichiro Mori, Takahiko Satoh, Yuichiro Matsuzaki

Abstract: Quantum metrology is a promising application of quantum technologies, enabling the precise measurement of weak external fields at a local scale. In typical quantum sensing protocols, a qubit interacts with an external field, and the amplitude of the field is estimated by analyzing the expectation value of a measured observable. Sensitivity can, in principle, be enhanced by increasing the number of… ▽ More Quantum metrology is a promising application of quantum technologies, enabling the precise measurement of weak external fields at a local scale. In typical quantum sensing protocols, a qubit interacts with an external field, and the amplitude of the field is estimated by analyzing the expectation value of a measured observable. Sensitivity can, in principle, be enhanced by increasing the number of qubits within a fixed volume, thereby maintaining spatial resolution. However, at high qubit densities, inter-qubit interactions induce complex many-body dynamics, resulting in multiple oscillations in the expectation value of the observable even for small field amplitudes. This ambiguity reduces the dynamic range of the sensing protocol. We propose a method to overcome the limitation in quantum metrology by adopting a quantum circuit learning framework using a parameterized quantum circuit to approximate a target function by optimizing the circuit parameters. In our method, after the qubits interact with the external field, we apply a sequence of parameterized quantum gates and measure a suitable observable. By optimizing the gate parameters, the expectation value is trained to exhibit a monotonic response within a target range of field amplitudes, thereby eliminating multiple oscillations and enhancing the dynamic range. This method offers a strategy for improving quantum sensing performance in dense qubit systems. △ Less

Submitted 8 May, 2025; originally announced May 2025.

Polarization-dependent photocurrent in a quadrilateral-shaped bulk crystalline tellurium chip with near-infrared light excitation

Authors: Hiro Munekata, Gakuto Kusuno, Kohei Miyazaki, Takuya Satoh

Abstract: We report the detection of zero-bias photocurrents induced by interband excitation using oblique near-infrared light (λ=0.780 μm) along the directions parallel and perpendicular to the helical axis in a millimeter-sized Te crystal. The photocurrent parallel to the helical axis exhibits a circular-polarization-dependent component, namely circular photogalvanic effect. We create a framework for esti… ▽ More We report the detection of zero-bias photocurrents induced by interband excitation using oblique near-infrared light (λ=0.780 μm) along the directions parallel and perpendicular to the helical axis in a millimeter-sized Te crystal. The photocurrent parallel to the helical axis exhibits a circular-polarization-dependent component, namely circular photogalvanic effect. We create a framework for estimating the gyrotropic photoconductivity tensor \b{eta}, the ratio between the circular-polarization-dependent photocurrent density and intensity of light, through which extrinsic \b{eta} values ranging from a few to a few tens of nA/W are obtained. Searching the \b{eta} values through existing literatures reveals that these values vary significantly with sample conditions, excitation wavelengths, and forms of crystallite samples. A particular interesting point found in our study is that the \b{eta} values for the interband excitation may be greater than those for intraband excitation as far as bulk Te is concerned. △ Less

Submitted 23 November, 2025; v1 submitted 1 April, 2025; originally announced April 2025.

Comments: 40 pages, 15 figures, 1 table, 55 references

Anti-pathogenic property of thermophile-fermented compost as a feed additive and its in vivo external diagnostic imaging in a fish model

Authors: Hirokuni Miyamoto, Shunsuke Ito, Kenta Suzuki, Singo Tamachi, Shion Yamada, Takayuki Nagatsuka, Takashi Satoh, Motoaki Udagawa, Hisashi Miyamoto, Hiroshi Ohno, Jun Kikuchi

Abstract: Fermentative recycling of organic matter is important for a sustainable society, but the functionality of fermented products needs to be adequately evaluated. Here, we clarify the antipathogenic properties for fish of a compost-type feed additive fermented by thermophilic Bacillaceae using non-edible marine resources as raw materials. After prior administration of the compost extract to seabream a… ▽ More Fermentative recycling of organic matter is important for a sustainable society, but the functionality of fermented products needs to be adequately evaluated. Here, we clarify the antipathogenic properties for fish of a compost-type feed additive fermented by thermophilic Bacillaceae using non-edible marine resources as raw materials. After prior administration of the compost extract to seabream as a fish model for 70 days, the mortality rate after 28 days of exposure to the fish pathogen Edwardsiella reached a maximum of 20%, although the rate was 60% without prior administration. Under such conditions, the serum complement activity of seabream increased, and the recovery time after anesthesia treatment was also fasten. Furthermore, the differences in the degree of smoothness and glossiness of the fish body surface depending on the administration were statistically shown by imaging techniques to evaluate the texture and color tone of field photographs. These results suggest that thermophile-fermented compost is effective as a functional feed additive against fish disease infection, and that such conditions can be estimated by body surface analysis. This study provides a new perspective for the natural symbiosis industry, as well as for the utilization of non-invasive diagnosis to efficiently estimate the quality of its production activities △ Less

Submitted 17 November, 2025; v1 submitted 28 March, 2025; originally announced March 2025.

Comments: 7 main figures and supplementary information

Quantitative Evaluation of Quantum/Classical Neural Network Using a Game Solver Metric

Authors: Suzukaze Kamei, Hideaki Kawaguchi, Shin Nishio, Takahiko Satoh

Abstract: To evaluate the performance of quantum computing systems relative to classical counterparts and explore the potential, we propose a game-solving benchmark based on Elo ratings in the game of tic-tac-toe. We compare classical convolutional neural networks (CCNNs), quantum or quantum convolutional neural networks (QNNs, QCNNs), and hybrid classical-quantum neural networks (Hybrid NNs) by assessing t… ▽ More To evaluate the performance of quantum computing systems relative to classical counterparts and explore the potential, we propose a game-solving benchmark based on Elo ratings in the game of tic-tac-toe. We compare classical convolutional neural networks (CCNNs), quantum or quantum convolutional neural networks (QNNs, QCNNs), and hybrid classical-quantum neural networks (Hybrid NNs) by assessing their performance based on round-robin matches. Our results show that the Hybrid NNs engines achieve Elo ratings comparable to those of CCNNs engines, while the quantum engines underperform under current hardware constraints. Additionally, we implement a QNN integrated with quantum communication and evaluate its performance to quantify the overhead introduced by noisy quantum channels, and the communication overhead was found to be modest. These results demonstrate the viability of using game-based benchmarks for evaluating quantum computing systems and suggest that quantum communication can be incorporated with limited impact on performance, providing a foundation for future hybrid quantum applications. △ Less

Submitted 10 November, 2025; v1 submitted 27 March, 2025; originally announced March 2025.

Comments: 12 pages, 15 figures

SU(4) gate design via unitary process tomography: its application to cross-resonance based superconducting quantum devices

Authors: Michihiko Sugawara, Takahiko Satoh

Abstract: We present a novel approach for implementing pulse-efficient SU(4) gates on cross resonance (CR)-based superconducting quantum devices. Our method introduces a parameterized unitary derived from the CR-Hamiltonian propagator, which accounts for static-$ZZ$ interactions. Leveraging the Weyl chamber's geometric structure, we successfully realize a continuous 2-qubit basis gate, $R_{ZZ}(θ)$, as an ec… ▽ More We present a novel approach for implementing pulse-efficient SU(4) gates on cross resonance (CR)-based superconducting quantum devices. Our method introduces a parameterized unitary derived from the CR-Hamiltonian propagator, which accounts for static-$ZZ$ interactions. Leveraging the Weyl chamber's geometric structure, we successfully realize a continuous 2-qubit basis gate, $R_{ZZ}(θ)$, as an echo-free pulse schedule on the IBM Quantum device ibm_kawasaki. We evaluate the average fidelity and gate time of various SU(4) gates generated using the $R_{ZZ}(θ)$ to confirm the advantages of our implementation. △ Less

Submitted 12 March, 2025; originally announced March 2025.

Comments: 12 pages, 10 figures

The Andreadakis Problem for the McCool groups

Authors: Jaques Darné, Naoya Enomoto, Takao Satoh

Abstract: In this short paper, we show that the McCool group does not satisfy the Andreadakis equality from degree $7$, and we give a lower bound for the size of the difference between the two relevant filtrations. As a consequence, we see that the Andreadakis problem for the McCool group does not stabilize. In this short paper, we show that the McCool group does not satisfy the Andreadakis equality from degree $7$, and we give a lower bound for the size of the difference between the two relevant filtrations. As a consequence, we see that the Andreadakis problem for the McCool group does not stabilize. △ Less

Submitted 6 March, 2025; v1 submitted 27 February, 2025; originally announced February 2025.

