Quantum computers: Achievements,implementation difficulties,and prospects

A review of the principles of operation of quantum computers and their elements is presented. The radical advantage of quantum algorithms for processing information over the classical ones is discussed, quantum entanglement is considered as the basic resource of quantum computations, and the most promising and interesting proposals on realization of quantum computers on the basis of trapped ions, nuclear spins, quantum dots, superconducting structures, and others are described. This review reflects the materials of the report presented at the scientific session of the Department of Nanotechnologies and Information Technologies of the Russian Academy of Sciences on February 25, 2010.     

Concentrational commensurate-incommensurate magnetic phase transition in Y1 − x Tb x Mn6Sn6

The magnetic state of Y_{1 ? x} Tb _x Mn₆Sn₆ (with x ≤ 0.25) alloy is studied at different temperatures and magnetic fields by neutron diffraction. The alloy with x _c = 0.22 exhibits an incommensurate-to-commensurate structure phase transition. The transition is accompanied by a decrease in the unit-cell volume. The weak dependence of the intensity of satellites on the x concentration and the monotonic displacement of their angular positions with increasing x allow us to conclude that the antiferromagnet → ferrimagnet transition occurs through the uniform magnetic state. The incommensurate phase in YMn₆Sn₆ exhibits four satellites, which are observed in the low-angle range of X-ray diffraction pattern and demonstrate different behavior with changing temperature. At 293 K, the antiferromagnet → ferromagnet transition in the Y_{1 ?x} Tb _x Mn₆Sn₆ compound can be induced by applied magnetic field, in particular, the field μ₀ H = 0.3 T induces the transition in Tb_0.15Y_0.85Mn₆Sn₆.     

Improving wear resistance of drilling tools fitted with synthetic diamond

The paper summarizes the findings of investigation of the influence of physicochemical and physical-mechanical properties of synthetic diamond grits on the drilling tool performance. Wear resistance of drilling tools is demonstrated to increase when they are fitted with synthetic diamond grits that are highly uniform in strength. The use of diamond grits with a better developed surface is found to provide a stronger grit retention in the bond and reduced drilling tool wear.     

Obtaining gunite-bodies with the additions of the waste products of the aluminum industry

Conclusions We studied the possibility of using the waste products of the aluminum industry as additives for obtaining gunite-bodies. In order to carry out guniting of the electrolytic cells, we suggested the application of the lining-slag type systems and the systems based on corundum for improving the service life of the refractory lining of these units.Translated from Ogneupory, No. 1, pp. 8–10, January, 1990.     

Estimating the Accuracy of the Indirect Method of Measurement of the Water Contamination of Crude Oil

A computational-experimental method is proposed for estimating the accuracy of measurement of the volume and mass of water in a crude oil stream.     

Chemical vapor deposition of isolated spherical diamond particles with embedded silicon-vacancy color centers onto the surface of synthetic opal

Isolated spherical diamond particles with embedded silicon-vacancy color centers are synthesized on a patterned surface of synthetic opal by chemical vapor deposition methods. The phase composition of the particles is determined and their structural and luminescence properties are studied. Prospects are discussed for the application of these particles as integrated spherical diamond microcavities, in which color centers are situated directly in the microcavities.