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Hole spins in silicon quantum dots (QDs) are a promising candidate for fault-tolerant quantum computing. To achieve the high-fidelity readout and high coherence required for fault tolerance, the evaluation of spin-blockade and state lifetimes is important because they can limit the qubit fidelities. In this study, we characterize these two figures of merit of many-hole qubits in silicon QDs. We report a spin-blockade lifetime of 5.1 μs, which is comparable with the values reported previously, and a spin-state lifetime of 0.91 ms, which is longer than the one measured in a few-hole silicon QD in a previous study. We furthermore provide insights into a many-hole spin state based on the estimated tunneling rate ratio.

The United States Department of Energy, the MH21-S Research Consortium of Japan, and the United States Geological Survey are collaborating to enable gas hydrate scientific drilling and extended-duration reservoir response testing on the Alaska North Slope. To feasibly execute such a test, a location is required that is accessible from existing roads and gravel pads and that can be occupied without disrupting ongoing industry operations. A review of potential locations meeting these criteria determined the likely occurrence of gas hydrate in two fine-grained marginal-marine sands of Tertiary age in the vicinity of the inactive “Kuparuk State 7-11-12” exploration pad in the western Prudhoe Bay Unit (PBU). Existing well and seismic data for that site were insufficient to preclude the potential for free gas occurrence within the deeper (and most prospective) target sand. Therefore, with support from the PBU Working Interest Owners, Alaska Department of Natural Resources, and Petrotechnical Resources Alaska, the Hydrate-01 Stratigraphic Test Well (STW) was drilled in December 2018 to confirm the suitability of the site for future gas hydrate scientific testing. The Hydrate-01 well was successfully drilled to −3290 ft (1003 m) subsea vertical depth at a bottom hole location of approximately 900 ft (∼275 m) east of the surface location. The drilling program featured acquisition of a full suite of logging while drilling data, the collection of side-wall pressure cores, and the installation of distributed temperature and distributed acoustic sensor fiber-optic cables. The log data acquired confirmed the occurrence of gas hydrate at high saturation in two target sands. Integrated evaluation of log and sidewall core data provide petrophysical and geomechanical property information that allow for potential reservoir response to depressurization to be simulated. The deeper “B1 sand” is deemed to be most favorable for reservoir response testing as a result of confirmed gas hydrate occurrence in sediments of high intrinsic permeability, location within 100 ft (30 m) of the base of gas hydrate stability, and minimal risk for direct communication with permeable water-bearing (hydrate-free) zones. The shallower “D1 sand” provides a secondary target that is differentiated by colder in situtemperatures and the interpreted direct hydraulic communication to a lower section of non-hydrate-bearing, water-saturated sand. The Hydrate-01 log data also confirm the occurrence of at least one sub-seismic fault in close proximity to the B1 sand reservoir. To better image the distribution of the gas-hydrate-bearing reservoir sections and associated faults, a three-dimensional (3D) vertical seismic profile was conducted in early 2019 using the distributed acoustic sensors installed as part of the Hydrate-01 STW completion. Detailed two-dimensional (2D) and 3D geologic models have been constructed to enable numerical simulations to inform the planning for potential future scientific tests of reservoir response to depressurization at the site.

The Hydrate-01 Stratigraphic Test Well was drilled at the Kuparuk 7-11-12 site on the Alaska North Slope in December 2018. Sonic log data provide compressional (P) and shear (S) slowness from which we determine gas hydrate saturation (Sgh) estimates using effective medium theory. The sonic Sghestimates compare favorably with Sghestimated from resistivity and nuclear magnetic resonance (NMR) logs, showing that gas hydrate occupies up to approximately 90% of the pore space in the target reservoir sands. The informally named B1 sand (2294 feet below mean sea level) shows lower VP/VSratios than the D1 sand (2770 feet below mean sea level), with the lower part of the B1 sand showing lower VP/VSratios than the upper part of the B1 sand. This corresponds to a stiffer, or more “cemented”, behavior for the lower B1 sand and less cemented behavior for the D1 sand. This trend could be due to differences in the reservoirs themselves or in the gas hydrate morphology or to both factors. We observe that the presence of gas hydrate in the upper B1 sand has greater impact on hydraulic permeability (measurements suggest a greater difference between intrinsic and effective permeability) than in the D1 sand, possibly related to gas hydrate morphology but more likely due simply to higher gas hydrate saturations in the upper B1 sand. Analyses of Sghrelative to porosity, shale fraction, and intrinsic permeability show that reservoir quality (as represented by these three metrics) exerts control on gas hydrate saturation. Grain size and mineralogy data show somewhat smaller grains and better sorting in the D1 reservoir relative to the upper B1 reservoir and smaller grains and greater clay fraction in the lower B1 reservoir relative to the other two reservoir zones. Together, these data suggest that reservoir characteristics play a role in the observed VP/VSpatterns, but gas hydrate morphology (possibly varying with saturation) must also be considered.

