National Institutes for Quantum and Radiological Science and Technology
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Determination of the optimal diamond surface for NV-NV entangled sensing
No full textIn the field of quantum sensing, quantum entangled states have the potential to beat the standard quantum limit (SQL) and to approach the Heisenberg limit (HL)1. Since the nitrogen-vacancy (NV) center is a qubit at room temperature, the entangled state among an NV array will offer new possibilities for quantum sensing and computing. However, considering decoherence, it is not clear whether entangled sensing can achieve sensitivity beyond the SQL under ambient conditions2,3. We have previously evaluated the decoherence of a shallow NV-NV pair. At Quantum Innovation (QI) 2024, we characterized the decoherence using noise spectroscopy and observed two types of noise with autocorrelation times on the ~μs and ~ns scales. Our results are consistent with previous studies, which attributed these noise sources to the surface electron spin bath and the surface-modified phonons4. As demonstrated by Y. Matsuzaki et al.3, the autocorrelation time is required to be comparable to the evolution time (~μs) for the entangled state. Therefore, we showed that the ratio of the coupling constants to the two types of noise determines whether the entangled state between NV-NV pair beats the SQL. Compared to the temperature-dependent phonon effects, the electron spin density is more readily controlled by surfacetermination techniques. Surface electron spins are a promising target for designing the decoherence environment surrounding NV-NV entangled sensors. In this study, to determine the optimal surface electron spin density for NV-NV entangled sensing, we calculated the flip-flop rate among surface electron spins, as well as the coupling constant to the NV center.Quantum Innovation 2025conference poste
Ferromagnetic nano-tips for manipulation of solid-state spin array
No full textA nitrogen vacancy (NV) center in a diamond functions as solid-state spin qubit at room temperature. To improve fidelity of spin manipulation, it is desirable for the orientation of the NV centers to be coaxial. However, coaxial NV centers share the same resonance frequency, which makes individual manipulation impossible under the uniformly magnetic field conditions typically employed. Therefore, we propose a technique that varying the applied magnetic field strength at coaxial NV centers, which able to separate the resonance frequencies. In this research, we design the technique of applying gradient magnetic field using ferromagnetic nano-tips.Physics and Application of Spatial structures on Spin, QuAntum state and Light (PASSQAL-2)conference poste
ダイヤモンド中の単一の鉛－空孔センターを用いた二光子干渉実験
No full text現在、原理的に盗聴が不可能とされる量子通信の研究が進められている[1]。 量子通信では主に、光子などの量子状態を量子もつれを用いて伝送するという 手法をとり[2]、その光源としてダイヤモンド中のⅣ族元素と空孔の欠陥構造で あるⅣ族－空孔センターが注目されている。その中でも鉛－空孔(PbV)センター は 10 K 以上でフーリエ限界線幅が得られ[3]、9 K 程度でミリ秒のスピンコヒー レンス時間が期待できる[4]。量子もつれの生成に用いる光子は区別不可能と呼 ばれる波長・線幅・偏光の一致した光子である必要があり、量子通信の実現にお いて重要な要素となる。区別不可能性の検証実験として Hong-Ou-Mandel(HOM) 干渉実験があるが、これまで PbV センターを用いて確認された例はない。そこ で本実験では、最初の段階としてひとつの PbV センターを用いての HOM 干渉 実験を行い、その区別不可能性を実証した。第39回ダイヤモンドシンポジウムconference presentatio
X-ray structural study of ESI complex formed by CYP105A1, a substrate, and an apparent noncompetitive inhibitor
