Dynamics of interaction between two-level atoms in a laser field and linear stationary optical dimensional resonances

Formulas for radiative forces acting on the atoms of a diatomic object in a field of external laser radiation are obtained with allowance made for the interatomic dipole-dipole interaction. It is shown that one can control the motion of the atoms by gradually varying the frequency of external laser radiation due to the presence of optical dimensional resonances in the spectrum of the diatomic object.     

An optical near-field microscope based on optical dimensional resonances of interacting atoms

A concept was suggested for an optical near-field microscope based on optical dimensional resonances in the system of a needle tip atom + a sample atom. High sensitivity and spatial resolution of an order of 1 nm were shown to be characteristic of this microscope. Furthermore, the instrument is applicable to a wide range of studied samples.     

Dynamics of two atoms in a quantized radiation field

We study a model with two atoms interacting with a single-mode quantized radiation field. We show the detailed quantum collapse and “revivals” in our system.     

Lamb shift in atoms interacting with a strong laser field

Radiative corrections to the energy levels of an atom interacting with a strong laser field have been investigated. A formula for the Lamb shift of the laser-dressed states is derived, which makes it possible to calculate this shift with an error up to α². Original Russian Text ? R.Kh. Gainutdinov, A.A. Mutygullina, 2009, published in Izvestiya Rossiiskoi Akademii Nauk. Seriya Fizicheskaya, 2009, Vol. 73, No. 2, pp. 292–293.     

Tunneling and above-barrier ionization of atoms in a laser radiation field

Calculations are made of the energy and angular distributions of photoelectrons during tunneling ionization of an atom or an ion under the action of high-power laser radiation (for all values of the Keldysh parameter γ). Cases of linear, circular, and elliptic polarizations of the electromagnetic wave are considered. The probability of above-barrier ionization of hydrogen atoms in a low-frequency laser field is calculated. Formulas are given for the momentum spectrum of the electrons when an atomic level is ionized by a general type of alternating electric field (for the case of linear polarization). An analysis is made of tunneling interference in the energy spectrum of the photoelectrons. Analytic approximations are discussed for the asymptotic coefficient C _κ of the atomic wave function at infinity (for s-wave electrons).     

The entanglement of two moving atoms interacting with a single-mode field via a three-photon process

In this paper, the entanglement of two moving atoms induced by a single-mode field via a three-photon process is investigated. It is shown that the entanglement is dependent on the category of the field, the average photon number N, the number p of half-wave lengths of the field mode and the atomic initial state. Also, the sudden death and the sudden birth of the entanglement are detected in this model and the results show that the existence of the sudden death and the sudden birth depends on the parameter and the category of the mode field. In addition, the three-photon process is a higher order nonlinear process.     

单模辐射场与耦合双原子Raman相互作用过程中光场的量子特性

研究了单模辐射场与耦合双原子Raman相互作用过程中光场的量子特性,讨论了系统耦合常数和初始状态对光场量子特性的影响.     

Single-atom entropy squeezing for two two-level atoms interacting with a single-mode radiation field

In this paper we consider a system of two two-level atoms interacting with a single-mode quantized electromagnetic field in a lossless resonant cavity via l-photon-transition mechanism. The field and the atoms are initially prepared in the coherent state and the excited atomic states, respectively. For this system we investigate the entropy squeezing, the atomic variances, the von Neumann entropy and the atomic inversions for the single-atom case. Also we comment on the relationship between spin squeezing and linear entropy. We show that the amounts of the nonclassical effects exhibited in the entropy squeezing for the present system are less than those produced by the standard Jaynes-Cummings model. The entropy squeezing can give information on the corresponding von Neumann entropy. Also the nonclassical effects obtained from the asymmetric atoms are greater than those obtained from the symmetric ones. Finally, the entropy squeezing gives better information than the atomic variances only for the asymmetric atoms.     

Entanglement properties between two atoms in the binomial optical field interacting with two entangled atoms

The temporal evolution of the degree of entanglement between two atoms in a system of the binomial optical field interacting with two arbitrary entangled atoms is investigated. The influence of the strength of the dipole–dipole interaction between two atoms, probabilities of the Bernoulli trial, and particle number of the binomial optical field on the temporal evolution of the atomic entanglement are discussed. The result shows that the two atoms are always in the entanglement state. Moreover, if and only if the two atoms are initially in the maximally entangled state, the entanglement evolution is not affected by the parameters, and the degree of entanglement is always kept as 1.     

Interference effects in the scattering of identical atoms in a laser radiation field

The properties of the collision integral in a quantum Boltzmann-type kinetic equation are studied under the conditions of spatially nonuniform distributions of colliding particles interacting with an external electromagnetic field. The components of the nonlinear resonances and the velocity distribution of the excited atoms, which are due to polarization transitions, are determined on the basis of the Kazantsev collision integral.     

运动纠缠双原子与薛定谔猫态光场相互作用系统的场熵演化

利用全量子理论,研究了运动纠缠双原子与薛定谔猫态光场相互作用系统的场熵演化特性,讨论了光场强弱、相干态间的相位角、原子的运动和场模结构参数对系统场熵的影响.结果表明：原子运动导致场熵演化具有周期性;当场强较弱时,奇相干态光场与运动原子的纠缠度最大,而偶相干态光场与运动原子的纠缠度最小, Yurke-Stoler相干态光场与运动原子的纠缠度值介于中间;当场强足够大时,分别处于Yurke-Stoler相干态,奇相干态和偶相干态的光场与运动原子的纠缠度相等,场熵演化特性相同;随着原子运动速度的增大或场模结构参数的增大,场熵的演化周期缩短,并且场与原子的纠缠度逐渐减弱.     

