応用物理学輪講 I
12月6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
2024年12月6日（金）16：50～18：50

Aグループ

座長
服部　航平
指導
教員名
有田　亮太郎　教授
座長
花田　達希
指導
教員名
平山　元昭　特任准教授
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） Magneto-optical experiments on promising perovskite solar cell material CsGeI3
要旨（英語） Magneto-optical measurements are powerful tools for determining crucial physical parameters relevant to solar cell applications. Measuring transmission or reflectivity spectrum under strong magnetic fields enables the determination of the exciton’s binding energy and the effective mass of carriers.
One of the halide perovskites, CsGeI3 emerges as a promising candidate for a solar cell absorption layer. A distinguishing feature of CsGeI3 from other perovskites is its ferroelectricity. Its strong ferroelectricity (spontaneous polarization: 20 µC/cm2) makes it difficult to form excitons.
However, this property could be advantages for solar cell applications, as reduced excitons lead to increased free carriers, although experimental measurement of excitons remains difficult.
In this presentation, I will present experimental methods and recent progress on this study.
発表言語 日本語
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 Toword 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 本田　和大
指導教員名 中村　泰信　教授
発表題目（英語） Investigating Annealing Effects on Josephson Junctions using the Merged-Element Transmon Qubit
要旨（英語） The transmon qubit is a simple nonlinear LC circuit composed of a Josephson junction (JJ) and a capacitor, which has been fundamental in quantum information research. Through intensive research efforts, the coherence time, which represents the qubit lifetime, has been steadily improving, reaching a level where it is now limited by material defects and quasiparticle tunneling phenomena. Consequently, recent attention has shifted toward understanding how material properties and manufacturing processes of qubit components affect their performance.
The Merged-element transmon qubit serves as an excellent research platform for better understanding the properties of Josephson junctions. By actively utilizing the intrinsic capacitance of the Josephson junction while minimizing the contribution of the shunt capacitance, the quality of the Josephson junction strongly influences the qubit's performance. Previous studies have investigated the effects of device annealing and explored alternative barrier materials beyond conventional aluminum oxide. In this presentation, I will explain the mergemon device design for
systematically investigating annealing effects and the expected improvements through annealing.
発表言語 日本語

Bグループ

座長
原田　潤
指導
教員名
芦原　聡　教授
発表者名 本多　健亮
指導教員名 芦原　聡　教授
発表題目（英語） Design of a Broadband, High-Resolution FTIR System for CO2 Jet Pump-Probe Spectroscopy
要旨（英語） Molecular vibration control is increasingly recognized as a promising method for steering chemical reactions. Mid-infrared pulses can selectively excite specific vibrational modes, thereby imparting energy to reactions of interest. This research aims to elucidate the relationship between molecular vibrational modes and chemical reaction efficiency, focusing on the conversion of CO₂ into HCOO.

In the experiment, a CO₂ molecular jet is introduced into a vacuum chamber, vibrationally excited using a mid-infrared pulse, and then collides with H atoms adsorbed on a Cu surface, facilitating its conversion to HCOO. Observing the vibrational modes of the CO₂ molecular jet is crucial for understanding the connection between vibrational excitation and conversion efficiency. This is achieved through pump-probe experiments.

For these experiments, a spectrometer with a wavelength range of 4 µm to 5 µm and a resolution of 0.05 cm⁻¹ is essential. This presentation will discuss the design and development of a high-resolution FTIR system tailored for CO₂ jet pump-probe spectroscopy, along with future perspectives of this study.
発表言語 日本語
発表者名 政岡　凜太郎
指導教員名 渡辺　悠樹　准教授
発表題目（英語） Rigorous lower bound of dynamic critical exponents in critical frustration-free systems
要旨（英語） Frustration-free systems are theoretically tractable quantum systems characterized by ground states that minimize all local terms in the Hamiltonian simultaneously. For gapped phases, frustration-free systems have been successful as models that approximate general systems. In contrast, for gapless systems, the assumption of frustration-freeness imposes significant constraints on their phase properties. While typical gapless systems exhibit dynamic critical exponent z = 1, all known examples of gapless frustration-free systems satisfy z >= 2.

In our study, we rigorously demonstrate, under certain technical assumptions about correlation functions, that the inequality z ≥ 2 holds based on the detectability lemma. This result ensures the unique nature of gapless frustration-free systems and establishes a no-go theorem for constructing frustration-free systems with z < 2.

Additionally, we discuss the notable connection between frustration-free systems and Markov processes. It is known that Markov processes which describe standard relaxation to equilibrium states can be mapped onto frustration-free systems. The inequality z>=2, long recognized but unproven in non-equilibrium statistical physics, finds a rigorous foundation through our quantum framework.
発表言語 日本語
発表者名 八木　春樹
指導教員名 Gong Zongping　准教授
発表題目（英語） Introduction and Recent Advances in Generalized Symmetries
要旨（英語） Symmetries play a pivotal role in theoretical physics, engendering profound implications such as conservation laws, eigenvalue degeneracies, and the classifications of quantum phases. In recent years, the study of generalized symmetries has emerged as a critical area of focus within condensed matter and particle physics, proposing that global symmetries in quantum field theories can be effectively conceptualized as topological defects.

A seminal body of work from a decade ago catalyzed the burgeoning interest in this area by introducing higher-form symmetries, thereby broadening the conventional constraints associated with the application of symmetries and their corresponding objects. This theoretical framework continues to rely fundamentally on group theory, akin to classical symmetry investigations. However, the advent of non-invertible symmetries three years prior marked a paradigm shift. These symmetries are articulated through category theory, a framework in which symmetry operations are not necessarily reversible. Although the implications of such symmetries have been recognized in lower-dimensional quantum field theories (QFTs), recent scholarly endeavors have substantially enhanced our comprehension of these phenomena in d≥3 QFTs.

The aim of this talk is to provide a brief introduction to the concept of generalized symmetries and to review the trajectory of recent advances in this domain.
発表言語 日本語
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