Fluctuation-electromagnetic interaction of a moving neutral particle with a condensed-medium surface: relativistic approach

A relativistic theory of the fluctuation-electromagnetic interaction of a moving small particle with a flat boundary of a homogeneous isotropic polarizable medium is presented for the first time with a maximum degree of completeness. The theory is based on the dipole approximation of fluctuation-electromagnetic theory. Fundamental relativistic expressions are derived for conservative and dissipative forces and heating power of a particle. These expressions reduce to earlier nonrelativistic results in particular cases. The results obtained in other approaches and experimental studies of fluctuation-electromagnetic interactions are critically analyzed.     

Counting atoms using interaction blockade in an optical superlattice

We report on the observation of an interaction blockade effect for ultracold atoms in optical lattices, analogous to the Coulomb blockade observed in mesoscopic solid state systems. When the lattice sites are converted into biased double wells, we detect a discrete set of steps in the well population for increasing bias potentials. These correspond to tunneling resonances where the atom number on each side of the barrier changes one by one. This allows us to count and control the number of atoms within a given well. By evaluating the amplitude of the different plateaus, we can fully determine the number distribution of the atoms in the lattice, which we demonstrate for the case of a superfluid and Mott insulating regime of 87Rb.     

Two-photon interaction of coherent radiation with a thin film of resonant atoms

The problem of the interaction of an ultrashort optical pulse and a thin film of resonant atoms under the conditions of two-photon absorption, third-harmonic generation, and the inverse effect of the latter on the pump pulse via Raman scattering is studied. The fact that the field acting on an atom differs from the macroscopic field in the film is also taken into consideration. It is shown that the polarization of the film undergoes dynamic relaxation even in the absence of irreversible relaxation, suppressing Rabi oscillations and establishing stationary values of the populations of the resonant energy levels and of the polarization of the film at the pump and the third-harmonic frequencies. Zh. éksp. Teor. Fiz. 115, 30–42 (January 1999)     

Production of three-dimensional entanglement for two atoms with a single resonant interaction

A scheme is proposed for generating three-dimensional maximally entangled states for two atoms. In the scheme the atoms are trapped in a two-mode cavity. The scheme only requires a single resonant interaction of the atoms with the cavity modes. Therefore, the scheme is very simple and required interaction time is very short, which is important in view of decoherence.     

The effect of surface channeling of neutral atoms

Special features of reflection of neutral atoms from crystal surfaces are considered in the case of grazing incidence. It is shown that polarization effects and the long-range part of the potential of interaction of ions with atomic chains and planes can play an important role in describing processes of reflection of atoms from the surface. The analysis in this paper shows that the polarization of accelerated neutral atoms in the case of grazing incidence on the surface can lead to the formation of bound surface states. The threshold condition for the angle of arrival of atoms at the plane at which the capture by such states is possible is obtained.     

Selective photochemical isotope “burning” upon the interaction of resonant laser radiation with atoms

The method of laser isotope separation based on selective excited-atom “burning” in a flow with buffer and reagent gases was implemented experimentally for zinc and rubidium. Selective excitation of isotopes was accomplished by the one-photon method using weak absorption lines and at the edge of the Doppler contour of atomic absorption with small isotope shift.     

Electric and magnetic mirrors and gratings for slowly moving neutral atoms and molecules

Those atoms or molecules which happen to have positive Stark or Zeeman energy shift (by virtue of their particular internal quantum state) are repelled by regions of high electrostatic or magnetostatic energy density, respectively. Using electrostatic or magnetostatic fields, which are periodic in a plane, it is possible to construct mirrors and gratings for slowly moving atoms and molecules. The theory of such devices is presented, together with some ideas for their fabrication.     

A new approach to the resonant interaction between atoms and strong electromagnetic field

The interaction of a two-level system with an intense electromagnetic field, is analysed by an approach which is capable of taking into account the character of interatomic collisions. This approach demonstrates why the Rabi shift cannot be observed in the Doppler limit, and clarifies the assumptions underlying the work of other authors.     

Observation of a resonant four-body interaction in cold cesium Rydberg atoms

Cold Rydberg atoms subject to long-range dipole-dipole interactions represent a particularly interesting system for exploring few-body interactions and probing the transition from 2-body physics to the many-body regime. In this work we report the direct observation of a resonant 4-body Rydberg interaction. We exploit the occurrence of an accidental quasicoincidence of a 2-body and a 4-body resonant Stark-tuned F?rster process in cesium to observe a resonant energy transfer requiring the simultaneous interaction of at least four neighboring atoms. These results are relevant for the implementation of quantum gates with Rydberg atoms and for further studies of many-body physics.     