No full textMany cytochrome P450 (CYP) inhibitors bind to the heme iron and compete with a substrate to bind to the active site. Such competitive inhibition indicates that the substrate or the inhibitor can bind to the active site. There are also CYP noncompetitive inhibitors that likely bind to allosteric sites that are distant from the active site of the enzyme. Noncompetitive inhibitors are believed to form an enzyme-substrate-inhibitor (ESI) complex. A previous docking simulation showed that noncompetitive inhibitors are bound to an allosteric site of CYP3A4, but the simulation assumed that noncompetitive inhibitors bind to this allosteric site and not to the active site. To date, there has been no experimental structural evidence of an ESI complex formed by CYP enzymes, whereas over nine hundred CYP protein structures have been deposited in the Protein Data Bank. We performed biochemical, X-ray crystallographic, and computational analyses of CYP105A1 from Streptomyces griceolus. CYP105A1 can catalyze 2-step hydroxylation reactions of vitamin D3, and this enzyme also metabolizes 12 types of anti-inflammatory drugs including diclofenac. Enzyme inhibition assays were performed using diclofenac as the substrate and ketoconazole, lanoconazole, and miconazole as imidazole containing inhibitors. The inhibition assays showed that ketoconazole and miconazole act as competitive inhibitors, whereas lanoconazole acts as a noncompetitive inhibitor of CYP105A1. We determined the X-ray structure of an ESI complex comprising CYP105A1, diclofenac, and lanoconazole. This structure shows that lanoconazole binds to the heme iron and that diclofenac closely interacts with the bound lanoconazole. Furthermore, the 4' hydroxylation site of diclofenac is distant from the heme iron in the ESI complex. Quantum mechanical calculations indicate that Cl-π and electrostatic interactions stabilize the formation of the ESI complex. Based on these results, we propose a mechanism for cooperative inhibition between a substrate and an apparent noncompetitive inhibitor.The 19th Conference of Asian Crystallographic Association 2025conference poste
トレニアフリル変異体で見られたサイトカイニン感受性の増大
No full text花弁のフリル化は花卉園芸植物の重要な育種目標の１つであるが、その原因となる分子機構はわかっていない。我々はトレニア（Torenia fournieri）に炭素イオンビームを照射し、M2集団から新規変異体frilly petal unduration1 (fpu1)を作出した。この変異体では花弁先端の鋸歯化と、花弁全体の波打ちがみられた。花弁の維管束を観察したところ、fpu1では野生型よりも維管束の分岐数が増加していた。トレニアの花芽にサイトカイニン（CK）を処理すると花弁がフリル状に変化することが知られている。CK処理によりフリル化した花弁の維管束の分岐数は野生型よりも多かったが、fpu1より少なかった。fpu1に低濃度のCK処理を行うと、野生型に高濃度でCK処理を行った時と同様の形態変化を示した。花芽の内生ホルモンの量を測定すると、CKの内生量が減少し、オーキシンが増加していた。また、不定芽誘導能を指標としたCKの感受性試験を行ったところ、fpu1の方が野生型と比較して多くの不定芽を誘導したことから、感受性が増加していることがわかった。したがって、fpu1ではCKの感受性が増加したことで低濃度処理を行った際にも高濃度処理と同様の形態変化を示したと考えられる。原因遺伝子の探索のために変異検出を行った結果、シロイヌナズナの導管形成抑制遺伝子XYLEM NAC DOMAIN1のオーソログ（TfXND1）のプロモーター領域に変異が生じており、葉と花芽でのTfXND1の発現量は野生型よりもfpu1の方が上昇していた。現在、形質転換実験によりTfXND1がfpu1の原因遺伝子であるかどうかを調査している。日本植物学会第89回大会conference presentatio
Efficient detection of statistical RF fields with a quantum sensor
No full textNuclear magnetic resonance (NMR) spectroscopy is widely used in fields ranging from chemistry, materials science to neuroscience. Nanoscale NMR spectroscopy using Nitrogen-vacancy (NV) centers in diamond has emerged as a promising platform due to an unprecedented sensitivity down to the single spin level. At the nanoscale, high nuclear spin polarization through spin fluctuations (statistical polarization) far outweighs thermal polarization. However, until now efficient NMR detection using coherent averaging techniques could not be applied to the detection of statistical polarization, leading to long measurement times. Here we present two protocols to enable coherent averaging of statistically oscillating signals through rectification. We demonstrate these protocols on an artificial radiofrequency signal detected with a single NV center at 2.7 T. The signal-to-noise scaling with number of measurements increases from 0.5 to 1, improving the measurement time significantly. The relevance of rectification for the detection of statistically polarized nuclear spins using ensembles of NV centers is outlined, paving the way for efficient nanoscale NMR spectroscopy.journal articl
