応用物理学輪講 I
10月17日
[注意事項]
発表の10日前までに　office[at]ap.t.u-tokyo.ac.jp　宛てに「氏名」「指導教員」「発表題目（英語）」「要旨（英語）」「発表言語（英語または日本語）」を送付して下さい。
発表日
2025年10月17日(金) 16：50～18：50

Aグループ

座長
菊池　春輝
指導
教員名
中村　泰信　教授
座長
木村　文彦
指導
教員名
石坂　香子　教授
発表者名 一李　建嬉
指導教員名 小芦　雅斗　教授
発表題目（英語） A quantum secret sharing protocol with anonimity and flexibility
要旨（英語） Quantum Secret Sharing (QSS) is a quantum cryptographic scheme where a secret is divided into multiple pieces, or "shares," and distributed among multiple participants. This method ensures that the secret can only be reconstructed when a sufficient number of participants cooperate, thereby offering a robust and secure way to manage sensitive information.
In this presentation, I will introduce a QSS protocol that utilizes Greenberger-Horne-Zeilinger (GHZ) states. This protocol offers two significant advantages. Firstly, it provides anonymity: whether you received a share of the secret is not revealed throughout the protocol. This capability is particularly valuable for applications requiring high privacy. Secondly, the protocol have flexibility, allowing participants to be added or removed dynamically without compromising the existing shared secret. This enables a practical QSS system capable of seamlessly changing group configurations.
発表言語 日本語
発表者名 植田　涼介
指導教員名 古川　亮　教授
発表題目（英語） Impact of Quench Depth on the Structural Formation in Colloidal Gelation
要旨（英語） Colloidal gels are soft matter composed of nanometer- to micrometer-sized particles dispersed in a fluid medium, forming a three-dimensional percolated network structure primarily driven by short-range attractive interactions. A distinctive feature of colloidal gels is that their mechanical  response strongly depend on the details of the network structure. Gel structure formation is significantly influenced by the shape and strength of the interaction potential, thermal fluctuations, and the dynamics governing its time evolution.
We systematically investigated how thermal fluctuations (quench depth) influence gelation and network structure. Using Brownian-dynamics simulations with a Morse potential, we found that the ratio of bond strength (potential depth) to thermal energy controls the kinetic pathways and, in turn, the resulting branch morphology and overall network structure.
We plan to investigate hydrodynamic effects on gelation in a systematic way. Although hydrodynamic interactions are believed to play a crucial role, comprehensive simulation studies remain limited by their huge computational cost. To enable such studies, we are developing a GPU-accelerated simulation framework, reducing run time well below that of standard CPU simulations. In this talk, I will briefly introduce the approach and report on the current status.
発表言語 日本語
発表者名 牛尾　誠
指導教員名 塚﨑　敦　教授
発表題目（英語） Toward high-mobility transistor based on hydrogenated layered germanium GeH
要旨（英語） Amid the growing demand for higher-performance transistors, it is claimed that the miniaturization of Si-based transistors is approaching its fundamental limits.
This study focuses on hydrogenated germanium (GeH), known as germanane. GeH is considered to be a potential material for high-mobility transistors due to its small effective mass. However, no experimental demonstration of high-mobility operation of GeH transistors has been reported so far. This presentation reports on my recent progress on the fabrication of high-quality GeH thin films, aiming toward the realization of high-mobility transistor operation.
発表言語 日本語
発表者名 大泉　幹
指導教員名 古澤　明　教授
発表題目（英語） Generating narrow wave-packet superpositions of vacuum and single-photon states
要旨（英語） Non-Gaussian states are indispensable for universal optical quantum computation. As a key resource for non-Gaussian gates, these states are generated in the field of quantum optics using heralding schemes that rely on photon detection. High-speed quantum computation requires non-Gaussian states with short temporal wave packets. Conventionally, the minimum wave packet width has been limited by factors such as the timing jitter of photon detectors and the bandwidth of homodyne detectors. To address this issue, our group has developed a method to generate non-Gaussian states using optical pulses and measure them with Phase-Sensitive Amplifier (PSA) homodyne detection. This has allowed us to produce states with a temporal wave packet width nearly 100 times shorter than those from conventional methods. In this work, we applied our technique to generate and measure a specific phase-sensitive non-Gaussian state: a superposition of the vacuum and single-photon states, denoted as α∣0⟩+β∣1⟩. Using a continuous-wave (CW) laser source, we generated a two-mode EPR state from a pump beam that was pulsed using an intensity modulator. A displacement operation was then performed on the idler mode. By detecting a photon from this displaced idler beam with a Superconducting Nanowire Single-Photon Detector (SNSPD), we probabilistically heralded the generation of the phase-sensitive state. By measuring the heralded signal beam with our PSA homodyne detector, we confirmed the generation of the α∣0⟩+β∣1⟩ state with a temporal wave packet width of 80 ps. This is a state with a wave packet nearly 100 times shorter than those generated using previous techniques.
発表言語 英語

