Entanglement may enhance the channel capacity in arbitrary dimensions

We consider explicitly two examples of d-dimensional quantum channels with correlated noise and show that, in agreement with previous results on Pauli qubit channels, there are situations where maximally entangled input states achieve higher values of the output mutual information than product states. We obtain a strong dependence of this effect on the nature of the noise correlations as well as on the parity of the space dimension, and conjecture that when entanglement gives an advantage in terms of mutual information, maximally entangled states achieve the channel capacity.Comment: 12 pages, 3 figure

Entanglement enhanced classical capacity of quantum communication channels with correlated noise in arbitrary dimensions

We study the capacity of d-dimensional quantum channels with memory modeled by correlated noise. We show that, in agreement with previous results on Pauli qubit channels, there are situations where maximally entangled input states achieve higher values of mutual information than product states. Moreover, a strong dependence of this effect on the nature of the noise correlations as well as on the parity of the space dimension is found. We conjecture that when entanglement gives an advantage in terms of mutual information, maximally entangled states saturate the channel capacity.Comment: 10 pages, 5 figure

Relativistic Doppler effect in quantum communication

When an electromagnetic signal propagates in vacuo, a polarization detector cannot be rigorously perpendicular to the wave vector because of diffraction effects. The vacuum behaves as a noisy channel, even if the detectors are perfect. The ``noise'' can however be reduced and nearly cancelled by a relative motion of the observer toward the source. The standard definition of a reduced density matrix fails for photon polarization, because the transversality condition behaves like a superselection rule. We can however define an effective reduced density matrix which corresponds to a restricted class of positive operator-valued measures. There are no pure photon qubits, and no exactly orthogonal qubit states.Comment: 10 pages LaTe

Nonadditivity effects in classical capacities of quantum multiple-access channels

We study classical capacities of quantum multi-access channels in geometric terms revealing breaking of additivity of Holevo-like capacity. This effect is purely quantum since, as one points out, any classical multi-access channels have their regions additive. The observed non-additivity in quantum version presented here seems to be the first effect of this type with no additional resources like side classical or quantum information (or entanglement) involved. The simplicity of quantum channels involved resembles butterfly effect in case of classical channel with two senders and two receivers.Comment: 5 pages, 5 figure

Development and Design of Energy Efficient Oil-Flooded Screw Compressors

It is estimated that about 17% of the world's generated power is used for compression. Thus all, even minor improvement of the efficiency of compressors will substantially reduce CO2 emission. This paper presents development of family of energy efficient oil-flooded screw compressors for Kirloskar Pneumatic Company Ltd. The developmental techniques adopted to improve efficiency such as introduction of superior 'N' rotor profile, rotor clearance management, performance calculation using 3D CCM (Computational Continuum Mechanics), direct parametric interface to CAD (Computer Aided Design), which contains bearing selection for complete 3D solid modelling. Also, contemporary prototyping and experimental investigation is supported by the fully computerised data acquisition and processing. The cumulative improvement of all these elements of the design process resulted in a very efficient machine which guarantees the competitive position of Kirloskar Pneumatic Company Limited in the screw compressor market

Strictly contractive quantum channels and physically realizable quantum computers

We study the robustness of quantum computers under the influence of errors modelled by strictly contractive channels. A channel $T$ is defined to be strictly contractive if, for any pair of density operators $\rho,\sigma$ in its domain, $\| T\rho - T\sigma \|_1 \le k \| \rho-\sigma \|_1$ for some $0 \le k < 1$ (here $\| \cdot \|_1$ denotes the trace norm). In other words, strictly contractive channels render the states of the computer less distinguishable in the sense of quantum detection theory. Starting from the premise that all experimental procedures can be carried out with finite precision, we argue that there exists a physically meaningful connection between strictly contractive channels and errors in physically realizable quantum computers. We show that, in the absence of error correction, sensitivity of quantum memories and computers to strictly contractive errors grows exponentially with storage time and computation time respectively, and depends only on the constant $k$ and the measurement precision. We prove that strict contractivity rules out the possibility of perfect error correction, and give an argument that approximate error correction, which covers previous work on fault-tolerant quantum computation as a special case, is possible.Comment: 14 pages; revtex, amsfonts, amssymb; made some changes (recommended by Phys. Rev. A), updated the reference

On the classical capacity of quantum Gaussian channels

The set of quantum Gaussian channels acting on one bosonic mode can be classified according to the action of the group of Gaussian unitaries. We look for bounds on the classical capacity for channels belonging to such a classification. Lower bounds can be efficiently calculated by restricting to Gaussian encodings, for which we provide analytical expressions.Comment: 10 pages, IOP style. v2: minor corrections, close to the published versio

ВОЗМОЖНОСТИ ОФЭКТ С ЦИТРАТОМ GA-67 И ПЭТ/КТ С 18-ДГ В ОЦЕНКЕ РАСПРОСТРАНЕННОСТИ ЛИМФОМЫ ХОДЖКИНА

Hodgkin disease  is a malignancy of lymphoid tissue,  at the age of 15 to 24 years it accounts  for 1⁄6 of all oncology disease. The aim of the study was to evaluate the benefits of single-photon emission computed tomography (SPECT) with citrate  gallium-67  and combined  positron  emission  tomography  (PET/CT) with 18-FDG in a patient  with Hodgkin disease.  Results:  SPECT  detected  no affected cervical nodes that  were found with PET/CT. Conclusion: presented in this article SPECT technique is not suitable for studying this patient. Limitations of the methods for this case and opportunities for overcoming the limitations are discussed.Лимфома Ходжкина является злокачественным новообразованием лимфоидной ткани, на долю которого в возрасте от 15 до 24 лет приходится 1⁄6 часть всех онкологических заболеваний. Цель исследования: оценить возможности методов однофотонной эмиссионной компьютерной томографии (ОФЭКТ) с цитратом галлия-67 и совмещенной позитронно-эмиссионной  томографии (ПЭТ/КТ) с 18-ФДГ  у больного с лимфомой Ходжкина. Результаты: ОФЭКТ не выявила пораженных шейных лимфатических узлов, которые были обнаружены при ПЭТ/КТ. Вывод: сцинтиграфия с цитратом 67Ga должна предполагать выполнение ОФЭКТ всех областей интереса