Predictive integrated modelling of the hybrid and baseline scenarios of JT-60SA in view of the second operational phase
No full textThe integrated modelling of two plasma scenarios, hybrid and baseline, envisaged for the second operational phase (OP2) of the JT-60SA tokamak has been performed using the 1.5-dimensional JINTRAC suite of codes and the Bohm/gyro-Bohm (BgB) semi-empirical transport model. The decision to use the BgB model is driven not only by its widespread application in predicting scenarios for JET and JT-60U similar to those anticipated for JT-60SA, but also by its low computational cost. Two versions of the hybrid scenario—3.7 MA/2.28 T and 2.7 MA/1.70 T with Paux = 19 MW—were optimized with respect to the reference METIS simulation to maintain a safety factor with a low magnetic shear region, qmin > 1 and low shine-through losses. The results suggest that a high-βN (∼3) regime with a high non-inductive current fraction (∼70%) could be achieved during the initial research phase at 2.7 MA/1.70 T and at a Greenwald density fraction ne/nGW = 0.4. Hybrid-like q profiles are expected to be more easily obtained at higher Greenwald density fractions (0.6–0.8), while at lower densities, challenges such as hollow current density profiles and reversed q profiles were mitigated by adjusting the negative-neutral beam injection power and the injector configuration. The baseline scenario—4.6 MA/2.28 T with Paux = 17.5 MW—demonstrated potential for high confinement performance, achieving values of βN ∼ 1.8, H98 ∼ 1.0, and Wth ∼ 10 MJ. A scan of the temperature pedestal height and its effect on plasma performance underscores the need to develop a physics-based model capable of accurately predicting the H-mode pedestal.journal articl
ダイヤモンドナノフォトニック構造中のSnV中心における電気機械変調
No full text本研究では、ダイヤモンド中の色中心を用いた量子トランスデューサの実現に向け、圧電材料を用いずに電気機械結合を利用したSnV中心とマイクロ波の結合に挑戦した。SiN光導波路上に配置したダイヤモンドフォトニック結晶中の単一SnV中心にバイアス電圧とマイクロ波を印加し、PLEのサイドバンド変調から、7.7 GHz付近にQ値160の共鳴を観測した。第86回応用物理学会 秋季学術講演会conference presentatio
Adiabatic optical fiber coupling for diamond quantum nanophotonic devices
No full textEfficient and stable interfaces between quantum devices and optical fibers are a key requirement for realizing large-scale quantum networks and distributed quantum computing. Adiabatic coupling between a diamond waveguide and a tapered fiber provides a promising route to broadband, efficient, and robust optical coupling [*]. In this work, we present the design, fabrication, and characterization of such interface. First, we performed FDTD simulations to optimize the diamond nanobeam geometry. These simulations predict a maximum coupling efficiency of 98% with an optimized design. Next, tapered optical fibers with angles <3° and tips <150 nm were fabricated using an optimized hydrofluoric acid etching process. Finally, we experimentally evaluated the coupling efficiency by measuring photoluminescence from nitrogen-vacancy centers in a diamond nanobeam through the fiber, yielding an efficiency of 14%. These results establish a clear design path for a practical interface. The gap between simulation and experiment highlights the need to improve physical contact and nanobeam fabrication. Future work will target these optimizations to realize a more efficient and robust packaged device, a critical component for quantum networks.The 2nd International Workshop on Quantum Information Engineering (QIE2025)conference poste