|氏名： 津坂 裕己
指導教員名： 芦原 聡 教授
発表題目（英語）： Vibrational ladder climbing with shaped mid-infrared pulses: Toward bond-selective control of chemical reactions
要旨（英語）： The mid-infrared (mid-IR) range of the spectrum corresponds to energies associated with molecular vibrations. Mid-IR ultrashort laser technologies have enabled multi-quantum vibrational excitation (or vibrational ladder climbing), and have opened a way to mode-selective control of chemical reactions. Deposition of sufficient energy into molecular vibrations participating in the reaction coordinate via IR laser excitation can promote a specific reaction while leaving the surrounding molecules undisturbed .
In such vibrational control of chemical reactions, the waveform of the mid-IR pulsed field has an important role in efficiently exciting molecular vibrations into higher lying states. In this study, we numerically investigate the optimal waveform of the mid-IR pulse for vibrational ladder climbing based on Liouville von-Neumann equation. In this presentation, we will discuss the simulation results with our future plans to experimentally demonstrate vibrational ladder climbing with shaped mid-IR pulses.
 K. Heyne and O. Ku?hn, J. Am. Chem. Soc. 141, 11730 (2019).
|氏名： 西澤 葉
指導教員名： 賀川 史敬 准教授
発表題目（英語）： Phase transition dynamics simulations using Phase-Field method
要旨（英語）： Phase transition process has been studied for a long time around the world. However, there are to be known about it. For example, it is known that there are growth-dominated process and nucleation-dominated process in transitions at metastable states. Which of the 2 process appear according to the condition like volume or temperature is still unclear.In this presentation, how the transition undergoes is shown under constant cooling condition in simple system using Phase-Field numerical simulation method. Phase-Field method has been widely used to simulate the solidification of various material. It can be used to show even quantitative crystallization or complex solidification like dendrite crystals.The results shown that volume and cooling rate have strong impact on the transition process. In small volume regions, the ratio of the volume and cooling rate define the process. Larger volume and smaller cooling rate result in finished growth-dominated phase transition and the inverse condition results in unfinish of transition (realization of metastable states in zero temperature). In large volume regions, the effects of volume vanish and the cooling rate define the process. The smallest cooling rate results in growth-dominated process and the larger results in nucleation-dominated process. The more larger results in unfinish of transition. In addition, in the moderate volume regions, the 2 features are mixed and complex volume/cooling rate dependence can be observed.
|氏名： 中津 裕貴
指導教員名： 福谷 克之 教授
発表題目（英語）： Development of Spin-Polarized Atomic Hydrogen source
要旨（英語）： The hydrogen atom consists of an electron and a proton, each of which has a spin1/2. The hydrogen atom exists in spin singlet and triplet states under the zero magnetic field, but the degeneracy can be resolved with a magnetic field. By using a hexapole magnet, we can select the particular spin states of the hydrogen atom. The purpose of our study is to develop a Spin-Polarized Atomic Hydrogen source (SPH) and then we can use SPH to understand the surface magnetic structure through comparing the spin polarization before and after SPH scattering. Furthermore, SPH will reveal the mechanism how hydrogen molecules are formed on surfaces and the interaction between the nuclear spin of hydrogen atoms and surfaces. In this presentation, I will talk about how to generate and detect SPH and our recent study about the reaction of toluene and hydrogen atoms, and future plans for the development of SPH.
|氏名： 花村 文哉
指導教員名： 古澤 明 教授
発表題目（英語）： Evaluation of non-Gaussianity of cubic phase measurement
要旨（英語）： Cubic phase gate, which is a non-Gaussian operation, plays an important role in optical quantum information processing. An experimental method to implement cubic phase gate using an ancillary state called cubic phase state has been proposed. This method consists of Gaussian operations and a non-Gaussian measurement("cubic phase measurement") of quadratures.
We implemented an approximated version of cubic phase measurement, using a superposition of vacuum and single photon as an ancillary state.
Non-Gaussianity of the measurement was evaluated by experimentally obtaining the Q function of POVM elements, and calculating nonlinear squeezing of them.
In this presentation, I will talk about these methods in detail.
 K. Miyata, et al., PRA 93, 022301 (2016).
|氏名： 二階堂 圭
指導教員名： 長谷川 達生 教授
発表題目（英語）： Control of Layered Structure and TFT Characteristics of Organic Semiconductor, PE-BTBT-Cn
要旨（英語）： Layered crystallinity of organic semiconductors plays an important role in high-performance thin film transistors (TFT), and substituting molecules by substituents such as alkyl chains is useful for the enhancement of layered crystallinity. 2-alkyl-7-phenylethynyl-benzothieno[3,2-b]benzothiophene (PE-BTBT-Cn) is a new rodlike organic semiconducting molecule, with the alkyl chain and the sufficiently long phenyl ethynyl group as substituents. PE-BTBT-Cn exhibits characteristically different layered structures depending on its alkyl chain length; the molecules of n = 8, 10, 12 show the bilayered structures like lipid layers, whereas n = 6 exhibits disordered single layered structure in which the long axis of molecules are not aligned.
Compared to molecules of n = 8, 10, 12, the TFT mobility of the single crystalline film of n = 6 was lower due to the disordered structure. However, the mobility of n = 6 was improved by mixing with a small amount of n = 12. This result indicates a drastic change in the layered structure. Next, to elucidate the origin of different layered structures, thermal analyses by differential scanning calorimetry (DSC) and powder X-ray diffraction in high temperature were performed. These measurements revealed that the layered structures of PE-BTBT-Cn are strongly correlated with the emergence of smectic E (SmE) phase, one of the liquid crystalline phases with highly ordered layered structure, in high temperature. Moreover, DSC measurements on mixtures of n = 6 and n = 12 indicated that the disordered structure of n = 6 is likely to be a state quenched from SmE phase. Based on these results, I will discuss the competition and the correlation between SmE phase and layered crystals.
|氏名： 馬場 正太郎
指導教員名： 中村 泰信 教授
発表題目（英語）： Flat and broadband Josephson parametric amplifier for single-shot measurement of superconducting qubits
要旨（英語）： A standard way to measure qubit states is a reflection measurement of a resonator coupled to qubit. This protocol is good because of small measurement back action and protection of qubit decoherence by readout resonators, but the low signal-to-noise ratio(SNR) is the problem. To improve SNR and measure qubits by one pulse, low noise and high gain amplifier is needed. For this purpose, the Josephson parametric amplifier(JPA) has been used.
To develop a fault-tolerant quantum computer with many superconducting qubits, one big issue to be solved is how to control many qubits in the dilution refrigerator and decrease the number of room temperature control instruments. Frequency-multiplexed qubit readout is one solution to tackle this problem. The bandwidth of JPA is too narrow for this purpose, so broadband JPA is needed for frequency-multiplexed qubit readout.
Two approaches are reported to construct broadband JPAs. One is to achieve impedance matching between JPA and the outside world coupled to JPA[1,2]. The other is to use a nonlinear transmission line with many Josephson junctions.
In this presentation, I will explain the operation and the impedance matching of JPAs and show how to extend the impedance matching of JPAs and widen the flat gain regime.
T.Roy et al., Appl. Phys. Lett. 107, 262601 (2015).
J.Y.Mutus et al., Appl. Phys. Lett. 104, 263513 (2014).
C.Macklin et al., Science 350, 307 (2015).