Entangling distant atoms by interference of polarized photons

We propose a scheme to generate the entangled state of two Lambda-type three-level atoms trapped in distant cavities by using interference of polarized photons. Two possible spontaneous emission channels of each excited atom result in a coherent superposition of the states of two atoms. The subsequent detection of the different polarized photons reveals that both atoms are in different ground states, but an interference effect prevents us from distinguishing which atom is in which ground state; the atoms are thus entangled. In comparison with the original proposal of interference-induced entanglement [C. Cabrillo, J. Cirac, P. Garcia-Fernandez, and P. Zoller, Phys. Rev. A 59, 1025 (1999)]], in our scheme the weakly driven condition is not required, and the influence of atomic excitement and atomic recoil on the entanglement fidelity can be eliminated.     

Natural shaping of the cylindrically polarized beams

We have experimentally and theoretically shown that the circularly polarized beam bearing a singly charged optical vortex propagating through a uniaxial crystal can be split after focusing into the radially and azimuthally polarized beams in the vicinity of the focal area provided that the polarization handedness and the vortex topological charge have opposite signs.     

Focus shaping of cylindrically polarized vortex beams by a high numerical-aperture lens

The focus-shaping technique of a cylindrically polarized vortex beam by a high numerical-aperture lens is reported. Such a polarized vortex beam is decomposed into radial and azimuthal polarization. It is shown that the total intensity distribution in the focal region is dependent not only on the numerical-aperture maximal angle and the polarization rotation angle but also on the topological charge. By choosing the proper combination of parameters, the adjustably confined flat-topped focus and focal hole can be obtained. The focus-shaping technique may find wide applications, such as optical tweezers, laser printing and material processing.     

Different time slices for different degrees of freedom in Feynman path integration

A general scheme is presented for using different numbers of ‘time slices’ for different degrees of freedom in a path integral evaluation of the Boltzmann operator for a large molecular system. This will be particularly useful, for example, in evaluating the ‘quantum instanton’ rate constant [cf. W.H. Miller, Y. Zhao, M. Ceotto, S. Yang. J. Chem. Phys., 119, 1329 (2003)] for H atom transfer reactions, or any applications involving atoms with largely differing masses.     

Superfrustration of charge degrees of freedom

We review recent results, obtained with P. Fendley, on frustration of quantum charges in lattice models for itinerant fermions with strong repulsive interactions. A judicious tuning of kinetic and interaction terms leads to models possessing supersymmetry. In such models frustration takes the form of what we call superfrustration: an extensive degeneracy of supersymmetric ground states. We present a gallery of examples of superfrustration on a variety of 2D lattices.     

Collectivity and single-particle degrees of freedom

Intruder rotational bands in ⁴⁵Sc and ⁴⁵Ti have been investigated up to the maximum aligned angular momentum by means of EUROBALL IV and the Recoil Filter Detector (RFD). The use of the RFD allowed for a reduction of the -line Doppler broadening and, moreover, for a determination of very short level lifetimes. In the studied nuclei, the estimated deformation shows a gradual disappearance of the collectivity at the highest available spins.Received: 19 November 2002, Revised: 14 March 2003, Published online: 2 March 2004PACS: 21.10.Tg Lifetimes - 21.60.Cs Shell model - 27.40. + z P. Bednarczyk: Present address: GSI, Darmstadt, GermanyM.B. Smith: Present address: TRIUMF, Vancouver, Canada     

Superstrings with tensor degrees of freedom

We add antisymmetric tensor degrees of freedom to the usual superstring coordinates. We show that super and kappa symmetries are only achieved for the spacetime dimensionD=4. We also address problems related to the quantization of the model and discuss the influences of this extended spacetime in the usual quantum field theory.     

On Green's function for cylindrically symmetric fields of polarized radiation

Analytic expressions for Green's function describing the process of transfer of polarized radiation in homogeneous isotropic infinite medium in case of cylindrical symmetry and nonconservative scattering are obtained. The solution is based on the set of systems of Abel integral equations of the first kind obtained using the principle of superposition, and the known expression of Green's function for radiation fields with plane-parallel symmetry. Eigenvalue decompositions for the corresponding matrices of generalized spherical functions are found. Using this result the systems of Abel integral equations are diagonalized, and the final solution is obtained.     

On pseudodynamics of internal degrees of freedom

The results concerning the study of the model formulated within the Grassmann algebra G₆ are presented. It is shown under what assumptions the model reproduces basic features of leptons as they follow from the model of the electroweak interactions. Orbital degrees of freedom are ignored throughout the paper.     

