arXiv subjects

Hitoshi Ishiwata

Publications and source records attributed to Hitoshi Ishiwata.

8 recordsLinked to original sources

arXiv2023

Fast coherent control of nitrogen-14 spins associated with nitrogen-vacancy centers in diamonds using dynamical decoupling

A nitrogen-vacancy (NV) center in a diamond enables the access to an electron spin, which is expected to present highly sensitive quantum sensors. Although exploiting a nitrogen nuclear spin improves the sensitivity, manipulating it using a resonant pulse requires a long gate time owing to its small gyromagnetic ratio. Another technique to control nuclear spins is a conditional rotation gate based on dynamical decoupling, which is faster but unavailable for nitrogen spins owing to the lack of transverse hyperfine coupling with the electron spin. In this study, we generated effective transverse coupling by applying a weak off-axis magnetic field. An effective coupling depends on the off-axis field; the conditional rotation gate on the nitrogen-14 spins of an NV center was demonstrated within 4.2 μs under an 1.8% off-axis field and a longitudinal field of approximately 280 mT. We estimated that a population transfer from the electron to nitrogen spins can be implemented with 8.7 μs. Our method is applicable to an ensemble of NV centers, in addition to a single NV center.

quant-ph↗

arXiv2021

Label-free phase change detection of lipid bilayers using nanoscale diamond magnetometry

The NV center in a diamond is a quantum sensor with exceptional quality for highly sensitive nanoscale analysis of NMR spectra and thermometry. In this study, we investigate nanoscale phase change detection of lipid bilayers utilizing ensemble-averaged nuclear spin detection from small volume ~ (6 nm)$^{3}$, which was determined by the depth of the NV center. Analysis of nanoscale NMR signal confirm thickness of lipid bilayer to be 6.2 nm $\pm$ 3.4 nm with proton density of 65 proton/nm$^{3}$ verifying formation of lipid bilayer on top of diamond sample. Correlation spectroscopy from nanoscale volume reveals quantum oscillation at 3.06 MHz corresponding to the Larmor frequency of proton at an applied magnetic field of 71.8 mT. The result of the correlation spectroscopy was compared with the 2D molecular diffusion model constructed by Monte Carlo simulation combined with results from molecular dynamics simulation. There is a change in diffusion constant from 1.5 $\pm$ 0.25 nm$^{2}$/$μ$s to 3.0 $\pm$ 0.5 nm$^{2}$/$μ$s when the temperature changes from 26.5 $^\circ$C to 36.0 $^\circ$C. Our results demonstrate that simultaneous observation of changes in translational diffusion and temperature is possible in label-free measurements using nanoscale diamond magnetometry. Our method paves the way for label-free imaging of cell membranes for understanding its phase composition and dynamics.

physics.app-ph↗

arXiv2020

Simultaneous Wide-field Imaging of Phase and Magnitude of AC Magnetic Signal Using Diamond Quantum Magnetometry

Spectroscopic analysis of AC magnetic signal using diamond quantum magnetometry is a promising technique for inductive imaging. Conventional dynamic decoupling like XY8 provides a high sensitivity of an oscillating magnetic signal with intricate dependence on magnitude and phase, complicating high throughput detection of each parameter. In this study, a simple measurement scheme for independent and simultaneous detection of magnitude and phase is demonstrated by a sequential measurement protocol. Wide-field imaging experiment was performed for an oscillating magnetic field with approximately 100$μ$m-squared observation area. Single pixel phase precision was $2.1^\circ$ for 0.76$μ$T AC magnetic signal. Our method enables potential applications including inductive inspection and impedance imaging.

cond-mat.mes-hall↗

arXiv2019

Nanodiamond integration with photonic devices

We discuss the progress in integration of nanodiamonds with photonic devices for quantum optics applications. Experimental results in GaP, SiO2 and SiC-nanodiamond platforms show that various regimes of light and matter interaction can be achieved by engineering color center systems through hybrid approaches. We present our recent results on the growth of color center-rich nanodiamond on prefabricated 3C-SiC microdisk resonators. These hybrid devices achieve up to five-fold enhancement of diamond color center light emission and can be employed for integrated quantum photonics.

cond-mat.mes-hall↗

arXiv2018

Wide-field diamond magnetometry with millihertz frequency resolution and nanotesla sensitivity

