Phase matching in β\beta-barium borate crystals for spontaneous parametric down-conversion

Spontaneous parametric down-conversion (SPDC) is the most widely used process for generating entangled photon pairs. In SPDC, a pump photon interacts with a nonlinear optical crystal and splits into two entangled photons called the signal and the idler photons. The SPDC process has been studied extensively in the last few decades for various pump and crystal configurations, and the entangled photon pairs produced by SPDC have been used in numerous experimental studies on quantum entanglement and entanglement-based real-world quantum-information applications. In this tutorial article, we present a thorough study of phase matching in $\beta$-barium borate (BBO) crystals for spontaneous parametric down-conversion and thereby also investigate the generation of entangled photons in such crystals. First, we present a theoretical derivation of two-photon wavefunction produced by SPDC in the frequency and transverse momentum bases. We then discuss in detail the effects due to various crystal and pump parameters including the length of the crystal, the angle between the optic axis and the pump propagation direction, the pump incidence angle on the crystal surface, the refraction at the crystal surfaces, and the pump propagation direction inside the crystal. These effects are extremely relevant in experimental situations. We then present our numerical and experimental results in order to illustrate how various experimental parameters affect the phase matching and thus the generation of entangled photons. Finally, using the two-photon wavefunction in the transverse wave-vector basis, we show how to derive the two-photon wavefunction in the OAM basis and thereby calculate the two-photon angular Schmidt spectrum. We expect this article to be useful for researchers working in various capacities with entangled photons generated by SPDC in BBO crystals.Comment: 23 pages, 14 figure

Modelling and enterprises-the past, the present and the future.

Industry has been practicing model-driven development in various flavours. In general it can be said that modelling and use of models have delivered on the promises of platform independence, enhanced productivity, and delivery certainty as regards development of software-intensive systems. Globalization market forces, increased regulatory compliance, ever-increasing penetration of internet, and rapid advance of technology are some of the key drivers leading to increased business dynamics. Increased number of factors impacting the decision and interdependency amongst the key drivers is leading to increased complexity in making business decisions. Also, enterprise software systems need to commensurately change to quickly support the business decisions. The paper presents synthesis of our experience over a decade and half in developing model-driven development technology and using it to deliver several business-critical software systems worldwide

Information content of note transitions in the music of J. S. Bach

Music has a complex structure that expresses emotion and conveys information. Humans process that information through imperfect cognitive instruments that produce a gestalt, smeared version of reality. How can we quantify the information contained in a piece of music? Further, what is the information inferred by a human, and how does that relate to (and differ from) the true structure of a piece? To tackle these questions quantitatively, we present a framework to study the information conveyed in a musical piece by constructing and analyzing networks formed by notes (nodes) and their transitions (edges). Using this framework, we analyze music composed by J. S. Bach through the lens of network science and information theory. Regarded as one of the greatest composers in the Western music tradition, Bach's work is highly mathematically structured and spans a wide range of compositional forms, such as fugues and choral pieces. Conceptualizing each composition as a network of note transitions, we quantify the information contained in each piece and find that different kinds of compositions can be grouped together according to their information content and network structure. Moreover, we find that the music networks communicate large amounts of information while maintaining small deviations of the inferred network from the true network, suggesting that they are structured for efficient communication of information. We probe the network structures that enable this rapid and efficient communication of information--namely, high heterogeneity and strong clustering. Taken together, our findings shed new light on the information and network properties of Bach's compositions. More generally, our framework serves as a stepping stone for exploring musical complexities, creativity and the structure of information in a range of complex systems.Comment: 22 pages, 13 figure; discussion in section IV and VII expanded, references added, results unchange

Valence fluctuation in Ce2_2Re3_3Si5_5 and Ising-type magnetic ordering in Pr2_2Re3_3Si5_5 single crystals

Single crystals of ${\rm Ce_2Re_3Si_5}$ and ${\rm Pr_2Re_3Si_5}$ have been grown by Czochralski method in a tetra-arc furnace. Powder x-ray diffraction confirmed that these compounds crystallize in the ${\rm U_2Mn_3Si_5}$-type tetragonal crystal structure with space group $P4/mnc$ (No. 128). The anisotropic physical properties have been studied comprehensively by measuring the magnetic susceptibility, isothermal magnetization, electrical transport and specific heat. The low value of magnetic susceptibility together with no magnetic transition down to $2$~K gives evidence that the Ce-ions are in the intermediate valence state in ${\rm Ce_2Re_3Si_5}$. On the other hand ${\rm Pr_2Re_3Si_5}$ revealed a magnetic ordering at $9$~K. The sharp drop in the magnetic susceptibility and a spin flip like metamagnetic transition, for $H~\parallel~[001]$ in the magnetization plot of ${\rm Pr_2Re_3Si_5}$ suggest an Ising-type antiferromagnetic ordering. Based on magnetic susceptibility and isothermal magnetization data, a detailed crystal electric field (CEF) analysis shows that degenerate ${J} = 4$ Hund's rule derived ground state of ${\rm Pr^{3+}}$ ion splits into nine singlets with an overall splitting of $1179$~K. The magnetic ordering in ${\rm Pr_2Re_3Si_5}$ is due to the exchange-generated admixture of the lowest lying CEF energy levels. Heat capacity data reveal a sharp peak at $9$~K, that confirms the bulk nature of the magnetic ordering in ${\rm Pr_2Re_3Si_5}$.Comment: 9 pages, 8 figure

Positive Outcomes of Human Resources Engagement and Impact on Motivation

For this study, I don’t intend to show teachers as victims of their school, nor that Human Resources is the only problem that needs to be fixed or that our education system is the issue. We only intended to question why teachers are always blamed, and their needs are ignored and always accused them of being demotivated. We mean to question how the education system functions with the lack of Human Resources practices and the methods and ideas that we can provide and help our teachers have a better future. We intend to discover what the best way to motivate and engage teachers through Human Resources practices is. What makes the admins dissatisfied with teachers’ performance, and is it the fault of the teachers. This study is a series of concerns and problems teachers (including ourselves) came across through our teaching years that nobody ever tried to see it from our point of view. This article is a group of chains and ideas that will give more value to teachers and encourage Human Resources to be more engaged and active in teachers lives through many methods and techniques. Furthermore, teachers’ demotivation and lack of engagement are causing burnouts and turnovers; we’ll try to show how Human Resources can help reduce these turnovers and burnouts through being more present and implement motivational systems and engagement models. This article will review previous literature related to Human Resources engagement and motivation positivity on teachers’ performance and productivity. It will discuss these demotivating factors and assess their impact on teachers’ performance and end with. This article will conclude by implementing more motivational and engagement systems and programs to enhance teachers performance, reduce turnovers, and make schools a better environment for students