Solid-state color centers with manipulable spin qubits and telecom-ranged fluorescence are ideal platforms for quantum communications and distributed quantum computations. In this work, we coherently control the nitrogen-vacancy (NV) center spins in silicon carbide at room temperature, in which the telecomwavelength emission is detected. Through carefully optimizing the implanted conditions, we improve the concentration of NV centers for about 4 times. Based on this, the coherent control of NV center spins is achieved at room temperature and the coherence time T2 * can be reached around 1 μs. Furthermore, the investigation of fluorescence properties of single NV centers shows that they are room temperature photostable single photon sources at telecom range. Taking the advantages of the technological mature materials, the experiment demonstrates that the NV centers in silicon carbide are promising systems for large-scale integrated quantum photonics and long-distance quantum networks.

Field emission data from aligned high-density carbon nanotubes (CNTs) with orientations parallel, 45°, and perpendicular to the substrate have been obtained. The large-area uniformly distributed CNTs were synthesized on smooth nickel substrates via dc plasma-assisted hot filament chemical vapor deposition. CNTs with diameters in the range of 100–200 nm were employed in this study. The different orientations were obtained by changing the angle between the substrate and the electrical field direction. The growth mechanism for the alignment and orientation control of CNTs has been discussed. The CNTs oriented parallel to the substrate have a lower onset applied field than those oriented perpendicular to the substrate. This result indicates that electrons can emit from the body of the CNT, which means that the CNT can be used as a linear emitter. The small radius of the tube wall and the existence of defects are suggested as the reasons for the emission of electrons from the body of the tubes.

We presented a high-sensitivity temperature detection using an implanted single Nitrogen-Vacancy center array in diamond. The high-order Thermal Carr-Purcell-Meiboom-Gill (TCPMG) method was performed on the implanted single nitrogen vacancy (NV) center in diamond in a static magnetic field. We demonstrated that under small detunings for the two driving microwave frequencies, the oscillation frequency of the induced fluorescence of the NV center equals approximately to the average of the detunings of the two driving fields. On basis of the conclusion, the zero-field splitting D for the NV center and the corresponding temperature could be determined. The experiment showed that the coherence time for the high-order TCPMG was effectively extended, particularly up to 108 µs for TCPMG-8, about 14 times of the value 7.7 µs for thermal Ramsey method. This coherence time corresponded to a thermal sensitivity of 10.1 mK/Hz 1/2 . We also detected the temperature distribution on the surface of a diamond chip in three different circumstances by using the implanted NV center array with the TCPMG-3 method. The experiment implies the feasibility for using implanted NV centers in high-quality diamonds to detect temperatures in biology, chemistry, material science and microelectronic system with high-sensitivity and nanoscale resolution.In recent years some thermal detection techniques have been developed to map temperature distribution with spatial resolution down to micrometer-nanometer range The NV center is a spin defect consisting of a substitutional nitrogen impurity adjacent to a carbon vacancy in diamond. It has increasingly attracted attention in recent years owing to its excellent properties, like photostability, biocompatibility, chemical inertness, and long spin coherence and relaxation times (∼ms in the isotopically pure diamond) at room temperature. These remarkable properties have been explored in many applications like quantum information processing, [12][13][14][15][16] metrologies such as magnetic field sensing, [17][18][19] electric field sensing, [20,21] force sensing, [22,23] thermal sensing, [8][9][10] single electron and nuclear spin sensing, [24][25][26] and external nuclear spin sensing. [27,28] In thermal sensing, Neumann et al. demonstrated the measurement of the temperature distribution on a glass coverslip using single NV center nanodiamonds as temperature sensors.[9] However, the thermal sensitivity was unsatisfactory due to the short coherence time. To address the short coherence time issue, Toyli et al. proposed the thermal Carr-Purcell-Meiboom-Gill (TCPMG) method and extended the spin coherence time up to 17 µs by TCPMG-2. [8] For further increasing the spin coherence time for the thermometry, in this work, we firstly studied the effects of the higher order TCPMG method applied on the implanted single NV centers in diamond at room temperature. In particular, a coherence time of 108 µs was obtained for TCPMG-8, about 14 times of the value 7.7 µs for Thermal Ramsey (T-Ramsey) method. This value corr...

Defects in silicon carbide have been explored as promising spin systems in quantum technologies. However, for practical quantum metrology and quantum communication, it is critical to achieve the on-demand shallow spin-defect generation. In this work, we present the generation and characterization of shallow silicon vacancies in silicon carbide by using different implanted ions and annealing conditions. The conversion efficiency of silicon vacancy of helium ions is shown to be higher than that by carbon and hydrogen ions in a wide implanted fluence range. Furthermore, after optimizing annealing conditions, the conversion efficiency can be increased more than 2 times. Due to the high density of the generated ensemble defects, the sensitivity to sense a static magnetic field can be research as high as 11.9 / z B TH   , which is about 15 times higher than previous results. By carefully optimizing implanted conditions, we further show that a single silicon vacancy array can be generated with about 80 % conversion efficiency, which reaches the highest conversion yield in solid state systems. The results pave the way for using on-demand generated shallow silicon vacancy for quantum information processing and quantum photonics. Keyword:Silicon carbide, silicon vacancy, implantation, magnetic sensing, single photon sources In recent years, color centers in silicon carbide (SiC) have been demonstrated as promising physical platforms for quantum science 1-11 . SiC is a well-known semiconductor material which has wide applications in high-power and high-temperature electronic devices. Moreover, SiC has technological advantages due to the welldeveloped device fabrication protocols and inch-scale growth. Besides some bright single photon emitters 3-7 , SiC also has two types of defect spins, including the silicon vacancy and divacancy defects 1,2,[8][9][10][11] . Similar with nitrogen-vacancy (NV) centers in diamond 12 , these spins can be polarized by optics and manipulated by microwaves at room temperature (RT). Moreover, their photoluminescence (PL) spectrum are in the

Field emission data from aligned graphitic nanofibers have been obtained. The aligned nanofibers are 50–100 nm in diameter and 6–10 μm in length, with a density of 109–1010/cm2. The fibers were grown on polycrystalline nickel substrate by plasma-assisted hot filament chemical vapor deposition using a gas mixture of nitrogen and acetylene. The onset of emission current in microampere level was detected at about 1.8 V/μm with an emission area of 1 mm2. The Fowler–Nordheim model was used to analyze the data obtained. The field emission current required for flat panel display can be easily achieved at 2.5 V/μm.