Nonclassicality in Weak Measurements

We examine weak measurements of arbitrary observables where the object is prepared in a mixed state and on which measurements with imperfect detectors are made. The weak value of an observable can be expressed as a conditional expectation value over an infinite class of different generalized Kirkwood quasi-probability distributions. "Strange" weak values for which the real part exceeds the eigenvalue spectrum of the observable can only be found if the Terletsky-Margenau-Hill distribution is negative, or, equivalently, if the real part of the weak value of the density operator is negative. We find that a classical model of a weak measurement exists whenever the Terletsky-Margenau-Hill representation of the observable equals the classical representation of the observable and the Terletsky-Margenau-Hill distribution is nonnegative. Strange weak values alone are not sufficient to obtain a contradiction with classical models. We propose feasible weak measurements of photon number of the radiation field. Negative weak values of energy contradicts all classical stochastic models, whereas negative weak values of photon number contradict all classical stochastic models where the energy is bounded from below by the zero-point energy. We examine coherent states in particular, and find negative weak values with probabilities of 16% for kinetic energy (or squared field quadrature), 8% for harmonic oscillator energy and 50% for photon number. These experiments are robust against detector inefficiency and thermal noise.Comment: 12 pages, 8 figure

Weak Measurements with Arbitrary Pointer States

The exact conditions on valid pointer states for weak measurements are derived. It is demonstrated that weak measurements can be performed with any pointer state with vanishing probability current density. This condition is found both for weak measurements of noncommuting observables and for $c$-number observables. In addition, the interaction between pointer and object must be sufficiently weak. There is no restriction on the purity of the pointer state. For example, a thermal pointer state is fully valid.Comment: 4 page

Development and evaluation of double locus sequence typing for molecular epidemiological investigations of Clostridium difficile.

Despite the development of novel typing methods based on whole genome sequencing, most laboratories still rely on classical molecular methods for outbreak investigation or surveillance. Reference methods for Clostridium difficile include ribotyping and pulsed-field gel electrophoresis, which are band-comparing methods often difficult to establish and which require reference strain collections. Here, we present the double locus sequence typing (DLST) scheme as a tool to analyse C. difficile isolates. Using a collection of clinical C. difficile isolates recovered during a 1-year period, we evaluated the performance of DLST and compared the results to multilocus sequence typing (MLST), a sequence-based method that has been used to study the structure of bacterial populations and highlight major clones. DLST had a higher discriminatory power compared to MLST (Simpson's index of diversity of 0.979 versus 0.965) and successfully identified all isolates of the study (100 % typeability). Previous studies showed that the discriminatory power of ribotyping was comparable to that of MLST; thus, DLST might be more discriminatory than ribotyping. DLST is easy to establish and provides several advantages, including absence of DNA extraction [polymerase chain reaction (PCR) is performed on colonies], no specific instrumentation, low cost and unambiguous definition of types. Moreover, the implementation of a DLST typing scheme on an Internet database, such as that previously done for Staphylococcus aureus and Pseudomonas aeruginosa ( http://www.dlst.org ), will allow users to easily obtain the DLST type by submitting directly sequencing files and will avoid problems associated with multiple databases

Nonclassicality of Thermal Radiation

It is demonstrated that thermal radiation of small occupation number is strongly nonclassical. This includes most forms of naturally occurring radiation. Nonclassicality can be observed as a negative weak value of a positive observable. It is related to negative values of the Margenau-Hill quasi-probability distribution.Comment: 3 pages, 3 figure

О частотно-контрастной характеристике системы технического зрения, построенной на КМОП- и ПЗС- сенсорах изображения

У процесі проектування системи технічного зору (СТЗ), важливим кроком є вибір сенсора зображення і об'єктива, які б задовольняли поставленим вимогам до роздільної здатності. Роздільна здатність датчика зображення визначається по частотно-контрастній характеристиці (ЧКХ). У даній роботі запропоновано новий метод теоретичної оцінки ЧКХ, який базується на топологічних параметрах сенсора зображення і параметрах об'єктива. Мета цього методу полягає у створенні зручного інструменту для попереднього визначення роздільної здатності системи формування зображень на ранніх етапах проектування системи технічного зору. Основна ідея методу полягає в розгляді сенсора зображення з позиції вихідного сигналу сенсора і параметрів, що впливають на нього, таких як, параметри освітленості, оптичної системи, сенсора зображення. У даній роботі була представлена залежність ЧКХ для різних параметрів сенсора зображення і об'єктива. Цей метод дозволяє розрахувати роздільну здатність системи формування зображення в площині досліджуваного об'єкта, що значно підвищує інформативність даної характеристики в сенсі проектування СТЗ.In the process of designing a machine vision system, a critical step is selecting an image sensor and optics that satisfy required parameters of resolution. The resolution of the image sensor is determined by modulation transfer function (MTF). In this paper a method for the theoretical estimation of MTF based on topologic parameters of the image sensor and parameters of lenses is proposed. The purpose of this work is development a method that will be handy instrument for the resolution calculation of the imaging system on the initial stage of the designing process of the machine vision. In this paper dependency of MTF for different parameters of image sensor and lenses were presented. This method can be used for calculation resolution of imaging system in object’s plain domain.В процессе проектирования системы технического зрения (СТЗ), важным шагом является выбор сенсора изображения и объектива, которые бы удовлетворяли требованиям, поставленным к разрешающей способности. Разрешение датчика изображения определяется по частотно-контрастной характеристике (ЧКХ). В данной работе предложен новый метод теоретической оценки ЧКХ, который основан на топологических параметрах сенсора изображения и параметрах объектива. Цель этого метода состоит в создании удобного инструмента для предварительного анализа разрешающей способности системы формирования изображения на ранних этапах проектирования системы технического зрения. Основная идея метода заключается в рассмотрении сенсора изображения с позиции выходного сигнала сенсора и параметров влияющих на него, таких как, параметры освещенности, оптической системы, сенсора изображения. В данной работе была представлена зависимость ЧКХ для различных параметров сенсора изображения и объектива. Этот метод позволяет рассчитать разрешающую способность системы формирования изображения в плоскости объекта, что значительно повышает информативность данной характеристики в смысле проектирования СТЗ

