Problem-specific Parameterized Quantum Circuits of the VQE Algorithm for Optimization Problems

The Variational Quantum Eigensolver (VQE) algorithm is attracting much attention to utilize current limited quantum devices. The VQE algorithm requires a quantum circuit with parameters, called a parameterized quantum circuit (PQC), to prepare a quantum state, and the quantum state is used to calculate the expectation value of a given Hamiltonian. Creating sophisticated PQCs is important from the perspective of the convergence speed. Thus, we propose problem-specific PQCs of the VQE algorithm for optimization problems. Our idea is to dynamically create a PQC that reflects the constraints of an optimization problem. With a problem-specific PQC, it is possible to reduce a search space by restricting unitary transformations in favor of the VQE algorithm. As a result, we can speed up the convergence of the VQE algorithm. Experimental results show that the convergence speed of the proposed PQCs is significantly faster than that of the state-of-the-art PQC

Synthesis and cationic polymerization of halogen bonding vinyl ether monomers

Halogen bonding is rapidly becoming recognized as a viable and useful intermolecular interaction in supramolecular chemistry. While various monomers amenable to radical polymerization methods containing halogen bonding donors have been developed, this study aims to expand the type of monomers that incorporate this intermolecular interaction to facilitate use of cationic polymerization by developing three novel vinyl ether monomers containing halogen bonding donor moieties: 2, 3, 5, 6-tetrafluoro-4-iodophenoxyethyl vinyl ether (C2I), 2, 3, 5, 6-tetrafluoro-4-iodophenoxybutyl vinyl ether (C4I), and 2-(2, 3, 5, 6-tetrafluoro-4-iodophenoxyethoxy)ethyl vinyl ether (O3I). Well controlled cationic polymerization is achievable through the use of a proton trap, 2, 6-di-tert-butylpyridine. The use of SnCl4 as a co-Lewis acid was found to accelerate the reaction. Between the three monomers, the difference in the chain length is shown to influence the reaction rate, with the longest chain demonstrating the fastest polymerization. Initial studies of the halogen bonding ability shows that halogen bonding exists for all three monomers but is most pronounced in C4I. The polymerized vinyl ethers also exhibit halogen bonding. Due to the ease of synthesis and polymerization, these are promising new monomers to increase functionality available for polymers synthesized using cationic polymerization

高原子価コバルト触媒を用いたC-H官能基化反応の開発

学位の種別: 課程博士審査委員会委員 : （主査）東京大学教授 金井 求, 東京大学教授 内山 真伸, 東京大学講師 尾谷 優子, 東京大学講師 占部 大介, 東京大学講師 宮本 和範University of Tokyo(東京大学

意図・行為・理由 : 意図と理由の選言説に基づいて、行為の反因果説を擁護する

学位の種別: 課程博士審査委員会委員 : （主査）東京大学教授 野矢 茂樹, 東京大学教授 梶谷 真司, 東京大学准教授 古荘 真敬, 東京大学准教授 鈴木 貴之, 慶応義塾大学教授 柏端 達也University of Tokyo(東京大学

Evaluation of single silicon vacancy centers in nanodiamonds created by ion implantation at cryogenic temperatures

Silicon vacancy (SiV) centers in diamonds have attracted much attention because of their stability and narrow emission linewidth, and are promising for applications in quantum information technology. SiV-center-encapsulated nanodiamonds have also attracted much attention because of their potential to be coupled to various photonic devices. One efficient way to fabricate nanodiamonds that contain SiV centers is Si ion implantation into nanodiamonds. However, the evaluation of a single SiV center in a nanodiamond produced by this method at low temperatures has not been performed. In this study, we report on the optical properties of a single SiV center in a nanodiamond produced by ion implantation at cryogenic temperatures. The emission spectrum from a single SiV center (g²(0) = 0.19) was observed with four distinct fine splittings of the zero-phonon line (ZPL) at 4 K. At an excitation power of 50µW, the full width at half maximum of the ZPL reached the spectrometer resolution limit (0.09 nm). The temperature dependence of the emission peak is consistent with that of the emission coming from an SiV center under high strain. The results obtained in this work suggest that nanodiamonds containing single SiV centers formed using this method will be an important building block for the realization of quantum information applications

Quantum reservoir computing with repeated measurements on superconducting devices

Reservoir computing is a machine learning framework that uses artificial or physical dissipative dynamics to predict time-series data using nonlinearity and memory properties of dynamical systems. Quantum systems are considered as promising reservoirs, but the conventional quantum reservoir computing (QRC) models have problems in the execution time. In this paper, we develop a quantum reservoir (QR) system that exploits repeated measurement to generate a time-series, which can effectively reduce the execution time. We experimentally implement the proposed QRC on the IBM's quantum superconducting device and show that it achieves higher accuracy as well as shorter execution time than the conventional QRC method. Furthermore, we study the temporal information processing capacity to quantify the computational capability of the proposed QRC; in particular, we use this quantity to identify the measurement strength that best tradeoffs the amount of available information and the strength of dissipation. An experimental demonstration with soft robot is also provided, where the repeated measurement over 1000 timesteps was effectively applied. Finally, a preliminary result with 120 qubits device is discussed

Spontaneous Regression of Hepatocellular Carcinoma with Portal Vein Tumor Thrombus

An 83-year-old man underwent transcatheter arterial chemoembolization (TACE) for a 20-mm hepatocellular carcinoma (HCC) in Couinaud’s segment 4. Computed tomography (CT) 4 months after TACE showed tumor thrombus in the portal vein in addition to diffuse metastases and arterioportal shunts in the left lobe. Although we performed the best supportive care, the tumor thrombus in the portal vein and tumors in the left lobe had completely disappeared on CT 16 months after the TACE. Rapidly grown portal vein tumor thrombus and arterioportal shunt might be the causes of spontaneous regression of HCC, probably associated with tumor hypoxia