Comments: 11 pages

Anomalous Nernst effect in Co thin films under laser irradiation

Authors: Soichiro Mochizuki, Itaru Sugiura, Tetsuya Narushima, Teruo Ono, Takuya Satoh, Kihiro T. Yamada

Abstract: The anomalous Nernst effect (ANE) generates electromotive forces transverse to temperature gradients and has attracted much attention for potential applications into alternative thermoelectric power generators. ANE efficiency is generally characterized by uniform temperature gradients in a steady state prepared by heaters. However, although focusing laser beams on a magnetic film can form much lar… ▽ More The anomalous Nernst effect (ANE) generates electromotive forces transverse to temperature gradients and has attracted much attention for potential applications into alternative thermoelectric power generators. ANE efficiency is generally characterized by uniform temperature gradients in a steady state prepared by heaters. However, although focusing laser beams on a magnetic film can form much larger temperature gradients, the laser-irradiation method has not been sufficiently considered for quantifying the ANE coefficient due to the difficulty in estimating the localized in-homogeneous temperature gradients. In this study, we present a quantitative study of ANE in Ru(5 nm)/Co($t_{\mathrm{Co}}$) ($t_{\mathrm{Co}}$ = 3, 5, 7, 10, 20, 40, and 60 nm) bilayers on sapphire (0001) substrates by combining a laser irradiation approach with finite-element analysis of temperature gradients under laser excitation. We find that the estimated ANE coefficients are consistent with previously reported values and one independently characterized using a heater. Our results also reveal the advantages of the laser irradiation method over the conventional method using heaters. Intensity-modulated laser beams can create ac temperature gradients as large as approximately 10$^3$ K/mm at a frequency of tens of kilohertz in a micrometer-scale region. △ Less

Submitted 2 November, 2025; v1 submitted 28 January, 2025; originally announced January 2025.

Comments: 30 pages, 13 figures. 1 table

Journal ref: Phys. Rev. Applied 24, 044101 (2015)

Resonance fluorescence spectra of a driven Kerr nonlinear resonator

Authors: Aree Taguchi, Katsuta Sakai, Aiko Yamaguchi, Yuya Kano, Yohei Kawakami, Tomohiro Yamaji, Tetsuro Satoh, Ayuka Morioka, Kiyotaka Endou, Yuichi Igarashi, Masayuki Shirane, Yasunobu Nakamura, Kazuki Koshino, Tsuyoshi Yamamoto

Abstract: Resonance fluorescence spectra of a driven Kerr nonlinear resonator is investigated both theoretically and experimentally. When the Kerr nonlinear resonator is driven strongly such that the induced Rabi frequency is comparable to or larger than the Kerr nonlinearity, the system cannot be approximated as a two-level system. We theoretically derive characteristic features in the fluorescence spectra… ▽ More Resonance fluorescence spectra of a driven Kerr nonlinear resonator is investigated both theoretically and experimentally. When the Kerr nonlinear resonator is driven strongly such that the induced Rabi frequency is comparable to or larger than the Kerr nonlinearity, the system cannot be approximated as a two-level system. We theoretically derive characteristic features in the fluorescence spectra such as the decrease of the center-peak intensity and the asymmetric sideband peaks in the presence of finite dephasing. Those features are consistently explained by the population of the initial dressed state and its transition matrix element to the final dressed state of the transition corresponding to each peak. Finally, we experimentally measure the resonance fluorescence spectra of a driven superconducting Kerr nonlinear resonator and find a quantitative agreement with our theory. △ Less

Submitted 7 January, 2025; v1 submitted 6 January, 2025; originally announced January 2025.

Comments: 18 pages, 10 figures

Magnetic resonance frequency of two-sublattice ferrimagnet with magnetic compensation temperature

Authors: Kouki Mikuni, Toshiki Hiraoka, Takumi Kuramoto, Yasuhiro Fujii, Akitoshi Koreeda, Sergii Parchenko, Andrzej Stupakiewicz, Takuya Satoh

Abstract: Ferrimagnetic materials with a compensation temperature have recently attracted interest because of their unique combination of ferromagnetic and antiferromagnetic properties. However, their magnetization dynamics near the compensation temperature are complex and cannot be fully explained by conventional ferromagnetic resonance (FMR) or exchange resonance modes. Therefore, practical models are nec… ▽ More Ferrimagnetic materials with a compensation temperature have recently attracted interest because of their unique combination of ferromagnetic and antiferromagnetic properties. However, their magnetization dynamics near the compensation temperature are complex and cannot be fully explained by conventional ferromagnetic resonance (FMR) or exchange resonance modes. Therefore, practical models are necessary to capture these dynamics accurately. In this study, we derived the analytical solutions for the magnetic resonance frequencies of compensated ferrimagnets over all temperature ranges, considering both the in-plane and out-of-plane orientations of the magnetization. Our solutions successfully reproduce the experimental data obtained from time-resolved magneto-optical Faraday rotation and Brillouin light scattering measurements for the in-plane and out-of-plane cases, respectively. This reproduction is achieved by incorporating the exchange stiffness and temperature dependence of the magnetic anisotropy into the free energy density. Additionally, at temperatures sufficiently far from the compensation temperature, our analytical solutions converge with the conventional FMR and exchange resonance models. △ Less

Submitted 22 November, 2024; originally announced November 2024.

Journal ref: J. Phys. Soc. Jpn. 94, 111001 (2025)

Evidence of relativistic field-derivative torque in nonlinear THz response of magnetization dynamics

Authors: Arpita Dutta, Christian Tzschaschel, Debankit Priyadarshi, Kouki Mikuni, Takuya Satoh, Ritwik Mondal, Shovon Pal

Abstract: Understanding the complete light-spin interactions in magnetic systems is the key to manipulating the magnetization using optical means at ultrafast timescales. The selective addressing of spins by terahertz (THz) electromagnetic fields via Zeeman torque is one of the most successful ultrafast means of controlling magnetic excitations. Here we show that this traditional Zeeman torque on the spins… ▽ More Understanding the complete light-spin interactions in magnetic systems is the key to manipulating the magnetization using optical means at ultrafast timescales. The selective addressing of spins by terahertz (THz) electromagnetic fields via Zeeman torque is one of the most successful ultrafast means of controlling magnetic excitations. Here we show that this traditional Zeeman torque on the spins is not sufficient, rather an additional relativistic field-derivative torque is essential to realize the observed magnetization dynamics. We accomplish this by exploring the ultrafast nonlinear magnetization dynamics of rare-earth, Bi-doped iron garnet when excited by two co-propagating THz pulses. First, by exciting the sample with an intense THz pulse and probing the magnetization dynamics using magneto-optical Faraday effect, we find the collective exchange resonance mode between rare-earth and transition metal sublattices at 0.48 THz. We further explore the magnetization dynamics via the THz time-domain spectroscopic means. We find that the observed nonlinear trace of the magnetic response cannot be mapped to the magnetization precession induced by the Zeeman torque, while the Zeeman torque supplemented by an additional field-derivative torque follows the experimental evidences. This breakthrough enhances our comprehension of ultra-relativistic effects and paves the way towards novel technologies harnessing light-induced control over magnetic systems. △ Less

Submitted 30 December, 2024; v1 submitted 10 August, 2024; originally announced August 2024.

Comments: 5 figures

On the structures of the Johnson cokernels of the basis-conjugating automorphism groups of free groups

Authors: Naoya Enomoto, Takao Satoh

Abstract: In this paper, we study the Johnson homomorphisms of basis-conjugating automorphism groups of free groups. We construct obstructions for the surjectivity of the Johnson homomorphisms. By using it, we determine its cokernels of degree up to four, and give further observations for degree greater than four. As applications, we give the affirmative answer for the Andreadakis problem for degree four.… ▽ More In this paper, we study the Johnson homomorphisms of basis-conjugating automorphism groups of free groups. We construct obstructions for the surjectivity of the Johnson homomorphisms. By using it, we determine its cokernels of degree up to four, and give further observations for degree greater than four. As applications, we give the affirmative answer for the Andreadakis problem for degree four. We show that the cup product map of the first cohomology groups of the basis-conjugating automorphism group of a free group into the second cohomology group is surjective. Finally, we calculate the twisted first cohomology groups of the braid-permutation automorphism groups of a free group. △ Less

Submitted 18 August, 2024; v1 submitted 7 March, 2024; originally announced March 2024.

