A5029076510- Quantum and electron transport phenomena
- Semiconductor Quantum Structures and Devices
- Quantum Information and Cryptography
- Advancements in Semiconductor Devices and Circuit Design
- Quantum Computing Algorithms and Architecture
- Quantum, superfluid, helium dynamics
- Quantum-Dot Cellular Automata
- Cold Atom Physics and Bose-Einstein Condensates
- Physics of Superconductivity and Magnetism
- Semiconductor materials and devices
- Spectroscopy and Quantum Chemical Studies
- Semiconductor materials and interfaces
- Advanced Chemical Physics Studies
- Quantum optics and atomic interactions
- Silicon Nanostructures and Photoluminescence
Pioneer (Japan)
2023-2024
RIKEN
2023-2024
RIKEN Center for Advanced Photonics
2023-2024
RIKEN Center for Quantum Computing
2023-2024
Japan Science and Technology Agency
2019-2021
Okinawa Institute of Science and Technology Graduate University
2019-2021
Delft University of Technology
2013-2018
QuTech
2016-2018
Keio University
2012
The gate fidelity and the coherence time of a qubit are important benchmarks for quantum computation. We construct using single electron spin in Si/SiGe dot control it electrically via an artificial spin-orbit field from micromagnet. measure average single-qubit $\approx$ 99$\%$ randomized benchmarking, which is consistent with dephasing slowly evolving nuclear spins substrate. measured dynamical decoupling extends up to 400 $\mu$s 128 pulses, no sign saturation. find evidence that limited...
A quantum computer comprises both qubits and their classical electronic interface. While much research is currently devoted solely to qubits, an efficient controller also urgently needed for a scalable computer. This study uses analytical techniques expose the effect of nonideal circuit blocks in on qubit fidelity, all required operations, how fidelity affected by limited performance general-purpose, room-temperature equipment typically used with few types available today. Tailor-made...
Spin qubits hosted in silicon (Si) quantum dots (QD) are attractive due to their exceptionally long coherence times and compatibility with the transistor platform. To achieve electrical control of spins for qubit scalability, recent experiments have utilized gradient magnetic fields from integrated micro-magnets produce an extrinsic coupling between spin charge, thereby electrically driving electron resonance (ESR). However, QDs experience a complex interplay spin, valley degrees freedom,...
We present a blueprint for building fault-tolerant quantum computer using the spin states of electrons on surface liquid helium. propose to use ferromagnetic micropillars trap single top them and generate local magnetic field gradient. Introducing gradient hybridizes charge degrees freedom, which allows us benefit from both long coherence time state long-range Coulomb interaction that affects state. concrete schemes realize single- two-qubit gates nondemolition readout. In our framework,...
We report that the electron spin relaxation time, T1, in a GaAs quantum dot with spin-1/2 ground state has 180 degree periodicity orientation of in-plane magnetic field. This been predicted for circular dots as due to interplay Rashba and Dresselhaus orbit contributions. Different from this prediction, we find extrema T1 do not occur when field is along [110] [1-10] crystallographic directions. deviation attributed an elliptical confining potential. The varies by more than order magnitude...
We demonstrate coherent driving of a single electron spin using second-harmonic excitation in Si/SiGe quantum dot. Our estimates suggest that the anharmonic dot confining potential combined with gradient transverse magnetic field dominates response. As expected, Rabi frequency depends quadratically on amplitude, and periodicity respect to phase drive is twice fundamental harmonic. The maximum observed for second harmonic just factor 2 lower than achieved first when at same power. Combined...
The valley degree of freedom is intrinsic to spin qubits in Si/SiGe quantum dots. It has been viewed alternately as a hazard, especially when the lowest valley-orbit splitting small compared thermal energy, or an asset, most prominently proposals use itself qubit. Here we present experiments which microwave electric field driving induces transitions between both and states. We show that this system highly nonlinear can be understood through dressed photon-orbital states, enabling unified...
We propose and experimentally demonstrate a new spectroscopic method, image-charge detection, for the Rydberg states of surface electrons on liquid helium. The excitation induces an image current in circuit to which are capacitively coupled. In contrast conventional microwave absorption measurement, this method makes it possible resolve transitions high-lying electrons. also show that can potentially be used detect quantum single electron, would pave way utilize helium computing.
In this review, we introduce a developing qubit platform: floating-electron-based qubits. Electrons floating in vacuum above the surface of liquid helium or solid neon emerge as promising candidates for qubits, especially due to their expected long coherence times. Despite being early stages, variety recent experiments from different groups have shown substantial potential role. We survey range theoretical proposals and experiments, primarily focusing on use spin state state, wherein charge...
We report the first direct observation of decay excited-state population in electrons trapped on surface liquid helium. The relaxation dynamics, which are governed by inelastic scattering processes system, probed real-time response to a pulsed microwave excitation. Comparison with theoretical calculations allows us establish dominant mechanisms for different temperatures. longest measured time is around $1\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$ at lowest temperature 135 mK, determined...
Pulsed electron paramagnetic resonance spectroscopy of the photoexcited, metastable triplet state oxygen-vacancy center in silicon reveals that lifetime m(s)=±1 sublevels differs significantly from m(s)=0 state. We exploit this significant difference decay rates to ground singlet achieve nearly ~100% electron-spin polarization within triplet. further demonstrate transfer a coherent spin to, and from, hyperfine-coupled, nearest-neighbor (29)Si nuclear spin. measure coherence time employed...
We report transport measurements on a Si/SiGe quantum dot subject to microwave excitation via an on-chip antenna. The response shows signatures of photon-assisted tunneling and only small effect charge stability. also explore the use d.c. current applied antenna for generating tunable, local magnetic field gradients put bounds achievable gradients, limited by heating reservoirs.
We developed a tunnel diode oscillator and characterized its performance, highlighting potential applications in the quantum state readout of electrons insemiconductors on liquid helium. This cryogenic microwave source demonstrates significant scalability for large-scale qubit systems due to compact design low power consumption only 1 uW, making it suitable integration 10 mK stage dilution refrigerator. The exhibits superior amplitude stability compared commercial sources. output frequency...
We present a blueprint for building fault-tolerant quantum computer using the spin states of electrons on surface liquid helium. propose to use ferromagnetic micropillars trap single top them and generate local magnetic field gradient. Introducing gradient hybridizes charge degrees freedom, which allows us benefit from both long coherence time state long-range Coulomb interaction that affects state. concrete schemes realize single- two-qubit gates quantum-non-demolition read-out. In our...
In this review, we introduce a developing qubit platform: floating-electron-based qubits. Electrons floating in vacuum above the surface of liquid helium or solid neon emerge as promising candidates for qubits, especially due to their expected long coherence times. Despite being early stages, variety recent experiments from different groups have shown substantial potential role. We survey range theoretical proposals and experiments, primarily focusing on use spin state state, wherein charge...