The nitrogen-vacancy (NV) center in diamond allows room-temperature wide-field quantum magnetometry and metrology for a small volume, which is an important technology for applications in biology. Although coherence of the NV center has a limited frequency resolution of diamond magnetometry to 10-100 kHz, recent studies have shown that a phase sensitive protocol can beat the coherence limit on a confocal setup. Here, we report a new measurement protocol, "iQdyne," for improving the frequency resolution of wide-field imaging beyond the coherence limit of the NV center. We demonstrate wide-field magnetometry with a frequency resolution of 238 mHz and a magnetic sensitivity of 65 nT/sqrtHz, which are superior to the conventional XY8-based technique, which paves the way to in vivo microscale nuclear magnetic resonance imaging. We find that the experimental performance of iQdyne agrees well with that of an analytical model.

quant-ph↗

arXiv2018

Highly sensitive macro-scale diamond magnetometer operated by dynamical decoupling sequence with coplanar waveguide resonator

Ultimate sensitivity for quantum magnetometry using nitrogen-vacancy (NV) centers in diamond is limited by number of NV centers and coherence time. Microwave irradiation with a high and homogeneous power density for a large detection volume is necessary to achieve highly sensitive magnetometer. Here, we demonstrate a microwave resonator to enhance the power density of the microwave field and an optical system with a detection volume of 1.4e-3 mm$^3$. The strong microwave field enables us to achieve 48 ns Rabi oscillation which is sufficiently faster than the phase relaxation time of NV centers. This system combined with a decoupling pulse sequence, XY16, extends the spin coherence time (T2) up to 27 times longer than that with a spin echo method. Consequently, we obtained an AC magnetic field sensitivity of 10.8 pT/Hz$^{1/2}$ using the dynamical decoupling pulse sequence.

quant-ph↗

arXiv2017

Perfectly Aligned Shallow Ensemble Nitrogen-Vacancy Centers in (111) Diamond

We report the formation of perfectly aligned, high-density, shallow nitrogen vacancy (NV) centers on the ($111$) surface of a diamond. The study involved step-flow growth with a high flux of nitrogen during chemical vapor deposition (CVD) growth, which resulted in the formation of a highly concentrated (>$10^{19}$ cm$^{-3}$) nitrogen layer approximately $10$ nm away from the substrate surface. Photon counts obtained from the NV centers indicated the presence of $6.1$x$10^{15}$-$3.1$x$10^{16}$ cm$^{-3}$ NV centers, which suggested the formation of an ensemble of NV centers. The optically detected magnetic resonance (ODMR) spectrum confirmed perfect alignment (more than $99$ %) for all the samples fabricated by step-flow growth via CVD. Perfectly aligned shallow ensemble NV centers indicated a high Rabi contrast of approximately $30$ % which is comparable to the values reported for a single NV center. Nanoscale NMR demonstrated surface-sensitive nuclear spin detection and provided a confirmation of the NV centers depth. Single NV center approximation indicated that the depth of the NV centers was approximately $9$-$10.7$ nm from the surface with error of less than $\pm$$0.8$ nm. Thus, a route for material control of shallow NV centers has been developed by step-flow growth using a CVD system. Our finding pioneers on the atomic level control of NV center alignment for large area quantum magnetometry.

cond-mat.mes-hall↗

arXiv2015

Hybrid Group IV Nanophotonic Structures Incorporating Diamond Silicon-Vacancy Color Centers

We demonstrate a new approach for engineering group IV semiconductor-based quantum photonic structures containing negatively charged silicon-vacancy (SiV$^-$) color centers in diamond as quantum emitters. Hybrid SiC/diamond structures are realized by combining the growth of nanoand micro-diamonds on silicon carbide (3C or 4H polytype) substrates, with the subsequent use of these diamond crystals as a hard mask for pattern transfer. SiV$^-$ color centers are incorporated in diamond during its synthesis from molecular diamond seeds (diamondoids), with no need for ionimplantation or annealing. We show that the same growth technique can be used to grow a diamond layer controllably doped with SiV$^-$ on top of a high purity bulk diamond, in which we subsequently fabricate nanopillar arrays containing high quality SiV$^-$ centers. Scanning confocal photoluminescence measurements reveal optically active SiV$^-$ lines both at room temperature and low temperature (5 K) from all fabricated structures, and, in particular, very narrow linewidths and small inhomogeneous broadening of SiV$^-$ lines from all-diamond nano-pillar arrays, which is a critical requirement for quantum computation. At low temperatures (5 K) we observe in these structures the signature typical of SiV$^-$ centers in bulk diamond, consistent with a double lambda. These results indicate that high quality color centers can be incorporated into nanophotonic structures synthetically with properties equivalent to those in bulk diamond, thereby opening opportunities for applications in classical and quantum information processing.

cond-mat.mtrl-sci↗