応用物理学輪講 I
6月27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6月27日(金) 16：50～18：50

Aグループ

座長
秋山　由洸
指導
教員名
小林　洋平　教授
発表者名 星　尊也
指導教員名 古澤　明　教授
発表題目（英語） Experimental Research Towards the Realization of High-Speed Optical Quantum Computing
要旨（英語）  The continuous-variable quantum state-based optical quantum computing platform offers advantages over other approaches in terms of scaling computational resources and enhancing computational speed. While extensive experimental research has been conducted to demonstrate these respective advantages, experimental studies that integrate these benefits remain unproven.
 In this talk, I will explain these individual advantages with reference to prior research and discuss protocols aimed at their integration, incorporating insights from recent experimental advancements.
発表言語 英語
発表者名 野田　源文
指導教員名 関　真一郎　教授
発表題目（英語） Realization of topological spin textures in a cubic rare-earth magnet
要旨（英語）    Topological spin textures, such as skyrmions and merons, have recently been explored in various condensed matter systems as a source of the associated emergent electromagnetic phenomena.
   Recently, skyrmionic spin textures have been discovered even in high-symmetry rare-earth compounds with hexagonal or tetragonal crystal structures, where the formation mechanism is attributed to spin interactions mediated by itinerant-electrons. These materials often host ultracompact skyrmions, making them promising for high-density spintronic applications.
   In this study, we investigate a rare-earth based compound crystallizing in a high-symmetry cubic crystal structure and examine its transport properties and magnetic structure. This presentation will highlight the detailed spin textures realized in this system, as revealed by resonant X-ray scattering. measurements.
発表言語 日本語
発表者名 橋爪　智紀
指導教員名 山本　倫久　教授
発表題目（英語） Coherent Control of Flying Electron Qubits Toward Long-Distance Preservation of Quantum Coherence
要旨（英語）   Realizing a practical quantum computer requires a scalable architecture capable of controlling many qubits.
Flying qubits—quantum information carriers that move through space—offer a promising approach, particularly in terms of integration and large-scale processing.
This talk introduces the basic principles of electron-based flying qubits implemented using a two-dimensional electron gas (2DEG) in a GaAs/AlGaAs heterostructure.
I will explain how single electrons, known as levitons, can be generated using Lorentzian voltage pulses, and how quantum gates can be implemented while preserving coherence.
In the second half, I will present my own experimental work, which investigates whether levitons can maintain coherence over macroscopic distances.
The talk concludes with a discussion on the potential of scalable quantum information processing using electronic flying qubits.
発表言語 日本語

Bグループ

座長
浅井　僚眞
指導
教員名
有田　亮太郎　教授
発表者名 濵野　直紀
指導教員名 香取　秀俊　教授
発表題目（英語） Excitation Measurement by cavity QED for Continuously operated Optical
Lattice Clock
要旨（英語） Continuously operated optical lattice clocks are attracting attention for their potential to improve frequency stability by eliminating the dead time associated with conventional spectroscopy cycles. However, atomic state detection in such systems is challenging because interrogation and measurement occur simultaneously. Fluorescence-based detection, commonly used in optical lattice clocks, causes heating and photon scattering. These effects become more problematic in continuous operation, where stray photons entering the spectroscopy region can further degrade frequency stability and accuracy.

To mitigate these issues, a minimally invasive measurement method based on cavity quantum electrodynamics (cavity QED) is proposed. By coupling atoms to a optical cavity, it is possible to extract information about the atomic excitation without significantly perturbing the system. This approach offers a promising alternative to fluorescence detection, particularly in the context of continuous optical lattice clocks.

In this presentation, I introduce the design concept of a small-scale optical cavity tailored for integration with a continuous clock system. I describe the intended operating principles, expected atom‒cavity interaction regimes, and the potential for mitigating measurement
back-action.
発表言語 ⽇本語
発表者名 廣田　和希
指導教員名 古澤　明　教授
発表題目（英語） Experiment on generating highly squeezed vacuum state with waveguide OPA
要旨（英語） Furusawa-Endo lab is studying optical quantum computing.When doing optical quantum computation, there is an important resource state called squeezed vacuum.The quality of this state is related with the noise that is induced in each calculation step.With the recent development of fabrication, it became possible to generate THz bandwidth high quality squeezed vacuum with a device called optical parametric amplifier(OPA).By using this OPA, we can achieve ultra fast quantum computation.But still, the squeezed vacuum state that is generated with this device is not as good as squeezed vacuum that is generated with another methods.Here, by doing the refinement of measurement system, we succeeded to measure squeezed vacuum that is the best quality in the world.I will be doing presentation about the squeezed vacuum and our updated result.
発表言語 英語
発表者名 藤川　紘晃
指導教員名 小濱　芳允　准教授
発表題目（英語） Investigating the effects of spin-orbit coupling and ferroelectricity on inorganic Germanium iodide perovskite
要旨（英語） Recently, metal halide perovskites caught attention as promising candidates for next-generation solar cells. Among them, a ferroelectric semiconductor, CsGeI3, possesses several unique properties. This material exhibits a spontaneous polarization of 20 μC/cm2, which is comparable to that of BaTiO3: 26 μC/cm2[1], and retains a relatively low band gap energy ~1.6 eV at room temperature unlike other ferroelectric materials [2]. In relation to these properties, band topology-induced phenomena have been predicted. The Rashba-Dresselhaus effect due to the spin-orbit coupling and the lack of the inversion symmetry is one of the predicted phenomena, where the Rashba splitting will occur at the conduction band minimum with the Rashba coefficient of ~ 0.93 eV・Å[3] (ex. BiTeI: 3.85 eV・Å[4]).

In this research, I investigate the influence of ferroelectricity and spin-orbit coupling on the band topology of CsGeI3 via spectroscopy under high magnetic fields. A key physical phenomenon in my experiments is the formation of Landau levels – discrete energy levels resulting from quantized cyclotron motion in magnetic fields. The observed field dependence of these energy levels enables us to estimate the effective mass of carriers and the effect of spin-orbit coupling. In this presentation, I will show the recent progress of my research.

[1] Y. Zhang et al., Sci. Adv. 8, eabj5881 (2022).
[2] R. Chen et al., J. Phys. Chem. C 127, 635–641 (2023).
[3] A. Popoola et al., J. Phys. Chem. C 128, 17806–17812 (2024).
[4] K. Ishizaka et al., Nat. Mater. 10, 521–526 (2011).
発表言語 日本語
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