Enhanced-sensitivity interferometry with phase-sensitive unbiased multiports

Here we introduce interferometric devices by combining optical feedback (cavities) with unbiased multiports, which unlike traditional beam dividers, allow light to reflect back out of the port from which it originated. By replacing the traditional, directionally-biased beam-splitter in a Michelson interferometer with an unbiased multiport, the functional dependence of the scattering amplitudes changes. As a result, the derivative of transmittance with respect to an external phase perturbation can be made substantially large. This significantly enhances the resolution of phase measurement, and allows the phase response curves to be altered in real time by tuning an externally-controllable phase shift

Interferometry and higher-dimensional phase measurements using directionally unbiased linear optics

Grover multiports are higher-dimensional generalizations of beam splitters, in which input to any one of the four ports has equal probability of exiting at any of the same four ports, including the input port. In this paper, we demonstrate that interferometers built from such multiports have novel features. For example, when combined with two-photon input and coincidence measurements, it is shown that such interferometers have capabilities beyond those of standard beam-splitter-based interferometers, such as easily controlled interpolation between Hong-Ou-Mandel (HOM) and anti-HOM behavior. Further, it is shown that the Grover-based analog of the Mach-Zehnder interferometer can make three separate phase measurements simultaneously. By arranging the transmission lines between the two multiports to lie in different planes, the same interferometer acts as a higher-dimensional Sagnac interferometer, allowing rotation rates about three different axes to be measured with a single device

Roles of Bond Alternation in Magnetic Phase Diagram of RMnO3

In order to investigate nature of the antiferromagnetic structures in perovskite RMnO3, we study a Heisenberg J1-J2 model with bond alternation using analytical and numerical approaches. The magnetic phase diagram which includes incommensurate spiral states and commensurate collinear states is reproduced. We discuss that the magnetic structure with up-up-down-down spin configuration (E-type structure) and the ferroelectricity emerge cooperatively to stabilize this phase. Magnetoelastic couplings are crucial to understand the magnetic and electric phase diagram of RMnO3.Comment: 5 pages, 6 figure

Metallic "Ferroelectricity" in the Pyrochlore Cd2Re2O7

A class of materials known as ``ferroelectric metals'' was discussed theoretically by Anderson and Blount in 1965 [Phys. Rev. Lett. 14, 217 (1965)], but to date no examples of this class have been reported. Here we present measurements of the elastic moduli of Cd2Re2O7 through the 200 K cubic-to-tetragonal phase transition. A Landau analysis of the moduli reveals that the transition is consistent with Cd2Re2O7 being classified as a ``ferroelectric metal'' in the weaker sense described by Anderson and Blount (loss of a center of symmetry). First-principles calculations of the lattice instabilities indicate that the dominant lattice instability corresponds to a two-fold degenerate mode with Eu symmetry, and that motions of the O ions forming the O octahedra dominate the energetics of the transition.Comment: 4 pages, 2 figure

УПРАВЛІННЯ ФІНАНСОВОЮ БЕЗПЕКОЮ БАНКІВ: ІНСТРУМЕНТАРІЙ МОДЕЛЮВАННЯ

The article is devoted to the development of the complex of economic and mathematical models to support decision–making on managing commercial banks financial security. Aggregated model of management system of commercial banks financial security is presented. Basic conceptual scheme of the bank’s financial security management is developed.The proposed modern modeling tools on the bases of multivariate, econometric, simulation methods and decision making methods make possible to do integrated complex analysis at all levels of the banking market. The results of research in particular assessment and analysis of the survival and spread of crises in the banking market, the research of the particular bank financial security level dynamics in terms of external and internal factors are the basis for the formation and selection of scenarios of financial security ensuring taking into account the features, opportunities and competitive advantages of each bank. The implementation of the proposed modeling tools of financial security makes possible to improve the efficiency and effectiveness of the commercial bank activity and its financial security level.В работе разработан комплекс экономико–математических моделей поддержки принятия решений по управлению финансовой безопасностью коммерческого банка. Представлена агрегированная модель системы управления финансовой безопасностью коммерческого банка. Разработана базисная концептуальная схема процесса управления финансовой безопасностью коммерческого банка. Предложено современный инструментарий моделирования на основе оценки и анализа выживаемости и распространения кризисных ситуаций на банковском рынке, исследования динамики уровня финансовой безопасности конкретного банка в условиях внешних и внутренних факторов влияния для формирования и выбора сценариев обеспечения финансовой безопасности, их внедрения и оценки эффективности реализации.В роботі розроблено комплекс економіко–математичних моделей підтримки прийняття рішень з управління фінансовою безпекою комерційного банку. Представлена агрегована модель системи управління фінансовою безпекою комерційного банку. Розроблена базисна концептуальна схема процесу управління фінансовою безпекою комерційного банку. Запропоновано сучасний інструментарій моделювання на основі оцінки та аналізу виживаності та розповсюдження кризових ситуацій на банківському ринку, дослідження динаміки рівня фінансової безпеки конкретного банку в умовах зовнішніх і внутрішніх факторів впливу для формування та вибору сценаріїв забезпечення фінансової безпеки, їх впровадження та оцінки ефективності реалізації

The Effect of ff-dd Magnetic Coupling in Multiferroic RRMnO3_3 Crystals

We have established detailed magnetoelectric phase diagrams of (Eu$_{0.595}$Y$_{0.405}$)$_{1-x}$Tb$_x$MnO$_3$ ($0 \le x \le 1$) and (Eu,Y)$_{1-x}$Gd$_x$MnO$_3$ ($0 \le x \le 0.69$), whose average ionic radii of $R$-site ($R$: rare earth) cations are equal to that of Tb$^{3+}$, in order to reveal the effect of rare earth 4$f$ magnetic moments on the magnetoelectric properties. In spite of the same $R$-site ionic radii, the magnetoelectric properties of the two systems are remarkably different from each other. A small amount of Tb substitution on $R$ sites ($x \sim 0.2$) totally destroys ferroelectric polarization along the a axis ($P_a$), and an increase in Tb concentration stabilizes the $P_c$ phase. On the other hand, Gd substitution ($x \sim 0.2$) extinguishes the $P_c$ phase, and slightly suppresses the $P_a$ phase. These results demonstrate that the magnetoelectric properties of $R$MnO$_3$ strongly depend on the characteristics of the rare earth 4$f$ moments.Comment: 10 pages, 5 figures Submitted to Journal of the Physical Society of Japa

Entangled-Photon Imaging of a Pure Phase Object

We demonstrate experimentally and theoretically that a coherent image of a pure phase object may be obtained by use of a spatially incoherent illumination beam. This is accomplished by employing a two-beam source of entangled photons generated by spontaneous parametric down-conversion. Though each of the beams is, in and of itself, spatially incoherent, the pair of beams exhibits higher-order inter-beam coherence. One of the beams probes the phase object while the other is scanned. The image is recorded by measuring the photon coincidence rate using a photon-counting detector in each beam. Using a reflection configuration, we successfully imaged a phase object implemented by a MEMS micro-mirror array. The experimental results are in accord with theoretical predictions.Comment: 11 pages, 3 figures, submittedto Phys. Rev. Let