Permeability of porous media, such as oil and gas reservoirs, is the crucial material parameter for predicting their hydraulic behavior. A nuclear magnetic resonance (NMR) analyzer is widely used as a powerful tool to predict permeability of various media. NMR T2(transverse or spin–spin) relaxation time distribution, which is related to pore size distribution, gives the information to allow calculation of effective (initial) permeability. In this study, we investigate effective, intrinsic (absolute), and relative water and gas permeabilities of hydrate-bearing pressure core samples. These samples were recovered from the Alaska North Slope 2018 Hydrate-01 Stratigraphic Test Well by sidewall pressure coring and then analyzed in a laboratory using both fluid flow test and NMR analyzer. The peak of the NMR T2distribution was measured at 10–20 ms using a laboratory NMR analyzer, which compares well with in situ measurements obtained via logging while drilling NMR data for two samples with high gas hydrate saturations (Sh= 76% and 74%). Further, comparison of laboratory NMR T2distribution after hydrate dissociation revealed that the hydrate existed in large pore spaces. Effective permeabilities predicted by the Timur-Coates (TC) model and the Schlumberger-Doll-Research (SDR) model, with T2cutoff 33 ms, were about an order of magnitude less than the laboratory measured values. Alternative TC model-based calculations with the T2cutoff reduced to 10 ms and a newly developed hydraulic radius model better matched the laboratory data. For the analysis of the intrinsic permeabilities, the TC model with a T2cutoff of 33 ms and SDR model were greater than the laboratory derived values, while the hydraulic radius model more closely matched the laboratory-derived values. In addition, permeability measurements were also made relative to gas and water under constant three-phase flow (water–gas–hydrate) conditions. After hydrate dissociation, a relative permeability curve was developed for each of the analyzed core samples based on the Corey petrophysical model. The results indicate that the gas permeability changed rapidly at high water saturation around 90%. Thus, we infer that the selection of relative reservoir parameters should focus on the higher water saturation conditions.

While accumulating evidence suggests a relation between the severity of alcohol dependence and the risk of its recurrence, the impact of dependence severity on the course of the disorder has not been carefully evaluated. The present study examined the impact of several severity indices of alcohol dependence on the drinking course after inpatient treatment. This prospective study was conducted over a 12‐month period following alcohol treatment at a specialized hospital. A total of 712 consecutively admitted alcohol‐dependent patients were targeted for enrollment at the time of their hospitalization, with 637 patients registered and followed. The characteristics and severity of the subjects were assessed using multiple methods at admission, with their course after discharge followed continuously using mailed questionnaires that queried them regarding their drinking behavior. Greater severity of dependence, assessed using the number of ICD‐10 diagnostic criteria met, was associated with a lower rate of abstinence during the study period (p= 0.035). The rate of abstinence also decreased significantly as the baseline blood gamma‐glutamyl transferase value and Alcohol Dependence Scale (ADS) score increased (p= 0.031 and p= 0.0002, respectively). In multivariate Cox proportional hazards analyses, the group with the most severe ADS scores had a significantly greater risk of relapse to drinking than the group with the least severe scores (HR = 2.67, p= 0.001). Dependence severity also associated with the drinking pattern; participants in both the controlled drinking group and the abstinence group had lower ADS scores at admission and a later age at first drinking (p= 0.001 and p< 0.001, respectively) than those with poorer drinking outcomes. The present study showed that more severe alcohol dependence predicts a poorer course after alcohol treatment, as reflected by findings on multiple measures. These results suggest that assessing the dependence severity at the outset of treatment could be useful both in predicting treatment outcome and targeting interventions to alcohol‐dependent individuals who need additional support in their recovery. The present prospective study showed that severe alcohol dependence predicted a poorer course after alcohol treatment from different viewpoints. The endorsed number in ICD‐10 diagnostic criteria, blood GGT value and Alcohol Dependence Scale (ADS) score at admission were associated with lower abstinence rates during the 12 months following discharge. These severity indices predicted not only the likelihood of abstinence, but also the drinking pattern. As the ADS severity level increased, the hazard ratios of relapse drinking also increased in multivariate hazards analyses.

