Undoing the effect of loss on quantum entanglement

Entanglement distillation is a process via which the strength and purity of quantum entanglement can be increased probabilistically. It is a key step in many quantum communication and computation protocols. In particular, entanglement distillation is a necessary component of the quantum repeater, a device which counters the degradation of entanglement that inevitably occurs due to losses in a communication line. Here we report an experiment on distilling the Einstein-Podolsky-Rosen (EPR) state of light, the workhorse of continuous-variable entanglement, using the technique of noiseless amplification. In contrast to previous implementations, the entanglement enhancement factor achievable by our technique is not fundamentally limited and permits recovering an EPR state with a macroscopic level of entanglement no matter how low the initial entanglement or how high the loss may be. In particular, we recover the original level of entanglement after one of the EPR modes has passed through a channel with a loss factor of 20. The level of entanglement in our distilled state is higher than that achievable by direct transmission of any state through a similar loss channel. This is a key bench-marking step towards the realization of a practical continuous-variable quantum repeater and other CV quantum protocols.Comment: 8 pages, 5 figure

Finite momentum meson correlation functions in a QCD plasma

The finite momentum meson spectral function (MSF) in the pseudoscalar channel is evaluated, adopting for the fermionic propagators HTL expressions. The different contributions to the meson spectral functions are clearly displayed. Our analysis may be of relevance for lattice studies of MSF based so far on the Maximum Entropy Method. As a further step the correlation function along the (imaginary-) temporal direction is evaluated.Comment: 29 pages, 25 figures, submitted to Nucl.Phys.

Parametric Generation of Second Sound by First Sound in Superfluid Helium

We report the first experimental observation of parametric generation of second sound (SS) by first sound (FS) in superfluid helium in a narrow temperature range in the vicinity of $T_\lambda$. The temperature dependence of the threshold FS amplitude is found to be in a good quantitative agreement with the theory suggested long time ago and corrected for a finite geometry. Strong amplitude fluctuations and two types of the SS spectra are observed above the bifurcation. The latter effect is quantitatively explained by the discreteness of the wave vector space and the strong temperature dependence of the SS dissipation length.Comment: 4 pages, 4 postscript figures, REVTE

Transformation of the Bryansk paleosol in microdepressions in the center of the East European forest-steppe during the maximum of valdai glaciation and in the Holocene

Recent and Late Pleistocene soils of the central forest-steppe in the East European Plain have been studied. The main objective of the work is to reveal changes in the properties of the Bryansk paleosol (final phase of MIS 3), one of the most important geosols of the Late Pleistocene. These changes could be induced by cryogenesis during the Valdai glaciation maximum (MIS 2) and by the Holocene pedogenesis (MIS 1) under different conditions of the modern microtopography. We have studied the catena of Holocene soils underlain by the Bryansk paleosol within a small closed depression in the Kazatskaya Steppe of the V.V. Alekhin Central Chernozemic Biospheric Reserve in Kursk oblas

Detection of antibodies to erythropoietin-based drugs: is it possible to create the universal test system?

Our aim was to compare different immobilized erythropoietin (EPO) preparations for their ability to detect anti-EPO IgG antibodies in blood sera of EPO-treated patients with ELISA technique. 294 serum samples of the patients treated with erythropoietin were analyzed. 127 serum samples of patients who did not receive recombinant human EPO (rhEPO) were studied for comparative analysis. ELISA assay was performed, and different rhEPO drugs were immobilized on the anti-EPO monoclonal antibody-coated plates. Horseradish peroxidase-conjugated mouse monoclonal antibodies to human IgG, IgG1, and IgG4 was used for detection. The following drugs were studied: recombinant human erythropoietin rhEPO-beta (Shandong Kexing Bioproducts), European standard of erythropoietin BRP 3, commercial drugs Aranesp (Amgen Europe B.V.), Mircera (F. Hoffmann-La Roche Ltd.), Eprex (Johnson & Johnson LLC), Eralfon (Pharmaceutical Company Sotex). The sensitivity of the method was expressed as a positivity index (IP). IP calculated as the ratio of OD from tested sera to OD at the cut-off levels. The latter was assumed as a mean OD±SD for serum samples from EPO-naive patients. The results were evaluated as positive with IP > 1.1, and negative at IP < 0.9. Results in the range of 0.9 ≤ IP < 1.1 were considered as unidentified. Among the 294 samples, 32 specimens were evaluated as positive or unidentified for total IgG anti-EPO antibodies. The unidentified samples were detected in 1.0-1.7% of all cases. IgG1 subclass antibodies were found in 50-56.3% of patients and IgG4 subclass antibodies, in 43.850% of the patients. Mann—Whitney test showed a significant difference between the test samples compared to control group for all the ELISA modifications (p = 0.001). The Kruskal—Wallis test did not show significant differences between the IP results obtained with any of five immobilized EPO drugs (p = 0.05). The correlation quotient of IP was in the range of 0.99-0.96 for total IgG and > 0.98 for two subclasses of antibodies. Linear regression coefficients were close to one, thus indicating absence of significant differences in the sensitivity of the compared methods. This study indicate the opportunity of using the similar test systems to determine anti-EPO antibodies in the patients treated with various rhEPO drugs. Therefore, it is possible to develop a universal commercial test system to this purpose

L-Glutamine peptides as a means of accelerated rehydration under intense physical activity in athletes

This review is devoted to the theory and practice of the use of glutamine dipeptides in sports. The pathway of L-Glutamine dipeptides is described from the moment of oral intake and entering the intestine to inclusion in intracellular metabolic processes of organs and tissues. The physico-chemical properties of L-Glutamine dipeptides are considered. Urgent effects of L-Glutamine dipeptides under conditions of physical stress and hydration stress, influence on motor and cognitive functions of athletes, positive influence on physical readiness of athletes for prolonged debilitating exercises, reduction of weight loss (rehydration) are described. Positive results of the study of the effect of oral administration of AH and electrolytes on the concentration of plasma electrolytes, physiological indices and neuromuscular fatigue in the process of endurance training, as well as neuroprotective and analgesic properties of L-Glutamine dipeptides are presented