Implementation of Fault-tolerant Quantum Logic Gates via Optimal Control

The implementation of fault-tolerant quantum gates on encoded logic qubits is considered. It is shown that transversal implementation of logic gates based on simple geometric control ideas is problematic for realistic physical systems suffering from imperfections such as qubit inhomogeneity or uncontrollable interactions between qubits. However, this problem can be overcome by formulating the task as an optimal control problem and designing efficient algorithms to solve it. In particular, we can find solutions that implement all of the elementary logic gates in a fixed amount of time with limited control resources for the five-qubit stabilizer code. Most importantly, logic gates that are extremely difficult to implement using conventional techniques even for ideal systems, such as the T-gate for the five-qubit stabilizer code, do not appear to pose a problem for optimal control.Comment: 18 pages, ioptex, many figure

Photon storage in Lambda-type optically dense atomic media. II. Free-space model

In a recent paper [Gorshkov et al., Phys. Rev. Lett. 98, 123601 (2007)], we presented a universal physical picture for describing a wide range of techniques for storage and retrieval of photon wave packets in Lambda-type atomic media in free space, including the adiabatic reduction of the photon group velocity, pulse-propagation control via off-resonant Raman techniques, and photon-echo based techniques. This universal picture produced an optimal control strategy for photon storage and retrieval applicable to all approaches and yielded identical maximum efficiencies for all of them. In the present paper, we present the full details of this analysis as well some of its extensions, including the discussion of the effects of non-degeneracy of the two lower levels of the Lambda system. The analysis in the present paper is based on the intuition obtained from the study of photon storage in the cavity model in the preceding paper [Gorshkov et al., Phys. Rev. A 76, 033804 (2007)].Comment: 26 pages, 8 figures. V2: significant changes in presentation, new references, higher resolution of figure

Quantum control theory for coupled 2-electron dynamics in quantum dots

We investigate optimal control strategies for state to state transitions in a model of a quantum dot molecule containing two active strongly interacting electrons. The Schrodinger equation is solved nonperturbatively in conjunction with several quantum control strategies. This results in optimized electric pulses in the THz regime which can populate combinations of states with very short transition times. The speedup compared to intuitively constructed pulses is an order of magnitude. We furthermore make use of optimized pulse control in the simulation of an experimental preparation of the molecular quantum dot system. It is shown that exclusive population of certain excited states leads to a complete suppression of spin dephasing, as was indicated in Nepstad et al. [Phys. Rev. B 77, 125315 (2008)].Comment: 24 pages, 9 figure

ЧИСЛЕННОЕ И АНАЛИТИЧЕСКОЕ РЕШЕНИЯ КРАЕВОЙ ЗАДАЧИ ДЛЯ УРАВНЕНИЯ ПАРАБОЛИЧЕСКОГО ТИПА В НЕЦИЛИНДРИЧЕСКОЙ ОБЛАСТИ

The article presents comparative analysis of the non-steady heat transfer problem solutions in the area of the border moving according to the law t under the conditions of temperature heating. The solutions were obtained using the method of difference schemes and analytically.В настоящей статье проведен сравнительный анализ решений задачи нестационарной теп-лопроводности в области с границей, движущейся по закону , в условиях температурного нагрева. Решения получены с помощью метода разностных схем и аналитически

Mother-fetus immunogenetic dialogue as a factor of progeny immune system development

Despite the advances in medicine, about 4 million children under the age of 6 months die annually around the world due to infection, which is 450 deaths per hour (UNISEF, 2009). The degree of development of the immune system of children born in time is determined by many factors, including the immunogenetic similarity or difference of mother and fetus organisms, which, in turn, is due to the genotypes of mating pairs, as well as the selection of surrogate mothers during in vitro fertilization. From our review of the literature, it follows that immunogenetic interactions of mother and fetus organisms, which occur at all stages of pre- and postnatal development, have a signifcant effect on the resistance of offspring to infections and allergens. Before implantation, the mother’s immune responses are formed under the influence of semen fluid antigens, leukocytes and cytokines, as well as under the influence of the genes of the major histocompatibility complex, which are expressed in embryos at the stage of two cells. After implantation, transplacental transfer of immunoglobulins and immunocompetent cells becomes of immunomodulating importance. It is important to emphasize that, although substances with a high molecular weight usually do not pass through the placenta, this rule does not apply to immunoglobulin G (IgG), which, with a molecular weight of about 160 kDa, overcomes the transplacental barrier due to binding to the fetal Fc receptor. The level of IgG in newborns usually correlates with the level of maternal antibodies. During the period of natural feeding, the immune protection of newborns is provided by the mechanisms of innate immunity and the factors of humoral immunity of mothers. It has been shown that immunoglobulins from the milk of many animal species are transferred through the neonatal intestinal epithelium to the blood. Since breast milk contains large amounts of various immunoactive components, including proteins, cytokines, hormones, immunoglobulins, exosomes containing micro-RNA, and viable immune cells, the immunomodulating effects of breast milk persist even after elimination of maternal immunoglobulins from the blood of the offspring, up to maturation. Analysis of a large body of experimental data shows that the study of mechanisms of “motherfetus” and “mother-newborn” interactions are the basis of a knowledge base needed to fnd means of life-long directed modulation of the descendants’ immune status

