Filtration mapping as complete Bell state analyzer for bosonic particles.

In this paper, we present the approach to complete Bell state analysis based on filtering mapping. The key distinctive feature of this appoach is that it avoids complications related to using either hyperentanglement or representation of the Bell states as concatenated Greenber-Horne-Zeilinger (C-GHZ) state to perform discrimination procedure. We describe two techniques developed within the suggested approach and based on two-step algorithms with two different types of filtration mapping which can be called the non-demolition and semi-demolition filtrations. In the method involving non-demolition filtration measurement the filtration process employs cross-Kerr nonlinearity and the probe mode to distinguish between the two pairs of the Bell states. In the case of semi-demolition measurement, the two states are unambiguously discriminated and hence destroyed, whereas filtraton keeps the other two states intact. We show that the measurement that destroys the single photon subspace in every mode and preserves the superposition of zero and two photons can be realized with discrete photodetection based on microresonator with atoms.

Security of subcarrier wave quantum key distribution against the collective beam-splitting attack.

We consider a subcarrier wave quantum key distribution (QKD) system, where quantum encoding is carried out at weak sidebands generated around a coherent optical beam as a result of electro-optical phase modulation. We study security of two protocols, B92 and BB84, against one of the most powerful attacks for this class of systems, the collective beam-splitting attack. Our analysis includes the case of high modulation index, where the sidebands are essentially multimode. We demonstrate numerically and experimentally that a subcarrier wave QKD system with realistic parameters is capable of distributing cryptographic keys over large distances in presence of collective attacks. We also show that BB84 protocol modification with discrimination of only one state in each basis performs not worse than the original BB84 protocol in this class of QKD systems, thus significantly simplifying the development of cryptographic networks using the considered QKD technique.

[Variability of satellite DNA in 2 groups of field mice (Rodentia, Microtinae)]. / Izmenchivost' satellitnoi DNK v dvukh gruppakh polevok (Rodentia, Microtinae).

Nuclear DNAs of three forms of Microtus juldashi--M. carruthersi (group 1) and of three subspecies of polytypic species Alticola macrotis (group 2) were compared. Intensive interpopulational karyotype differentiation was observed in both groups, particularly, for centromeric heterochromatin quantity and localization. As satellite DNAs (satDNAs) were present in C-heterochromatin of the Rodents groups studied, the latter were used as a model for comparison of the satDNAs in the species in statu nascendi. With this view, the nuclear DNAs were studied by means of the neutral CsCl equilibrium centrifugation. In both groups examined, no correlation was found between the presence, the characteristics of the satDNAs and morphological as well as cytogenetic features of the animals. These results are an indirect confirmation of the idea, according to which satDNA does not possibly play significant role in the development of the reproductive isolation and species formation.

[A comparative study of Dicrostonyx torquatus chionopaes Allen DNA with different numbers of B-chromosomes]. / Sravnitel'noe izuchenie DNK kopytnykh lemmingov Dicrostonyx torquatus chionopaes Allen s razkucgbtn jikucgestvim V-khromosom.

In order to elucidate the possible relationship between the karyotype and the polynucleotide sequence organization in DNA, comparison was made between DNA from the liver of Dicrostonyx torquatus chionapaes Allen with different numbers of B-chromosomes (2n = 47-49, 1-3 B-chromosomes; 2n = 52-54,6-8 B-chromosomes). The reassociation kinetics patterns for denatured DNA fragments (about 300 nucleotides long) were obtained by the batch hydroxyapatite method. The analysis of these patterns showed a approximately 10% increase in the proportion of reiterated nucleotide sequences in the DNA of animals with 6-8 B-chromosomes. The increase in the proportion of reiterations in DNA correlated with increase in the number of B-chromosomes can be regarded as an indirect confirmation of the heterochromatic nature of B-chromosomes. The individual fractions of reiterated nucleotide sequences (C0t = 1.0) were isolated from studied DNas. The reassociation kinetics of these fractions and the thermostability of resulting duplexes were examined. The revealed differences are indicative of a certain dissimilarity in the polynucleotide sequences organization that correlate with variation in the number of B-chromosomes. The heterochromatic and euchromatic. DNAas from the liver cell nuclei of animals carrying different numbers of B-chromosomes were studied by thermal denaturation analysis and neutral CsCl equilibrium centrifugation. In the heterochromatic DNAs from livers of D. t. chionopaes with 6-8 B-chromosomes additional components enriched with AT-pairs were revealed. The specific features of DNA correlated with increase in the number of B-chromosomes are discussed in connection with peculiarities of B-chromosomes behaviour and their evolution in Dicrostonyx torquatus chionapaes.

[A method of comparison of DNA polynucleotide sequences]. / Metod sopostavleniia polinukleotidnykh posledovatel'nostei DNK

The results of a comparative analysis of the kinetic curves of reassociation of DNA of closely related species of Microtus (Microtus arvalis, Microtus oeconomus oeconomus, Microtus oeconomus Chachlovi) are presented. A five power polynomial was used as a mathematical model of the kinetic DNA reassociation curves. The values of polynomial coefficients and the theoretical value, both with statistical deviations dispersion, have been estimated with the help of a standard computer programme. The modified Fischer criterium was used for comparing the model kinetic curves of reassociation of the above species and of subspecies of Microtus, and to estimate the significance of the difference between two random means. A pair-wise comparison of the model curves shows that the similarity of the DNA polynucleotide sequences in two subspecies is less expressed than in two species of Microtus. A method of comparison of DNA nucleotide sequences is suggested on the basis of mathematical models of kinetic curves of DNA reassociation.