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Nuclear magnetic resonance techniques are widely used in the natural sciences but they lack sensitivity. Therefore, large sample volumes or long measurement times are necessary. In this work, we investigate the polarization of bulk 13 C nuclei in a diamond above the thermal equilibrium at room temperature. Previously studied mechanisms utilize direct coupling to nitrogen vacancy centers or the additional assistance of substitutional nitrogen impurities for this purpose. We exploit strongly coupled nitrogen vacancy centers as polarization sources. We study two approaches to transfer the optically induced polarization of the electron spins of the nitrogen vacancy centers to nearby nuclear spins. First, the electron-nuclear polarization transfer is achieved by energy matching conditions or, second, by magnetic field sweeps inducing Landau–Zener-like transitions. Simulations according to a quantum mechanical system consisting of two coupled nitrogen vacancy centers and a weakly coupled 13 C spin show an excellent agreement with the experimental data. Both approaches allow a reduction of the measurement time by roughly three orders of magnitude. [ABSTRACT FROM AUTHOR]

Amides are well known for their potential as anticaking agents for sodium chloride. We have investigated what is the ideal structure for an amide based anticaking agent and what features lead to effective anticaking. Through a series of experiments, we have found that a triple-branched structure, with the three branches radiating from the same nitrogen centre, is the only effective compound for preventing caking for sodium chloride. We conclude that this is likely due to bonding between the atoms of the amide functional group and the ions of sodium chloride, with an extra bond from the central nitrogen giving a strong attachment to the surface, thus leading to blocking of growth. We have also outlined a list of four categories, of which a compound must obey all of in order to act as an effective anticaking agent. [ABSTRACT FROM AUTHOR]

The nitrogen-vacancy (NV) color center in diamond is an atom-like system in the solid-state which specific spin properties can be efficiently used as a sensitive magnetic sensor. An external magnetic field induces Zeeman shifts of the NV center levels which can be measured using optically detected magnetic resonance (ODMR). In this work, we quantitatively map the vectorial structure of the magnetic field produced by a sample close to the surface of a CVD diamond hosting a thin layer of NV centers. The magnetic field reconstruction is based on a maximum-likelihood technique which exploits the response of the four intrinsic orientations of the NV center inside the diamond lattice. The sensitivity associated to a 1 μm area of the doped layer, equivalent to a sensor consisting of approximately 10 NV centers, is of the order of 2 μT/√Hz. The spatial resolution of the imaging device is 480 nm, limited by the numerical aperture of the optical microscope which is used to collect the photoluminescence of the NV layer. The effectiveness of the method is illustrated by the accurate reconstruction of the magnetic field created by a DC current inside a copper wire deposited on the diamond sample. Graphical abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We present the controlled creation of single nitrogen-vacancy (NV) centers via ion implantation at the center of a photonic crystal cavity which is fabricated in an ultrapure, single crystal diamond membrane. High-resolution placement of NV centers is achieved using collimation of a 5 keV-nitrogen ion beam through a pierced tip of an atomic force microscope. We demonstrate coupling of the implanted NV centers' broad band fluorescence to a cavity mode and observe Purcell enhancement of the spontaneous emission. The results are in good agreement with a master equation model for the cavity coupling. [ABSTRACT FROM AUTHOR]

The control and stabilisation of the charge state of nitrogen-vacancy centres in diamond is an important issue for the achievement of reliable processing of spin-based quantum information. The effect of phosphorous and boron doping of diamond on the charge state of nitrogen-vacancy (NV) centres is shown here. Ensembles of NV centres are produced at a depth of 60 nm in ultrapure diamond by implantation of nitrogen ions. Overlapping with the NV ensembles, donor and acceptor doped regions of different doping levels are prepared by ion implantation of phosphorus and boron followed by annealing in vacuum at 1500 °C. We show how the charge state of NV centres is controlled by the presence of phosphorous or boron atoms in their neighbourhood. For the lowest doping level, spectral measurements on the ensemble of NV centres reveal a higher amount of NV0 in the case of boron and a higher amount of NV− in the case of phosphorus, as compared with undoped regions. This behaviour is strengthened when the doping level is increased. Interestingly, the charge state control of native silicon-vacancy centres is also evidenced. Finally, we discuss the role of the surface termination of diamond on the average charge state of the NV ensemble (still dominant even at a depth of 60 nm) and confirm that the surface 2D-hole-gas (H-termination) can be compensated by nitrogen itself. [ABSTRACT FROM AUTHOR]

