We investigate spin and optical properties of individual nitrogen-vacancy centers located within 1-10 nm from the diamond surface. We observe stable defects with a characteristic optically detected magnetic resonance spectrum down to lowest depth. We also find a small, but systematic spectral broadening for defects shallower than about 2 nm. This broadening is consistent with the presence of a surface paramagnetic impurity layer [Tisler et al., ACS Nano 3, 1959] largely decoupled by motional averaging. The observation of stable and well-behaved defects very close to the surface is critical for single-spin sensors and devices requiring nanometer proximity to the target.

We realize a single particle microscope by using deterministically extracted laser-cooled ^{40}Ca^{+} ions from a Paul trap as probe particles for transmission imaging. We demonstrate focusing of the ions to a spot size of 5.8±1.0  nm and a minimum two-sample deviation of the beam position of 1.5 nm in the focal plane. The deterministic source, even when used in combination with an imperfect detector, gives rise to a fivefold increase in the signal-to-noise ratio as compared with conventional Poissonian sources. Gating of the detector signal by the extraction event suppresses dark counts by 6 orders of magnitude. We implement a Bayes experimental design approach to microscopy in order to maximize the gain in spatial information. We demonstrate this method by determining the position of a 1  μm circular hole structure to a precision of 2.7 nm using only 579 probe particles.

Single dopant atoms or dopant-related defect centers in a solid state matrix provide an attractive platform for quantum simulation of topological states [1], for quantum computing and communication, due to their potential to realize a scalable architecture compatible with electronic and photonic integrated circuits [2][3][4][5][6][7]. The production of such quantum devices calls for deterministic single atom doping techniques because conventional stochastic doping techniques are cannot deliver appropriate architectures. Here, we present the fabrication of arrays of praseodymium color centers in YAG substrates, using a deterministic source of single laser-cooled Pr + ions. The beam of single Pr + ions is extracted from a Paul trap and focused down to 30(9) nm. Using a confocal microscope we determine a conversion yield into active color centers up to 50% and realizing a placement accuracy of better than 50 nm. PACS numbers:Deterministic doping methods at the nm-scale provide a route towards scalable quantum information processing in solid state systems. Prominent examples of atomic systems in solid state hosts for quantum computing are single phosphorus atoms in silicon [8,9] and spin correlated pairs of such donors [10,11] which have led to studies of the scalability of large arrays of coupled donors [8]. Alternatively, single color centers [12] and the growing variety of single rare-earth ions (REI) doped into crystalline hosts have also been employed [2,3,[13][14][15][16]. Driven by proposed quantum applications, the need to deterministically place single dopants into nanostructured devices has led to the development of various techniques related to the silicon material system [17,18]. Crystalline hosts of color centers and REI, however, typically exhibit poor electronic properties, which inhibits single ion detection via active substrates [17] and therefore an alternative technique for deterministic implantation of dopants is required. Here, we present an inherently deterministic method for single ion implantation based on a segmented Paul trap which allows for implantation in any solid state material with a broad range of implantation energies.For characterizing the implantation method, we use single praseodymium ion detection in yttrium aluminum garnet (YAG) crystals based on upconversion microscopy. This detection scheme requires implanted praseodymium ions to arrange in the proper lattice position and reach the Pr 3+ charge state through a suitable annealing and activation procedure. An accurate determination of the ratio of detected ions to implanted ions, commonly referred to as implantation yield, has been performed for the first time at the level of single ions and will further foster the optimization of annealing procedures. In comparison to previous implantation-based nitrogen and silicon vacancy color center generation experiments [19], we achieve more than 20 times higher yield for the implantation of Pr + in YAG, even at much lower implantation energies with correspondingly smaller straggling-rela...

341 97 32748The control and stabilisation of the charge state of nitrogenvacancy 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 8C. 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 NV 0 in the case of boron and a higher amount of NV À 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.