共查询到20条相似文献,搜索用时 10 毫秒
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S. N. Molotkov 《JETP Letters》2008,88(10):693-697
Is there a fundamental limit on the key distribution distance in quantum cryptography? Are there quantum key distribution protocols approaching this limit and how close can they approach this limit? The answer to the first question is both yes and no. A general answer to the first question can be given without considering a particular quantum key distribution protocol and its implementation. The answer to the second question is given by a particular protocol for which the distribution distance is close to the theoretical limit and the achievement of this value is limited by our possibilities of correcting errors using classical codes rather than by the quantum key distribution protocol itself. 相似文献
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Cynthia J. Jameson 《Molecular physics》2013,111(7):723-727
Monte Carlo simulations of the cage-to-cage jumps of Xe atoms in a crystalline zeolite using the experimentally observed molecular rate constants for cage-to-cage jumps were carried out to determine if there is a systematic spatial correlation of the distributions of Xe atoms among the cages at equilibrium. The neighbours of cages having an Xe occupancy that is less than the average occupancy are found to have distributions that are skewed toward higher occupancy compared with the overall distribution. On the other hand, the neighbours of cages having an Xe occupancy that is greater than the average occupancy are found to have distributions that are skewed toward lower occupancy than the overall distribution. 相似文献
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Cabello and Nakamura have shown [A. Cabello, Phys. Rev. Lett. 90, 190401 (2003)10.1103/PhysRevLett.90.190401] that the Kochen-Specker theorem can be applied to two-dimensional systems if one uses positive operator-valued measures (POVM). We show that the contextuality in their models is not of the Kochen-Specker type, but it is rather a result of not keeping track of the whole system on which the measurement is performed. This is connected to the fact that there is no one-to-one correspondence between the POVM elements and projectors on the extended Hilbert space, and the same POVM element has to originate from two different projectors when used in Cabello-Nakamura models. Moreover, we propose a hidden-variable formulation of the above models. 相似文献
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ZHANG Aimin HUANG Xiaodi LIN Jing 《声学学报:英文版》2005,24(4):300-311
When the signals received by any two array elements are not fully correlated, the performance of DOA (Direction Of Arrival) estimation methods might degrade if the plane-wave model assumption is still used. For narrowband uniform linear array, by utilizing the property of Toeplitz matrix, it is proved that the received signals can be expressed as the sum of several plane-wave signals, which can be viewed as the "splitting" parts of the true sources. The "splitting" of sources makes it difficult to estimate the true number of sources. As a result, spurious peaks might occur in the spatial spectrum when subspace-based high-resolution spatial spectrum estimation technique is used. 相似文献
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Samuel MA 《Physical review letters》1986,57(25):3133-3135
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Hilton RR 《Physical review letters》1990,65(23):2850-2852
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J.P. Kemp U.H.E. Hansmann Zheng Yu Chen 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(2):371-374
The similarity in the thermodynamic properties of two completely different theoretical models for the helix-coil transition
is examined critically. The first model is an all-atomic representation for a poly-alanine chain, while the second model is
a minimal helix-forming model that contains no system specifics. Key characteristics of the helix-coil transition, in particular,
the effective critical exponents of these two models agree with each other, within a finite-size scaling analysis.
