Coherent scattering of an atom in the field of a standing wave under conditions of initial quantum correlation of subsystems

Coherent scattering of a two-level atom in the field of a quantized standing wave of a micromaser is considered under conditions of initial quantum correlation between the atom and the field. Such a correlation can be produced by a broadband parametric source. The interaction leading to scattering of the atom from the nonuniform field occurs in the dispersion limit or in the wing of the absorption line of the atom. Apart from the quantized field, the atom simultaneously interacts with two classical counterpropagating waves with different frequencies, which are acting in the plane perpendicular to the atom’s propagation velocity and to the wavevector of the standing wave. Joint action of the quantized field and two classical waves induces effective two-photon and Raman resonance interaction on the working transition. The effective Hamiltonian of the interaction is derived using the unitary transformation method developed for a moving atom. A strong effect is detected, which makes it possible to distinguish the correlated initial state of the atom and the field in the scattering of atom from the state of independent systems. For all three waves, scattering is not observed when systems with quantum correlation are prepared using a high-intensity parametric source. Conversely, when the atom interacts only with the nonuniform field of the standing wave, scattering is not observed in the case of the initial factorized state.     

Resonant scattering of three-level Rydberg atoms in a microwave field

We examine the theory of potential scattering of Rydberg atoms in a microwave field. The model of a three-level atom is employed to calculate the radiative force emerging in the resonant coherent interaction with the microwave field for the case of a two-photon resonance and high intensities, using the method of quasienergies of the system consisting of the atom and the field. We determine the probabilities of Landau-Zener transitions in the spatial regions where under two-photon resonance conditions the quasienergies of the atoms approach one another by a small quantity. We also study the dynamics of the variation of the spatial profile of a beam of Rydberg atoms caused by resonant scattering. Finally, we give the results of the first experimental observation of the variation of the transverse beam profile when Rydberg atoms pass through a nonuniform microwave field formed in a rectangular waveguide and in resonance with the two-photon 36P–37P transition. Zh. éksp. Teor. Fiz. 111, 796–815 (March 1997)     

Atom interferometry with a weakly interacting Bose-Einstein condensate

We demonstrate the operation of an atom interferometer based on a weakly interacting Bose-Einstein condensate. We strongly reduce the interaction induced decoherence that usually limits interferometers based on trapped condensates by tuning the s-wave scattering length almost to zero via a magnetic Feshbach resonance. We employ a 39K condensate trapped in an optical lattice, where Bloch oscillations are forced by gravity. The fine-tuning of the scattering length down to 0.1 a_(0) and the micrometric sizes of the atomic sample make our system a very promising candidate for measuring forces with high spatial resolution. Our technique can be in principle extended to other measurement schemes opening new possibilities in the field of trapped atom interferometry.     

Resonant decay of a two state atom interacting with a massless non-relativistic quantised scalar field

We consider a model Hamiltonian derived from the interaction of an atom with a non-relativistic massless quantized field. The model atom has two states, and the interaction is linear in the field operator. We do not make the rotating wave approximation and there is no infrared cutoff. We prove that the excited state of the atom with no photons present decays at an approximately exponential rate in accordance with the predictions of time dependent perturbation theory. The proof requires some analyticity and regularity assumptions on the interaction between atom and field. These imply in particular that the interaction goes to zero at least as fast ask ², ask0, wherek is the photon momentum.     

A stochastic posterior Schrödinger equation for counting nondemolition measurement

A stochastic model of the continuous counting nondemolition measurement of photons emitted by an excited atom in a quantum electromagnetic field is given. It is proved that the posterior dynamics of such an atom is described by a new nonlinear stochastic wave equation showing the relaxation of the atom to its ground state due to the photon emission.     

Tunable second-order sideband effects in hybrid optomechanical cavity assisted with a Bose—Einstein condensate

We theoretically investigated a second-order optomechanical-induced transparency (OMIT) process of a hybrid optomechanical system (COMS), which a Bose—Einstein condensate (BEC) in the presence of atom—atom interaction trapped inside a cavity with a moving end mirror. The advantage of this hybrid COMS over a bare COMS is that the frequency of the second mode is controlled by the s-wave scattering interaction. Based on the traditional linearization approximation, we derive analytical solutions for the output transmission intensity of the probe field and the dimensionless amplitude of the second-order sideband (SS). The numerical results show that the transmission intensity of the probe field and the dimensionless amplitude of the SS can be controlled by the s-wave scattering frequency. Furthermore, the control field intensities, the effective detuning, the effective coupling strength of the cavity field with the Bogoliubov mode are used to control the transmission intensity of the probe field and the dimensionless amplitude of the SS.     

Scattering of atoms in the field of counterpropagating light waves. Effect of initial conditions

The scattering of an atom in the field of counterpropagating light waves is studied under conditions such that the state of the atom is a superposition of the ground and excited states. For the case in which this superposition is created by the field of a traveling wave, the momentum distribution function of the atom after scattering by a standing wave is found analytically in the approximation of a short interaction time, when the atom’s motion can be neglected. Longer interactions of the atom with the field are studied numerically. We also consider the case of counterpropagating light waves consisting of Gaussian or supergaussian pulses. Zh. éksp. Teor. Fiz. 113, 563–572 (February 1998)     

Thermal Entanglement Between a Jaynes-Cummings Atom and an Isolated Atom

We studied the entanglement of a quantum system consisting of a Jaynes-Cummings atom, thermal lossless cavity and an isolated atom. The analytical expressions of the atom-atom negativity for separable and entangled initial atomic states were obtained. The influence of a detuning between the atomic transition frequency and the field frequency and direct dipole-dipole interaction on an atom-atom entanglement is examined. We showed that for a separable initial atomic states a detuning might cause high atom-atom entanglement in the presence of the dipole-dipole interaction. We also obtained that for an entangled initial atomic state a detuning causes a stabilization of an entanglement oscillations both for model with dipole-dipole interaction and model without such interaction.     

