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 共查询到10条相似文献,搜索用时 31 毫秒
1.
石国升  王志刚  赵纪军  胡钧  方海平 《中国物理 B》2011,20(6):68101-068101
Using density functional theory computation, we show that sodium ions and hydrated sodium ions can be strongly adsorbed onto a hydrophobic graphite surface via cation-π interactions. The key to this cation-π interaction is the coupling of the delocalized π states of graphite and the empty orbitals of sodium ions. This finding implies that the property of the graphite surface is extremely dependent on the existence of the ions on the surface, suggesting that the hydrophobic property of the graphite surface may be affected by the existence of the sodium ions.  相似文献   

2.
Bohr's principle of complementarity has a long history and it is an important topic in quantum theory, among which the famous example is the duality relation. The relation between visibility C and distinguishability D,C~2+D~2≤ 1, has long been recognized as the only representative of the duality relation. However, recent researches have shown that this inequality is not good enough because it is not tight for multipath interferometers. Meanwhile, a tight bound for the multipath interferometer has been put forward. Here we design and experimentally implement a three-path interferometer coupling with path indicator states. The wave property of photons is characterized by l_1-norm coherence measure, and the particle property is based on distinguishability of the indicator states. The new duality relation of the three-path interferometer is demonstrated in our experiment, which bounds the union of a right triangle and a part of elliptical area inside the quadrant of a unit circle. Data analysis confirms that the new bound is tight for photons in three-path interferometers.  相似文献   

3.
郝亚江  梁九卿 《中国物理》2006,15(6):1161-1171
Based on the exact solution of the time-dependent Schrodinger equation for two-species Bose-Einstein condensates (BECs) consisting of two hyperfine states of the atoms coupled by a tuned adiabatic and time-varying Raman coupling, we obtain analytically the entanglement dynamics of the system with various initial states, particularly the SU(2) coherent state, for both of cases with and without the nonlinear interactions. It is shown that the effect of nonlinear interaction on the entanglement appears only in a longer time period depending on the BEC parameters.  相似文献   

4.
A model of the perturbed complex Toda chain (PCTC) to describe the dynamics of a Bose-Einstein condensate (BEC) N-soliton train trapped in an applied combined external potential consisting of both a weak harmonic and tilted periodic component is first developed. Using the developed theory, the BEC N-soliton train dynamics is shown to be well approximated by 4N coupled nonlinear differential equations, which describe the fundamental interactions in the system arising from the interplay of amplitude, velocity, centre-of-mass position, and phase. The simplified analytic theory allows for an efficient and convenient method for characterizing the BEC N-soliton train behaviour. It further gives the critical values of the strength of the potential for which one or more localized states can be extracted from a soliton train and demonstrates that the BEC N-soliton train can move selectively from one lattice site to another by simply manipulating the strength of the potential.  相似文献   

5.
Based on Presnel-Kirchhoff diffraction theory, we set up a diffraction model of nonlinear optical media to Gaussian beam, which can interpret the Z-scan phenomenon from a new way. This theory is not only well consistent with the conventional Z-scan theory in the case of small nonlinear phase shift, but also can fit for the lager nonlinear phase shift. Numeric computations indicate the shape of the .Z-scan curve is greatly affected by the value of the nonlinear phase shift. The symmetric dispersion-like Z-scan curve is only valid for small nonlinear phase shift (|Δφ0| < π), but with increasing the nonlinear phase shift, the valley of the transmittance is severely suppressed and the peak is greatly enhanced. Further calculations show some new interesting results.  相似文献   

6.
徐俊  胡响明 《中国物理快报》2006,23(10):2725-2728
The coherent effects including counter-rotating coupling on spontaneous emission are presented for a microwave driven V-type three-level atom. Novel coherent effects are realized: (i) There is an infinite series of spectral lines, which are separated by the microwave frequency, independent of the separation of the excited states, no matter whether the microwave transition is resonant or not. This is in sharp contrast to the case of the weak coupling, where the spectral interval is mainly determined by the separation of the excited states. (ii) Selective appearance and inhibition of the spectral lines are obtained simply by varying the microwave Rabi frequency. (iii) Spectral lines have a twofold structure. The physical mechanisms are analysed by employing the dressed states representation.  相似文献   

7.
The magnetic and electronic properties of the geometrically frustrated triangular antiferromagnet CuCrO2 are investigated by first principles through density functional theory calculations within the generalized gradient approximations (GGA)+U scheme. The spin exchange interactions up to the third nearest neighbours in the ab plane as well as the coupling between adjacent layers are calculated to examine the magnetism and spin frustration. It is found that CuCrO2 has a natural two-dimensional characteristic of the magnetic interaction. Using Monte-Carlo simulation, we obtain the Neel temperature to be 29.9 K, which accords well with the experimental value of 24 K. Based on non-collinear magnetic structure calculations, we verify that the incommensurate spiral-spin structure with (110) spiral plane is believable for the magnetic ground state, which is consistent with the experimental observations. Due to intra-layer geometric spin frustration, parallel helical-spin chains arise along the a, b, or a + b directions, each with a screw-rotation angle of about 120°. Our calculations of the density of states show that the spin frustration plays an important role in the change of d-p hybridization, while the spin-orbit coupling has a very limited influence on the electronic structure.  相似文献   

8.
The Rydberg states of neutral atoms are strongly polarisable and possess long lifetimes because of high energies which can lead to strong and long range dipole-dipole interactions.The energy levels corresponding to these states are shifted because of dipole-dipole interactions and can be used to block transitions of more than one excitation in the Rydberg regime.This reputed Rydberg blockade is obtained when the excitation is shifted out of resonance by these interactions.Electromagnetically induced transparency(EIT)is sensitive to a small detuning.At large distances,up to several micrometers,the interactions can interrupt the EIT consequence.Herein we investigate a novel scheme based on EIT and Rydberg blockade and performed a simulation of a controlled-NOT(C-NOT)quantum gate which is critical for quantum computation by using neutral atoms.  相似文献   

9.
In recent years, linear fractal sea surface models have been developed for the sea surface in order to establish an electromagnetic backscattering model. Unfortunately, the sea surface is always nonlinear, particularly at high sea states. We present a nonlinear fractal sea surface model and derive an electromagnetic backscattering model. Using this model, we numerically calculate the normalized radar cross section (NRCS) of a nonlinear sea surface. Comparing the averaged NRCS between linear and nonlinear fractal models, we show that the NRCS of a linear fractal sea surface underestimates the NRCS of the real sea surface, especially for sea states with high fractal dimensions, and for dominant ocean surface gravity waves that are either very short or extremely long.  相似文献   

10.
We present an analytical analysis of the spatial resolution of quantum ghost imaging implemented by entangled photons from a general, spontaneously parametric, down-conversion process. We find that the resolution is affected by both the pump beam waist and the nonlinear crystal length. Hence, we determined a method to improve the resolution for a certain imaging setup. It should be noted that the resolution is not uniquely related to the degree of entanglement of the photon pair since the resolution can be optimized for a certain degree of entanglement. For certain types of Einstein-Podolsky-Rosen(EPR) states——namely the momentum-correlated or momentum-positively correlated states——the resolution exhibits a simpler relationship with the pump beam waist and crystal length. Further, a vivid numerical simulation of ghost imaging is presented for different types of EPR states,which supports our analysis. This work discusses applicable references to the applications of quantum ghost imaging.  相似文献   

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