Nanopositioning of a diamond nanocrystal containing a single NV defect center

Precise control over the position of a single quantum object is important for many experiments in quantum science and nanotechnology. We report on a technique for high-accuracy positioning of individual diamond nanocrystals. The positioning is done with a home-built nanomanipulator under real-time scanning electron imaging, yielding an accuracy of a few nanometers. This technique is applied to pick up, move and position a single NV defect center contained in a diamond nanocrystal. We verify that the unique optical and spin properties of the NV center are conserved by the positioning process.Comment: 3 pages, 3 figures; high-resolution version available at http://www.ns.tudelft.nl/q

Efficient and robust fiber coupling of superconducting single photon detectors

We applied a recently developed fiber coupling technique to superconducting single photon detectors (SSPDs). As the detector area of SSPDs has to be kept as small as possible, coupling to an optical fiber has been either inefficient or unreliable. Etching through the silicon substrate allows fabrication of a circularly shaped chip which self aligns to the core of a ferrule terminated fiber in a fiber sleeve. In situ alignment at cryogenic temperatures is unnecessary and no thermal stress during cooldown, causing misalignment, is induced. We measured the quantum efficiency of these devices with an attenuated tunable broadband source. The combination of a lithographically defined chip and high precision standard telecommunication components yields near unity coupling efficiency and a system detection efficiency of 34% at a wavelength of 1200 nm. This quantum efficiency measurement is confirmed by an absolute efficiency measurement using correlated photon pairs (with $\lambda$ = 1064 nm) produced by spontaneous parametric down-conversion. The efficiency obtained via this method agrees well with the efficiency measured with the attenuated tunable broadband source

Deterministic nano-assembly of a coupled quantum emitter - photonic crystal cavity system

The interaction of a single quantum emitter with its environment is a central theme in quantum optics. When placed in highly confined optical fields, such as those created in optical cavities or plasmonic structures, the optical properties of the emitter can change drastically. In particular, photonic crystal (PC) cavities show high quality factors combined with an extremely small mode volume. Efficiently coupling a single quantum emitter to a PC cavity is challenging because of the required positioning accuracy. Here, we demonstrate deterministic coupling of single Nitrogen-Vacancy (NV) centers to high-quality gallium phosphide PC cavities, by deterministically positioning their 50 nm-sized host nanocrystals into the cavity mode maximum with few-nanometer accuracy. The coupling results in a 25-fold enhancement of NV center emission at the cavity wavelength. With this technique, the NV center photoluminescence spectrum can be reshaped allowing for efficient generation of coherent photons, providing new opportunities for quantum science.Comment: 13 pages, 4 figure

Tunable HMF hydrogenation to furan diols in a flow reactor using Ru/C as catalyst

5-hydroxymethylfurfural (HMF), accessible from various feedstocks, represents an important renewable platform-chemical, precursor for valuable biofuels and bio-based chemicals. In this work, the continuous hydrogenation of an aqueous solution of HMF to give strategic monomers, 2,5-bis(hydroxymethyl)furan (BHMF) and 2,5-bis(hydroxymethyl)tetrahydrofuran (BHMTHF) was investigated in a continuous flow reactor adopting a commercial Ru/C (5 wt%) as catalyst. The influence of the main process variables on products yield and selectivity was studied and optimized. The highest BHMF and BHMTHF yields of 87.9 and 93.7 mol%, respectively, were achieved by tuning the catalyst contact time, keeping all other variables constant (temperature, pressure, hydrogen flow rate, initial HMF concentration). Intraparticle diffusion limitation for hydrogen and HMF was shown to occur at some of the tested conditions by performing the HMF hydrogenation with different catalyst particle sizes, confirmed by calculations. Constant catalyst activity was observed up to 6 h time-on-stream and then gradually reduced. Fresh and spent catalyst characterization showed no significant sintering and negligible leaching of ruthenium during time-on-stream. A decrease of the specific surface area was observed, mainly due to humin deposition which is likely the reason for catalyst deactivation. Catalyst performance could be restored to initial values by a thorough washing of the catalyst

Engineered arrays of NV color centers in diamond based on implantation of CN- molecules through nanoapertures

We report a versatile method to engineer arrays of nitrogen-vacancy (NV) color centers in dia- mond at the nanoscale. The defects were produced in parallel by ion implantation through 80 nm diameter apertures patterned using electron beam lithography in a PMMA layer deposited on a diamond surface. The implantation was performed with CN- molecules which increased the NV defect formation yield. This method could enable the realization of a solid-state coupled-spin array and could be used for positioning an optically active NV center on a photonic microstructure.Comment: 12 pages, 3 figure

