Fabrication and measurement of a niobium persistent current qubit

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.Includes bibliographical references (p. 192-201).Recent successes with superconducting Josephson junction qubits make them prime candidates for the implementation of quantum computing. This doctoral thesis details the study of a niobium Josephson junction circuit for quantum computing applications. The thesis covers two main areas: 1) the fabrication of sub-micron niobium Josephson junction devices using a Nb/Al/A1Ox/Nb trilayer process and 2) measurements of unique quantum properties of a superconducting device proposed as a quantum bit--the Persistent Current (PC) qubit. The thesis discusses the fabrication of niobium Josephson junction devices which is integral to the design and measurement of the circuit. The devices were fabricated at MIT Lincoln Laboratory using optical projection lithography to define features. A technique to produce more uniform critical-current densities across a wafer is developed within the scope of the thesis. We also introduce experimental work on the PC qubit performed at dilution refrigerator temperatures (T [approximately] 12mK). Microwave spectroscopy was used to map the energy level separation between macroscopic quantum states of the qubit system. We measured the intrawell energy relaxation time [tau]d between quantum levels in this particular device. The intrawell relaxation measurements are important in determining whether a promising decoherence time can be achieved in Nb-based Josephson devices, which has a more mature fabrication process compared to other superconducting fabrication processes.by Daniel Yuki Nakada.Ph.D

Significant contribution of subseafloor microparticles to the global manganese budget

Ferromanganese minerals are widely distributed in subseafloor sediments and on the seafloor in oceanic abyssal plains. Assessing their input, formation and preservation is important for understanding the global marine manganese cycle and associated trace elements. However, the extent of ferromanganese minerals buried in subseafloor sediments remains unclear. Here we show that abundant (108–109 particles cm−3) micrometer-scale ferromanganese mineral particles (Mn-microparticles) are found in the oxic pelagic clays of the South Pacific Gyre (SPG) from the seafloor to the ~100 million-year-old sediments above the basement. Three-dimensional micro-texture, and major and trace element compositional analyses revealed that these Mn-microparticles consist of poorly crystalline ferromanganese oxides precipitating from bottom water. Based on our findings, we extrapolate that 1.5–8.8 × 1028 Mn-microparticles, accounting for 1.28–7.62 Tt of manganese, are globally present in oxic subseafloor sediments. This estimate is at least two orders of magnitude larger than the manganese budget for nodules and crusts on the seafloor. Subseafloor Mn-microparticles thus contribute significantly to the global manganese budget.This study was supported in part by the Japan Society for the Promotion of Science (JSPS) Strategic Fund for Strengthening Leading-Edge Research and Development (to JAMSTEC and F.I.), the JSPS Funding Program for Next Generation World-Leading Researchers (GR102 to F.I.), JSPS Grant-in-Aid for Scientific Research (24687004 and 15H05608 to Y.M., 25871219 to G.-I.U., 15H02810 to R.W., 18H04134, 17H06458 and 17H04582 to Y.T., and 26251041 to F.I.), JSPS Grant-in-Aid for JSPS Fellows (14J00199 to G.-I.U.), and Ministry of Education, Culture, Sports, Science, and Technology (MEXT) Fund Leading Initiative for Excellent Young Researchers (to Kochi University and G.-I.U.)

Mitochonic Acid 5 (MA-5) Facilitates ATP Synthase Oligomerization and Cell Survival in Various Mitochondrial Diseases

Mitochondrial dysfunction increases oxidative stress and depletes ATP in a variety of disorders. Several antioxidant therapies and drugs affecting mitochondrial biogenesis are undergoing investigation, although not all of them have demonstrated favorable effects in the clinic. We recently reported a therapeutic mitochondrial drug mitochonic acid MA-5 (Tohoku J. Exp. Med., 2015). MA-5 increased ATP, rescued mitochondrial disease fibroblasts and prolonged the life span of the disease model “Mitomouse” (JASN, 2016). To investigate the potential of MA-5 on various mitochondrial diseases, we collected 25 cases of fibroblasts from various genetic mutations and cell protective effect of MA-5 and the ATP producing mechanism was examined. 24 out of the 25 patient fibroblasts (96%) were responded to MA-5. Under oxidative stress condition, the GDF-15 was increased and this increase was significantly abrogated by MA-5. The serum GDF-15 elevated in Mitomouse was likewise reduced by MA-5. MA-5 facilitates mitochondrial ATP production and reduces ROS independent of ETC by facilitating ATP synthase oligomerization and supercomplex formation with mitofilin/Mic60. MA-5 reduced mitochondria fragmentation, restores crista shape and dynamics. MA-5 has potential as a drug for the treatment of various mitochondrial diseases. The diagnostic use of GDF-15 will be also useful in a forthcoming MA-5 clinical trial