MSC Class: 20F28; 20F14; 20J06

Sublattice-selective inverse Faraday effect in ferrimagnetic rare-earth iron garnet

Authors: Toshiki Hiraoka, Ryo Kainuma, Keita Matsumoto, Kihiro T. Yamada, Takuya Satoh

Abstract: We performed time-resolved pump--probe measurements using rare-earth iron garnet \ce{Gd3/2Yb1/2BiFe5O12} as a two-sublattice ferrimagnet. We measured the initial phases of the magnetic resonance modes below and above the magnetization compensation temperature to clarify the sublattice selectivity of the inverse Faraday effect in ferrimagnets. A comparison of the time evolution of magnetization est… ▽ More We performed time-resolved pump--probe measurements using rare-earth iron garnet \ce{Gd3/2Yb1/2BiFe5O12} as a two-sublattice ferrimagnet. We measured the initial phases of the magnetic resonance modes below and above the magnetization compensation temperature to clarify the sublattice selectivity of the inverse Faraday effect in ferrimagnets. A comparison of the time evolution of magnetization estimated using the equations of motion revealed that the inverse Faraday effect occurring in ferrimagnetic materials has sublattice selectivity. This is in striking contrast to antiferromagnets, in which the inverse Faraday effect acts on each sublattice identically. The initial phase analysis can be applied to other ferrimagnets with compensation temperatures. △ Less

Submitted 27 December, 2023; originally announced December 2023.

Comments: 4 pages, 5 figures

Journal ref: J. Phys. Soc. Jpn. 93, 023702 (2024)

Spectroscopy of flux-driven Kerr parametric oscillators by reflection coefficient measurement

Authors: Aiko Yamaguchi, Shumpei Masuda, Yuichiro Matsuzaki, Tomohiro Yamaji, Tetsuro Satoh, Ayuka Morioka, Yohei Kawakami, Yuichi Igarashi, Masayuki Shirane, Tsuyoshi Yamamoto

Abstract: We report the spectroscopic characterization of a Kerr parametric oscillator (KPO) based on the measurement of its reflection coefficient under a two-photon drive induced by flux modulation. The measured reflection spectra show good agreement with numerical simulations in term of their dependence on the two-photon drive amplitude. The spectra can be interpreted as changes in system's eigenenergies… ▽ More We report the spectroscopic characterization of a Kerr parametric oscillator (KPO) based on the measurement of its reflection coefficient under a two-photon drive induced by flux modulation. The measured reflection spectra show good agreement with numerical simulations in term of their dependence on the two-photon drive amplitude. The spectra can be interpreted as changes in system's eigenenergies, transition matrix elements, and the population of the eigenstates, although the linewidth of the resonance structure is not fully explained. We also show that the drive-amplitude dependence of the spectra can be explained analytically by using the concepts of Rabi splitting and the Stark shift. By comparing the experimentally obtained spectra with theory, we show that the two-photon drive amplitude at the device can be precisely determined, which is important for the application of KPOs in quantum information processing. △ Less

Submitted 21 September, 2023; v1 submitted 19 September, 2023; originally announced September 2023.

Digital quantum simulator for the time-dependent Dirac equation using discrete-time quantum walks

Authors: Shigetora Miyashita, Takahiko Satoh, Michihiko Sugawara, Naphan Benchasattabuse, Ken M. Nakanishi, Michal Hajdušek, Hyensoo Choi, Rodney Van Meter

Abstract: We introduce a quantum algorithm for simulating the time-dependent Dirac equation in 3+1 dimensions using discrete-time quantum walks. Thus far, promising quantum algorithms have been proposed to simulate quantum dynamics in non-relativistic regimes efficiently. However, only some studies have attempted to simulate relativistic dynamics due to its theoretical and computational difficulty. By lever… ▽ More We introduce a quantum algorithm for simulating the time-dependent Dirac equation in 3+1 dimensions using discrete-time quantum walks. Thus far, promising quantum algorithms have been proposed to simulate quantum dynamics in non-relativistic regimes efficiently. However, only some studies have attempted to simulate relativistic dynamics due to its theoretical and computational difficulty. By leveraging the convergence of discrete-time quantum walks to the Dirac equation, we develop a quantum spectral method that approximates smooth solutions with exponential convergence. This mitigates errors in implementing potential functions and reduces the overall gate complexity that depends on errors. We demonstrate that our approach does not require additional operations compared to the asymptotic gate complexity of non-relativistic real-space algorithms. Our findings indicate that simulating relativistic dynamics is achievable with quantum computers and can provide insights into relativistic quantum physics and chemistry. △ Less

Submitted 31 May, 2023; originally announced May 2023.

Comments: 11 pages, 5 figures

Generation of third-harmonic spin oscillation from strong spin precession induced by terahertz magnetic near fields

Authors: Zhenya Zhang, Fumiya Sekiguchi, Takahiro Moriyama, Shunsuke C. Furuya, Masahiro Sato, Takuya Satoh, Yu Mukai, Koichiro Tanaka, Takafumi Yamamoto, Hiroshi Kageyama, Yoshihiko Kanemitsu, Hideki Hirori

Abstract: The ability to drive a spin system to state far from the equilibrium is indispensable for investigating spin structures of antiferromagnets and their functional nonlinearities for spintronics. While optical methods have been considered for spin excitation, terahertz (THz) pulses appear to be a more convenient means of direct spin excitation without requiring coupling between spins and orbitals or… ▽ More The ability to drive a spin system to state far from the equilibrium is indispensable for investigating spin structures of antiferromagnets and their functional nonlinearities for spintronics. While optical methods have been considered for spin excitation, terahertz (THz) pulses appear to be a more convenient means of direct spin excitation without requiring coupling between spins and orbitals or phonons. However, room-temperature responses are usually limited to small deviations from the equilibrium state because of the relatively weak THz magnetic fields in common approaches. Here, we studied the magnetization dynamics in a HoFeO3 crystal at room temperature. A custom-made spiral-shaped microstructure was used to locally generate a strong multicycle THz magnetic near field perpendicular to the crystal surface; the maximum magnetic field amplitude of about 2 T was achieved. The observed time-resolved change in the Faraday ellipticity clearly showed second- and third-order harmonics of the magnetization oscillation and an asymmetric oscillation behaviour. Not only the ferromagnetic vector M but also the antiferromagnetic vector L plays an important role in the nonlinear dynamics of spin systems far from equilibrium. △ Less

Submitted 28 March, 2023; originally announced March 2023.

Journal ref: Nature Communications 14, 1795 (2023)

Leveraging hardware-control imperfections for error mitigation via generalized quantum subspace

Authors: Yasuhiro Ohkura, Suguru Endo, Takahiko Satoh, Rodney Van Meter, Nobuyuki Yoshioka

Abstract: In the era of quantum computing without full fault-tolerance, it is essential to suppress noise effects via the quantum error mitigation techniques to enhance the computational power of the quantum devices. One of the most effective noise-agnostic error mitigation schemes is the generalized quantum subspace expansion (GSE) method, which unifies various mitigation algorithms under the framework of… ▽ More In the era of quantum computing without full fault-tolerance, it is essential to suppress noise effects via the quantum error mitigation techniques to enhance the computational power of the quantum devices. One of the most effective noise-agnostic error mitigation schemes is the generalized quantum subspace expansion (GSE) method, which unifies various mitigation algorithms under the framework of the quantum subspace expansion. Specifically, the fault-subspace method, a subclass of GSE method, constructs an error-mitigated quantum state with copies of quantum states with different noise levels. However, from the experimental aspect, it is nontrivial to determine how to reliably amplify the noise so that the error in the simulation result is efficiently suppressed. In this work, we explore the potential of the fault-subspace method by leveraging the hardware-oriented noise: intentional amplification of the decoherence, noise boost by insertion of identity, making use of crosstalk, and probabilistic implementation of noise channel. We demonstrate the validity of our proposals via both numerical simulations with the noise parameters reflecting those in quantum devices available via IBM Quantum, and also experiments performed therein. △ Less

Submitted 23 March, 2023; v1 submitted 14 March, 2023; originally announced March 2023.

