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1.
Hrant Yeritsyan Aram Sahakyan Sergey Nikoghosyan Vachagan Harutiunian Volodia Gevorkyan Norair Grigoryan Eleonora Hakhverdyan Yeghis Keheyan Rudolf Gevorgyan Hakob Sargisyan 《Central European Journal of Physics》2005,3(4):610-622
The results of dielectric properties and direct current specific electric conductivity measurements in Armenian natural clinoptilolite
samples are presented. Electron irradiation with energy 8 MeV and thermal treatment of samples are performed to elucidate
possible enhancement mechanisms of clinoptilolite parameters. The results are discussed on the basis of new point structural
defects formation and recombination of initial ones in samples. It was shown that the irradiation dose of 3·1016 el/cm2 is critical for natural zeolite structural change, which is manifested by significant changes in dielectric properties and
other characteristics. The samples subjected to high temperature heating after electron irradiation, in comparison with an
unquenched one, have a significantly higher (about an order of magnitude) value of specific conductivity. 相似文献
2.
In this paper we review the quenching dynamics of a quantum XY spin-1/2 chain in the presence of a transverse field, when the transverse field or the anisotropic interaction is quenched
at a slow but uniform rate. We also extend the results to the cases in which the system starts with any arbitrary initial
condition as opposed to the initial fully magnetically aligned state which has been extensively studied earlier. The evolution
is non-adiabatic in the time interval when the parameters are close to their critical values, and is adiabatic otherwise.
The density of defects produced due to nonadiabatic transitions is calculated by mapping the many-particle system to an equivalent
Landau-Zener problem. We show that in one dimension the density of defects in the final state scales as 1/√τ irrespective of the initial condition, where τ is the quenching time-scale. However, the magnitude of density of defects is found to depend on the initial condition.
相似文献
3.
Computer simulation of a many-particle quantum system is bound to reach the inevitable limits of its ability as the system size increases. The primary reason for this is that the memory size used in a classical simulator grows polynomially whereas the Hilbert space of the quantum system does so exponentially. Replacing the classical simulator by a quantum simulator would be an effective method of surmounting this obstacle. The prevailing techniques for simulating quantum systems on a quantum computer have been developed for purposes of computing numerical algorithms designed to obtain approximate physical quantities of interest. The method suggested here requires no numerical algorithms; it is a direct isomorphic translation between a quantum simulator and the quantum system to be simulated. In the quantum simulator, physical parameters of the system, which are the fixed parameters of the simulated quantum system, are under the control of the experimenter. A method of simulating a model for high-temperature superconducting oxides, the t–J model, by optical control, as an example of such a quantum simulation, is presented. 相似文献
4.
Janos Polonyi 《Central European Journal of Physics》2003,1(1):1-71
These introductory notes are about functional renormalization group equations and some of their applications. It is emphasised
that the applicability of this method extends well beyond critical systems, it actually provides us a general purpose algorithm
to solve strongly coupled quantum field theories. The renormalization group equation of F. Wegner and A. Houghton is shown
to resum the loop-expansion. Another version, due to J. Polchinski, is obtained by the method of collective coordinates and
can be used for the resummation of the perturbation series. The genuinely non-perturbative evolution equation is obtained
by a manner reminiscent of the Schwinger-Dyson equations. Two variants of this scheme are presented where the scale which
determines the order of the successive elimination of the modes is extracted from external and internal spaces. The renormalization
of composite operators is discussed briefly as an alternative way to arrive at the renormalization group equation. The scaling
laws and fixed points are considered from local and global points of view. Instability induced renormalization and new scaling
laws are shown to occur in the symmetry broken phase of the scaler theory. The flattening of the effective potential of a
compact variable is demonstrated in case of the sine-Gordon model. Finally, a manifestly gauge invariant evolution equation
is given for QED. 相似文献
5.
Liudvikas Pranevičius Darius Milčius Liudas Pranevičius Vaiva Širvinskaitë Jurgita Nomgaudyte Jean-Paul Rivier Claude Templier 《Central European Journal of Physics》2004,2(1):67-89
This paper presents a generalized approach to the mechanisms of oxidation, hydrogenation and nitriding of metals under ion
irradiation with reactive particles at elevated temperatures. Experimental results on the plasma oxidation of bilayered Y/Zr
films, the plasma hydrogenation of Mg films and the ion beam (1.2 keV N
2
+
) nitriding of stainless steel are presented and discussed. We make special emphasis on the analysis of surface effects and
their role in the initiation of mixing of bilayered films, the ingress of reactive species in the bulk and the restructuring
of the surface layers. It is suggested that primary processes driving reactive atoms from the surface into the bulk are surface
instabilities induced by thermal and ballistic surface atom relocations under reactive adsorption and ion irradiation, respectively.
The diffusion of adatoms and vacancies, at temperature when they become mobile, provide the means to relax the surface energy.
