Single organic molecules for photonic quantum technologies.

Isolating single molecules in the solid state has allowed fundamental experiments in basic and applied sciences. When cooled down to liquid helium temperature, certain molecules show transition lines that are tens of megahertz wide, limited by only the excited-state lifetime. The extreme flexibility in the synthesis of organic materials provides, at low costs, a wide palette of emission wavelengths and supporting matrices for such single chromophores. In the past few decades, their controlled coupling to photonic structures has led to an optimized interaction efficiency with light. Molecules can hence be operated as single-photon sources and as nonlinear elements with competitive performance in terms of coherence, scalability and compatibility with diverse integrated platforms. Moreover, they can be used as transducers for the optical read-out of fields and material properties, with the promise of single-quanta resolution in the sensing of charges and motion. We show that quantum emitters based on single molecules hold promise to play a key role in the development of quantum science and technologies.

Nanoscale Spin Manipulation with Pulsed Magnetic Gradient Fields from a Hard Disc Drive Writer.

The individual and coherent control of solid-state based electron spins is important covering fields from quantum information processing and quantum metrology to material research and medical imaging. Especially for the control of individual spins in nanoscale networks, the generation of strong, fast, and localized magnetic fields is crucial. Highly engineered devices that demonstrate most of the desired features are found in nanometer size magnetic writers of hard disk drives (HDD). Currently, however, their nanoscale operation in particular comes at the cost of excessive magnetic noise. Here, we present HDD writers as a tool for the efficient manipulation of single as well as multiple spins. We show that their tunable gradients of up to 100 µT/nm can be used to spectrally address individual spins on the nanoscale. Their gigahertz bandwidth allows one to switch control fields within nanoseconds, faster than characteristic time scales such as Rabi and Larmor periods, spin-spin couplings, or optical transitions, thus extending the set of feasible spin manipulations. We used the fields to drive spin transitions through nonadiabatic fast passages or to enable the optical readout of spin states in strong misaligned fields. Building on these techniques, we further apply the large magnetic field gradients for microwave selective addressing of single spins and show its use for the nanoscale optical colocalization of two emitters.

Intraspecific variability of popcorn S7 lines for phosphorus efficiency in the soil.

The expansion of agriculture, coupled with the need for sustainable cropping, is one of the greatest challenges of the scientific community working on the generation of new cultivars adapted to abiotic stress conditions. The aim of this study was to evaluate the variability of popcorn lines as to responsiveness and efficiency in phosphorus use, as a first step towards the implementation of a breeding program interested in the practice of sustainable agriculture. Twenty-five popcorn lines were evaluated in two locations with different phosphorus levels in the soil, using a randomized block design. The following traits were measured: plant height, ear height, female flowering date, male flowering date, male-female flowering interval, ear diameter, ear length, 100-grain weight, grain yield, popping expansion, and expanded popcorn volume per hectare. A combined analysis of variance and test of means were performed, and the lines were classified as to their phosphorus use efficiency, according to their production performance in the different environments. The genetic diversity between the lines was estimated by Tocher's and UPGMA clustering methods, using generalized Mahalanobis distance. Lines L59, P7, P2, P3, P4, P8, P10, P9, L66, L70, L69, and P5 were efficient and responsive, whereas lines L75, L80, L61, L77, L63, L65, P1, L54, L53, L88, and L71 were inefficient and nonresponsive. Genetic variability was greater in the environments with low phosphorus in the soil, suggesting that the selection pressure exerted in the stressing environment is a decisive factor to obtain a higher expression of variability.

Indices estimated using REML/BLUP and introduction of a super-trait for the selection of progenies in popcorn.

Selection indices commonly utilize economic weights, which become arbitrary genetic gains. In popcorn, this is even more evident due to the negative correlation between the main characteristics of economic importance - grain yield and popping expansion. As an option in the use of classical biometrics as a selection index, the optimal procedure restricted maximum likelihood/best linear unbiased predictor (REML/BLUP) allows the simultaneous estimation of genetic parameters and the prediction of genotypic values. Based on the mixed model methodology, the objective of this study was to investigate the comparative efficiency of eight selection indices estimated by REML/BLUP for the effective selection of superior popcorn families in the eighth intrapopulation recurrent selection cycle. We also investigated the efficiency of the inclusion of the variable "expanded popcorn volume per hectare" in the most advantageous selection of superior progenies. In total, 200 full-sib families were evaluated in two different areas in the North and Northwest regions of the State of Rio de Janeiro, Brazil. The REML/BLUP procedure resulted in higher estimated gains than those obtained with classical biometric selection index methodologies and should be incorporated into the selection of progenies. The following indices resulted in higher gains in the characteristics of greatest economic importance: the classical selection index/values attributed by trial, via REML/BLUP, and the greatest genotypic values/expanded popcorn volume per hectare, via REML. The expanded popcorn volume per hectare characteristic enabled satisfactory gains in grain yield and popping expansion; this characteristic should be considered super-trait in popcorn breeding programs.

Proposal of a super trait for the optimum selection of popcorn progenies based on path analysis.

A challenge faced by popcorn breeding programs is the existence of a negative correlation between the two main traits, popping expansion and yield, which hinders simultaneous gains. The objective of this study was to investigate the use of a new variable or super trait, which favors the reliable selection of superior progenies. The super trait 'expanded popcorn volume per hectare' was introduced in the evaluation of 200 full-sib families of the eighth recurrent intrapopulation selection cycle, which were arranged in randomized blocks with three replicates in two environments. Although the inability to obtain simultaneous gains through selection via popping expansion or yield was confirmed, the super trait was positively associated with both yield and popping expansion, allowing simultaneous gains via indirect selection using 'expanded popcorn volume per hectare' as the main trait. This approach is recommended because this super trait can be used in breeding programs to optimize selective gains for the crop.

