A5046424306- Quantum and electron transport phenomena
- Advancements in Semiconductor Devices and Circuit Design
- Semiconductor Quantum Structures and Devices
- Semiconductor materials and devices
- Surface and Thin Film Phenomena
- Interconnection Networks and Systems
- Quantum Computing Algorithms and Architecture
- Magnetic properties of thin films
- Molecular Junctions and Nanostructures
- Advanced Optical Network Technologies
- Quantum Information and Cryptography
- Graphene research and applications
- Software-Defined Networks and 5G
- GaN-based semiconductor devices and materials
- Nuclear physics research studies
- Quantum-Dot Cellular Automata
- Atomic and Molecular Physics
- Quantum Dots Synthesis And Properties
- Parallel Computing and Optimization Techniques
- 2D Materials and Applications
- Physics of Superconductivity and Magnetism
- ZnO doping and properties
- Astronomical and nuclear sciences
- Embedded Systems Design Techniques
- Radio Frequency Integrated Circuit Design
Tohoku University
1997-2025
RIKEN Center for Emergent Matter Science
2016-2025
Spintronics Research Network of Japan
2020-2025
Advanced Institute of Materials Science
2023-2025
Tokyo University of Agriculture and Technology
2023
Juntendo University Urayasu Hospital
2022
Tokyo Institute of Technology
2022
The University of Tokyo
2010-2019
RIKEN
2005-2019
Doshisha University
2019
Fault-tolerant quantum operation is a key requirement for the development of computing. This has been realized in various solid-state systems including isotopically purified silicon which provides nuclear spin free environment qubits, but not industry standard natural (unpurified) silicon. Here we demonstrate an addressable fault-tolerant qubit using double dot with micromagnet optimally designed fast control. optimized design allows us to achieve optimum Rabi oscillation quality factor Q =...
Cross sections of 1n-removal reactions from the neutron-rich nucleus Mg37 on C and Pb targets parallel momentum distributions residues target have been measured at 240 MeV/nucleon. A combined analysis these distinct nuclear- Coulomb-dominated reaction data shows that ground state has a small 1n separation energy 0.22−0.09+0.12 MeV an appreciable p-wave neutron single-particle strength. These results confirm lies near edge "island inversion" sizable halo component, heaviest such system...
We present the nuclear matrix element for neutrinoless double-beta decay of ^{48}Ca based on large-scale shell-model calculations including two harmonic oscillator shells (sd and pf shells). The excitation spectra ^{48}Ti, two-neutrino are reproduced in good agreement to experimental data. find that is enhanced by about 30% compared pf-shell calculations. This reduces lifetime almost a factor 2. matrix-element increase mostly due pairing correlations associated with cross-shell sd-pf...
Transition metal dichalcogenides (TMDs) exhibit unique properties and potential applications when reduced to one-dimensional (1D) nanoribbons (NRs), owing quantum confinement high edge densities. However, effective growth methods for self-aligned TMD NRs are still lacking. We demonstrate a versatile approach lattice-guided of dense, aligned MoS 2 NR arrays via chemical vapor deposition (CVD) on anisotropic sapphire substrates, without tailored surface steps. This method enables the synthesis...
We demonstrate fast universal electrical spin manipulation with inhomogeneous magnetic fields. With Rabi frequency up to 127 MHz, we leave the conventional regime of strong nuclear-spin influence and observe a spin-flip fidelity > 96%, distinct chevron pattern in spectral-time domain, resonance linewidth limited by frequency, not dephasing rate. In addition, establish z-rotations 54 MHz directly controlling phase. Our findings will significantly facilitate tomography error correction...
Tailoring spin coupling to electric fields is central spintronics and spin-based quantum information processing. We present an optimal micromagnet design that produces appropriate stray magnetic mediate fast electrical manipulations in nanodevices. quantify the practical requirements for spatial field inhomogeneity tolerance misalignment with spins, propose a scheme improve spin-rotation frequency (to exceed 50 MHz GaAs nanostructures). then validate our by experiments separate devices. Our...
We report on the first spectroscopy study of very neutron-rich nucleus (36)(12)Mg24 using direct two-proton knockout reaction 9Be(38Si,36Mg+gamma)X at 83 MeV/nucleon. The energy excited 2+ state 36Mg, E(2+(1)=660(6) keV, was measured. magnitude partial cross sections to ground and 2+(1) is indicative strong intruder admixtures in lowest-lying states as suggested by Monte Carlo shell-model calculations.
We extract the phase coherence of a qubit defined by singlet and triplet electronic states in gated GaAs triple quantum dot, measuring on timescales much shorter than decorrelation time environmental noise. In this non-ergodic regime, we observe that is boosted several dephasing times emerge, depending how stability extracted. elucidate their mutual relations, demonstrate they reflect noise short-time dynamics.
We demonstrate a new method for projective single-shot measurement of two electron spin states (singlet versus triplet) in an array gate-defined lateral quantum dots GaAs. The has very high fidelity and is robust with respect to electric magnetic fluctuations the environment. It exploits long-lived metastable charge state, which increases both contrast duration signal distinguishing outcomes. This allows us evaluate error spin-to-charge conversion separately. specify conditions under this...