Received 8 December 1999 相似文献
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It is demonstrated that, for high-Fresnel-number focusing systems illuminated by certain classes of partially coherent light, it is possible to produce a local minimum of intensity at the geometrical focus. Such an effect is possible even though the average intensity in the entrance plane of the lens is uniform. An explanation is offered for this effect, and potential applications are considered. 相似文献
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《Journal of Molecular Spectroscopy》1987,124(1):190-198
We report MRD-CI calculations on the ground state X2Π and the excited states A2Σ+ and B2Π of the CNO molecule in linear geometry. The surfaces for oxygen and carbon extraction are calculated using a limited CI expansion of 47 configuration state functions; in the vicinity of the minima obtained with this procedure large-scale CI calculations are carried out including deter-mination of the spin-orbit splitting of the 2Π states of the minima. We find that the B2Π state will be difficult to detect spectroscopically due to an avoided crossing just at the equilibrium geometry of the ground state at RCN = 2.25 a.u., RNO = 2.30 a.u. Accordingly we find two shallow minima for B2Π at RCN = 2.33 a.u., RNO = 2.91 a.u. and RCN = 2.78 a.u., RNO = 2.28 a.u., respectively. 相似文献
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Spaces with a Weyl-type connection and torsion of a special type that are determined by the structure of the differentiability conditions in the algebra of complex quaternions are considered. These conditions are consistent only if the curvature of the connection is self-dual. The Maxwell and SL(2,?) Yang–Mills fields associated with the irreducible components of the connection also turn out to be self-dual, so that the corresponding equations are fulfilled on the solutions of the generating system. Using the twistor structure of the latter, its general solution is obtained. The singular locus has a string-like (particle-like) structure generating the self-consistent algebraic dynamics of the string system. 相似文献
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Y. K. Akhmetbekov A. V. Bilsky D. M. Markovich A. A. Maslov P. A. Polivanov I. S. Tsyryul’nikov M. I. Yaroslavtsev 《Thermophysics and Aeromechanics》2009,16(3):325-333
Measurement results on the mean velocity fields and fields of velocity pulsations in the supersonic flows obtained by means
of the PIV measurement set “POLIS” are presented. Experiments were carried out in the supersonic blow-down and stationary
wind tunnels at the Mach numbers of 4.85 and 6. The method of flow velocity estimate in the test section of the blow-down
wind tunnel was grounded by direct measurements of stagnation pressure in the setup settling chamber. The size of tracer particles
introduced into the supersonic flow by a mist generator was determined; data on the structure of pulsating velocity in a track
of an oblique-cut gas-dynamic whistle were obtained under the conditions of self-oscillations. 相似文献
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Shigeo Kubota 《Optical Review》2012,19(6):432-435
Spatial coherence of the scanning laser beam was observed on the Young??s experimental set up using 50-??m-wide, 200-??m-separation double slits, which measured the less than unity fringe visibility in the Fraunhofer diffraction pattern of the double slits illuminated by the scanning laser beam at horizontal scan frequency 21 kHz, while approximately unity in case of the illumination by the laser beam at rest. This fact allow us to use the Zernike??s approximation when applying the van Cittert Zernike theorem to the scanning laser system such as the laser pico-projectors in order to estimate its speckle contrast in the projected image on the screen diffuser. The predicted and measured speckle contrasts showed excellent agreement on the screen illuminated by the laser projector. 相似文献
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Xin Yang Dong Yan Qianqian Bao Yan Zhang Cuili Cui 《Central European Journal of Physics》2014,12(12):813-821
Owing to interference induced by spontaneous emission, the density-matrix equations in a three-level Λ-type system have an additional coherence term, which plays a critical role in modulating the inversionless gain and electromagnetically induced transparency effect. In addition, it is shown that spontaneously generated coherence (SGC) has an effect on the entanglement between an atom and a photon of the coupling laser field by calculating the degree of entanglement (DEM) of the atomic system. In this paper, we investigate the influence of the SGC effect on atom-photon entanglement in a Λ-type system, which generally remains a high entangled state. When an incoherent pump source is introduced, we find that the SGC effect could exert considerable influence on the atom reduced entropy under certain conditions for both transient and steady states. More interestingly, such an incoherent pump field could actively affect the short-time dynamic behaviors of the transient quantum entangled state at a certain range of pump rate as a typical coherent case. 相似文献
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T. Sekihara A. Martínez Torres D. Jido E. Oset 《The European Physical Journal A - Hadrons and Nuclei》2012,48(1):10
We study the photoproduction of φ mesons in deuteron, paying attention to the modification of the cross-section from bound
protons to the free ones. For this purpose we take into account Fermi motion in single scattering and rescattering of φ to
account for φ absorption on a second nucleon as well as the rescattering of the proton on the neutron. We find that the contribution
of the double scattering for φ is much smaller than the typical cross-section of γp → φp in free space, which implies a very small screening of the φ production in deuteron. The contribution from the proton rescattering,
on the other hand, is found to be not negligible compared to the cross-section of γp → φp in free space, and leads to a moderate reduction of the φ photoproduction cross-section on a deuteron at forward angles if
the LEPS set-up is taken into account. The Fermi motion allows contribution of the single scattering in regions forbidden
by phase-space in the free case. In particular, we find that for momentum transfer squared close to the maximum value, the
Fermi motion changes drastically the shape of dσ/dt, to the point that the ratio of this cross-section to the free one becomes very sensitive to the precise value of t chosen, or the size of the bin used in an experimental analysis. Hence, this particular region of t does not seem to be the most indicated to find effects of a possible φ absorption in the deuteron. This reaction is studied
theoretically as a function of t and the results are contrasted with recent experiments at LEPS and Jefferson Lab. The effect of the experimental angular
cuts at LEPS is also discussed, providing guidelines for future experimental analyses of the reaction. 相似文献