Genetic variability affecting Exserohilum turcicum resistance in popcorn lines grown under high and low phosphorus conditions.

Northern leaf blight (NLB), caused by Exserohilum turcicum, is one of the main foliar diseases that affect popcorn culture. Farmers use many control measures to minimize damage caused by this disease, among which, the use of cultivars with genetic resistance is the most effective and economical. The aim of this study was to investigate genetic variability influencing resistance to NLB in 25 popcorn maize lines grown under high and low phosphorus conditions in relation to foliar fungal disease caused by E. turcicum. We evaluated the disease incidence and severity, by analysis of variance and cluster test (Scott-Knott). There was sufficient genetic variability between strains for resistance traits. Genotypic variance was higher than environmental variance, and had more discriminatory power. We conclude that new progenies could be selected for the establishment of future populations. P-7, P-9, L-59, L-71, and L-76 progenies possess promising characteristics that simultaneously reduce the severity and the incidence of NLB in popcorn plants.

Monolithic diamond optics for single photon detection.

In this work, we experimentally demonstrate a novel and simple approach that uses off-the-shelf optical elements to enhance the collection efficiency from a single emitter. The key component is a solid immersion lens made of diamond, the host material for single color centers. We improve the excitation and detection of single emitters by one order of magnitude, as predicted by theory.

Strong extinction of a laser beam by a single molecule.

We present an experiment where a single molecule strongly affects the amplitude and phase of a laser field emerging from a subwavelength aperture. We achieve a visibility of -6% in direct and +10% in cross-polarized detection schemes. Our analysis shows that a close to full extinction should be possible using near-field excitation.

Nanometer resolution and coherent optical dipole coupling of two individual molecules.

By performing cryogenic laser spectroscopy under a scanning probe electrode that induces a local electric field, we have resolved two individual fluorescent molecules separated by 12 nanometers in an organic crystal. The two molecules undergo a strong coherent dipole-dipole coupling that produces entangled sub- and superradiant states. Under intense laser illumination, both molecules are excited via a two-photon transition, and the fluorescence from this doubly excited system displays photon bunching. Our experimental scheme can be used to optically resolve molecules at the nanometer scale and to manipulate the degree of entanglement among them.

Molecular characterization of a new arcelin-5 gene.

Arcelins are insecticidal proteins found in some wild accessions of the common bean, Phaseolus vulgaris. They are grouped in six allelic variants and arcelin-5 is the variant with the highest inhibitory effect on the development of Zabrotes subfasciatus larvae. Characterization of the protein and its genes resulted in the identification of three polypeptides and the isolation of two genes that encode the Arc5a and Arc5b polypeptides. Here we describe a new gene, Arc5-III. The protein it encodes has 81% amino acid identity with the derived amino acid sequences of Arc5-I and Arc5-II. The Arc5-III gene is highly expressed in developing seeds and at a much lower level in roots. Data obtained by a combination of two-dimensional gel electrophoresis, protein sequencing and MALDI-TOF mass spectrometry analysis support the conclusion that Arc5-III encodes a polypeptide present in Arc5c band. Using ion-exchange chromatography, three fractions containing arcelin-5 polypeptides were eluted by increasing the salt concentration. The three fractions contain various amounts of the three arc-5 polypeptides and inhibit the growth of Zabrotes subfasciatus larvae differentially, suggesting differences in insecticidal activity among the arcelin-5 isoforms.

Photocurrent measurements for laterally resolved interface characterization.

A miniaturized optical set-up based on a CD-ROM player optic was developed for LAPS (light addressable potentiometric sensors). A focus of 2.6 microm was achieved using this easy to handle device. The lateral resolution of LAPS measurements can be improved by using GaAs as the semiconductor material instead of Si. The diffusion length of the minority charge carriers was determined to be smaller than 3.1 microm. A new method called SPIM (scanning photo-induced impedance microscopy) is described. Using this technique, the impedance of thin films can be measured with lateral resolution.

The effect of arcelin-1 on the structure of the midgut of bruchid larvae and immunolocalization of the arcelin protein.

Some wild accessions of the common bean (Phaseolus vulgaris) contain a family of proteins called arcelins, that are toxic to the larvae of certain bruchid species. Among the six allelic variants of arcelin tested so far, arcelin-5 and arcelin-1 confer the highest level of resistance against the Mexican bean weevil, Zabrotes subfasciatus. The same proteins are not toxic to the bean weevil, Acanthoscelides obtectus, which is also a serious pest of cultivated beans. Arcelins belong to the bean lectin family that includes phytohemaggutinins and alpha-amylase inhibitors. Although homologous to lectins, arcelins are themselves only very weak lectins, and their binding properties have not been clearly established. The toxic properties of arcelins may be related to their recognition of and interaction with the glycoproteins and other constituents of the membranes along the digestive tract of insects. Since arcelin-1 was shown to have growth inhibitory effects for the larvae of Z. subfasciatus but not of A. obtectus, we examined the effect of an arcelin-1 containing diet on the structure of the cells that line the intestinal tract of the larvae of these two bruchid species, and used antibodies against arcelin to examine the distribution of arcelin within the cells and tissues. Here we show that dietary arcelin-1 caused an alteration of the gut structure and the penetration of arcelin into the haemolymph in Z. subfasciatus but not in A. obtectus. These results lead us to suggest that arcelins exert their toxic effect by severely damaging the epithelial cells.