応用物理学輪講 I
7月5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7月5日（金）16：50～18：50

Aグループ

座長
池原　至恩
指導
教員名
武田　俊太郎　准教授
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） Theoretical proposal for realization of the waveform-controllable quantum light source
要旨（英語） Highly non-classical quantum states of light, such as single-photon states and Schrodinger's cat states, are indispensable for realizing quantum information processing that is classically computationally difficult. To achieve faster and more precise processing, it is necessary to prepare quantum states with appropriate temporal waveforms for each application. However, typically, the waveform of quantum states generated by the heralding schemes with a photon detector was determined by the system's characteristics, such as a cavity. Therefore, we had to recompose the setup to generate quantum states with different waveforms. Against this background, we have devised a scheme to programmatically shape the waveforms by intensity-modulating the light toward the photon detector in front of the cavity. In this presentation, I will explain the theory of this scheme.
発表言語 英語
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 by using infrared femtosecond pulses
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]. Previously, 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]. Aiming at promoting ERR, in this study, we’ll show the trial of ladder climbing excitation of molecules in liquid phase by using infrared femtosecond pulses.
発表言語 日本語
発表者名 三島　萌登
指導教員名 小芦　雅斗　教授
発表題目（英語） Evaluation of Entanglement Purification Protocols in Distributed Quantum Computing Using Surface Codes
要旨（英語） In quantum computing with quantum error correction, an increasing number of qubits are required to reduce logical error rates. Building a large-scale system with a large number of qubits, however, presents significant challenges. Distributed quantum computing addresses this issue by allocating a small number of qubits at each node and connecting these nodes via entanglement. Typically, generating pure entangled states is challenging, therefore, entanglement purification is employed, in which extracts a few purer entangled states from many noisy ones. A major challenge in entanglement purification is the necessity for postselection, which can induce decoherence in other entangled states and qubits when output states are postselected. This study introduces a scheme in which postselection is not used, so all output states are utilized. We analyze scenarios in which entanglement purification is applied to physical Bell pairs, and all the output states are used for syndrome measurements in surface codes. Then we propose a figure of merit for entanglement purification protocols based on their impact on the logical error rates of surface codes. Numerical calculations demonstrate that the figure of merit is closely related to the logical error rates.
発表言語 日本語

Bグループ

座長
石原　由貴
指導
教員名
Max　Hirschberger　准教授
発表者名 井ノ上　慎一
指導教員名 中村　泰信　教授
発表題目（英語） Frequency collision analysis of coupler-driven two-qubit gate outside the straddling regime
要旨（英語） The coupler-driven two-qubit gate approach has recently been proposed as an alternative scheme to avoid frequency collisions, a known issue with the traditional transmon two-qubit gate scheme. The proposed scheme requires a high-intensity drive but circumvents the constraints of what is known as the "straddling regime", showing high resilience to frequency collisions in small-scale systems.

We have numerically shown that the proposed gate, the coupler-assisted-swap (CAS) gate, achieves significantly higher parameter flexibility than traditional gates in a three-qubit system.
However, we also found several higher-order frequency collisions that could limit the parameter flexibility of our gate.

In this presentation, we will attempt to quantify the conditions of frequency collisions through numerical and semi-analytical approaches.
We will then show how the higher-order collisions affect qubit parameter allocation in large-scale systems based on our scheme.
発表言語 日本語
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） Inverse magneto-conductance design by automatic differentiation
要旨（英語） Electrical conductance of quantum wires exhibits complicated patterns as a function of external magnetic fields, which result from the quantum interference of conduction electrons. These patterns are directly connected to microscopic structures in the quantum wire, such as defects or potential distributions. In this study, we introduce an inverse design framework method that determines the microscopic structures based on specific magneto-conductance patterns. We demonstrate that our framework accurately identifies defects and can be effectively applied to various complicated patterns. Additionally, we discuss techniques for designing structures that facilitate experimental investigation.
発表言語 英語
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） Chiral Thermoelectricity
要旨（英語） Since the Bloch wave packets in chiral crystals satisfy screw symmetry, "pseudo-angular momentum (PAM)" is conserved. Previously, only the orbital PAM was considered, but by including spin PAM in the calculations, it is possible to explain a new type of band splitting in chiral crystals. This band split can work as a PAM matching filter at the chiral-achiral interface. As a result, an extremely high conduction electron spin polarization rate is realized in chiral crystals. This effect is called "Chirality-Induced-Spin-Selectivity (CISS)", which enables nonreciprocal transport via Zeeman coupling. In this study, we tried to measure the combination effect with CISS and thermoelectric conversion to observe nonreciprocal thermoelectric phenomena. We will introduce the measurement results in chiral thermoelectric material Te in this presentation.
発表言語 英語
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