The termal deformation reducing in sheet metal at manufacturing parts by CNC cutting machines

In various industries for the manufacturing of parts (workpieces) from sheet metal the CNC machines for thermal cutting (laser/plasma/gas cutting) are used. During process of thermal cutting, various deformations of the metal can occur, that cause the distortion of the geometric forms and sizes of the cut parts. These distortions are caused both by the uneven distribution of temperature in the sheet, and by certain geometric characteristics of the cutting process. Geometric characteristics are determined by the set sequence (order) of cutting of figured parts, as well as by selecting the piercing points of sheet material, i.e. the places of inserting the tool into the material. Previously, the authors formulated heuristic geometric rules, that allow reducing the value of geometric deformations of parts produced by the CNC cutting machines. To comply with these rules, users of Computer-Aided Design (CAM) systems that are used to generate NC programs, have to use interactive design methods. One of these rules (so-called "Part Hardness Rule") refers to the selecting the location of points for inserting (piercing) a CNC machine tool into the material. The paper describes a model based on the use of the heat conduction equation, which makes it possible to calculate the temperature of the sheet material at each moment of cutting process. The computational experiments showed that the points, which according to the "Part Hardness Rule" can't be used for piercing, have a higher material temperature than the points that satisfy this rule. In the paper the results of the computational experiments are given. Another rule (socalled "Sheet Hardness Rule"), which also reduces the deformation of the material during thermal cutting, refers to the order of parts cutting from the sheet. A heuristic algorithm that automatically generates the order of cutting parts that satisfy the rules of "Part Hardness" and of "Sheet Hardness" is developed. Developed software allows us to abandon the interactive methods of the NC programs generation for the thermal cutting of figured parts on CNC machines. © 2019 IOP Publishing Ltd. All rights reserved.Russian Foundation for Basic Research, RFBRThe work was supported by the Russian Foundation for Basic Research (grant 19-01-00573)

