Canopy influence on soil properties in Austrian pine artificial stands

The aim of the present study is to track changes in the canopy (cover-abundance of the tree layer) of vegetation and cover of the forest litter, and the relationship between them and the dynamics of soil parameters in Austrian pine (Pinus nigra Arn.) plantations. The objects of study are 50-80-year-old artificial plantations of Austrian pine located in the xerothermic oak belt of five mountains in the area of Sofia. In each mountain, three test plots (SPs) were laid out, each measuring 400 m2 (Table 1). The main reason for choosing PP is the cover abundance of the first layer. Within each SP, the following metrics are measured: cover-abundance (%) of vegetation in each layer; the cover of plant litter (%). From all SPs, soil samples were taken from three depths: 0-10 cm, 10-20 cm and 20 -30 cm. An analysis of the content of soil organic matter was carried out, including: total nitrogen (N), the C/N ratio – calculation method, the reaction of the soil solution (pH) in the aqueous extract and the mechanical composition of the soil.The results show that the properties of the studied soils change to a significant extent in accordance with the cover abundance, especially in the first floor of the vegetation. Soil organic matter content, C/N ratio and mechanical composition are the indicators that most clearly reflect the relationship between the canopy and the cover of plant litter on the one hand, and soil properties. The proven, statistically significant differences in the values of these indicators emphasize the role of vegetation in soil-forming processes, the formation and change of soil fertility

Terahertz-Mediated Microwave-to-Optical Transduction

Transduction of quantum signals between the microwave and the optical ranges will unlock powerful hybrid quantum systems enabling information processing with superconducting qubits and low-noise quantum networking through optical photons. Most microwave-to-optical quantum transducers suffer from thermal noise due to pump absorption. We analyze the coupled thermal and wave dynamics in electro-optic transducers that use a two-step scheme based on an intermediate frequency state in the THz range. Our analysis, supported by numerical simulations, shows that the two-step scheme operating with a continuous pump offers near-unity external efficiency with a multi-order noise suppression compared to direct transduction. As a result, two-step electro-optic transducers may enable quantum noise-limited interfacing of superconducting quantum processors with optical channels at MHz-scale bitrates

FiND: Few-shot three-dimensional image-free confocal focusing on point-like emitters

Confocal fluorescence microscopy is widely applied for the study of point-like emitters such as biomolecules, material defects, and quantum light sources. Confocal techniques offer increased optical resolution, dramatic fluorescence background rejection and sub-nanometer localization, useful in super-resolution imaging of fluorescent biomarkers, single-molecule tracking, or the characterization of quantum emitters. However, rapid, noise-robust automated 3D focusing on point-like emitters has been missing for confocal microscopes. Here, we introduce FiND (Focusing in Noisy Domain), an imaging-free, non-trained 3D focusing framework that requires no hardware add-ons or modifications. FiND achieves focusing for signal-to-noise ratios down to 1, with a few-shot operation for signal-to-noise ratios above 5. FiND enables unsupervised, large-scale focusing on a heterogeneous set of quantum emitters. Additionally, we demonstrate the potential of FiND for real-time 3D tracking by following the drift trajectory of a single NV center indefinitely with a positional precision of < 10 nm. Our results show that FiND is a useful focusing framework for the scalable analysis of point-like emitters in biology, material science, and quantum optics.Comment: 17 pages, 7 figure

Ultrabright room-temperature single-photon emission from nanodiamond nitrogen-vacancy centers with sub-nanosecond excited-state lifetime

Ultrafast emission rates obtained from quantum emitters coupled to plasmonic nanoantennas have recently opened fundamentally new possibilities in quantum information and sensing applications. Plasmonic nanoantennas greatly improve the brightness of quantum emitters by dramatically shortening their fluorescence lifetimes. Gap plasmonic nanocavities that support strongly confined modes are of particular interest for such applications. We demonstrate single-photon emission from nitrogen-vacancy (NV) centers in nanodiamonds coupled to nanosized gap plasmonic cavities with internal mode volumes about 10 000 times smaller than the cubic vacuum wavelength. The resulting structures features sub-nanosecond NV excited-state lifetimes and detected photon rates up to 50 million counts per second. Analysis of the fluorescence saturation allows the extraction of the multi-order excitation rate enhancement provided by the nanoantenna. Efficiency analysis shows that the NV center is producing up to 0.25 billion photons per second in the far-field

Electron spin contrast of Purcell-enhanced nitrogen-vacancy ensembles in nanodiamonds

Nitrogen-vacancy centers in diamond allow for coherent spin state manipulation at room temperature, which could bring dramatic advances to nanoscale sensing and quantum information technology. We introduce a novel method for the optical measurement of the spin contrast in dense nitrogen-vacancy (NV) ensembles. This method brings a new insight into the interplay between the spin contrast and fluorescence lifetime. We show that for improving the spin readout sensitivity in NV ensembles, one should aim at modifying the far field radiation pattern rather than enhancing the emission rate