Nitrogen-vacancy (NV -) color centers in diamond were created by implantation of 7 keV 15 N (I = ½) ions into type IIa diamond. Optically detected magnetic resonance was employed to measure the hyperfine coupling of the NV -centers. The hyperfine spectrum from 15 NV -arising from implanted 15 N can be distinguished from 14 NVcenters created by native 14 N (I = 1) sites. Analysis indicates 1 in 40 implanted 15 N atoms give rise to an optically observable 15 NV -center. This report ultimately demonstrates a mechanism by which the yield of NV -center formation by nitrogen implantation can be measured.

Diamond is a very attractive material for micromachining: it has high mechanical hardness, high Young's modulus, a low coefficient of friction, high thermal conductivity, and a low thermal expansion coefficient. It is chemically inert and biocompatible. Optically, it is transparent over the widest range of the electromagnetic spectrum (from 220 nm to the far infrared), has a high refractive index, and exhibits a vast inventory of luminescent centers (> 500 electronic, > 150 vibrational), many of which are related to impurities or defects in the crystalline structure.[1] Some of these can therefore be controlled and engineered. Of particular interest is the nitrogen vacancy (NV -) center that possesses very promising quantum properties. [2] At present, despite the prospects for such luminescent centers, no fabrication schemes have been demonstrated for integrated microphotonic devices in diamond. The micromachining of three-dimensional structures in bulk diamond is technologically challenging; [3][4][5][6] therefore, most existing techniques are based on the use of chemical vapor deposition (CVD) of polycrystalline films combined with selective ablation or replication processes that employ masking and molding. Previous work reports the use of such methods to produce scanning probe tips and cantilevers, [3] field emitters, [4] microelectromechanical systems (MEMS), [5] nanoelectromechanical systems (NEMS), [6] and microfluidic channels. [7] Two-dimensional microstructures (holes and trenches) can be drilled in single crystals by means of high-power laser ablation. [8,9] Compared to single-crystal diamond, CVD polycrystalline diamond has poor optical transparency and inferior and lessreproducible mechanical properties. This constitutes a limitation for many technological applications. Here we report a new method for the fabrication of freestanding microstructures in bulk single-crystalline diamond. The method takes advantage of the fact that ion irradiation of diamond followed by thermal annealing induces a phase transformation to amorphous carbon, which can be selectively etched to leave freestanding diamond structures. We also report the construction of an optical waveguide structure integrated with total internal reflection mirrors, constituting the first waveguide fabricated in single-crystal diamond. Potential applications of this technique are in the development of fully integrated quantum photonic devices employing photoluminescent centers in diamond, and in the field of MEMS, microfluidics, and biophysics.Our method is inspired by the diamond lift-off technique, which was initially developed as a method to remove thin layers from bulk diamond samples.[10] The present work is based on MeV ion implantation followed by thermal annealing to create a buried sacrificial layer at a well-defined depth. Patterned milling with a focused ion beam (FIB) is then used to expose defined regions of the sacrificial layer to selective chemical etching and subsequent lift-off. A final thermal-annealing step is employed to r...

Nitrogen vacancy (NV) centers in diamond have distinct promise as solid-state qubits. This is because of their large dipole moment, convenient level structure and very long room-temperature coherence times. In general, a combination of ion irradiation and subsequent annealing is used to create the centers, however for the rigorous demands of quantum computing all processes need to be optimized, and decoherence due to the residual damage caused by the implantation process itself must be mitigated. To that end we have studied photoluminescence (PL) from NV$^-$, NV$^0$ and GR1 centers formed by ion implantation of 2MeV He ions over a wide range of fluences. The sample was annealed at $600^{\circ}$C to minimize residual vacancy diffusion, allowing for the concurrent analysis of PL from NV centers and irradiation induced vacancies (GR1). We find non-monotic PL intensities with increasing ion fluence, monotonic increasing PL in NV$^0$/NV$^-$ and GR1/(NV$^0$ + NV$^1$) ratios, and increasing inhomogeneous broadening of the zero-phonon lines with increasing ion fluence. All these results shed important light on the optimal formation conditions for NV qubits. We apply our findings to an off-resonant photonic quantum memory scheme using vibronic sidebands

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Coherent population trapping at zero magnetic field was observed for nitrogen-vacancy centers in diamond under optical excitation. This was measured as a reduction in photoluminescence when the detuning between two excitation lasers matched the 2.88 GHz crystal-field splitting of the color center ground states. This behavior is highly sensitive to strain, which modifies the excited states, and was unexpected following recent experiments demonstrating optical readout of single nitrogen-vacancy electron spins based on cycling transitions. These results demonstrate for the first time that three-level Lambda configurations suitable for proposed quantum information applications can be realized simultaneously for all four orientations of nitrogen-vacancy centers at zero magnetic field.