Coarse graining of nonbonded degrees of freedom

We investigate the physical meaning of coarse-grained beads generated by coarse graining of nonbonded particles such as solvent molecules in a solution. Starting from the partition function, we analytically coarse grain an N-particle fluid to a system containing N-2 of the original particles plus a bead representing the two remaining particles. As a direct consequence of the lack of bonding interactions, the resulting effective potential becomes independent of the bead coordinates, i.e., ideal-gas-like, in the thermodynamic limit. Thus, there are no conservative forces between coarse-grained beads representing assemblies of nonbonded molecules nor between these beads and any other species in the system.     

Chiral dynamics with quark degrees of freedom

The possibility to detect DCC fluctuations is discussed. It is shown that interactions with quark background and dissipative effects due to interactions in the chiral field may result in damping of fluctuations. Since the magnitude of fluctuations depends strongly on the initial state and speed of chiral phase transition an accurate evaluation of all modifying processes is required to predict the observability of DCCs.     

Nucleon-nucleon correlations with quark degrees of freedom

A dynamical equation of two nucleons in a nucleus is formulated in the nonrelativistic quark model including Pauli blocking due to the other nucleons. This equation is solved with a model wave function containing the possiblity of six-quark bags with different radii. It is shown that the Pauli blocking effect is emphasized by the non-nucleonic degrees of freedom represented by six-quark bags. The modification of the quark momentum distribution for correlated nucleons is calculated and probabilities of non-NN components in nuclei are estimated.     

Heat transfer between two degrees of freedom

A particularly simple chaotic nonequilibrium open system with two Cartesian degrees of freedom, characterized by two distinct temperatures T(x) and T(y), is introduced. The two temperatures are maintained by Nose-Hoover canonical-ensemble thermostats. Both the equilibrium (no net heat transfer) and nonequilibrium (dissipative) Lyapunov spectra are characterized for this simple system.     

Intrinsic stochasticity with many degrees of freedom

We study a simple model equation describing a system with an infinity of degrees of freedom which displays an intrinsically chaotic behavior. Some concepts of fully developed turbulence are discussed in relation to this model. We also develop an approach based on Lyapunov exponent measurements. Numerical results on the distribution of Lyapunov numbers and the power spectrum of the associated Lyapunov vectors are presented and briefly discussed.     

Nonlinear two-mode squeezing obtained by analysing two-mode exponential quadrature operators in entangled state representation

By analysing the properties of two-mode quadratures in an entangled state representation (ESR) we derive from ESR some complicated exponential quadrature operators for nonlinear two-mode squeezing, which directly leads to wave function of the nonlinear squeezed state in ESR.     

基于增强拉曼散射的光子-原子双模压缩态的实现

拉曼散射过程中利用原子系综中初始制备的自旋激发(原子相干性),以及注入与原子系综中初始制备的自旋激发相关联的种子光场都可以极大的提高光场频率转换的效率,实现增强拉曼散射.本文理论上计算了增强拉曼散射过程中原子-光场量子界面的正交分量的量子起伏,得到了相干性导致的增强拉曼散射,只能在一定的范围内稍微提高初始光子-原子的压缩度;而关联增强拉曼散射,能够制备很强的光子-原子间的双模压缩.这样强压缩度的光子-原子量子界面,对于利用光场和原子系统实现量子精密测量研究有着非常重要的应用.     

Effect of spherical aberration on tightly focused cylindrically polarized vortex beams

In this paper attention is given to the effects of primary spherical aberration on the cylindrical polarized vortex beam based on the vector diffraction theory. It is observed that by properly choosing the polarization angle and topological charge one can obtain many novel focal patterns suitable for optical tweezers, laser printing and material process. However, it is observed that the focusing objective with spherical aberration generates structural modification and positional shift of the generated focal structure.     

Remarkable spectral difference between different polarized modes in four-level two-electron atomic system

The spectral difference between different polarized modes in two-dimensional (2D) four-level two-electron atomic system is investigated by simultaneously solving Maxwell's equations and rate equations of electronic population. A new physical model including pumping dynamics is introduced, and the transitions between the energy levels are governed by coupling rate equations and the Pauli Exclusion Principle. Results indicated that polarized lasing modes have different field pattern, spectral range, and intensity. The photons in TE field are easier to leak from random media than those in TM field. The quality factor of TM modes is larger than that of TE modes and the loss of TM modes to be lower than that of TE modes. The spectral properties in four-level two-electron atomic system are polarization-dependent.