Cross talk compensation in multimode continuous-variable entanglement distribution.

Two-mode squeezed states are scalable and robust entanglement resources for continuous-variable and hybrid quantum information protocols that are realized at a distance. We consider the effect of a linear cross talk in the multimode distribution of two-mode squeezed states propagating through parallel similar channels. First, to reduce degradation of the distributed Gaussian entanglement, we show that the initial two-mode squeezing entering the channel should be optimized already in the presence of a small cross talk. Second, we suggest simultaneous optimization of relative phase between the modes and their linear coupling on a receiver side prior to the use of entanglement, which can fully compensate the cross talk once the channel transmittance is the same for all the modes. For the realistic channels with similar transmittance values for either of the modes, the cross talk can be still largely compensated. This method relying on the mode interference overcomes an alternative method of entanglement localization in one pair of modes using measurement on another pair and feed-forward control. Our theoretical results pave the way to more efficient use of multimode continuous-variable photonic entanglement in scalable quantum networks with cross talk.

New perception of Zn(II) and Mn(II) removal mechanism on sustainable sunflower biochar from alkaline batteries contaminated water.

The combination of several methods (X-ray diffraction, X-ray photoelectron spectroscopy, energy dispersive X-ray analysis, infrared spectroscopy) was applied to study the changes that have occurred during the adsorption of Zn(II) and Mn(II) ions on a carbonized sunflower sample for understanding a mechanism of heavy metals adsorption. Sunflower biochar was obtained from the stem and inflorescences sunflower wastes through pyrolysis at 600 °C for 30 min. According to the infrared spectroscopy and Boehm titration data, this carbonized material has acidic and basic functional groups on its surface, but they do not participate in the metal ions adsorption. However, the synthesized carbon proved to be a sustainable high-effective adsorbent for zinc(II) and manganese(II) ions removal with adsorption capacity 138.3 mg g-1 of Zn2+ and 45.4 mg g-1 for Mn2+. Surface analysis of the carbonized material by energy dispersive X-ray analysis, X-ray diffraction, and X-ray photoelectron spectroscopy indicated the presence of soluble and insoluble inorganic salts, such as KCl, NaCl, NaHCO3, KHCO3, CaCO3, MgCO3. It was established, that during the adsorption process, soluble salts are washed away, and new insoluble ones are formed assisting by Zn(II) and Mn(II) ions. It has been revealed that the adsorptive removal of Zn2+ and Mn2+ is caused by the precipitation mechanism. The efficiency of removing Zn(II) and Mn(II) ions from water contaminated with battery waste by the same mechanism is shown.

Production of high-performance lead(II) ions adsorbents from pea peels waste as a sustainable resource.

This research deals with a highly efficient, selective, low-cost, and recyclable adsorbent for the fast removal of lead (Pb)(II) ions from aqueous solutions, and an investigation of the related adsorption mechanisms. Three types of materials were prepared from pea peels waste using simple, energy-efficient and environmentally friendly treatment. Obtained adsorbents were characterized by elemental analysis, infrared spectroscopy, scanning electron microscopy, Boehm titration, and the main parameters were determined. The highest adsorption capacity was observed for the biochar prepared by heating of pea peels at 600°C for 30 minutes. The uptake of Pb(II) ions on pea peels-derived samples was examined as a function of pH, contact time, and initial Pb2+ concentration. Obtained results from adsorption experiments of Pb(II) ions on the biochar surface indicate high adsorption capacity, and the possibility of its preconcentration and selective removal in the presence of zinc(II) and cadmium(II) ions. This confirms a potential application of such materials in water remediation.

Feasibility of quantum key distribution with macroscopically bright coherent light.

We address feasibility of continuous-variable quantum key distribution using bright multimode coherent states of light and homodyne detection. We experimentally verify the possibility to properly select signal modes by matching them with the local oscillator and this way to decrease the quadrature noise concerned with unmatched bright modes. We apply the results to theoretically predict the performance of continuous-variable quantum key distribution scheme using multimode coherent states in scenarios where modulation is applied either to all the modes or only to the matched ones, and confirm that the protocol is feasible at high overall brightness. Our results open the pathway towards full-scale implementation of quantum key distribution using bright light, thus bringing quantum communication closer to classical optics.