Comments: 11 pages, 10 figures

Sub-millimeter propagation of antiferromagnetic magnons via magnon-photon coupling

Authors: Ryo Kainuma, Keita Matsumoto, Toshimitsu Ito, Takuya Satoh

Abstract: For the realization of magnon-based current-free technologies, referred to as magnonics, all-optical control of magnons is an important technique for both fundamental research and practical applications. Magnon-polariton is a coupled state of magnon and photon in a magnetic medium, expected to exhibit magnon-like controllability and photon-like high-speed propagation. While recent studies have obs… ▽ More For the realization of magnon-based current-free technologies, referred to as magnonics, all-optical control of magnons is an important technique for both fundamental research and practical applications. Magnon-polariton is a coupled state of magnon and photon in a magnetic medium, expected to exhibit magnon-like controllability and photon-like high-speed propagation. While recent studies have observed magnon-polaritons as modulation of incident terahertz waves, the influence of magnon-photon coupling on magnon propagation properties remains unexplored. This study aimed to observe the spatiotemporal dynamics of coherent magnon-polaritons through time-resolved imaging measurements. BiFeO$_3$ was selected as the sample due to its anticipated strong coupling between magnons and photons. The observed dynamics suggest that antiferromagnetic magnons can propagate over long distances, up to hundreds of micrometers, through strong coupling with photons. These results enhance our understanding of the optical control of magnonic systems, thereby paving the way for terahertz opto-magnonics. △ Less

Submitted 10 June, 2024; v1 submitted 3 February, 2023; originally announced February 2023.

Comments: 17 pages, 2 figures

Journal ref: npj Spintronics 2, 31 (2024)

Correlated oscillations in Kerr parametric oscillators with tunable effective coupling

Authors: T. Yamaji, S. Masuda, A. Yamaguchi, T. Satoh, A. Morioka, Y. Igarashi, M. Shirane, T. Yamamoto

Abstract: We study simultaneous parametric oscillations in a system composed of two distributed-element-circuit Josephson parametric oscillators in the single-photon Kerr regime coupled via a static capacitance. The energy of the system is described by a two-bit Ising Hamiltonian with an effective coupling whose amplitude and sign depend on the relative phase between parametric pumps. We demonstrate that th… ▽ More We study simultaneous parametric oscillations in a system composed of two distributed-element-circuit Josephson parametric oscillators in the single-photon Kerr regime coupled via a static capacitance. The energy of the system is described by a two-bit Ising Hamiltonian with an effective coupling whose amplitude and sign depend on the relative phase between parametric pumps. We demonstrate that the binary phases of the parametric oscillations are correlated with each other, and that the parity and strength of the correlation can be controlled by adjusting the pump phase. The observed correlation is reproduced in our simulation taking pure dephasing into account. The present result demonstrates the tunability of the Hamiltonian parameters by the phase of external microwave, which can be used in the Ising machine hardware composed of the KPO network. △ Less

Submitted 27 June, 2023; v1 submitted 27 December, 2022; originally announced December 2022.

Comments: 11 pages, 11 figures

Journal ref: Phys. Rev. Applied 20, 014057 (2023)

Chiral phonons: circularly polarized Raman spectroscopy and $\textit{ab initio}$ calculations in a chiral crystal tellurium

Authors: Kyosuke Ishito, Huiling Mao, Kaya Kobayashi, Yusuke Kousaka, Yoshihiko Togawa, Hiroaki Kusunose, Jun-ichiro Kishine, Takuya Satoh

Abstract: Recently, phonons with chirality (chiral phonons) have attracted significant attention. Chiral phonons exhibit angular and pseudo-angular momenta. In circularly polarized Raman spectroscopy, the peak split of the $Γ_3$ mode is detectable along the principal axis of the chiral crystal in the backscattering configuration. In addition, peak splitting occurs when the pseudo-angular momenta of the inci… ▽ More Recently, phonons with chirality (chiral phonons) have attracted significant attention. Chiral phonons exhibit angular and pseudo-angular momenta. In circularly polarized Raman spectroscopy, the peak split of the $Γ_3$ mode is detectable along the principal axis of the chiral crystal in the backscattering configuration. In addition, peak splitting occurs when the pseudo-angular momenta of the incident and scattered circularly polarized light are reversed. Until now, chiral phonons in binary crystals have been observed, whereas those in unary crystals have not been observed. Here, we observe chiral phonons in a chiral unary crystal Te. The pseudo-angular momentum of the phonon is obtained in Te by an $\textit{ab initio}$ calculation. From this calculation, we verified the conservation law of pseudo-angular momentum in Raman scattering. From this conservation law, we determined the handedness of the chiral crystals. We also evaluated the true chirality of the phonons using a measure with symmetry similar to that of an electric toroidal monopole. △ Less

Submitted 28 January, 2023; v1 submitted 5 December, 2022; originally announced December 2022.

Journal ref: Chirality 1- 8 (2023)

Observation of quasi-elastic light scattering in BiFeO$_3$

Authors: Eiichi Oishi, Yasuhiro Fujii, Akitoshi Koreeda, Takuya Satoh, Toshimitsu Ito

Abstract: We observed quasi-elastic light scattering (QELS) in BiFeO$_3$ using Raman spectroscopy over a temperature range of 300-860 K. The QELS has two components: a narrow and broad component. The temperature dependence of the intensity and linewidth of the broad component differed below and beyond the Néel point, and the broad QELS may have a magnetic origin. We observed quasi-elastic light scattering (QELS) in BiFeO$_3$ using Raman spectroscopy over a temperature range of 300-860 K. The QELS has two components: a narrow and broad component. The temperature dependence of the intensity and linewidth of the broad component differed below and beyond the Néel point, and the broad QELS may have a magnetic origin. △ Less

Submitted 11 August, 2022; originally announced August 2022.

Comments: 10 pages, 4 figures

Reflectivity of Venus' dayside disk during the 2020 observation campaign: outcomes and future perspectives

Authors: Yeon Joo Lee, Antonio García Muñoz, Atsushi Yamazaki, Eric Quémerais, Stefano Mottola, Stephan Hellmich, Thomas Granzer, Gilles Bergond, Martin Roth, Eulalia Gallego-Cano, Jean-Yves Chaufray, Rozenn Robidel, Go Murakami, Kei Masunaga, Murat Kaplan, Orhan Erece, Ricardo Hueso, Petr Kabáth, Magdaléna Špoková, Agustín Sánchez-Lavega, Myung-Jin Kim, Valeria Mangano, Kandis-Lea Jessup, Thomas Widemann, Ko-ichiro Sugiyama , et al. (6 additional authors not shown)

Abstract: We performed a unique Venus observation campaign to measure the disk brightness of Venus over a broad range of wavelengths in August and September 2020. The primary goal of the campaign is to investigate the absorption properties of the unknown absorber in the clouds. The secondary goal is to extract a disk mean SO$_2$ gas abundance, whose absorption spectral feature is entangled with that of the… ▽ More We performed a unique Venus observation campaign to measure the disk brightness of Venus over a broad range of wavelengths in August and September 2020. The primary goal of the campaign is to investigate the absorption properties of the unknown absorber in the clouds. The secondary goal is to extract a disk mean SO$_2$ gas abundance, whose absorption spectral feature is entangled with that of the unknown absorber at the ultraviolet (UV) wavelengths. A total of 3 spacecraft and 6 ground-based telescopes participated in this campaign, covering the 52 to 1700~nm wavelength range. After careful evaluation of the observational data, we focused on the data sets acquired by 4 facilities. We accomplished our primary goal by analyzing the reflectivity spectrum of the Venus disk over the 283-800 nm wavelengths. Considerable absorption is present in the 350-450 nm range, for which we retrieved the corresponding optical depth by the unknown absorber. The result shows a consistent wavelength dependence of the relative optical depth with that at low latitudes during the Venus flyby by MESSENGER in 2007 (Pérez-Hoyos et al. 2018), which was expected because the overall disk reflectivity is dominated by low latitudes. Last, we summarize the experience obtained during this first campaign that should enable us to accomplish our second goal in future campaigns. △ Less

Submitted 27 July, 2022; originally announced July 2022.

