応用物理学輪講 I
12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
2021年12月17日(金)16:50〜

Aグループ

座長
松井 彬
指導
教員名
有田 亮太郎 教授
座長
松澤 郁也
指導
教員名
福谷 克之 教授
発表者名 渡辺 友太
指導教員名 有田 亮太郎 教授
発表題目(英語) Quantum and temperature effects on crystal structure of superhydride: A path integral molecular dynamics study
要旨(英語)  Superhydrides are attracting attention as high Tc superconductor candidates. One of those materials, LaH10, exhibits superconductivity with Tc of 250 K under high pressure. In previous study, quantum nuclear fluctuation was found to be symmetrize the predicted crystal structure which varied from the crystal structure observed experimentally. We considered that adding temperature effect on top of the quantum effect is meaningful since temperature is one of the controllable parameters. We found that both the classical and quantum fluctuation can symmetrize the crystal structure by our PIMD calculations. We also performed the simulations on YH10, which is expected to have higher Tc than LaH10. Through our calculations, we found that quantum effect lengthen the H-H bond length in both materials.
発表言語 日本語
発表者名 胡 耀宗
指導教員名 渡辺 悠樹 准教授
発表題目(英語) The isolated Heisenberg magnet as a quantum time crystal
要旨(英語)  As we all know, spontaneous symmetry breaking is a very important concept in many-body physics, which describes the system would be in a state that does not have the symmetry of this systems' Hamiltonian. The most typical example is so-called space crystal, whose density varies periodically with spatial coordinates, breaking the spatial translation symmetry of Hamiltonian. Since time and space have corresponding places in Lorentz symmetries, it is natural to suppose that such a multi-body system may exist, whose physical properties change periodically with time, breaking the symmetry of time translation. This type of systems is called time crystals. This concept was first proposed by Wilczek in 2012.
 In this seminar, I will talk about a theoretical work by Marko Medenjak, Berislav Bu, and Dieter Jaksch. They propose an isolated system under quantum quench as a possible candidate for time crystals. This is a system that everyone is familiar with: XXZ Spin-1/2 chain. The authors demonstrate the feasibility of this model as time crystal from analytical and numerical works by analyzing the ‘extensive dynamical symmetry’ in the model.
発表言語 英語
発表者名 黄 驤
指導教員名 中野 匡規 特任准教授
発表題目(英語) Interlayer-space engineering of van der Waals layered materials
要旨(英語)  Compared with their conventional 3D counterparts, matters’ properties exhibit intriguing changes when their dimension is reduced.
 Among the huge varieties of low-dimension, and low-dimension-like systems, the family of transition metal dichalcogenides (TMDCs) – a kind of van der Waals (vdWs) layered materials, attract many researchers’ interest.
 The members of TMDCs family share similar structures, but with a spectrum of different properties, including insulators, semiconductors, semimetals, superconductors, etc. This provides us a good platform to study the physical properties with relatively controlled and tunable parameters.
 In this study, we focus on intercalating heavy transition metals into the interlayer-space of TMDCs – their vdWs gap, using the technique of molecular beam epitaxy (MBE). And to make the system thin enough to approach the 2D limitation.
発表言語 英語
発表者名 大島 敦史
指導教員名 石坂 香子 教授
発表題目(英語) Study of electronic structure of ternary palladates CaPd3O4 and effect of La doping.
要旨(英語)  CaPd3O4 is a candidate material for narrow-gap semiconductors and insulator-to-metal transitions have been reported to occur under a wide range of hole-dopant(such as Na, Li) levels. When doped with carriers, this material is also expected to have high thermoelectric effect.
 In this presentation, I will focus on La-doped CaPd3O4 and I will show transport experiments and angle-integrated photoemission studies of La-doped CaPd3O4.
発表言語 日本語

Bグループ

座長
堀 智洋
指導
教員名
十倉 好紀 卓越教授
座長
増木 亮太
指導
教員名
有田 亮太郎 教授
発表者名 米津 和真
指導教員名 武田 俊太郎 准教授
発表題目(英語) Continuous-variable entangled state generation by a programmable dual-loop photonic circuit
要旨(英語)  In a quantum computer, quantum operations are performed for the input states. In a conventional method using light, input light sources and optical elements are arranged in space. However, this method has some problems. Firstly, it is not scalable. As the number of inputs increases, more light sources are required. Also, when executing a large number of steps, a large number of optical elements are required. That means that it is so difficult to make a large-scale quantum computer by this conventional method. Secondly, it is not programable. To execute different gates, it is required to rebuild the photonic circuit. To solve these problems, an optical quantum computing architecture based on a dual-loop circuit was proposed. This circuit is scalable and programable. It is known that this dual-loop circuit can perform arbitrary beam splitter operations. In this experiment, we constructed this dual-loop circuit and are aiming to demonstrate that it can perform arbitrary beam splitter operations through the evaluation of entangled states generated by these operations.
発表言語 英語
発表者名 何 若凡
指導教員名 古澤 明 教授
発表題目(英語) Real-time Photon Number Resolving using FPGA
要旨(英語)  For realizing optical quantum information processing,
Photon-Number-Resolving-Detector (PNRD) which can count photons in optical pulse is key component because PNRD can be used for non-Gaussian state preparation which required for input state and ancilla state of optical quantum computer for example. For this purpose, any state must be prepared on demand of computation. Therefore, PNRD should have real-time detection capability.
 Currently known PNRD methods, such as Transition Edge Sensor (TES) and Superconducting Nanostrip Photon Detector (SNSPD), need subsequently signal processing to extract Photon Number information from output waveshape. Therefore, to realize real-time PNRD, ultra-fast and low-latency signal processing unit is essential. Field Programable Gate Array (FPGA) which have user editable logic circuit is one solution because of its capability to fulfill both criteria. Here, I have done proof of concept as following. First, I did an experimental implementation of waveshape processing algorithm on FPGA for TES. Second, I conducted a validation of FPGA with real TES signal.
 In the presentation, I will talk about these results.
発表言語 英語
発表者名 JEONG Byung Kyu
指導教員名 古澤 明 教授
発表題目(英語) Development of broadband, long-lived optical quantum memory
要旨(英語)  In measurement-based quantum computing, quantum memory is an effective tool of generating non-deterministic entangled states at a high rate. Especially for optical quantum computing, cavity-based quantum memory is being widely used. However, previous methods bear a critical trade-off between storage time and bandwidth. Both variables depend on the reflectance of cavity mirrors, where high reflectance leads to narrow bandwidth, and low reflectance leads to short storage time.
 In this presentation, a method to circumvent this trade-off will be suggested. Variable reflectance of the shutter cavity is realized by replacing the output mirror for a polarization beam-splitter, and real-time modulation of polarization with a Pockels cell.
発表言語 英語