Single Nitrogen-Vacancy (NV) centers in diamond close to the crystal surface are very promising magnetic field sensors with very high sensitivity. Here, we report the enhanced creation of very shallow (less than 3 nm below the diamond surface) NV centers by using fluorine and oxygen plasma treatment. We observe a four fold increase-from 0.11% to about 0.45% in the production yield when the sample surface is terminated with fluorine or oxygen atoms. This effect is explained by the stabilization of the NV's negative charge state which is influenced by the various defects present on the diamond surface. [ABSTRACT FROM AUTHOR]

The creation of nitrogen-vacancy (NV) centres in diamond is nowadays well controlled using nitrogen implantation and annealing. Although the high-resolution placement of NV centres has been demonstrated using either collimation through pierced tips of an atomic force microscope (AFM) or masks with apertures made by electron beam lithography, a targeted implantation into pre-defined structures in diamond may not be achieved using these techniques. We show that a beam of nitrogen ions can be focused to approximately 100 nm using focused ion beam (FIB) technology. The nitrogen ion beam is produced using an electron cyclotron resonance (ECR) plasma source. Combined with a scanning electron microscope, the nitrogen-FIB offers new possibilities for the targeted creation of single defects in diamond. This maskless technology is suitable for example for the creation of optical centres in the cavities of photonic crystals or in diamond tips for scanning magnetometry. [ABSTRACT FROM AUTHOR]

Coherent coupling between single quantum objects is at the very heart of modern quantum physics. When the coupling is strong enough to prevail over decoherence, it can be used to engineer quantum entangled states. Entangled states have attracted widespread attention because of applications to quantum computing and long-distance quantum communication. For such applications, solid-state hosts are preferred for scalability reasons, and spins are the preferred quantum system in solids because they offer long coherence times. Here we show that a single pair of strongly coupled spins in diamond, associated with a nitrogen-vacancy defect and a nitrogen atom, respectively, can be optically initialized and read out at room temperature. To effect this strong coupling, close proximity of the two spins is required, but large distances from other spins are needed to avoid deleterious decoherence. These requirements were reconciled by implanting molecular nitrogen into high-purity diamond. [ABSTRACT FROM AUTHOR]

For many applications of the nitrogen-vacancy(NV) center in diamond,the understanding and active control of its charge state is highlydesired. In this work, we demonstrate the reversible manipulationof the charge state of a single NV center from NV–across NV0to a nonfluorescent, dark state by using anall-diamond in-plane gate nanostructure. Applying a voltage to thein-plane gate structure can influence the energy band bending sufficientlyfor charge state conversion of NV centers. These diamond in-planestructures can function as transparent top gates, enabling the distantcontrol of the charge state of NV centers tens of micrometers away from the nanostructure. [ABSTRACT FROM AUTHOR]

Single charge nanoscale detection in ambient conditions is a current frontier in metrology that has diverse interdisciplinary applications. Here, such single charge detection is demonstrated using two nitrogen-vacancy (NV) centers in diamond. One NV center is employed as a sensitive electrometer to detect the change in electric field created by the displacement of a single electron resulting from the optical switching of the other NV center between its neutral (NV0) and negative (NV-) charge states. As a consequence, our measurements also provide direct insight into the charge dynamics inside the material. [ABSTRACT FROM AUTHOR]

We study decoherence of a single nitrogen-vacancy (NV) center induced by the 13C nuclear spin bath of diamond. By comparing Hahn-Echo experiments on single and double-quantum transitions of the NV triplet ground state we demonstrate that this bath can be tuned into two different regimes. At low magnetic fields, the nuclei behave as a quantum bath which causes decoherence by entangling with the NV central spin. At high magnetic fields, the bath behaves as a source of classical magnetic field noise, which creates decoherence by imprinting a random phase on the NV central spin. [ABSTRACT FROM AUTHOR]