Photon-Number-Splitting versus Cloning Attacks in Practical Implementations of the Bennett-Brassard 1984 protocol for Quantum Cryptography

In practical quantum cryptography, the source sometimes produces multi-photon pulses, thus enabling the eavesdropper Eve to perform the powerful photon-number-splitting (PNS) attack. Recently, it was shown by Curty and Lutkenhaus [Phys. Rev. A 69, 042321 (2004)] that the PNS attack is not always the optimal attack when two photons are present: if errors are present in the correlations Alice-Bob and if Eve cannot modify Bob's detection efficiency, Eve gains a larger amount of information using another attack based on a 2->3 cloning machine. In this work, we extend this analysis to all distances Alice-Bob. We identify a new incoherent 2->3 cloning attack which performs better than those described before. Using it, we confirm that, in the presence of errors, Eve's better strategy uses 2->3 cloning attacks instead of the PNS. However, this improvement is very small for the implementations of the Bennett-Brassard 1984 (BB84) protocol. Thus, the existence of these new attacks is conceptually interesting but basically does not change the value of the security parameters of BB84. The main results are valid both for Poissonian and sub-Poissonian sources.Comment: 11 pages, 5 figures; "intuitive" formula (31) adde

"Negative phase" of the heart rate and stroke volume in young athletes after the Harvard step test

Changes in the heart rate (HR) and stroke volume (SV) after the Harvard step test have been studied in young athletes at different stages of multiyear training. At the initial stage of training, the HR of young swimmers and skiers transiently decreased after the test below the starting values; i.e., during the recovery period, a "negative phase" of the HR was observed. After the test, the SVs of these athletes also decreased below the starting values, following the pattern of the pulse negative phase. However, the HR and SV negative phases were not synchronous. With advancement in the training level of the young swimmers and skiers, decreases in the HR and SV below the starting values were observed more seldom, and such decreases were virtually absent at the advanced stage. No decreases in the HR or SV after the Harvard step test were observed in young ice hockey players or gymnasts. © Pleiades Publishing, Inc. 2006

Changes in stroke volume in rat pups during adaptation to various regimens of motor activity

Experiments on rat pups showed that regular exercise for 4 weeks starting from day 14 after birth considerably increased stroke volume. Similar dynamics of stroke volume was observed in subsequent period of restraint locomotion. Experimental hypokinesia starting from day 14 after birth significantly limited the age-dependent increase in SV. However, subsequent exercise training promoted the increase in stroke volume in these rats. In trained rats the regulation of stroke volume during hypokinesia remained unchanged, while in restrained rats subsequent training was associated with considerable reduction of sympathetic regulation of stroke volume

On the nature of ferromagnetism in oxide semiconductors doped with 3d-elements

The origin and mechanisms of ferromagnetism in the new class of magnetic materials, oxide-diluted magnetic semiconductors (ODMS), are examined in a framework of the Stoner-Anderson model. Within the Green function formalism, a condition (the Stoner criterion) for nucleation of ferromagnetism is obtained for itinerant electrons in the narrow defect (vacancy) band, and an additional contribution due to interaction with 3d magnetic ions is derived. The "trigger" character of the transition to the ferromagnetic state in ODMS is discussed in its dependence on the type and concentration of 3d magnetic impurity dopant. The results of calculations are compared with the experimental data for the spontaneous magnetic moment in semiconducting titanium dioxide (TiO2) doped with 3d magnetic ions and containing various concentrations of oxygen vacancies

Pumping action of the heart in rat pups subjected to muscle training at different terms of postnatal ontogeny

Experiments performed on random-bred rat pups showed that muscle training during earlier terms of postnatal ontogeny produce more pronounced changes in the pumping function of the heart. © Springer Science+Business Media, Inc. 2005

Continuous Synthesis of Hydrogenated Graphene in Thermal Plasma

© 2018, Pleiades Publishing, Ltd. A single-stage catalyst free synthesis of hydrogenated graphene was studied in the process of methane conversion in a helium plasma jet created by a plasma torch at the power up to 45 kW and the pressure of 710 Torr. The synthesis products were studied by the methods of scanning and transmission electron microscopy, thermal analysis, Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction analysis

On the question of structure of ZnO thin films formed by IBAD and subsequently implanted with silver ions

© 2018 Institute of Physics Publishing. All rights reserved. Nanocrystalline ZnO thin films with a thickness of ∼ 235 nm were synthesized by ion beam-assisted deposition (IBAD) technique using a metal target of zinc and oxygen (O2) as a reactive gas. The near-surface region of the synthesized films was subsequently implanted with 30 keV Ag+ ions in the fluence range of (0.25-1)×1017 ion/cm2 at high ion current density of 12 μA/cm2. The structure parameters and morphology of as-deposited and subsequently implanted with silver ions ZnO films were investigated by X-ray diffraction and scanning electron microscopy techniques. It was found that the as-deposited ZnO films have inhomogeneous structure, which consists of nanocrystallites and disordered amorphous phase. The nanocrystallites of the obtained ZnO thin films have values of lattice parameters higher than for a bulk ZnO. Subsequent implantation with silver ions leads to a significant radiation heating and microstress relaxation of the film as well as to an increase in the size of nanocrystallites due to the amorphous phase

Magnetic Resonance Study of Fe-Implanted TiO<inf>2</inf> Rutile

© 2017, Springer-Verlag Wien.Single-crystal (100) and (001) TiO2 rutile substrates have been implanted with 40 keV Fe+ at room temperature with high doses in the range of (0.5–1.5) × 1017 ions/cm2. A ferromagnetic resonance (FMR) signal has been observed for all samples with the intensity and the out-of-plane anisotropy increasing with the implantation dose. The FMR signal has been related to the formation of a percolated metal layer consisting of close-packed iron nanoparticles in the implanted region of TiO2 substrate. Electron spin resonance (ESR) signal of paramagnetic Fe3+ ions substituting Ti4+ positions in the TiO2 rutile structure has been also observed. The dependences of FMR resonance fields on the DC magnetic field orientation reveal a strong in-plane anisotropy for both (100) and (001) substrate planes. An origin of the in-plane anisotropy of FMR signal is attributed to the textured growth of the iron nanoparticles. As result of the nanoparticle growth aligned with respect to the structure of the rutile host, the in-plane magnetic anisotropy of the samples reflects the symmetry of the crystal structure of the TiO2 substrates. Crystallographic directions of the preferential growth of iron nanoparticles have been determined by computer modeling of anisotropic ESR signal of substitutional Fe3+ ions

Long-lived photoinduced absorption in granular molybdenum disulfide thin films

© 2018 Institute of Physics Publishing. All rights reserved. We present results of the differential photoinduced absorption spectra investigation of the molybdenum disulfide nanogranular thin films. The films were produced by means of a sulfurization of pre-deposited by magnetron sputtering thin molybdenum films. It has been shown that photoexcitation with the light quanta with the energy higher than the bandgap leads to a modification of the absorption spectra in the visible range. Possible nature of the photoinduced absorption spectra will be discussed

Synthesis and properties of the molybdenum and tungsten disulfide thin films

© Published under licence by IOP Publishing Ltd.In the paper results of thin film synthesis and primary characterization of molybdenum and tungsten disulfides are presented. The synthesis is performed by means of the high-temperature sulfurization of the metallic Mo and W films in the flow of argon. Chemical and phase compositions and morphology of thin films are reported. Optical transmission and Raman spectra are presented and discussed