応用物理学輪講 I
12月8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
2023年12月8日(金)16:50~18:50

Aグループ

座長
坪内 健人
指導
教員名
沙川 貴大 教授
座長
長瀨 理仁
指導
教員名
沙川 貴大 教授
発表者名 平﨑 雄太
指導教員名 齊藤 英治 教授
発表題目(英語) Detection of temporal fluctuation in superconducting qubits for quantum error mitigation
要旨(英語) We have investigated instability of a superconducting quantum computer by continuously monitoring the qubit output. We found that qubits exhibit a step-like change in the error rates. This change is repeatedly observed, and each step persists for several minutes. By analyzing the correlation between the increased errors and anomalous variance of the output, we demonstrate quantum error mitigation based on post-selection. We have reduced the errors from 5.4% to 1.6% in a Bell state measurement and from 17.5% to 12.0% in a quantum volume circuit. Numerical analysis on the proposed method was also conducted.
発表言語 日本語
発表者名 平田 裕也
指導教員名 齊藤 英治 教授
発表題目(英語) Nonlinear transport in helical system
要旨(英語) In crystals with sufficiently broken symmetry, nonlinear transport phenomena are allowed to occur. As for electron transport, itinerant electrons can sense inversion symmetry breaking of unit crystal lattice through spin-orbit interaction (SOI). Particularly, helical environment induced SOI have gained attention in recent years. In helical lattice structure, the electron hopping accompanies spin-flip due to the conservation of local angular momentum, which leads to peculiar type of SOI and energy band splitting among (L,S) levels.

In our research, we control the energy bands of thin-film Te, a helical semiconductor, via chirality, gate voltage and magnetic field, to investigate its nonlinear thermal response. In this presentation, we will discuss the origin of these phenomena and experimental strategies to observe nonlinear thermoelectric transport.
発表言語 英語
発表者名 町永 明海
指導教員名 武田 俊太郎 准教授
発表題目(英語) High-rate generation of optical non-Gaussian quantum states by generalized photon subtraction
要旨(英語) An optical Schrodinger's cat state is one of the important non-Gaussian quantum states in the field of optical quantum information processing with continuous variables. Generating cat states at high rates is a supreme challenge in this field. We show both theoretically and experimentally that generalized photon subtraction can improve the generation rate by a factor of several to several tens of times compared to conventional methods. I will present these achievements.
発表言語 英語

Bグループ

座長
千葉 速樹
指導
教員名
香取 秀俊 教授
座長
陳 遥知
指導
教員名
小芦 雅斗 教授
発表者名 原田 潤
指導教員名 芦原 聡 教授
発表題目(英語) Vibrational ladder climbing of carbon dioxide in an ionic liquid
要旨(英語) By strongly exciting molecular vibrations using infrared pulses, it is possible to control chemical reactions, such as selectively breaking and forming chemical bonds [1]. Recently, we have successfully demonstrated driving of liquid-phase molecular dissociation by employing plasmonic near-fields of mid-IR pulses on a metal surface [2].

The electrochemical carbon dioxide reduction reaction (ERR) is one of the hopeful applications of vibrational excitation, which is an essential pathway to solve global warming. It has been theoretically suggested that ERR can be promoted by vibrational excitation [3]. In this study, we demonstrated to reach a high vibrational level by ladder climbing excitation of molecules in an ionic liquid using infrared femtosecond pulses. In this presentation, we will report on the results of infrared pump-probe spectroscopy experiments.

[1] K. Heyne, O. Kuhn, J. Am. Chem. Soc. 141, 11730(2019)
[2] I. Morichika, K. Murata, A. Sakurai, K. Ishii, and S. Ashihara, Nat. Commun. 10, 3893 (2019).
[3] A. lvarez et al., Chem. Phys. Chem. 18, 3135 (2017).
発表言語 日本語
発表者名 肥田 宏太郎
指導教員名 中村 泰信 教授
発表題目(英語) Flux-trapping fluxonium
要旨(英語) Among many types of superconducting qubits, the fluxonium qubit is a promising candidate for the physical realization of a superconducting quantum computer thanks to its long coherence time and large anharmonicity
at its optimal operation point, called the sweet spot.

The main obstacle to scaling up fluxonium is the necessity of external flux bias. It is required to realize its sweet spot but leads to a lot of problems such as wiring overhead and crosstalk.

To solve this issue, we focused on fluxoid quantization. In this presentation, I will introduce the flux-trapping fluxonium, which can realize its sweet spot without external flux bias thanks to fluxoid quantization inside its superconducting ring.
発表言語 英語