Comments: Accepted for publication in PSJ, 45 pages, 13 figures

Amplitude Amplification for Optimization via Subdivided Phase Oracle

Authors: Naphan Benchasattabuse, Takahiko Satoh, Michal Hajdušek, Rodney Van Meter

Abstract: We propose an algorithm using a modified variant of amplitude amplification to solve combinatorial optimization problems via the use of a subdivided phase oracle. Instead of dividing input states into two groups and shifting the phase equally for all states within the same group, the subdivided phase oracle changes the phase of each input state uniquely in proportion to their objective value. We p… ▽ More We propose an algorithm using a modified variant of amplitude amplification to solve combinatorial optimization problems via the use of a subdivided phase oracle. Instead of dividing input states into two groups and shifting the phase equally for all states within the same group, the subdivided phase oracle changes the phase of each input state uniquely in proportion to their objective value. We provide visualization of how amplitudes change after each iteration of applying the subdivided phase oracle followed by conventional Grover diffusion in the complex plane. We then show via numerical simulation that for normal, skew normal, and exponential distribution of objective values, the algorithm can be used to amplify the probability of measuring the optimal solution to a significant degree independent of the search space size. In the case of skew normal and exponential distributions, this probability can be amplified to be close to unity, making our algorithm near deterministic. We then modify our algorithm in order to demonstrate how it can be extended to a broader set of objective value distributions. Finally, we discuss the speedup compared to classical schemes using the query complexity model, and show that our algorithm offers a significant advantage over these classical approaches. △ Less

Submitted 1 May, 2022; originally announced May 2022.

Comments: 9 pages, 7 figures, comments welcome

Journal ref: 2022 IEEE International Conference on Quantum Computing and Engineering (QCE), pp. 22-30 (2022)

Estimation of symbiotic bacterial structure in a sustainable seagrass ecosystem on recycled management

Authors: Hirokuni Miyamoto, Nobuhiro Kawachi, Atsushi Kurotani, Shigeharu Moriya, Wataru Suda, Kenta Suzuki, Makiko Matsuura, Naoko Tsuji, Teruno Nakaguma, Chitose Ishii, Arisa Tsuboi, Chie Shindo, Tamotsu Kato, Motoaki Udagawa, Takashi Satoh, Satoshi Wada, Hiroshi Masuya, Hisashi Miyamoto, Hiroshi Ohno, Jun Kikuchi

Abstract: Seagrass meadows play an essential role in blue carbon and aquatic ecosystem services. However, methods for the flourishing of seagrass are still being explored. Here, data from 49 public coastal surveys on the distribution of seagrass and seaweed around the onshore aquaculture facilities are revalidated, and an exceptional area where the seagrass Zostera marina thrives was found. The bacterial po… ▽ More Seagrass meadows play an essential role in blue carbon and aquatic ecosystem services. However, methods for the flourishing of seagrass are still being explored. Here, data from 49 public coastal surveys on the distribution of seagrass and seaweed around the onshore aquaculture facilities are revalidated, and an exceptional area where the seagrass Zostera marina thrives was found. The bacterial population there showed an apparent decrease in the pathogen candidates belonging to the order Flavobacteriales. Moreover, structure equation modeling and a linear non-Gaussian acyclic model based on the machine learning data estimated an optimal symbiotic bacterial group candidate for seagrass growth as follows: the Lachnospiraceae and Ruminococcaceae families as gut-inhabitant bacteria, Rhodobacteraceae as photosynthetic bacteria, and Desulfobulbaceae as cable bacteria modulating oxygen or nitrate reduction and oxidation of sulfide. These observations confer a novel perspective on the seagrass symbiotic bacterial structures critical for blue carbon and low-pathogenic marine ecosystems in aquaculture. △ Less

Submitted 30 December, 2022; v1 submitted 12 February, 2022; originally announced February 2022.

Comments: 54 pages, 3 figures, 16 supporting information

Agricultural quality matrix-based multiomics structural analysis of carrots in soils fertilized with thermophile-fermented compost

Authors: Hirokuni Miyamoto, Katsumi Shigeta, Wataru Suda, Yasunori Ichihashi, Naoto Nihei, Makiko Matsuura, Arisa Tsuboi, Naoki Tominaga, Masahiko Aono, Muneo Sato, Shunya Taguchi, Teruno Nakaguma, Naoko Tsuji, Chitose Ishii, Teruo Matsushita, Chie Shindo, Toshiaki Ito, Tamotsu Kato, Hiroshi Ohno, Atsushi Kurotani, Hideaki Shima, Shigeharu Moriya, Sankichi Horiuchi, Takashi Satoh, Kenichi Mori , et al. (6 additional authors not shown)

Abstract: Compost is used worldwide as a soil conditioner for crops, but its functions have still been explored. Here, the omics profiles of carrots were investigated, as a root vegetable plant model, in a field amended with compost fermented with thermophilic Bacillaceae for growth and quality indices. Exposure to compost significantly increased the productivity, antioxidant activity, red color, and taste… ▽ More Compost is used worldwide as a soil conditioner for crops, but its functions have still been explored. Here, the omics profiles of carrots were investigated, as a root vegetable plant model, in a field amended with compost fermented with thermophilic Bacillaceae for growth and quality indices. Exposure to compost significantly increased the productivity, antioxidant activity, red color, and taste of the carrot root and altered the soil bacterial composition with the levels of characteristic metabolites of the leaf, root, and soil. Based on the data, structural equation modeling (SEM) estimated that L-2-aminoadipate, phenylalanine, flavonoids and / or carotenoids in plants were optimally linked by exposure to compost. The SEM of the soil estimated that the genus Paenibacillus, L-2-aminoadipate and nicotinamide, and S-methyl L-cysteine were optimally involved during exposure. These estimates did not show a contradiction between the whole genomic analysis of compost-derived Paenibacillus isolates and the bioactivity data, inferring the presence of a complex cascade of plant growth-promoting effects and modulation of the nitrogen cycle by compost itself. These observations have provided information on the qualitative indicators of compost in complex soil-plant interactions and offer a new perspective for chemically independent sustainable agriculture through the efficient use of natural nitrogen. △ Less

Submitted 31 March, 2023; v1 submitted 7 February, 2022; originally announced February 2022.

Comments: 6 figures, 1 Table, and support information

A novel sustainable role of compost as a universal protective substitute for fish, chicken, pig, and cattle, and its estimation by structural equation modeling

Authors: Hirokuni Miyamoto, Wataru Suda, Hiroaki Kodama, Hideyuki Takahashi, Yumiko Nakanishi, Shigeharu Moriya, Kana Adachi, Nao Kiriyama, Masaya Wada, Daisuke Sudo, Shunsuke Ito, Shunsuke Ito, Minami Shibata, Shinji Wada, Takako Murano, Hitoshi Taguchi, Chie Shindo, Arisa Tsuboi, Naoko Tsuji, Makiko Matsuura, Chitose Ishii, Teruno Nakaguma, Toshiyuki Ito, Toru Okada, Teruo Matsushita , et al. (18 additional authors not shown)

Abstract: Natural decomposition of organic matter is essential in food systems, and compost is used worldwide as an organic fermented fertilizer. However, as a feature of the ecosystem, its effects on the animals are poorly understood. Here we show that oral administration of compost and/or its derived thermophilic Bacillaceae, i.e., Caldibacillus hisashii and Weizmannia coagulans, can modulate the prophyla… ▽ More Natural decomposition of organic matter is essential in food systems, and compost is used worldwide as an organic fermented fertilizer. However, as a feature of the ecosystem, its effects on the animals are poorly understood. Here we show that oral administration of compost and/or its derived thermophilic Bacillaceae, i.e., Caldibacillus hisashii and Weizmannia coagulans, can modulate the prophylactic activities of various industrial animals. The fecal omics analyses in the modulatory process showed an improving trend dependent upon animal species, environmental conditions, and administration. However, structural equation modeling (SEM) estimated the grouping candidates of bacteria and metabolites as standard key components beyond the animal species. In particular, the SEM model implied a strong relationship among partly digesting fecal amino acids, increasing genus Lactobacillus as inhabitant beneficial bacteria and 2-aminoisobutyric acid involved in lantibiotics. These results highlight the potential role of compost for sustainable protective control in agriculture, fishery, and livestock industries. △ Less

Submitted 27 November, 2022; v1 submitted 26 January, 2022; originally announced January 2022.

