Angular Schmidt Modes in Spontaneous Parametric Down-Conversion

We report a proof-of-principle experiment demonstrating that appropriately chosen set of Hermite-Gaussian modes constitutes a Schmidt decomposition for transverse momentum states of biphotons generated in the process of spontaneous parametric down conversion. We experimentally realize projective measurements in Schmidt basis and observe correlations between appropriate pairs of modes. We perform tomographical state reconstruction in the Schmidt basis, by direct measurement of single-photon density matrix eigenvalues.Comment: 5 pages, 4 figure

Experimental study of the vidicon system for information recording using the wide-gap spark chamber of gamma - telescope gamma-I

The development of the gamma ray telescope is investigated. The wide gap spark chambers, used to identify the gamma quanta and to determine the directions of their arrival, are examined. Two systems of information recording with the spark chambers photographic and vidicon system are compared

Self-calibrating Tomography for Angular Schmidt Modes in Spontaneous Parametric Down-Conversion

We report an experimental self-calibrating tomography scheme for entanglement characterization in high-dimensional quantum systems using Schmidt decomposition techniques. The self-tomography technique based on maximal likelihood estimation was developed for characterizing non-ideal measurements in Schmidt basis allowing us to infer both Schmidt eigenvalues and detecting efficiencies.Comment: 10 pages, 11 figure

Near-threshold collisional dynamics in the \u3ci\u3ee\u3csup\u3e−\u3c/sup\u3ee\u3csup\u3e+\u3c/sup\u3ep\u3c/i\u3e system

We study e+-H(n) and Ps(n)-p collisions near the three-body breakup threshold and thresholds for the charge-transfer processes.We show that classical trajectoryMonte Carlo (CTMC) simulations for the three-body breakup agree reasonably well in this energy region with quantum-mechanical convergent close-coupling (CCC) calculations even if the initial hydrogen atom or positronium atom is in the ground state. The threshold behavior of the three-body breakup cross section in e+-H(1s) and Ps(1s)-p collisions agrees with the Wannier law with Klar’s exponent and obeys the classical scaling laws, although some deviation from the Klar-Wannier behavior is observed in the CCC results. Below the threshold the agreement between CTMC and CCC disappears. In particular the CTMC method fails completely for the processes of H formation in Ps(1s)-p collisions and Ps formation in e+-H collisions well below the three-body breakup threshold. For higher initial states the CTMC results below the threshold improve substantially, in accordance with the correspondence principle. This is explained by comparing the quantum-mechanical threshold laws with the classical laws

Antiproton collisions with excited positronium

We present results of calculations of several processes resulting from positronium (Ps) collisions with antiprotons: antihydrogen formation, Ps breakup, and nPs-changing collisions. Calculations utilize the quantum convergent close-coupling (CCC) method and the classical trajectory Monte Carlo (CTMC) method. We identify a region of Ps principal quantum numbers nPs and Ps energies where the classical description is valid and where the CCC calculations become computationally too expensive. This allows us to present the most complete and reliable set of cross sections in a broad range of nPs and initial orbital momentum quantum numbers lPs which are necessary for experiments with antihydrogen at CERN

Stochastic Chemical Kinetics with Energy Parameters

International audienceAbstact: We introduce new models of energy redistribution in stochastic chemical kinetics with several molecule types and energy parameters. The main results concern the situations when there are product form measures. Using a probabilistic interpretation of the related Boltzmann equation, we find some invariant measures explicitly and prove convergence to them.Résumé : Nous introduisons de nouveaux modèles de réseaus de cinétique chimique, avec plusieurs types de molécules et de redistribution d'énergie. Les principaux résultats concernent les cas où les mesures invariantes ont une forme produit. Grâce à une interprétation probabiliste, certaines de ces mesures sont calculées explicitement et on montre qu'elles sont effectivement atteintes par convergence

Estimation of the Size of Open Star Clusters by Analyzing Their Cumulative Distribution Functions

В данной работе описывается метод определения угловых размеров рассеянных звездных скоплений, основанный на анализе и обработке кумулятивной функции распределения (КФР). КФР сглаживается и дважды дифференцируется, после чего по виду второй производной оцениваются размеры скоплений. Описанный метод позволяет получать оценки радиусов ядер, средних размеров скоплений и размеров их внешних оболочек. Исходя из полученных данных, можно оценить также количество звезд, принадлежащих ядру и всему скоплению. Метод был применен к 46 рассеянным скоплениям, выбранным из каталога [1].This work describes a method for determining the angular size of open star clusters based on the analysis and processing of cumulative distribution functions. Cumulative distribution function is smoothed and differentiated twice, after which the size of clusters is determined by the form of the second derivative. The described method makes it possible to obtain estimates of the nuclei radii, average radii of clusters and the size of their outer shells. Based on the data obtained, it is also possible to estimate the number of stars belonging to the core and the entire cluster. The method was applied to 46 open clusters selected from [1].Коллектив авторов благодарит Д. А. Ковалеву за научное руководство

Open Clusters Radial Velocity Estimations Using Convergence Point Method

В работе проводятся оценки средних лучевых скоростей для выборки звездных скоплений, полученные двумя независимыми методами. Прямые оценки проводятся по данным Gaia DR3 о лучевых скоростях. Косвенные оценки проводятся самосогласованным методом, основанным на методе точки схождения. Проводятся сравнение полученных значений и анализируются причины отклонений. Уточняются критерии применимости метода точки схождения для оценки средней лучевой скорости скопления.Estimations of open clusters average radial velocities are performed using two independent methods. Direct estimations are based on Gaia DR3 data on radial velocities. Indirect estimations are carried using self-consistent method based on convergence point method. Comparison of the results is performed as well as the deviations analysis. Criteria of the convergence point method applicability for cluster average radial velocity estimations are specified

The Impact of Double Stars Formation Laws Related to the Components Masses on Their Position on a CMD

В работе исследуется зависимость количества звезд от их удаления от изохроны одиночных звезд на диаграмме «цвет — звездная величина». Рассматривались разные законы распределения двойных звезд по отношению масс компонент. Были получены распределения как сильно несогласующиеся с наблюдаемыми данными для Alessi 9, так и требующие дальнейшего рассмотрения.In this work dependence of stars quantity on their distance from single stars isochrone on a color magnitude diagram was investigated. Different double stars distribution laws in relation to the components masses were considered. Distributions both highly inconsistent with observed Alessi 9 data and requiring further consideration were received

Structure and magnetic properties of LiNi1-xCoxPO4 magnetoelectrics with x = (0, 0.1, and 0.2)

We present the magnetic properties of LiNi1-xCoxPO4 magnetoelectrics, with x = (0-0.2), and their analysis of concentration dependences. Samples have been synthesized by a glycerol-nitrate method. To refine crystal structure X-ray diffraction measurements were carried out. Magnetic measurements were performed at the external magnetic field of 500 Oe over the temperature range (2-300) K. The neutron powder diffraction patterns of LiNi0.9Co0.1PO4 were recorded over temperature interval from 4.4 K up to 25 K. The partial doping in the LiNi1-xCoxPO4 magnetoelectrics the Ni ions for Co ions leads to a narrowing of the temperature interval where the incommensurate phase is established. © Published under licence by IOP Publishing Ltd.3.6121.2017/8.902.The work was supported by MES of RF (contract No. 3.6121.2017/8.9), and by Act 211 Government of RF (contract No. 02.A03.21.0006)