It is recognized that the stabilizing effect of surface adatom diffusion is significant at temperatures below 300–350°C. As
the temperature increases, the role of surface adatom diffusion decreases and processes in the bulk become dominant. The atoms
of subsurface monolayers occupy energetically favorable sites on the surface, and result in reduced surface energy. 相似文献
6.
Besides the well-known Shannon entropy, there is a set of Shannon-like entropies which have applications in statistical and
quantum physics. These entropies are functions of certain parameters and converge toward Shannon entropy when these parameters
approach the value 1. We describe briefly the most important Shannon-like entropies and present their graphical representations.
Their graphs look almost identical, though by superimposing them it appears that they are distinct and characteristic of each
Shannon-like entropy. We try to formulate the alternative entropic uncertainty relations by means of the Shannon-like entropies
and show that all of them equally well express the uncertainty principle of quantum physics. 相似文献
7.
Sushanta Dattagupta 《Pramana》2002,59(2):203-219
We present an ‘overview’ of coherence-to-decoherence transition in certain selected problems of condensed matter physics.
Our treatment is based on a subsystem-plus-environment approach. All the examples chosen in this paper have one thing in common
— the environmental degrees of freedom are taken to be bosonic and their spectral density of excitations is assumed to be
‘ohmic’. The examples are drawn from a variety of phenomena in condensed matter physics involving, for instance, quantum diffusion
of hydrogen in metals, Landau diamagnetism and c-axis transport in high T
c superconductors. 相似文献
8.
9.
We present a discussion on local quantum correlations and their relations with entanglement. We prove that a vanishing coefficient
of quantum correlations implies separability. The new results on locally decomposable maps which we obtain in the course of
the proof also seem to be of independent interest. 相似文献
10.
Proton conductivity phenomena in 10% Y-doped barium and strontium cerate are investigated experimentally and by quantum molecular dynamics simulations. In particular the impact of deviations from the cubic perovskite structure on the formation and mobility of protonic charge carriers is investigated. For Y: SrCeO3, which shows a larger deviation from the ideal cubic perovskite structure, the concentration and mobility of protonic defects is significantly lower than for Y: BaCeO3. The first is due to the decay of the oxygen position into two sites, only one of which is involved in the formation of protonic defects. The symmetry reduction also leads to the formation of different one-dimensional proton diffusion paths, and unfavourable jumps between such paths are supposed to control the macroscopic proton diffusion coefficient in Y: SrCeO3. The analysis suggests the formation of strong but transient hydrogen bonds and inter-octa-hedra proton transfer between vertices for SrCeO3 in contrast to just intra-octahedra proton transfer for BaCeO3. Whereas for BaCeO3 the proton transfer step is identified to be rate-limiting at T= 1000 K, for SrCeO3 both proton transfer and reorientation are found to be of similar magnitude. 相似文献
11.
Physical consequences of ionic diffusion processes play a major role on the outcome of electrophysiology experiments due to
both their contribution to the ionic transmembrane transport and phenomena taking place at the measuring instruments interface.
As most of the time heterogenities in biological media with respect to ionic diffusion constants are disregarded, we intended
to look upon the general case of ionic diffusion at the interface of two liquids on which gradients of these diffusion constants
no longer can be neglected. We developed a theoretical model for the diffusion potential which emerges at an aqueous interface
under gradients of concentration and diffusion constants. The experimental validation of our model was achieved through potential
difference measurements of the diffusion potential between two solutions containing sodium chloride (NaCl) and glycerine solutions
of various concentrations. Within the studied domain of the electrical charge mobility ratio, we noticed that experimental
results are in agreement with the theoretically inferred diffusion potential values. This demonstrates that the resulting
relationship for the diffusion potential inferred from our model could be applied for other cases, as well. When the ionic
solutions contains an indefinite quantity of glycerine or an unknown substance able to modify diffusion constants of sodium
and chloride, it was shown that through measurements of the diffusion potential one can infer the unknown concentration of
glycerine and the modified ionic mobility ratio. This, in turn, builds up the foundation for a novel yet simple and efficient
analitycal sensing device for quantitative determination in the field. 相似文献
12.
Using K-causal relation introduced by Sorkin and Woolgar [1], we generalize results of Garcia-Parrado and Senovilla [2,3]
on causal maps. We also introduce causality conditions with respect to K-causality which are analogous to those in classical
causality theory and prove their inter-relationships. We introduce a new causality condition following the work of Bombelli
and Noldus [4] and show that this condition lies in between global hyperbolicity and causal simplicity. This approach is simpler
and more general as compared to traditional causal approach [5,6] and it has been used by Penrose et al [7] in giving a new proof of positivity of mass theorem. C
0-space-time structures arise in many mathematical and physical situations like conical singularities, discontinuous matter
distributions, phenomena of topology-change in quantum field theory etc.
相似文献
13.
Cu diffusion along clean Si(111), (110) and (100) surfaces are investigated by Auger electron spectroscopy and low energy
electron diffraction. The effective diffusion coefficients of copper are measured in the temperature range from 500 to 650°C.