QuISP: a Quantum Internet Simulation Package

Authors: Ryosuke Satoh, Michal Hajdušek, Naphan Benchasattabuse, Shota Nagayama, Kentaro Teramoto, Takaaki Matsuo, Sara Ayman Metwalli, Takahiko Satoh, Shigeya Suzuki, Rodney Van Meter

Abstract: We present an event-driven simulation package called QuISP for large-scale quantum networks built on top of the OMNeT++ discrete event simulation framework. Although the behavior of quantum networking devices have been revealed by recent research, it is still an open question how they will work in networks of a practical size. QuISP is designed to simulate large-scale quantum networks to investiga… ▽ More We present an event-driven simulation package called QuISP for large-scale quantum networks built on top of the OMNeT++ discrete event simulation framework. Although the behavior of quantum networking devices have been revealed by recent research, it is still an open question how they will work in networks of a practical size. QuISP is designed to simulate large-scale quantum networks to investigate their behavior under realistic, noisy and heterogeneous configurations. The protocol architecture we propose enables studies of different choices for error management and other key decisions. Our confidence in the simulator is supported by comparing its output to analytic results for a small network. A key reason for simulation is to look for emergent behavior when large numbers of individually characterized devices are combined. QuISP can handle thousands of qubits in dozens of nodes on a laptop computer, preparing for full Quantum Internet simulation. This simulator promotes the development of protocols for larger and more complex quantum networks. △ Less

Submitted 13 December, 2021; originally announced December 2021.

Comments: 17 pages, 12 figures

Journal ref: 2022 IEEE International Conference on Quantum Computing and Engineering (QCE), pp 353-364 (2022)

A Quantum Internet Architecture

Authors: Rodney Van Meter, Ryosuke Satoh, Naphan Benchasattabuse, Takaaki Matsuo, Michal Hajdušek, Takahiko Satoh, Shota Nagayama, Shigeya Suzuki

Abstract: Entangled quantum communication is advancing rapidly, with laboratory and metropolitan testbeds under development, but to date there is no unifying Quantum Internet architecture. We propose a Quantum Internet architecture centered around the Quantum Recursive Network Architecture (QRNA), using RuleSet-based connections established using a two-pass connection setup. Scalability and internetworking… ▽ More Entangled quantum communication is advancing rapidly, with laboratory and metropolitan testbeds under development, but to date there is no unifying Quantum Internet architecture. We propose a Quantum Internet architecture centered around the Quantum Recursive Network Architecture (QRNA), using RuleSet-based connections established using a two-pass connection setup. Scalability and internetworking (for both technological and administrative boundaries) are achieved using recursion in naming and connection control. In the near term, this architecture will support end-to-end, two-party entanglement on minimal hardware, and it will extend smoothly to multi-party entanglement and the use of quantum error correction on advanced hardware in the future. For a network internal gateway protocol, we recommend (but do not require) qDijkstra with seconds per Bell pair as link cost for routing; the external gateway protocol is designed to build recursively. The strength of our architecture is shown by assessing extensibility and demonstrating how robust protocol operation can be confirmed using the RuleSet paradigm. △ Less

Submitted 13 December, 2021; originally announced December 2021.

Comments: 17 pages, 7 numbered figures

Journal ref: 2022 IEEE International Conference on Quantum Computing and Engineering (QCE), pp. 341-352 (2022)

Simultaneous execution of quantum circuits on current and near-future NISQ systems

Authors: Yasuhiro Ohkura, Takahiko Satoh, Rodney Van Meter

Abstract: In the NISQ era, multi-programming of quantum circuits (QC) helps to improve the throughput of quantum computation. Although the crosstalk, which is a major source of noise on NISQ processors, may cause performance degradation of concurrent execution of multiple QCs, its characterization cost grows quadratically in processor size. To address these challenges, we introduce palloq (parallel allocati… ▽ More In the NISQ era, multi-programming of quantum circuits (QC) helps to improve the throughput of quantum computation. Although the crosstalk, which is a major source of noise on NISQ processors, may cause performance degradation of concurrent execution of multiple QCs, its characterization cost grows quadratically in processor size. To address these challenges, we introduce palloq (parallel allocation of QCs) for improving the performance of quantum multi-programming on NISQ processors while paying attention to the combination of QCs in parallel execution and their layout on the quantum processor, and reducing unwanted interference between QCs caused by crosstalk. We also propose a software-based crosstalk detection protocol that efficiently and successfully characterizes the hardware's suitability for multi-programming. We found a trade-off between the success rate and execution time of the multi-programming. This would be attractive not only to quantum computer service but also to users around the world who want to run algorithms of suitable scale on NISQ processors that have recently attracted great attention and are being enthusiastically investigated. △ Less

Submitted 30 December, 2021; v1 submitted 13 December, 2021; originally announced December 2021.

Comments: 10 pages, 10 figures

Report number: 2500210

Journal ref: IEEE Transactions on Quantum Engineering, vol. 3, pp. 1-10, 2022, Art no. 2500210

Truly chiral phonons in α-HgS

Authors: Kyosuke Ishito, Huiling Mao, Yusuke Kousaka, Yoshihiko Togawa, Satoshi Iwasaki, Tiantian Zhang, Shuichi Murakami, Jun-ichiro Kishine, Takuya Satoh

Abstract: Chirality is a manifestation of the asymmetry inherent in nature. It has been defined as the symmetry breaking of the parity of static objects, and the definition was extended to dynamic motion such that true and false chiralities were distinguished. Recently, rotating, yet not propagating, atomic motions were predicted and observed in two-dimensional materials, and they were referred to as "chira… ▽ More Chirality is a manifestation of the asymmetry inherent in nature. It has been defined as the symmetry breaking of the parity of static objects, and the definition was extended to dynamic motion such that true and false chiralities were distinguished. Recently, rotating, yet not propagating, atomic motions were predicted and observed in two-dimensional materials, and they were referred to as "chiral phonons" . A natural development would be the discovery of truly chiral phonons that propagate while rotating in three-dimensional materials. Here, we used circularly polarised Raman scattering and first-principles calculations to identify truly chiral phonons in chiral bulk crystals. This approach enabled us to determine the chirality of a crystal in a non-contact and non-destructive manner. In addition, we demonstrated that the law of the conservation of pseudo-angular momentum holds between circularly polarised photons and chiral phonons. These findings are expected to help develop ways for transferring the pseudo-angular momentum from photons to electron spins via the propagating chiral phonons in opto-phononic-spintronic devices. △ Less

Submitted 13 October, 2022; v1 submitted 22 October, 2021; originally announced October 2021.

Journal ref: Nat. Phys. 19, 35-39 (2023)

Quantum-gate decomposer

Authors: Ken M. Nakanishi, Takahiko Satoh, Synge Todo

Abstract: Efficient decompositions of multi-qubit gates are essential in NISQ applications, where the number of gates or the circuit depth is limited. This paper presents efficient decompositions of CCZ and CCCZ gates, typical multi-qubit gates, under several qubit connectivities. We can construct the CCZ gate with only four CZ-depth when the qubit is square-shaped, including one auxiliary qubit. In T-shape… ▽ More Efficient decompositions of multi-qubit gates are essential in NISQ applications, where the number of gates or the circuit depth is limited. This paper presents efficient decompositions of CCZ and CCCZ gates, typical multi-qubit gates, under several qubit connectivities. We can construct the CCZ gate with only four CZ-depth when the qubit is square-shaped, including one auxiliary qubit. In T-shaped qubit connectivity, which has no closed loop, we can decompose the CCCZ gate with 17 CZ gates. While previous studies have shown a CCCZ gate decomposition with 14 CZ gates for the fully connected case, we found only four connections are sufficient for 14 CZ gates' implementation. The search for constraint-sufficient decompositions is aided by an optimization method we devised to bring the parameterized quantum circuit closer to the target quantum gate. We can apply this scheme to decompose any quantum gates, not only CCZ and CCCZ. Such decompositions of multi-qubit gates, together with the newly found CCZ and CCCZ decompositions, shorten the execution time of quantum circuits and improve the accuracy of complex quantum algorithms on near future QPUs. △ Less

Submitted 27 September, 2021; originally announced September 2021.

Comments: 7 pages, 4 figures

Grover search revisited; application to image pattern matching

Authors: Hiroyuki Tezuka, Kouhei Nakaji, Takahiko Satoh, Naoki Yamamoto

Abstract: The landmark Grover algorithm for amplitude amplification serves as an essential subroutine in various type of quantum algorithms, with guaranteed quantum speedup in query complexity. However, there have been no proposal to realize the original motivating application of the algorithm, i.e., the database search or more broadly the pattern matching in a practical setting, mainly due to the technical… ▽ More The landmark Grover algorithm for amplitude amplification serves as an essential subroutine in various type of quantum algorithms, with guaranteed quantum speedup in query complexity. However, there have been no proposal to realize the original motivating application of the algorithm, i.e., the database search or more broadly the pattern matching in a practical setting, mainly due to the technical difficulty in efficiently implementing the data loading and amplitude amplification processes. In this paper, we propose a quantum algorithm that approximately executes the entire Grover database search or pattern matching algorithm. The key idea is to use the recently proposed approximate amplitude encoding method on a shallow quantum circuit, together with the easily implementable inversion-test operation for realizing the projected quantum state having similarity to the query data, followed by the amplitude amplification operation that is independent to the target data index. We provide a thorough demonstration of the algorithm in the problem of image pattern matching. △ Less

Submitted 30 September, 2021; v1 submitted 24 August, 2021; originally announced August 2021.