Coherent energy transfer from one atom to another under a selective excitation of one of them by a field of continuous optical radiation and optical size resonances

The existence of a new sort of optical size resonances formed due to the self-consistent coherent interaction of atoms when one of them is excited by a field of continuous optical radiation is proved. The processes of energy transfer from the thus-excited atom to large (of the order of several wavelengths) interatomic distances are considered. It is shown that these processes can be observed in the wave zone upon the interference of the optical fields formed by the oscillating dipole moments of the interacting atoms.     

Quantum electrodynamics resonances in a pulsed laser field

This review contains theoretical study of resonant quantum electrodynamics processes in a pulsed laser field. The approximation is examined when the pulse width is considerably greater than the characteristic time of wave oscillations. The lepton??s interaction with the Coulomb potential of a nucleus and each other is considered in the Born approximation. It is demonstrated that the resonant differential cross section of a process in a pulsed light fields may considerably exceed the corresponding cross section in an absence of a laser field. Results obtained may be experimentally verified by the scientific facilities at the SLAC National Accelerator Laboratory and FAIR (Facility for Antiproton and Ion Research, Darmstadt, Germany) project.     

Boundary-value problems in near-field optical microscopy and optical size resonances

We have solved a boundary-value problem for a ball probe interacting with a flat dielectric surface in an external optical radiation field. This interaction gives rise to the optical size resonance at frequencies significantly different from the natural frequencies of two-level atoms both in the medium and in the probe with allowance for the local field corrections. These resonances depend significantly on the distance from the probe center to the surface, on the ball probe size, on the concentration of two-level atoms in the probe and in the medium, on the spectral line width, and on the atomic inversion. The field strengths inside and outside the ball probe and a semiinfinite dielectric medium have been calculated in the near-field and wave zones. It is shown that the proposed electrodynamic theory of optical near-field microscopy agrees with the results of experimental measurements.     

Dynamics of a moving five-level atom interacting with cavity fields

We study the entanglement between a single five-level atom interacting with a one-mode cavity field in the case where the atomic motion is taken into account. The field entropy of this system is investigated under the nonresonant conditions. The effects of the detuning parameter and the atomic motion on the degree of entanglement are investigated. We show that both the detuning and atomic motion play important roles in the evolution of the von Neumann entropy and atomic populations.     

Trapping and storage of atoms in a laser field

Analysis of the possibility of spatial trapping of cold atoms in a standing-wave laser field is presented. It is shown that cold atoms can be trapped for a long time in region ≈ λ in a nonresonant standing-wave field. In a resonant standing-wave field cold atoms can be stored for a long time in the region determined by the cross-section of the laser beam. Trapping and storage together with cooling of atoms that has been suggested earlier allow us in specific cases to increase the sensitivity and the resolution of spectroscopic studies.     

Elementary processes involving Rydberg atoms and molecules in an intense laser radiation field

An analytical review of the theory of elementary atomic and molecular processes in the field of intense laser monochromatic radiation is presented. The discussion focuses on near-threshold processes involving Rydberg intermediate complexes, which play an important role in Earth’s upper atmosphere. The possibilities of the stationary method of radiative scattering matrix, based on the formalism of the renormalized Lippmann-Schwinger equations, are demonstrated. The approach is used to describe in a unified way a variety of near-threshold processes, the probability amplitudes of which are elements of the radiative scattering matrix for all possible reaction channels. They also include processes of restructuring of the particles (predissociation, associative ionization, exchange reactions, etc.), which in principle cannot be described using traditional nonstationary theories.     

Collision of atoms under action of external magnetic and laser radiation fields with formation of Fano-Feshbach resonances

We investigate collision of two atoms in an external magnetic field and in the field of laser radiation with formation of Fano-Feshbach resonances. At one-photon resonance of laser radiation with two discrete vibrational states of molecule the dressed states are formed (Autler-Townes effect) which form Fano-Feshbach resonances in interaction with the external magnetic field. In addition, the lower molecular vibrational state is coupled with the continuum of the elastic channel via also LICS (laser-induced continuum structure) forming laser-induced resonance. We obtain cross-sections of elastic and inelastic resonant scattering and expression for the scattering length depending on the external magnetic and laser radiation fields.     

Quantum-electrodynamic effects for atoms in a laser field

Quantum-electrodynamic radiation corrections to atomic energy levels in the presence of monochromatic laser field are considered as radiation shifts of quasienergies. General expressions are obtained for self-energy part of radiation shifts for an arbitrary multilevel atomic system. As an appendix, the radiation shifts of spectral lines of atomic resonance transitions are investigated.     

Dynamics of interacting qubits in a strong alternating electromagnetic field

The populations of energy levels of interacting qubits have been studied as functions of the field amplitude and other control parameters for a constant frequency of the external electromagnetic field. It has been found that the qubit coupling constant strongly affects the quantum-coherent Landau-Zener transitions between the qubit states and the formation of an interference pattern in level populations, depending on the field parameters. It has been demonstrated that it is possible to determine the qubit coupling constant by Landau-Zener interferometry.