Bグループ

座長
清永　優斗
指導
教員名
十倉　好紀　卓越教授
座長
黒田　清太
指導
教員名
長谷川　達生　教授
発表者名 大岡　真太郎
指導教員名 武田　俊太郎　准教授
発表題目（英語） Experimental Classification of Continuous-variable Optical Quantum States Using Quantum Machine Learning
要旨（英語） One of the primary goals in developing practical quantum computers is to demonstrate quantum advantage, where the performance of a quantum computer surpasses that of a classical computer. A promising algorithm for achieving this is Quantum Machine Learning. It utilizes a quantum computer to perform machine learning tasks, typically for traditional "classical data." However, it is challenging for current quantum computers to experimentally demonstrate quantum advantage for classical data. Although some advantages have been theoretically proposed, it is often limited to non-practical tasks. To overcome this, algorithms that process quantum states themselves as "quantum data" are drawing attention.
In our work, we theoretically showed that analyzing quantum data with our quantum machine learning protocol is exponentially more efficient than the traditional quantum-state-tomography analysis. Moreover, we experimentally demonstrated this algorithm using an optical circuit and successfully analyzed the continuous-variable quantum states. In this presentation, I will discuss the details of our quantum machine learning protocol and the results of our experiment.
発表言語 英語
発表者名 大澤　優太
指導教員名 中島　多朗　准教授
発表題目（英語） Unpolarized neutron scattering study on multiferroic Mn₃WO₆
要旨（英語） Magneto-electric multiferroics, which simultaneously exhibit ferroelectric polarization and magnetic orders, have been extensively studied in recent condensed matter physics. Since their ferroelectric properties arise from magnetic inversion symmetry breakings, multiferroics can display novel cross-correlated phenomena such as magnetic-field-control of electric polarization, which would be applicable to future electronic devices.

In the present study, we focus on a new multiferroic compound Mn₃WO₆. This system has a centrosymmetric rhombohedral crystal structure belonging to the space group of R-3 at room temperature, and exhibits spontaneous electric polarization below the magnetic transition temperatures. To elucidate the origin of the multiferroicity of this compound, we investigated the crystal and magnetic structures by unpolarized neutron scattering experiments at the 5G PONTA spectrometer in JRR-3. In this talk, we will present a brief review of multiferroics and neutron scattering technique, and show the preliminary results of the crystal and magnetic structure analyses of Mn₃WO₆.
発表言語 日本語
発表者名 大平　至波
指導教員名 小濱　芳允　准教授
発表題目（英語） Influence of high magnetic field on the orbital degree of freedom in Lacunar spinel GeV4S8
要旨（英語） The Jahn-Teller (JT) transition, originating from the lifting of orbital degeneracy, is usually independent of magnetic transitions. While magnetic-field-induced JT transitions are known in 4f-electron systems with strong spin-orbit coupling (SOC), they have rarely been observed in 3d-electron systems with weak SOC[1].

The lacunar spinel GeV4S8 adopts a cubic structure (space group F-43m) at room temperature and is well described by a molecular-orbital picture with an S = 1 moment localized on a V4 tetrahedral cluster. GeV4S8 undergoes a JT transition to the orthorhombic space group Imm2 at TJT = 32 K and subsequently exhibits an antiferromagnetic (AFM) transition at TN = 17 K . Notably, a magnetic-field-induced phase transition occurs near 40 T, not only from the low-temperature AFM phase but also from the intermediate-temperature paramagnetic phase suggesting a field-induced JT transition whose microscopic mechanism remains unresolved. [2]

In this study, we aim to clarify the nature of this field-induced phase transition in GeV4S8 through magnetization, dilatometry, and x-ray diffraction measurements. In this presentation, I will discuss our experimental results and current progress.


[1] K. Kishimoto et al., Phys. Rev. B 82, 012103 (2010).

[2] V. Felea et al., Phys. Rev. B 101, 064413 (2020).
発表言語 日本語
発表者名 岡野　修平
指導教員名 島崎　佑也　特任准教授
発表題目（英語） Optical spectroscopy of strongly correlated electronic states in semiconductor Γ-valley moiré system
要旨（英語） Semiconductor moiré superlattices using transition metal dichalcogenides (TMDs) are becoming established as a platform for simulating strongly correlated electron physics, reproducing a variety of properties such as strongly correlated insulating states and superconductivity. The properties of these moiré systems have been primarily evaluated at the K-point of the base materials. However, to further expand these systems from the perspective of coupling different electronic systems, it is crucial to realize and evaluate moiré systems at the Γ-point.
In this study, we realized a moiré band at the Γ-point by creating a TMD heterostructure. Through exciton spectroscopy measurements, we were able to observe a Mott insulator state and a strongly correlated insulating state at fractional filling.
発表言語 日本語
応用物理学輪講 I一覧ページへ戻る