It is shown that the Cu transport along silicon surface occurs by the diffusion of Cu atoms through Si bulk and the segregation
of Cu atoms to the surface during the diffusion process. It is found that the segregation coefficients of Cu to silicon surface
during the diffusion process depend on surface orientation. 相似文献
14.
B. Michel 《Fortschritte der Physik》1982,30(5):233-310
The current situation, trends and possibilities in Continuum Mechanics are reviewed. Special attention is given to its application in solid state physics as well on a phenomenological as on the microscopic scale. Current problems in Micromechanics of solids, such as mechanical interactions of defects near surfaces and interfaces and interfaces are dealt with. Recent investigations on the generalized J-integral concepts in fracture mechanics are discussed too. The paper gives some information on new trends of micromechanics towards micromechanics towards micro-continuum-thermodynamics. Some remarks are presented concerning stress-assisted diffusion phenomena as a special case of the generalized mechanics of diffusion. The possibilities of the powerfull finite element method (FEM) in micromechanics of continuous media are spoken about. The interrelation between continuum mechanics and quantum mechanics is discussed about, the possibility of quantum states of cracks too. 相似文献
15.
We present an overview of two models of quantum random walk. In the first model, the discrete quantum random walk, we present
the explicit solution for the recurring amplitude of the quantum random walk on a one-dimensional lattice. We also introduce
a new method of solving the problem of random walk in the most general case and use it to derive the hitting amplitude for
quantum random walk on the hypercube. The second is a special model based on a local interaction between neighboring spin-1/2
particles on a one-dimensional lattice. We present explicit results for the relevant quantities and obtain an upper bound
on the speed of convergence to limiting probability distribution. 相似文献
16.
S. K. Islam F. C. Jain 《International Journal of Infrared and Millimeter Waves》1998,19(12):1649-1659
A high performance quantum interference transistor (QUIT) realized using high mobility 1-D MODFET channels is presented. The operation of this 1-D QUIT is based on electrostatic Aharonov-Bohm quantum interference effect. The channel length of the device is smaller than the inelastic coherence length of the electrons in the quantum well wire channel, otherwise scattering will randomize electron's phase and destroy the quantum interference effect. Transport characteristics of the 0.2 m channel 1-D QUIT are calculated at 4.2 °K and compared with a two-dimensional QUIT device reported in literature. Our calculations show a significant improvement of the transconductance in one-dimensional transistors compared with its two-dimensional counterpart. The maximum frequency of operation of the 1-D QUIT is in the Tera Hertz regime, which makes it very attractive device for high frequency applications. 相似文献
17.
S. G. Nedel’ko M. A. Krysyuk A. L. Apanasenko L. N. Lymarenko Z. T. Moroz 《Journal of Applied Spectroscopy》1997,64(1):55-61
Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped
with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly
described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation
(5.5·104 Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum
cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics
of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure
crystals is analyzed (preliminarily).
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997. 相似文献
18.
Implementation of quantum controlled phase gate and preparation of multiparticle entanglement in cavity QED
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Schemes are presented for realizing quantum controlled phase gate and preparing an N-qubit W-like state, which are based on the large-detuned interaction among three-state atoms, dual-mode cavity and a classical pulse. In particular, a class of W states that can be used for perfect teleportation and superdense coding is generated by only one step. Compared with the previous schemes, cavity decay is largely suppressed because the cavity is only virtually excited and always in the vacuum state and the atomic spontaneous emission is strongly restrained due to a large atom-field detuning. 相似文献
19.
Carl M. Bender 《Czechoslovak Journal of Physics》2004,54(10):1027-1038
It has recently been shown that a non-Hermitian Hamiltonian H possessing an unbroken PT symmetry (i) has a real spectrum that is bounded below, and (ii) defines a unitary theory of quantum mechanics with positive norm. The proof of unitarity requires a linear operator C, which was originally defined as a sum over the eigenfunctions of H. However, using this definition it is cumbersome to calculate C in quantum mechanics and impossible in quantum field theory. An alternative method is devised here for calculating C directly in terms of the operator dynamical variables of the quantum theory. This new method is general and applies to a variety of quantum mechanical systems having several degrees of freedom. More importantly, this method can be used to calculate the C operator in quantum field theory. The C operator is a new time-independent observable in PT-symmetric quantum field theory. 相似文献
20.
Satyabrata Adhikari Sunandan Gangopadhyay 《International Journal of Theoretical Physics》2009,48(2):403-408
Recently, a new class of W-states has been defined by Agarwal and Pati (Phys. Rev. A 74:062320, 2006) and it has been shown that they can be used as a quantum channel for teleportation and superdense coding. In this work,
we identify those three-qubit states from the set of the new class of W-states which are most efficient or suitable for quantum teleportation. We show that with some probability
is best suited for teleportation channel in the sense that it does not depend on the input state. 相似文献