A5102009467- Quantum and electron transport phenomena
- Advancements in Semiconductor Devices and Circuit Design
- Semiconductor Quantum Structures and Devices
- Semiconductor materials and devices
- Quantum Computing Algorithms and Architecture
- Quantum Information and Cryptography
- Quantum-Dot Cellular Automata
- Magnetic properties of thin films
- Surface and Thin Film Phenomena
- Neural Networks and Applications
- Physics of Superconductivity and Magnetism
- Neural Networks and Reservoir Computing
- Semiconductor Lasers and Optical Devices
- Microwave and Dielectric Measurement Techniques
- Integrated Circuits and Semiconductor Failure Analysis
- Semiconductor materials and interfaces
- Near-Field Optical Microscopy
- Molecular Junctions and Nanostructures
- Low-power high-performance VLSI design
- Machine Learning and Algorithms
- Advanced Electron Microscopy Techniques and Applications
- Logic, Reasoning, and Knowledge
- Electronic Packaging and Soldering Technologies
- Blind Source Separation Techniques
- Silicon Nanostructures and Photoluminescence
The University of Tokyo
2011-2025
Tokyo University of Science
2025
Tokyo Institute of Technology
2021-2024
RIKEN Center for Emergent Matter Science
2015-2024
UNSW Sydney
2019-2023
Centre for Quantum Computation and Communication Technology
2019-2021
RIKEN
2018-2019
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 =...
Abstract A fault-tolerant quantum processor may be configured using stationary qubits interacting only with their nearest neighbours, but at the cost of significant overheads in physical per logical qubit. Such could reduced by coherently transporting across chip, allowing connectivity beyond immediate neighbours. Here we demonstrate high-fidelity coherent transport an electron spin qubit between dots isotopically-enriched silicon. We observe precession inter-site tunnelling regime and...
Spin qubits in silicon quantum dots offer a promising platform for computer as they have long coherence time and scalability. The charge sensing technique plays an essential role reading out the spin qubit well tuning device parameters therefore its performance terms of measurement bandwidth sensitivity is important factor experiments. Here we demonstrate fast sensitive by radio-frequency reflectometry undoped, accumulation-mode Si/SiGe double dot. We show that large parasitic capacitance...
Quantum computation relies on accurate measurements of qubits not only for reading the output calculation, but also to perform error correction. Most proposed scalable silicon architectures utilize Pauli blockade triplet states spin-to-charge conversion. In recent experiments, there have been instances when instead conventional readout, is sustained between parallel spin configurations, with $|T_0\rangle$ relaxing quickly singlet state and leaving $|T_+\rangle$ $|T_-\rangle$ blockaded --...
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 implementation of a resonantly driven singlet-triplet spin qubit in silicon. The is defined by the two-electron antiparallel states and universal quantum control provided through resonant drive exchange interaction at frequency. exhibits long ${T}_{2}^{*}$ exceeding $1\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$ that limited dephasing due to $^{29}\mathrm{Si}$ nuclei rather than charge noise thanks symmetric operation large micromagnet Zeeman field gradient. randomized benchmarking...
Abstract While single-shot detection of silicon spin qubits is now a laboratory routine, the need for quantum error correction in large-scale computing device demands non-demolition (QND) implementation. Unlike conventional counterparts, QND readout imposes minimal disturbance to probed polarization and can therefore be repeated extinguish measurement errors. Here, we show that an electron qubit measured highly manner by probing another neighboring dot Ising-coupled spin. The high fidelity...
We detect correlations in qubit-energy fluctuations of non-neighboring qubits defined isotopically purified Si/Si-Ge quantum dots. At low frequencies (where the noise is strongest), correlation coefficient reaches 10% for a next-nearest-neighbor qubit-pair separated by 200 nm. Correlations with charge-sensor signal reach up to 70%, proving that observed electrical origin. A simple theoretical model quantitatively reproduces measurements and predicts polynomial decay interqubit distance. Our...
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...
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.
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...
Frequency-multiplexed radio-frequency (RF) reflectometry is a promising technique for large-scale quantum dot-based qubit systems because it enables simultaneous readout of multiple qubits and helps to reduce the wiring density in peripheral circuits. However, conventional L-C-type matching circuits, resonator frequency tunability limited by poor design flexibility shunt capacitance hence circuit. Recently, L-L-type circuits comprising series inductor have been proposed address this issue....
We prepare a gate-defined quadruple quantum dot to study the gate-tunability of single dots with finite inter-dot tunnel couplings. The measured charging energies various double suggest that size is governed by gate geometry. For triple and we gate-tunable Particularly for find effective coupling between side significantly depends on alignment center potential. These results imply present device has performance relevant implementing spin-based four-qubit systems controllable exchange
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...
Semiconductor quantum dots (QDs) are promising hosts for computers because of their scalability. In order to expedite the development process, there is a strong need fully automated tuning QDs that allows en masse characterization newly fabricated devices and control over large-scale systems with appreciable variability. Machine learning has been actively explored as means this end; however, challenges remain in terms versatility different tasks device types. study, we explore model-based...
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.
Complete characterization of the errors that occur in using sets logic gates is critical to developing technology fault-tolerant quantum computing, but current tomography methods are either slow or include unchecked assumptions. This study presents a self-consistent method for process both fast and flexible. The technique complements broad suite existing tools, may potentially allow pulse optimization further increase gate fidelities.
Feedback control of qubits is a highly demanded technique for advanced quantum information protocols such as error correction. Here we demonstrate active reset silicon spin qubit using feedback control. The based on non-demolition readout the and according to results, which enabled by hardware data processing sequencing. We incorporate cumulative protocol, enhancing initialization fidelity above limitation imposed accuracy single QND measurement fidelity. Based an analysis suggest way...