Quantum entanglement is a fundamental property of coherent quantum states and an essential resource for quantum computing1. In large-scale quantum systems, the error accumulation requires concepts for quantum error correction. A first step toward error correction is the creation of genuinely multipartite entanglement, which has served as a performance benchmark for quantum computing platforms such as superconducting circuits2,3, trapped ions4and nitrogen-vacancy centres in diamond5. Among the candidates for large-scale quantum computing devices, silicon-based spin qubits offer an outstanding nanofabrication capability for scaling-up. Recent studies demonstrated improved coherence times6–8, high-fidelity all-electrical control9–13, high-temperature operation14,15and quantum entanglement of two spin qubits9,11,12. Here we generated a three-qubit Greenberger–Horne–Zeilinger state using a low-disorder, fully controllable array of three spin qubits in silicon. We performed quantum state tomography16and obtained a state fidelity of 88.0%. The measurements witness a genuine Greenberger–Horne–Zeilinger class quantum entanglement that cannot be separated into any biseparable state. Our results showcase the potential of silicon-based spin qubit platforms for multiqubit quantum algorithms.

Interfacing qubits with peripheral control circuitry poses one of the major common challenges toward realization of large-scale quantum computation. Spin qubits in silicon quantum dots (QDs)are particularly promising for scaling up, owing to the potential benefits from the know-how of the semiconductor industry. In this paper, we focus on the interposer technique as one of the potential solutions for the quantum–classical interface problem and report DC and RF characterization of a silicon QD device mounted on an interposer. We demonstrate flip-chip interconnection with the qubit device down to 4.2 K by observing Coulomb diamonds. We furthermore propose and demonstrate a laser-cut technique to disconnect peripheral circuits no longer in need. These results may pave the way toward system-on-a-chip quantum–classical integration for future quantum processors.

Spin qubits in silicon quantum dots offer a promising platform for a quantum computer as they have a long coherence time and scalability. The charge sensing technique plays an essential role in reading out the spin qubit as well as tuning the device parameters, and therefore, its performance in terms of measurement bandwidth and sensitivity is an important factor in spin qubit experiments. Here we demonstrate fast and sensitive charge sensing by radio frequency reflectometry of an undoped, accumulation-mode Si/SiGe double quantum dot. We show that the large parasitic capacitance in typical accumulation-mode gate geometries impedes reflectometry measurements. We present a gate geometry that significantly reduces the parasitic capacitance and enables fast single-shot readout. The technique allows us to distinguish between the singly- and doubly occupied two-electron states under the Pauli spin blockade condition in an integration time of 0.8 μs, the shortest value ever reported in silicon, by the signal-to-noise ratio of 6. These results provide a guideline for designing silicon spin qubit devices suitable for the fast and high-fidelity readout.

Single nuclear spins in the solid state are a potential future platform for quantum computing1–3, because they possess long coherence times4–6and offer excellent controllability7. Measurements can be performed via localized electrons, such as those in single atom dopants8,9or crystal defects10–12. However, establishing long-range interactions between multiple dopants or defects is challenging13,14. Conversely, in lithographically defined quantum dots, tunable interdot electron tunnelling allows direct coupling of electron spin-based qubits in neighbouring dots15–20. Moreover, the compatibility with semiconductor fabrication techniques21may allow for scaling to large numbers of qubits in the future. Unfortunately, hyperfine interactions are typically too weak to address single nuclei. Here we show that for electrons in silicon metal–oxide–semiconductor quantum dots the hyperfine interaction is sufficient to initialize, read out and control single 29Si nuclear spins. This approach combines the long coherence times of nuclear spins with the flexibility and scalability of quantum dot systems. We demonstrate high-fidelity projective readout and control of the nuclear spin qubit, as well as entanglement between the nuclear and electron spins. Crucially, we find that both the nuclear spin and electron spin retain their coherence while moving the electron between quantum dots. Hence we envision long-range nuclear–nuclear entanglement via electron shuttling3. Our results establish nuclear spins in quantum dots as a powerful new resource for quantum processing.