Optical clock with ultracold neutral atoms

We demonstrate how to realize an optical clock with neutral atoms that is competitive to the currently best single ion optical clocks in accuracy and superior in stability. Using ultracold atoms in a Ca optical frequency standard, we show how to reduce the relative uncertainty to below 10(-15). We observed atom interferences for stabilization of the laser to the clock transition with a visibility of 0.36, which is 70% of the ultimate limit achievable with atoms at rest. A novel scheme was applied to detect these atom interferences with the prospect to reach the quantum projection noise limit at an exceptional low instability of 4 x 10(-17) in 1 s.     

Bipartite entanglement purification with neutral atoms

We theoretically study bipartite entanglement purification with neutral atoms via cavity-assistant interaction and linear optical elements. We focus on entanglement distillation and the recurrence protocol, whose performances under idealized and realistic conditions are discussed. The implementation of these purification protocols has been tested with numerical simulations. We analyze the performance and stability of all required operations and emphasize that all techniques are feasible with current experimental technology.     

Fluctuation-induced electromagnetic interaction of a moving particle with a plane surface

The most general (nonrelativistic) formulas for the force of attraction to the surface and for the drag of a nonrelativistic atom moving parallel to it, as well as for the lateral and normal forces acting on a moving dipole molecule and on a charged particle (in the case of parallel and perpendicular motion), are derived for the first time in the framework of the fluctuational electromagnetic theory. The dependences of these forces on the velocity, temperature, separation, and dielectric properties of the atom and the surface are derived. The effect of the nondissipative resonance interaction between a moving neutral atom and the field of surface plasmons, as well as the possible emergence of a positive (accelerating) force acting on the atom (nanoprobe), is substantiated theoretically. The role of dynamic fluctuational forces and their possible experimental measurement when using the quartz microbalance technique and an atomic-force microscope (in the dynamic mode), as well as during deceleration of atomic beams in open nanotubes, are considered. The correctness of the obtained results is confirmed by their agreement with most of the available theoretical relations derived by other authors.     

A self consistent approach to the transport equation for moving atoms in interaction with laser fields

The transport equations for moving atoms in interaction with laser fields, are derived using the hamiltonian in terms of the quantum dynamical variables for the center of mass motion and by introducing suitably defined local density matrices. Use is also made of the phase space variables associated with the quantum dynamical variables of center of mass and the projection operator techniques.     

Micromanipulation of neutral atoms with nanofabricated structures

A large variety of trapping and guiding potentials can be designed by bringing cold atoms close to charged or current carrying material objects. We describe the basic principles of constructing microscopic traps and guides and how to load atoms into them. The simplicity and versatility of these methods will allow for miniaturization and integration of atom optical elements into matter-wave quantum circuits on Atom Chips. These could form the basis for robust and widespread applications in atom optics, ranging from fundamental studies in mesoscopic physics to possibly quantum information systems. Received: 20 December 1999 / Revised version: 7 March 2000 / Published online: 5 April 2000     

Charging and stabilization of Pd atoms and clusters on an electron-rich MgO surface

We report density functional theory calculations on the interaction of Pd atoms and small Pd clusters with an electron-rich MgO surface. This surface can be generated by forming a specific kind of defects, named (H⁺)(e⁻) centers, using well known chemical recipes. By deposition of gas-phase Pd atoms on the properly functionalized MgO surface, one can generate collections of small Pd cluster anions with peculiar chemical properties. The (H⁺)(e⁻) centers act as nucleation sites for diffusing Pd atoms and favor the formation of small, thermally stable clusters. The presence of an extra charge on the metal cluster results in a large vibrational red-shift of adsorbed CO molecules. The present results intend to stimulate experimental work to produce stable metal cluster anions on the surface of an ionic oxide.     

Microsolvation of neutral dopants in small He clusters: relative locations of Li and Na atoms

Quantum Calculations of binding energies and spatial distributions are carried out using Diffusion Monte Carlo (DMC) methods for several bosonic helium clusters containing lithium and sodium atoms as neutral impurities. The global interaction forces have been constructed via sum-of-potentials models with accurate empirical potentials for the two-body (2B) forces, disregarding many-body (MB) effects on such weakly interacting systems. The results clearly show that both impurities can bind to the helium clusters but that they chiefly reside outside them and do not undergo microsolvation.     

利用V-型三能级原子与双模腔场的共振相互作用制备纠缠W态

提出了一种利用V-型三能级原子与双模腔场的共振相互作用制备多原子及多腔场纠缠W态的新方案,并用共生纠缠度研究了该模型中的纠缠演化和热纠缠现象.     

Trapping and manipulating neutral atoms with electrostatic fields

We report on experiments with cold thermal (7)Li atoms confined in combined magnetic and electric potentials. A novel type of three-dimensional trap was formed by modulating a magnetic guide using electrostatic fields. We observed atoms trapped in a string of up to six individual such traps, a controlled transport of an atomic cloud over a distance of 400 microm, and a dynamic splitting of a single trap into a double well potential. Applications for quantum information processing are discussed.