The coherence of electron spin qubits in semiconductor quantum dots suffers mostly from low-frequency noise. During the past decade, efforts have been devoted to mitigate such noise by material engineering, leading substantial enhancement dephasing time for an idling qubit. However, role environmental during manipulation, which determines control fidelity, is less understood. We demonstrate qubit whose driven evolution limited high-frequency charge rather than quasistatic inherent any...
Zinc oxide (ZnO) has garnered much attention as a promising material for quantum devices due to its unique characteristics. To utilize the potential of ZnO devices, development fundamental technological elements such high-speed readout and charge sensing capabilities become essential. In this study, we address these challenges by demonstrating radio-frequency (rf) reflectometry in dots, thus advancing qubit applications. A device is fabricated on high-quality heterostructure, featuring...
To realize practical quantum computers, a large number of bits (qubits) will be required. Semiconductor spin qubits offer advantages such as high scalability and compatibility with existing semiconductor technologies. However, the increases, manual qubit tuning becomes infeasible, motivating automated approaches. In this study, we use U-Net, neural network method for object detection, to identify charge transition lines in experimental stability diagrams. The extracted are analyzed using...
Detection of single-electron charges in solid-state nanodevices is a key technique semiconductor quantum bit readout for information processing and probing electronic properties nanostructures. This detection has been achieved using gate-based readouts sensitive charge sensors including dot sensors, with their speed enhanced by high-speed rf reflectometry. Recently, real-time data from reflectometry attracted much attention to processing. In this paper, we propose sequential method based on...
We report the realization of an array four tunnel coupled quantum dots in single electron regime, which is first required step toward a scalable solid state spin qubit architecture. achieve efficient tunability system but also find out that conditions to realize blockade readout are not as straightforwardly obtained for double and triple dot circuits. use simple capacitive model series quadruple circuit investigate its complex charge diagrams able most suitable configurations future Pauli...
Quantum dot arrays provide a promising platform for quantum information processing. For universal simulation and computation, one central issue is to demonstrate the exhaustive controllability of states. Here, we report addressable manipulation three single electron spins in triple using technique combining electron-spin-resonance micro-magnet. The micro-magnet makes local Zeeman field difference between neighboring much larger than nuclear fluctuation, which ensures driving by shifting...
Scaling up qubits is a necessary step to realize useful systems of quantum computation. Here, we demonstrate coherent manipulations four individual electron spins using micro-magnet method in each dot quadruple dot—the largest number dots used for the single spin control multiple dots. We observe Rabi oscillations through resonance, evaluate spin-electric coupling dots, and finally discuss practical approaches independently address containing even more
A semiconductor quintuple quantum dot with two charge sensors and an additional contact to the center from electron reservoir is fabricated demonstrate concept of scalable architecture. This design enables formation five dots as confirmed by measurements states three nearest respective sensor. The gate performance measured stability diagram well reproduced a capacitance model.These results provide important step towards realizing controllable large scale multiple systems.
Single-spin qubits in semiconductor quantum dots proposed by Loss and DiVincenzo (LD qubits) hold promise for universal computation with demonstrations of a high single-qubit gate fidelity above 99.9 % two-qubit gates conjunction long coherence time. However, initialization readout qubit is orders magnitude slower than control, which detrimental implementing measurement-based protocols such as error-correcting codes. In contrast, singlet-triplet (ST) qubit, encoded two-spin subspace, has the...
Electron spins in semiconductor quantum dots are good candidates of bits for information processing. Basic operations the qubit have been realized recent years: initialization, manipulation single spins, two entanglement operations, and readout. Now it becomes crucial to demonstrate scalability this architecture by conducting spin on a scaled up system. Here, we single-electron resonance quadruple dot. A few-electron dot is formed within magnetic field gradient created micro-magnet. We...
Quantum coherence of superposed states, especially entangled is indispensable for many quantum technologies. However, it vulnerable to environmental noises, posing a fundamental challenge in solid-state systems including spin qubits. Here we show scheme entanglement engineering where pure dephasing assists the generation at distant sites chain electron spins confined semiconductor dots. One party an pair, prepared single site, transferred next site and then adiabatically swapped with third...
Colloidal quantum dots are sub-10 nm semiconductors treated with liquid processes, rendering them attractive candidates for single-electron transistors operating at high temperatures. However, there have been few reports on using colloidal due to the difficulty in fabrication. In this work, we fabricated single oleic acid-capped PbS dot coupled nanogap metal electrodes and measured tunneling. We observed size-dependent carrier transport, orbital-dependent electron charging energy...
Charge state recognition in quantum dot devices is important the preparation of bits for information processing. Toward auto-tuning larger-scale devices, automatic charge by machine learning has been demonstrated. For further development this technology, an understanding operation model, which usually a black box, will be useful. In study, we analyze explainability model estimating states dots gradient weighted class activation mapping. This technique highlights regions image predicting...