Разработка микронасосной системы для поддержки кровообращения

Introduction. Support systems currently used in modern cardiac surgery to provide partial or complete, permanent or temporary replacement of cardiac function are frequently characterized by large dimensions, thus requiring major surgical interventions. Low invasiveness can be ensured by reducing the size of the implanted part of such systems, allowing these devices to be inserted through the femoral artery.Aim. Development of a minimally invasive micropump system to support blood circulation.Materials and methods. Based on the analysis of implementation of micropump circulatory support systems (MCSS), the configuration, operational principles and main components of such a system were determined. When designing a micropump, as a unit defining the weight and size parameters of the entire system, numerical and experimental methods were used to optimize its flow path based on the condition of minimizing blood injury and thrombus formation. The lubrication and cooling system was developed by solving the thermodynamic problem of heat removal. The electronic control unit was developed on the basis of accumulated experience in the design and operation of control units for circulatory support systems.Results. A micropump with a diameter of 6.5 mm and a length of 43 mm with the required hydro- and hemodynamic parameters was designed. The device ensures minimal trauma and thrombus formation. The main MCSS parameters, as well as its main components (electric drives, lubrication and cooling systems), were defined. The configuration and operational principles of the electronic control unit (ECU), consisting in a microprocessor-based control system with feedback, were developed. The ECU built-in software manages the rotational speed of the electric drives of the micropump and coolant supply pump in the required range. In addition, the software is used to measure, display and register the MCSS operational parameters, as well as to monitor their operation in the required ranges and to exchange data between the ECU and the PC.Conclusion. All the necessary documentation for the MCSS nodes and components was prepared. These nodes and components ensure the hydro- and hemodynamic parameters required for the use of the developed minimally invasive micropump system. Future work will address the stages of MCSS assembly and debugging.Введение. В современной кардиохирургии для обеспечения частичной или полной, постоянной или временной замены функции сердца применяются системы поддержки, имеющие размеры, требующие проведения серьезной хирургической операции. Для обеспечения малой инвазивности требуется существенно уменьшить размеры имплантируемой части системы, что позволит вводить эти устройства через бедренную артерию.Цель работы. Разработка малоинвазивной микронасосной системы для поддержки кровообращения.Материалы и методы. На основе анализа технологии применения системы поддержки кровообращения (МСПК) разработан ее состав, принцип работы, спроектированы основные ее узлы и элементы. При проектировании микронасоса как узла, определяющего массогабаритные параметры всей системы, используются численные и экспериментальные методы оптимизации его проточной части из условия минимизации травмы крови и тромбообразования. При разработке системы смазки и охлаждения решалась термодинамическая задача по обеспечению отвода тепла. Электронный блок управления разработан на основании накопленного опыта проектирования и эксплуатации блоков управления клинически применяемых систем вспомогательного кровообращения.Результаты. Спроектирован микронасос диаметром 6,5 мм и длиной 43 мм с требуемыми гемо- и гидродинамическими параметрами, обеспечивающий минимальную травму и тромбообразование. Определены основные параметры и спроектированы узлы и элементы МСПК (электроприводы, система смазки и охлаждения). Разработан состав и принцип работы электронного блока управления (ЭБУ), который представляет собой микропроцессорную систему управления МСПК с обратной связью. Встроенное программное обеспечение ЭБУ позволяет управлять частотой вращения электроприводов микронасоса и насоса подачи охлаждающей жидкости в требуемом диапазоне, измерять, отображать, регистрировать режимные параметры работы МСПК, а также осуществлять контроль их работы в требуемых диапазонах, обмениваться данными между ЭБУ и компьютером.Заключение. Подготовлена документация на узлы и элементы МСПК, обеспечивающие требуемые гидро- и гемодинамические параметры, необходимые для применения микронасосной малоинвазивной системы, что позволяет перейти к сборке и отладке узлов и элементов МСПК в целом

The dynamic model of enterprise revenue management

The article presents the dynamic model of enterprise revenue management. This model is based on the quadratic criterion and linear control law. The model is founded on multiple regression that links revenues with the financial performance of the enterprise. As a result, optimal management is obtained so as to provide the given enterprise revenue, namely, the values of financial indicators that ensure the planned profit of the organization are acquired

Stripes in Doped Antiferromagnets: Single-Particle Spectral Weight

Recent photoemission (ARPES) experiments on cuprate superconductors provide important guidelines for a theory of electronic excitations in the stripe phase. Using a cluster perturbation theory, where short-distance effects are accounted for by exact cluster diagonalization and long-distance effects by perturbation (in the hopping), we calculate the single-particle Green's function for a striped t-J model. The data obtained quantitatively reproduce salient (ARPES-) features and may serve to rule out "bond-centered" in favor of "site-centered" stripes.Comment: final version as appeared in PRL; (c) 2000 The American Physical Society; 4 pages, 4 figure

Carbon nanotube-based quantum pump in the presence of superconducting lead

Parametric electron pump through superconductor-carbon-nanotube based molecular devices was investigated. It is found that a dc current, which is assisted by resonant Andreev reflection, can be pumped out from such molecular device by a cyclic variation of two gate voltages near the nanotube. The pumped current can be either positive or negative under different system parameters. Due to the Andreev reflection, the pumped current has the double peak structure around the resonant point. The ratio of pumped current of N-SWNT-S system to that of N-SWNT-N system (I^{NS}/I^N) is found to approach four in the weak pumping regime near the resonance when there is exactly one resonant level at Fermi energy inside the energy gap. Numerical results confirm that in the weak pumping regime the pumped current is proportional to the square of the pumping amplitude V_p, but in the strong pumping regime the pumped current has the linear relation with V_p. Our numerical results also predict that pumped current can be obtained more easily by using zigzag tube than by using armchair tube