Interaction of Charged 3D Soliton with Coulomb Center

The Einstein - de Broglie particle-soliton concept is applied to simulate stationary states of an electron in a hydrogen atom. According to this concept, the electron is described by the localized regular solutions to some nonlinear equations. In the framework of Synge model for interacting scalar and electromagnetic fields a system of integral equations has been obtained, which describes the interaction between charged 3D soliton and Coulomb center. The asymptotic expressions for physical fields, describing soliton moving around the fixed Coulomb center, have been obtained with the help of integral equations. It is shown that the electron-soliton center travels along some stationary orbit around the Coulomb center. The electromagnetic radiation is absent as the Poynting vector has non-wave asymptote $O(r^{-3})$ after averaging over angles, i.e. the existence of spherical surface corresponding to null Poynting vector stream, has been proved. Vector lines for Poynting vector are constructed in asymptotical area.Comment: LaTeX ,12 page

On the clustering phase transition in self-gravitating N-body systems

The thermodynamic behaviour of self-gravitating $N$-body systems has been worked out by borrowing a standard method from Molecular Dynamics: the time averages of suitable quantities are numerically computed along the dynamical trajectories to yield thermodynamic observables. The link between dynamics and thermodynamics is made in the microcanonical ensemble of statistical mechanics. The dynamics of self-gravitating $N$-body systems has been computed using two different kinds of regularization of the newtonian interaction: the usual softening and a truncation of the Fourier expansion series of the two-body potential. $N$ particles of equal masses are constrained in a finite three dimensional volume. Through the computation of basic thermodynamic observables and of the equation of state in the $P - V$ plane, new evidence is given of the existence of a second order phase transition from a homogeneous phase to a clustered phase. This corresponds to a crossover from a polytrope of index $n=3$, i.e. $p=K V^{-4/3}$, to a perfect gas law $p=K V^{-1}$, as is shown by the isoenergetic curves on the $P - V$ plane. The dynamical-microcanonical averages are compared to their corresponding canonical ensemble averages, obtained through standard Monte Carlo computations. A major disagreement is found, because the canonical ensemble seems to have completely lost any information about the phase transition. The microcanonical ensemble appears as the only reliable statistical framework to tackle self-gravitating systems. Finally, our results -- obtained in a ``microscopic'' framework -- are compared with some existing theoretical predictions -- obtained in a ``macroscopic'' (thermodynamic) framework: qualitative and quantitative agreement is found, with an interesting exception.Comment: 19 pages, 20 figure

Quantum theory of successive projective measurements

We show that a quantum state may be represented as the sum of a joint probability and a complex quantum modification term. The joint probability and the modification term can both be observed in successive projective measurements. The complex modification term is a measure of measurement disturbance. A selective phase rotation is needed to obtain the imaginary part. This leads to a complex quasiprobability, the Kirkwood distribution. We show that the Kirkwood distribution contains full information about the state if the two observables are maximal and complementary. The Kirkwood distribution gives a new picture of state reduction. In a nonselective measurement, the modification term vanishes. A selective measurement leads to a quantum state as a nonnegative conditional probability. We demonstrate the special significance of the Schwinger basis.Comment: 6 page

Nonclassical Properties of Coherent States

It is demonstrated that a weak measurement of the squared quadrature observable may yield negative values for coherent states. This result cannot be reproduced by a classical theory where quadratures are stochastic $c$-numbers. The real part of the weak value is a conditional moment of the Margenau-Hill distribution. The nonclassicality of coherent states can be associated with negative values of the Margenau-Hill distribution. A more general type of weak measurement is considered, where the pointer can be in an arbitrary state, pure or mixed.Comment: 4 pages. Some arguments rewritten, reference added to quant-ph/0402050. Conclusion unchange