Spin dynamics in the optical cycle of single nitrogen-vacancy centres in diamond

We investigate spin-dependent decay and intersystem crossing in the optical cycle of single negatively-charged nitrogen-vacancy (NV) centres in diamond. We use spin control and pulsed optical excitation to extract both the spin-resolved lifetimes of the excited states and the degree of optically-induced spin polarization. By optically exciting the centre with a series of picosecond pulses, we determine the spin-flip probabilities per optical cycle, as well as the spin-dependent probability for intersystem crossing. This information, together with the indepedently measured decay rate of singlet population provides a full description of spin dynamics in the optical cycle of NV centres. The temperature dependence of the singlet population decay rate provides information on the number of singlet states involved in the optical cycle.Comment: 11 pages, 5 figure

Quantum Statistics of Surface Plasmon Polaritons in Metallic Stripe Waveguides

Single surface plasmon polaritons are excited using photons generated via spontaneous parametric down-conversion. The mean excitation rates, intensity correlations and Fock state populations are studied. The observed dependence of the second order coherence in our experiment is consistent with a linear uncorrelated Markovian environment in the quantum regime. Our results provide important information about the effect of loss for assessing the potential of plasmonic waveguides for future nanophotonic circuitry in the quantum regime.Comment: 21 pages, 6 figures, published in Nano Letters, publication date (web): March 27 (2012

Принципы организации объектно-ориентированных систем обработки неформализованной информации

Рассматривается класс логико-аналитических систем, использующих специальные лингвистические процессоры и базы знаний (БЗ) для обработки потоков неформализованных документов с целью решения пользовательских задач. На первом этапе формализации текста документа извлекаются информационные объекты и связи, которые образуют структуры знаний и запоминаются в БЗ. На уровне БЗ организуются различные виды анализа и объектных поисков: поиск похожих объектов и ситуаций, поиск по связям и другие. Рассматриваются основные компоненты подобных систем, называемых объектно-ориентированными, их особенности при использовании в различных приложениях: при обработке криминальной информации, при автоматической формализации резюме (заявок на работу), в системах обработки СМИ с выделением террористических групп и их деяний.A class of the logical-analytical systems using special linguistic processors and knowledge bases is considered. Such systems are called object-oriented. These systems are employed for processing of the unstructured documents flow for the user problems decision. At the first stage the document text is formalized: information objects and links are extracted and transferred into the knowledge structures which are stored in the knowledge base (KB). At the level of KB various kinds of analysis and object search are organized: the search for similar objects and situations, the search on the basis of links and other types of search. The basic components of these systems, their main features and the particular use in different applications are considered.The system operation in the subject areas of criminal information processing, automatic formalization of summary texts (applications for work), mass media analysis for extracting information about terrorist formations and their activities are presented

Functional stacking of three resistance genes against Phytophthora infestans in potato

Functional stacking of broad spectrum resistance (R) genes could potentially be an effective strategy for more durable disease resistance, for example, to potato late blight caused by Phytophthora infestans (Pi). For this reason, three broad spectrum potato R genes (Rpi), Rpi-sto1 (Solanum stoloniferum), Rpi-vnt1.1 (S. venturii) and Rpi-blb3 (S. bulbocastanum) were selected, combined into a single binary vector pBINPLUS and transformed into the susceptible cultivar Desiree. Among the 550 kanamycin resistant regenerants, 28 were further investigated by gene specific PCRs. All regenerants were positive for the nptII gene and 23 of them contained the three Rpi genes, referred to as triple Rpi gene transformants. Detached leaf assay and agro-infiltration of avirulence (Avr) genes showed that the 23 triple Rpi gene transformants were resistant to the selected isolates and showed HR with the three Avr effectors indicating functional stacking of all the three Rpi genes. It is concluded that Avr genes, corresponding to the R genes to be stacked, must be available in order to assay for functionality of each stack component. No indications were found for silencing or any other negative effects affecting the function of the inserted Rpi genes. The resistance spectrum of these 23 triple Rpi gene transformants was, as expected, a sum of the spectra from the three individual Rpi genes. This is the first example of a one-step approach for the simultaneous domestication of three natural R genes against a single disease by genetic transformation

Superconducting nanowire single-photon detectors: physics and applications

Single-photon detectors based on superconducting nanowires (SSPDs or SNSPDs) have rapidly emerged as a highly promising photon-counting technology for infrared wavelengths. These devices offer high efficiency, low dark counts and excellent timing resolution. In this review, we consider the basic SNSPD operating principle and models of device behaviour. We give an overview of the evolution of SNSPD device design and the improvements in performance which have been achieved. We also evaluate device limitations and noise mechanisms. We survey practical refrigeration technologies and optical coupling schemes for SNSPDs. Finally we summarize promising application areas, ranging from quantum cryptography to remote sensing. Our goal is to capture a detailed snapshot of an emerging superconducting detector technology on the threshold of maturity.Comment: 27 pages, 5 figures, Review article preprint versio