Natural gas hydrates (or methane hydrates) could become a major energy source but could also exacerbate global warming, because as the climate warms, hydrate deposits deep under the oceans or in permafrost may release methane into the atmosphere. There are many shallow deposits of gas hydrates in fine‐grained muddy sediments on the seafloor. However, the mechanical properties of these sediments have not yet been investigated because of the engineering challenges in coring and testing at in situ temperatures and pressures. Here we present the first uniaxial and triaxial strength and stiffness measurements of pure massive natural gas hydrates and muddy sediments containing hydrate nodules obtained by pressure coring. As a result, we were able to observe the hydrate undergoing a catastrophic brittle failure. Its strength and deformation moduli were 3 and 300 MPa, respectively. Muddy sediments containing hydrate nodules had the same strength as that of hydrate‐free sediments. The first strength and stiffness data for shallow gas hydrate deposits were investigated by pressure core analysisMassive natural gas hydrates show catastrophic brittle failures, with strength and deformation moduli of 3 and 300 MPa, respectivelyMuddy sediments containing hydrate nodules had the same strength as that of hydrate‐free sediments

Measurements of quantum systems inevitably involve disturbance in various forms. Within the limits imposed by quantum mechanics, there exists an ideal projective measurement that does not introduce a back action on the measured observable, known as a quantum non-demolition (QND) measurement1,2. Here we demonstrate an all-electrical QND measurement of a single electron spin in a gate-defined quantum dot. We entangle the single spin with a two-electron, singlet–triplet ancilla qubit via the exchange interaction3,4and then read out the ancilla in a single shot. This procedure realizes a disturbance-free projective measurement of the single spin at a rate two orders of magnitude faster than its relaxation. The QND nature of the measurement protocol5,6enables enhancement of the overall measurement fidelity by repeating the protocol. We demonstrate a monotonic increase of the fidelity over 100 repetitions against arbitrary input states. Our analysis based on statistical inference is tolerant to the presence of the relaxation and dephasing. We further exemplify the QND character of the measurement by observing spontaneous flips (quantum jumps)7of a single electron spin. Combined with the high-fidelity control of spin qubits8–13, these results will allow for various measurement-based quantum state manipulations including quantum error correction protocols14. While measurement of an electron spin commonly destroys it, the quantum non-demolition measurement implemented here for an electron spin qubit in a semiconductor quantum dot preserves the measured spin and allows for exponential suppression of readout errors by repeated measurements.

We examined the crystallographic properties of natural gas hydrates (GHs) in hydrate-bearing sandy sediment sampled from new wells near the second offshore gas-production wells in the Daini–Atsumi knoll region of the eastern Nankai Trough (NT) area, Japan. The sediment layers in the Daini–Astumi knoll area include a silt-dominant (thin turbidite) unit, a sand–mud alternation sequence (upper side), and a thick sandy turbidite sequence (deeper side). GHs are concentrated in the sand–mud alternation and thick sandy turbidite sequences. In the literature, all GH crystals in the eastern NT are structure I (sI) methane (CH4) hydrates. In the sand layers of the sand–mud alternation sequences, we similarly observed sI CH4hydrate crystals, but in the thick sandy turbidite sequence, Raman spectroscopy revealed sI hydrates enclosing both CH4and ethane (C2H6). In this sequence, we also observed the C–C vibrations of C2H6in structure II (sII) large (51264) cages and the C–H vibrations of CH4in sII small (512) cages. The sII hydrates enclosing CH4and C2H6were discovered in the deeper, thick sandy turbidite sequence near the bottom surface reflection. As the C2H6–to-CH4composition ratio increased, the hydrate structure changed from sI to sII. Our new discovery of sII hydrates in the deeper layers of the eastern NT area is consistent with our previous study, which showed that the C2H6composition ratio increases at deeper sampling depths.

