17 research outputs found
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