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Nitrogen-vacancy centers possessing nuclear spins are promising candidates for a novel nuclear spin gyroscope. Preparation of a nuclear spin state is a crucial step to implement a sensor that utilizes a nuclear spin. In a low magnetic field, such a preparation utilizes population transfer, from polarized electronic spin to nuclear spin, using microwave pulses. The use of the narrowband microwave pulse proposed earlier is inefficient when magnetic transitions are not well resolved, particularly when applied to diamond with a natural abundance of carbon atoms or dense ensembles of nitrogen-vacancy centers. In this study, the authors performed optimization of the pulse shape for 3 relatively easily accessible pulse shapes. The optimization was done for a range of magnetic transition linewidths, corresponding to the practically important range of nitrogen concentrations (5-50 ppm). It was found that, while at low nitrogen concentrations, optimized pulse added very little to simple square shape pulse, and in the case of dense nitrogen-vacancy ensembles, with a rather wide magnetic transition width of 1.5 MHz optimal pulses, a factor of 15% improvement in the population of the target state was observed.

A rotation sensor is one of the key elements of inertial navigation systems and compliments most cell phone sensor sets used for various applications. Currently, inexpensive and efficient solutions are mechanoelectronic devices, which nevertheless lack long-term stability. Realization of rotation sensors based on spins of fundamental particles may become a drift-free alternative to such devices. Here, we carry out a proof-of-concept experiment, demonstrating rotation measurements on a rotating setup utilizing nuclear spins of an ensemble of nitrogen vacancy centers as a sensing element with no stationary reference. The measurement is verified by a commercially available microelectromechanical system gyroscope.

The sensitivity of the nitrogen-vacancy (NV) color centers in diamond-based magnetometers strongly depends on the number of NV centers involved in the measurement. Unfortunately, an increasing concentration of NV centers leads to a decrease in their dephasing and coherence times if the nitrogen content exceeds a certain threshold level (approximately 10 17 c m - 3 or 0.6 ppm). Here, we demonstrate that this increased dephasing can be efficiently compensated for by optimizing the electron irradiation dose in postprocessing procedures in the vicinity of the threshold concentration, thus extending the range of possible useful concentrations of NV centers in diamonds with a natural carbon content.

A microwave antenna configuration shaped as coaxial resonant coils is proposed for exciting magnetic dipole transitions of the optical ground state of the nitrogen—vacancy color center in diamond. The field within the antenna is simulated, field amplitudes are experimentally measured.

NV centers in diamond recommend themselves as good sensors of environmental fields as well as detectors of diamond impurities. In particular, C-centers, often also called ${{p}_{1}}$-centers, can be detected via double electron-electron resonance. This resonance can be used to measure the C-center concentration. Here, we measured the concentration of C-centers in several diamond plates and investigated the influence of the free precession time of the NV center on the observed contrast in the measured double electron-electron resonance spectrum. The dependence of the resonance amplitudes and widths on the concentration of C-centers as well as the length of the combined C-center driving and NV-center $\pi$-pulse is also discussed. The optimal contrast-free precession time was determined for each C-center concentration, showing a strong correlation with both the concentration of C-centers and the NV-center ${{T}_{2}}$ time.

The possibility of controlled creation of NV centers at any given depth have a substantial potential for quantum information processing and sensor applications. Here we report on creation of localized NV centers using nitrogen delta doping during a chemical vapor deposition diamond growth process. Using confocal microscopy, we investigated optical properties of as grown NV centers in delta-doped layer, demonstrated availability of isolated space clusters of color centers in the layer, analyzed space distribution of these clusters, and using seconds-order correlation function measurements demonstrated that clusters contain from one to few color centers.

In this work, we study the optical properties of NV centers in detonation nanodiamonds and SiV centers in HPHT nanodiamonds with the size about 10 nm. We experimentally measure the size of nanodiamonds with color centers on the substrate. We demonstrate that detonation nanodiamonds have tendency to aggregate, whereas HPHT diamond may lay as single digit crystals. In despite of the aggregation and ultrasmall size, these nanodiamonds still contain bright single color center with antibunching photon statistics.

International audience; Ultrasmall (about 10 nm), low-strain, artificially produced diamonds with an internal, active color center have substantial potential for quantum information processing and biomedical applications. Thus, it is of great importance to be able to artificially produce such diamonds. Here, we report on the high-pressure, high-temperature synthesis of such nanodiamonds about 10 nm in size and containing an optically active, single silicon-vacancy color center. Using special sample preparation technique, we were able to prepare samples containing single nanodiamonds on the surface. By correlating atomic-force microscope images and confocal optical images, we verified the presence of optically active color centers in single nanocrystals, and using second-order correlation measurements, we proved the single-photon emission statistics of these nanodiamonds. These color centers have nonblinking, spectrally narrow emission with narrow distribution of spectral width and positions of zero-phonon line, thus proving the high quality of the nanodiamonds produced.

In this paper, we realize growth of the delta doped layer (3 nm thick) with high concentration of nitrogen atoms (about 1.4 × 1019 cm−3) during CVD diamond growth process. We experimentally investigate the distribution of the nitrogen inside the grown layer and formation of the NV centers during such growth. Using confocal microscopy, we analyze the spatial distribution of the NV centers and investigate the formation efficiency of the NV centers in delta doped layers. The spatial distribution is measured by two methods, using second-order correlation function and emission volume analysis, and NV center concentration is found to be 3.9 ± 0.6 and 2.7 ± 0.2 μm-2 consequently. The divergence between the methods is discussed. As-grown NV centers formation efficiency was found to be 30 times lower than in the case of uniform doped diamond growth. Nevertheless, coherence time of an electron spin for a single NV center inside the delta layer was found to be around 1 μs which is quite reasonable given the concentration of the nitrogen in the sample.

The nitrogen-vacancy (NV) center in diamond has been found to be a powerful tool for various sensing applications. In particular, in ensemble-based sensors, the main ``workhorse'' so far has been optically detected electron resonance. Utilization of the nuclear spin has the potential to significantly improve sensitivity in rotation and magnetic field sensors. Ensemble-based sensors consume a substantial amount of power, leading to noticeable heating of the diamond and thus requiring an understanding of temperature-related shifts. In this paper, we provide a detailed study of the temperature shift of the hyperfine components of the NV center.