The isolation of qubits from noise sources, such as surrounding nuclear spins and spin–electric susceptibility1–4 , has enabled extensions of quantum coherence times in recent pivotal advances towards the concrete implementation of spin-based quantum computation. In fact, the possibility of achieving enhanced quantum coherence has been substantially doubted for nanostructures due to the characteristic high degree of background charge fluctuations5–7 . Still, a sizeable spin–electric coupling will be needed in realistic multiple-qubit systems to address single-spin and spin–spin manipulations8–10 . Here, we realize a single-electron spin qubit with an isotopically enriched phase coherence time (20 μs)11,12 and fast electrical control speed (up to 30 MHz) mediated by extrinsic spin–electric coupling. Using rapid spin rotations, we reveal that the free-evolution dephasing is caused by charge noise—rather than conventional magnetic noise—as highlighted by a 1/fspectrum extended over seven decades of frequency. The qubit exhibits superior performance with single-qubit gate fidelities exceeding 99.9% on average, offering a promising route to large-scale spin-qubit systems with fault-tolerant controllability. Quantum control on an isotopically enriched Si spin qubit is demonstrated with ultrahigh gate fidelities and long coherence times —  even in the presence of sizeable charge noise.

RF reflectometry is a promising technique for spin qubit readout, suitable for large-scale integrated qubit systems by combination with multiplexing techniques and gate-based readout. However, one of the challenges in such systems would be that the accuracy of RF readout of individual qubits can be degraded by crosstalk among dense RF readout lines. In this study, we propose a mixed-mode RF reflectometry to reduce the effect of the crosstalk and verify its effectiveness by electromagnetic field simulations. The results of the simulations show the possibility of suppressing the influence of crosstalk by using mixed modes.

It is necessary to load single electrons into individual quantum dots (QDs) in an array for implementing fully scalable silicon-based quantum computers. However, this single-electron loading would be impacted by the variability of the QD characteristics, and suppressing this variability is highly challenging even in the state-of-the-art silicon front-end process. Here, we used a single-electron pump (SEP) for loading single electrons into a QD array as a preparatory step to use electrons as spin qubits. We used parallel gates in the QD array as a SEP and demonstrated 100 MHz operation with an accuracy of 99% at 4 K. By controlling the timing of a subsequent gate synchronously as a shutter, we found that the jitter representing electron transfer was less than 10 ns, which would be acceptable for a typical operating speed of around 1 MHz for silicon qubits.

On the basis of hypothetical particle‐level mechanisms, several constitutive models of hydrate‐bearing sediments have been proposed previously for gas production. However, to the best of our knowledge, the microstructural large‐strain behaviors of hydrate‐bearing sediments have not been reported to date because of the experimental challenges posed by the high‐pressure and low‐temperature testing conditions. Herein, a novel microtriaxial testing apparatus was developed, and the mechanical large‐strain behavior of hydrate‐bearing sediments with various hydrate saturation values (Sh= 0%, 39%, and 62%) was analyzed using microfocus X‐ray computed tomography. Patchy hydrates were observed in the sediments at Sh= 39%. The obtained stress‐strain relationships indicated strengthening with increasing hydrate saturation and a brittle failure mode of the hydrate‐bearing sand. Localized deformations were quantified via image processing at the submillimeter and micrometer scale. Shear planes and particle deformation and/or rotation were detected, and the shear band thickness decreased with increasing hydrate saturation. A microtriaxial testing apparatus was developed for analyzing hydrate‐bearing sand via X‐ray computed tomographySoil particles and hydrate in the shear band significantly move and rotate at the microscaleThe thickness of the shear band decreased with increasing hydrate saturation

The hydrate morphology of natural gas hydrate-bearing (GH) sediments recovered from the eastern Nankai trough area was investigated under hydrostatic pressurized conditions that prevent dissociation of gas hydrates in a sediment. We developed a novel X-ray computed tomography system and an attenuated total reflection infrared (ATR-IR) probe for use in the Instrumented Pressure Testing Chamber for our set of Pressure-Core Nondestructive Analysis Tools (PNATs), which can measure the sediment structure, primary wave velocity (PWV), density, and shear strength under pressurized conditions. The hydrate saturation values estimated using the ATR-IR absorption bands of H2O molecules strongly correlate with PWV. Assuming homogeneity of hydrate distribution in the planes perpendicular to the sample depth direction, the hydrate morphology of natural GH sediments in the eastern Nankai trough area demonstrated a load-bearing morphology type. The predicted hydrate morphology results are in good agreement with data reported in the literature. The combination of PNATs including ATR-IR spectroscopy can be used to estimate the properties of GH sediments without the release of pressure to atmospheric conditions in order to model gas hydrate reservoirs for natural gas production.