Comments: 15 pages, 10 figures

Journal ref: Phys. Rev. A 105, 032440 (2022)

Ultrafast Optomagnonics in Ferrimagnetic Multi-Sublattice Garnets

Authors: Andrzej Stupakiewicz, Takuya Satoh

Abstract: This review discusses the ultrafast magnetization dynamics within the gigahertz to terahertz frequency range in ferrimagnetic rare-earth iron garnets with different substitutions. In these garnets, the roles of spin-orbit and exchange interactions have been detected using femtosecond laser pulses via the inverse Faraday effect. The all-optical control of spin-wave and Kaplan-Kittel exchange resona… ▽ More This review discusses the ultrafast magnetization dynamics within the gigahertz to terahertz frequency range in ferrimagnetic rare-earth iron garnets with different substitutions. In these garnets, the roles of spin-orbit and exchange interactions have been detected using femtosecond laser pulses via the inverse Faraday effect. The all-optical control of spin-wave and Kaplan-Kittel exchange resonance modes in different frequency ranges is shown. Generation and localization of the electric field distribution inside the garnet through the metal-bound surface plasmon-polariton strongly enhance the amplitude of the exchange resonance modes. The exchange resonance mode in yttrium iron garnets was observed using circularly polarized Raman spectroscopy. The results of this study may be utilized in the development of a wide class of optomagnonic devices in the gigahertz to terahertz frequency range. △ Less

Submitted 14 July, 2021; originally announced July 2021.

Journal ref: J. Phys. Soc. Jpn. 90, 081008 (2021)

Graph kernels encoding features of all subgraphs by quantum superposition

Authors: Kaito Kishi, Takahiko Satoh, Rudy Raymond, Naoki Yamamoto, Yasubumi Sakakibara

Abstract: Graph kernels are often used in bioinformatics and network applications to measure the similarity between graphs; therefore, they may be used to construct efficient graph classifiers. Many graph kernels have been developed thus far, but to the best of our knowledge there is no existing graph kernel that considers all subgraphs to measure similarity. We propose a novel graph kernel that applies a q… ▽ More Graph kernels are often used in bioinformatics and network applications to measure the similarity between graphs; therefore, they may be used to construct efficient graph classifiers. Many graph kernels have been developed thus far, but to the best of our knowledge there is no existing graph kernel that considers all subgraphs to measure similarity. We propose a novel graph kernel that applies a quantum computer to measure the graph similarity taking all subgraphs into account by fully exploiting the power of quantum superposition to encode every subgraph into a feature. For the construction of the quantum kernel, we develop an efficient protocol that removes the index information of subgraphs encoded in the quantum state. We also prove that the quantum computer requires less query complexity to construct the feature vector than the classical sampler used to approximate the same vector. A detailed numerical simulation of a bioinformatics problem is presented to demonstrate that, in many cases, the proposed quantum kernel achieves better classification accuracy than existing graph kernels. △ Less

Submitted 30 March, 2021; originally announced March 2021.

Comments: 13 pages, 9 figures, 1 table

Journal ref: IEEE J. Emerg. Sel. Top. Circuits Syst. Volume: 12, Issue: 3 (2022) 602-613

Ultrafast amplification and non-linear magneto-elastic coupling of coherent magnon modes in an antiferromagnet

Authors: D. Bossini, M. Pancaldi, L. Soumah, M. Basini, F. Mertens, M. Cinchetti, T. Satoh, O. Gomonay, S. Bonetti

Abstract: We investigate the role of domain walls in the ultrafast magnon dynamics of an antiferromagnetic NiO single crystal in a pump-probe experiment with variable pump photon energy. Analysing the amplitude of the energy-dependent photo-induced ultrafast spin dynamics, we detect a yet unreported coupling between the material's characteristic THz- and a GHz-magnon modes. We explain this unexpected coupli… ▽ More We investigate the role of domain walls in the ultrafast magnon dynamics of an antiferromagnetic NiO single crystal in a pump-probe experiment with variable pump photon energy. Analysing the amplitude of the energy-dependent photo-induced ultrafast spin dynamics, we detect a yet unreported coupling between the material's characteristic THz- and a GHz-magnon modes. We explain this unexpected coupling between two orthogonal eigenstates of the corresponding Hamiltonian by modelling the magneto-elastic interaction between spins in different domains. We find that such interaction, in the non-linear regime, couples the two different magnon modes via the domain walls and it can be optically exploited via the exciton-magnon resonance. △ Less

Submitted 12 August, 2021; v1 submitted 20 March, 2021; originally announced March 2021.

Comments: 6 pages, 4 figures

Journal ref: Phys. Rev. Lett. 127, 077202 (2021)

Fast acquisition of spin-wave dispersion by compressed sensing

Authors: Ryo Kainuma, Keita Matsumoto, Takuya Satoh

Abstract: For the realization of magnonic devices, spin-wave dispersions need to be identified. Recently, the time-resolved pump-probe imaging method combined with the Fourier transform was demonstrated for obtaining the dispersions in the lower-wavenumber regime. However, the measurement takes a long time when the sampling rate is sufficiently high. Here, we demonstrated the fast acquisition of spin-wave d… ▽ More For the realization of magnonic devices, spin-wave dispersions need to be identified. Recently, the time-resolved pump-probe imaging method combined with the Fourier transform was demonstrated for obtaining the dispersions in the lower-wavenumber regime. However, the measurement takes a long time when the sampling rate is sufficiently high. Here, we demonstrated the fast acquisition of spin-wave dispersions by using the compressed sensing technique. Further, we quantitatively evaluated the consistency of the results. Our results can be applied to other various pump-probe measurements, such as observations based on the electro-optical effects. △ Less

Submitted 23 February, 2021; originally announced February 2021.

Comments: 5 pages, 4 figures

Journal ref: Appl. Phys. Express 14, 033004 (2021)

Pulse-engineered Controlled-V gate and its applications on superconducting quantum device

Authors: Takahiko Satoh, Shun Oomura, Michihiko Sugawara, Naoki Yamamoto

Abstract: In this paper, we demonstrate that, by employing OpenPulse design kit for IBM superconducting quantum devices, the controlled-V gate (CV gate) can be implemented in about half the gate time to the controlled-X (CX or CNOT gate) and consequently 65.5\% reduced gate time compared to the CX-based implementation of CV. Then, based on the theory of Cartan decomposition, we characterize the set of all t… ▽ More In this paper, we demonstrate that, by employing OpenPulse design kit for IBM superconducting quantum devices, the controlled-V gate (CV gate) can be implemented in about half the gate time to the controlled-X (CX or CNOT gate) and consequently 65.5\% reduced gate time compared to the CX-based implementation of CV. Then, based on the theory of Cartan decomposition, we characterize the set of all two-qubit gates implemented with only two or three CV gates; using pulse-engineered CV gates enables us to implement these gates with shorter gate time and possibly better gate fidelity than the CX-based one, as actually demonstrated in two examples. Moreover, we showcase the improvement of linearly-coupled three-qubit Toffoli gate, by implementing it with the pulse-engineered CV gate, both in gate time and the averaged output-state fidelity. These results imply the importance of our CV gate implementation technique, which, as an additional option for the basis gate set design, may shorten the overall computation time and consequently improve the precision of several quantum algorithms executed on a real device. △ Less

Submitted 26 April, 2022; v1 submitted 11 February, 2021; originally announced February 2021.