ОПЫТ ПРИМЕНЕНИЯ АППАРАТА HISTOSCANNING В РАННЕЙ ДИАГНОСТИКЕ РАКА ПРЕДСТАТЕЛЬНОЙ ЖЕЛЕЗЫ

In September 2011, the Research Institute of Uronephrology and Human Reproductive Health began to use an apparatus for the early diagnosis of prostate cancer. One hundred and fifty-six studies have been conducted by now. In the examinees, the level of prostate-specific antigen was estimated to be in the range of 1.09 to 209 ng/ml. The results of the studies confirm European data on the sensitivity and specificity of this procedure.В сентябре 2011 г. в НИИ уронефрологии и репродуктивного здоровья человека начали использовать аппарат для ранней диагностики рака предстательной железы. На настоящий момент выполнено 156 исследований. Уровень простатспецифического антигена у обследуемых определялся в диапазоне от 1,09 до 209 нг/мл. Результаты исследований подтверждают европейские данные о чувствительности и специфичности данной методики

ПОЛУЧЕНИЕ АЛЮМОКЕРАМИЧЕСКИХ КАРКАСНЫХ КОМПОЗИТОВ НА ОСНОВЕ МАХ-ФАЗЫ Ti2AlC МЕТОДОМ СВС-ПРЕССОВАНИЯ

A one-stage manufacturing technology of aluminum-ceramic skeleton composites by combining the processes of self-propagating hightemperature synthesis (SHS) of a porous skeleton formed by the MAX phase of the Ti2AlC composition and its impregnation by the aluminum melt under the pressure (SHS compaction). A composition of the exothermic charge 2Ti + C + 22,5 wt % Al + 10 wt % TiH2, which provides the formation of a porous skeleton of the Ti2AlC phase without impurity phases by the SHS technology, is selected. It is shown that when impregnating the hot SHS skeleton with aluminum, new phases are formed such as the MAX phase (Ti3AlC2), titanium carbide (TiC), and titanium aluminide (Al3Ti). However, the content of the basic MAX phase remains high, and the ceramic component of the material consists of Ti2AlC by 76 %. When analyzing the microstructure, it is revealed that the composite has certain residual porosity after the impregnation and cooling. The influence of the impregnation pressure (q = 22, 28 and 35 MPa) on the distribution of the aluminum content over the height and radius of the diametral sample section is investigated experimentally. It is shown that the nonuniform Al distribution over the sample bulk is caused by the nonuniform pressure and temperature fields as well as different compactibility of hot inner and colder outer sample parts. The degree of compaction of characteristic zones is leveled as the impregnation pressure increases, and composition inhomogeneity over the sample bulk decreases. The difference of aluminum concentration over the sample bulk at q = 35 MPa does not exceed 5 %. By the hardness level (HB ≈ 150 kg/mm2), the SHS-compacted aluminum-ceramic skeleton composite based on the Ti2AlC MAX phase corresponds to high-strength Al–Zn–Mg–Cu aluminum alloys.Рассмотрена одностадийная технология получения алюмокерамических каркасных композитов путем совмещения процессов самораспространяющегося высокотемпературного синтеза (СВС) пористого каркаса из МАХ-фазы состава Ti2AlC и его пропитки под давлением расплавом алюминия (метод СВС-прессования). Выбран состав экзотермической шихты 2Ti + C + + 22,5мас.%Al + 10мас.%TiH2, обеспечивающий получение по технологии СВС пористого каркаса МАХ-фазы Ti2AlC без примесных фаз. Показано, что при пропитке алюминием горячего СВС-каркаса образуются новые фазы: МАХ-фаза (Ti3AlC2), карбид (TiC) и алюминид (Al3Ti) титана. Вместе с тем содержание базовой МАХ-фазы остается высоким, и керамический компонент материала на 76 % состоит из Ti2AlC. При анализе микроструктуры выявлено, что после пропитки и охлаждения композит имеет некоторую остаточную пористость. Выполнены экспериментальные исследования влияния давления пропитки (q = 22, 28 и 35 МПа) на распределение содержания алюминия по высоте и радиусу диаметрального сечения образца. Показано, что неоднородное распределение Al по объему образца обусловлено неоднородными полями давления и температуры и разной уплотняемостью горячих внутренних и более холодных наружных объемов образца. При увеличении давления пропитки степень уплотнения характерных зон выравнивается и неоднородность состава по объему образца уменьшается. При q = 35 МПа разность концентраций алюминия по объему образца не превышает 5 %. По уровню твердости (HB ≈ 150 кг/мм2) СВС-прессованный алюмокерамический каркасный композит на основе МАХ-фазы Ti2AlC соответствует алюминиевым сплавам высокой прочности Al–Zn–Mg–Cu