Understanding the mechanical behaviors of carbon dioxide/methane hydrate-bearing sediments is essential for assessing the feasibility of CO2displacement recovery methods to produce methane from hydrate reservoirs. In this study, a series of drained triaxial compression tests were conducted on synthetic carbon dioxide hydrate-bearing sediments under various conditions. A comparative analysis was also made between carbon dioxide and methane hydrate-bearing sediments. The stress-strain curves, shear strength, and the effects of hydrate saturation, effective confining stress, and temperature on the mechanical behaviors were investigated. Our experimental results indicate that the newly formed carbon dioxide hydrate would keep the reservoir mechanically stable when CH4-CO2gas exchange took place in a relatively short period of time and spatially well distributed in the pore space. Experiments of CO2injection in methane hydrate-bearing sediments are necessary to confirm this hypothesis.

A high-pressure low-temperature plane strain testing apparatus was developed for visualizing the deformation of methane hydrate-bearing sand due to methane hydrate production. Using this testing apparatus, plane strain compression tests were performed on pure Toyoura sand and methane hydrate-bearing sand with localized deformation measurements. From the results, it was observed that the methane hydrate-free specimens, despite their relatively high density, showed changes in compressive volume. Marked increases in the initial stiffness and strength of the methane hydrate-bearing sand were observed (methane hydrate saturation of SMH=60%). Moreover, the volumetric strain changed from compressive to dilative. For the specimens with methane hydrate, a dilative behavior above SMH=0% was observed. An image analysis showed that the shear bands of the methane hydrate-bearing sand were thinner and steeper than those of the host sand. In addition, the dilative volumetric strain in the shear band increased markedly when methane hydrate existed in the pore spaces.

A series of triaxial tests has been carried out on the mechanical properties and dissociation characteristics of sands containing methane hydrate using an innovative high pressure apparatus which has been developed to reproduce the in-situ conditions expected during proposed methane extraction methods. It was found that the strength of MH sand increased with MH saturation due to particle bonding. Dissociation by heating caused large axial strains for samples with an initial shear stress and total collapse for samples consolidated in the metastable zone. In the case of dissociation by de-pressurization, axial strains were generated by increasing effective stress until a stable equilibrium was reached. However, re-pressurization led to the collapse in the metastable zone.

We developed a 16 x 8 quantum dot array and CMOS circuit hybrid chip (Q-CMOS). By optimizing the transistor design of Q-CMOS formed by fully depleted (FD)-SOI, it is possible to selectively control each of 16 x 8 quantum dots, and obtained characteristics of quantum dot variation for the first time. Due to the mesoscopic effect, the variation in the characteristics of the quantum dots is larger than the threshold voltage variation of the transistors. Thus, we have obtained an important finding that it is necessary to suppress the variability in order to realize a large-scale quantum computer. We have also confirmed that the characteristics of the quantum dots change depending on the applied gate voltages.

We investigate gate voltage dependence of electrical readout noise in high-speed rf reflectometry using gallium arsenide quantum dots. The fast Fourier transform spectrum from the real time measurement reflects build-in device noise and circuit noise including the resonator and the amplifier. We separate their noise spectral components by model analysis. Detail of gate voltage dependence of the flicker noise is investigated and compared to the charge sensor sensitivity. We point out that the dominant component of the readout noise changes by the measurement integration time.

Holes in silicon exhibit an enhanced spin-orbit interaction compared to electrons, which can be used for electrical spin manipulation, but causes spin decoherence. Here we investigate the level detuning and magnetic field dependence of the leakage current through a physically-defined, p-type MOS double quantum dot in silicon. The current peak positions show spin funnel features which we attribute to mixing of the excited singlet with the spin-polarized triplet states, assisted by the strong spin-orbit interaction and interdot tunneling. The magnetic field angle dependence of these features may present an alternative way to extract the Lande g-factor anisotropy.

Tailoring spin coupling to electric fields is central to spintronics and spin-based quantum information processing. We present an optimal micromagnet design that produces appropriate stray magnetic fields to mediate fast electrical spin manipulations in nanodevices. We quantify the practical requirements for spatial field inhomogeneity and tolerance for misalignment with spins, and propose a design scheme to improve the spin-rotation frequency (to exceed 50 MHz in GaAs nanostructures). We then validate our design by experiments in separate devices. Our results will open a route to rapidly control solid-state electron spins with limited lifetimes and to study coherent spin dynamics in solids.