Comments: 9 pages, 14 figures

Journal ref: IEEE Transactions on Quantum Engineering, Volume: 3 (2022)

Brightness modulations of our nearest terrestrial planet Venus reveal atmospheric super-rotation rather than surface features

Authors: Y. J. Lee, A. García Muñoz, T. Imamura, M. Yamada, T. Satoh, A. Yamazaki, S. Watanabe

Abstract: Terrestrial exoplanets orbiting within or near their host stars' habitable zone are potentially apt for life. It has been proposed that time-series measurements of reflected starlight from such planets will reveal their rotational period, main surface features and some atmospheric information. From imagery obtained with the Akatsuki spacecraft, here we show that Venus' brightness at 283, 365, and… ▽ More Terrestrial exoplanets orbiting within or near their host stars' habitable zone are potentially apt for life. It has been proposed that time-series measurements of reflected starlight from such planets will reveal their rotational period, main surface features and some atmospheric information. From imagery obtained with the Akatsuki spacecraft, here we show that Venus' brightness at 283, 365, and 2020 nm is modulated by one or both of two periods of 3.7 and 4.6 days, and typical amplitudes <10% but occasional events of 20-40%. The modulations are unrelated to the solid-body rotation; they are caused by planetary-scale waves superimposed on the super-rotating winds. Here we propose that two modulation periods whose ratio of large-to-small values is not an integer number imply the existence of an atmosphere if detected at an exoplanet, but it remains ambiguous whether the atmosphere is optically thin or thick, as for Earth or Venus respectively. Multi-wavelength and long temporal baseline observations may be required to decide between these scenarios. Ultimately, Venus represents a false positive for interpretations of brightness modulations of terrestrial exoplanets in terms of surface features. △ Less

Submitted 24 November, 2020; v1 submitted 18 November, 2020; originally announced November 2020.

Journal ref: Nature Communications 11 (2020) 5720

Spectroscopic observation of the crossover from a classical Duffing oscillator to a Kerr parametric oscillator

Authors: T. Yamaji, S. Kagami, A. Yamaguchi, T. Satoh, K. Koshino, H. Goto, Z. R. Lin, Y. Nakamura, T. Yamamoto

Abstract: We study microwave response of a Josephson parametric oscillator consisting of a superconducting transmission-line resonator with an embedded dc-SQUID. The dc-SQUID allows to control the magnitude of a Kerr nonlinearity over the ranges where it is smaller or larger than the photon loss rate. Spectroscopy measurements reveal the change of the microwave response from a classical Duffing oscillator t… ▽ More We study microwave response of a Josephson parametric oscillator consisting of a superconducting transmission-line resonator with an embedded dc-SQUID. The dc-SQUID allows to control the magnitude of a Kerr nonlinearity over the ranges where it is smaller or larger than the photon loss rate. Spectroscopy measurements reveal the change of the microwave response from a classical Duffing oscillator to a Kerr parametric oscillator in a single device. In the single-photon Kerr regime, we observe parametric oscillations with a well-defined phase of either $0$ or $π$, whose probability can be controlled by an externally injected signal. △ Less

Submitted 23 February, 2022; v1 submitted 6 October, 2020; originally announced October 2020.

Journal ref: Phys. Rev. A 105, 023519 (2022)

Efficient Construction of a Control Modular Adder on a Carry-Lookahead Adder Using Relative-phase Toffoli Gates

Authors: Kento Oonishi, Tomoki Tanaka, Shumpei Uno, Takahiko Satoh, Rodney Van Meter, Noboru Kunihiro

Abstract: Control modular addition is a core arithmetic function, and we must consider the computational cost for actual quantum computers to realize efficient implementation. To achieve a low computational cost in a control modular adder, we focus on minimizing KQ, defined by the product of the number of qubits and the depth of the circuit. In this paper, we construct an efficient control modular adder wit… ▽ More Control modular addition is a core arithmetic function, and we must consider the computational cost for actual quantum computers to realize efficient implementation. To achieve a low computational cost in a control modular adder, we focus on minimizing KQ, defined by the product of the number of qubits and the depth of the circuit. In this paper, we construct an efficient control modular adder with small KQ by using relative-phase Toffoli gates in two major types of quantum computers: Fault-Tolerant Quantum Computers (FTQ) on the Logical layer and Noisy Intermediate-Scale Quantum Computers (NISQ). We give a more efficient construction compared to Van Meter and Itoh's, based on a carry-lookahead adder. In FTQ, $T$ gates incur heavy cost due to distillation, which fabricates ancilla for running $T$ gates with high accuracy but consumes a lot of specially prepared ancilla qubits and a lot of time. Thus, we must reduce the number of $T$ gates. We propose a new control modular adder that uses only 20% of the number of $T$ gates of the original. Moreover, when we take distillation into consideration, we find that we minimize $\text{KQ}_{T}$ (the product of the number of qubits and $T$-depth) by running $Θ\left(n / \sqrt{\log n} \right)$ $T$ gates simultaneously. In NISQ, CNOT gates are the major error source. We propose a new control modular adder that uses only 35% of the number of CNOT gates of the original. Moreover, we show that the $\text{KQ}_{\text{CX}}$ (the product of the number of qubits and CNOT-depth) of our circuit is 38% of the original. Thus, we realize an efficient control modular adder, improving prospects for the efficient execution of arithmetic in quantum computers. △ Less

Submitted 15 December, 2021; v1 submitted 1 October, 2020; originally announced October 2020.

Journal ref: IEEE Transactions on Quantum Engineering 3 (2022): 1-18

Selective imaging of terahertz electric field of phonon-polariton in LiNbO$_3$

Authors: Keita Matsumoto, Takuya Satoh

Abstract: Coherent phonon-polaritons have attracted a considerable amount of interest owing to their relevance to nonlinear optics and terahertz (THz)-wave emissions. Therefore, it is important to analyze the THz electric-fields of phonon-polaritons. However, in the majority of previous measurements, only a single component of the THz electric field was detected. In this paper, we demonstrate that pump-prob… ▽ More Coherent phonon-polaritons have attracted a considerable amount of interest owing to their relevance to nonlinear optics and terahertz (THz)-wave emissions. Therefore, it is important to analyze the THz electric-fields of phonon-polaritons. However, in the majority of previous measurements, only a single component of the THz electric field was detected. In this paper, we demonstrate that pump-probe electro-optical imaging measurements using the Stokes parameters of probe polarization enable the phase-resolved selective detection of THz electric-field components that are associated with the phonon-polariton. We experimentally distinguish the mode profiles of ordinary and extraordinary phonon-polaritons, and clarify the excitation mechanism as optical rectification. These results are explained by numerical calculations of Maxwell equations for the THz electric field. The technique of selectively observing the THz electric field components may be useful for designing efficient THz-wave emitters. △ Less

Submitted 29 September, 2020; v1 submitted 8 July, 2020; originally announced July 2020.

Comments: 11 pages, 4 figures

Journal ref: Phys. Rev. B 102, 094313 (2020)

A Long-lived Sharp Disruption on the Lower Clouds of Venus

Authors: J. Peralta, T. Navarro, C. W. Vun, A. Sánchez-Lavega, K. McGouldrick, T. Horinouchi, T. Imamura, R. Hueso, J. P. Boyd, G. Schubert, T. Kouyama, T. Satoh, N. Iwagami, E. F. Young, M. A. Bullock, P. Machado, Y. J. Lee, S. S. Limaye, M. Nakamura, S. Tellmann, A. Wesley, P. Miles

Abstract: Planetary-scale waves are thought to play a role in powering the yet-unexplained atmospheric superrotation of Venus. Puzzlingly, while Kelvin, Rossby and stationary waves manifest at the upper clouds (65--70 km), no planetary-scale waves or stationary patterns have been reported in the intervening level of the lower clouds (48--55 km), although the latter are probably Lee waves. Using observations… ▽ More Planetary-scale waves are thought to play a role in powering the yet-unexplained atmospheric superrotation of Venus. Puzzlingly, while Kelvin, Rossby and stationary waves manifest at the upper clouds (65--70 km), no planetary-scale waves or stationary patterns have been reported in the intervening level of the lower clouds (48--55 km), although the latter are probably Lee waves. Using observations by the Akatsuki orbiter and ground-based telescopes, we show that the lower clouds follow a regular cycle punctuated between 30$^{\circ}$N--40$^{\circ}$S by a sharp discontinuity or disruption with potential implications to Venus's general circulation and thermal structure. This disruption exhibits a westward rotation period of $\sim$4.9 days faster than winds at this level ($\sim$6-day period), alters clouds' properties and aerosols, and remains coherent during weeks. Past observations reveal its recurrent nature since at least 1983, and numerical simulations show that a nonlinear Kelvin wave reproduces many of its properties. △ Less

Submitted 27 May, 2020; originally announced May 2020.

Comments: 21 pages, 10 figures, 2 animated figures and 2 tables

Journal ref: Geophysical Research Letters, Volume 47, Issue 11, 16 June 2020, e2020GL087221