原子与单模场相互作用中克尔效应与斯塔克效应的统一处理

处理了包含克尔效应和斯塔克效应的原子与场相互作用模型。由于在其有效哈密顿中作了旋转波近似，两种效应的影响可以归结为对原子与场失谐的改变，这种失谐变化依赖于一个系统的守恒量。研究表明，克尔效应和斯塔克效应在一定条件下是等价的。研究了当场的初态为宏观可区分量子迭加态时，光子的反聚束效应。探讨了在广义的克尔介质中原子与场相互作用模型的求解。     

激光场中量子散射三重微分散射截面的研究

在量子散射框架下,对真实激光场引进多光子相互作用准静态过程模型,考虑束缚-自由跃迁中电磁场的规范一致性及电子与激光场长程相互作用的极限,研究激光场对量子散射过程中三重微分散射截面的影响.多数共面非对称情况下激光场对三重微分散射截面有提升作用,此外靶原子处于激发态时binary峰出现分裂,激光场对三重微分散射截面也有放大作用.     

激光场中量子散射三重微分散射截面的研究

在量子散射框架下,对真实激光场引进多光子相互作用准静态过程模型,考虑束缚-自由跃迁中电磁场的规范一致性及电子与激光场长程相互作用的极限,研究激光场对量子散射过程中三重微分散射截面的影响。多数共面非对称情况下激光场对三重微分散射截面有提升作用,此外靶原子处于激发态时binary峰出现分裂,激光场对三重微分散射截面也有放大作用。     

Vacuum-stimulated raman scattering based on adiabatic passage in a high-finesse optical cavity

We report on the first observation of stimulated Raman scattering from a Lambda-type three-level atom, where the stimulation is realized by the vacuum field of a high-finesse optical cavity. The scheme produces one intracavity photon by means of an adiabatic passage technique based on a counterintuitive interaction sequence between pump laser and cavity field. This photon leaves the cavity through the less-reflecting mirror. The emission rate shows a characteristic dependence on the cavity and pump detuning, and the observed spectra have a subnatural linewidth. The results are in excellent agreement with numerical simulations.     

Model of the interaction potential of an atom with a hard corrugated surface incorporating a stationary potential well

We propose a new atom-surface interaction potential model which is designed for use in the recent exact theory for the elastic scattering of an atom by a hard corrugated surface model which incorporates a stationary attractive potential well [N. García, F.O. Goodman, V. Celli and N.R. Hill, Phys. Rev. B (1979)]. The model parameters are adjusted to obtain a best-fit to all available experimental data on atom-surface bound-state energies, and comparisons are also made with the latest theoretical data, with satisfactory results.     

On the Scattering of the Electron off the Hydrogen Atom and the Helium Ion Below and Above the Ionization Threshold: Temkin–Poet Model

We generalize here the splitting approach to the long range (Coulomb) interaction for the three body scattering problem. With this approach, the exterior complex rotation technique can be applied for systems with asymptotic Coulomb interaction. We illustrate the method with calculations of the electron scattering on the hydrogen atom and positive helium ion in the frame of the Temkin–Poet model.     

Quantum Mechanics of Two-Field Parametric Frequency Converter Interacting with a Single Atom

In this communication we deal with a new model Hamiltonian representing the interaction between a two-level atom and two electromagnetic field modes in a cavity. The interaction between the modes has been taken into account and considered to be of a parametric frequency converter type. The model can be regarded as a generalization of two different systems: the Jaynes–Cummings model (atom–field interaction) and the two-mode frequency converter model (field–field interaction). Under a certain condition an exact solution for the equations of motion in the Heisenberg picture is given. The wavefunction in the Schrödinger picture is also constructed and used to discuss some statistical properties related to the model. We assume that the fields are initially in coherent states. We discuss atomic inversion, photon number distribution, squeezing and other phenomena. We show in all cases that the system is very sensitive to any variation in the mean photon numbers.     

Dynamics of an atom coupled through a parametric frequency converter with quantum and classical fields

In this communication we introduce a model of a two-level system which represents the interaction between an atom and external quantum and classical electric fields through a parametric frequency converter. We show that the system can be reduced to an effective Jaynes-Cummings model by adequate adjustment of the field coupling in the frequency converter. The atom dynamics and the atom-quantum field entanglement are then shown to be controlled through the classical field.     

Optical control of magnetic Feshbach resonances in Bose gases

We theoretically investigate optical control of magnetic Feshbach resonance in Bose gases with two optical fields. The two optical fields couple two ground states through an excited state. Compared with the usual single-optical scheme, two optical fields can greatly suppress the inelastic loss resulting from spontaneous emission by the destructive quantum interference. Using the mean field theory, the analytical formula of the scattering length is obtained. The results show that the scattering length can be modified in a large range by changing the Rabi frequency or the optical field frequency. The strong atom–molecule interaction has obvious effect on the scattering length.     

Generation of strongly squeezed states for a cavity field with a single atom

We propose a scheme to realize strong squeezing for a cavity field with a single three-level atom. In the scheme the atom is sent through the cavity initially filled with a coherent field. The atom dispersively interacts with the cavity field, which is displaced by a microwave resource during the interaction. Then, a selective measurement on the atom collapses the field to a superposition of an even coherent state with a vacuum state, which exhibits strong squeezing. The scheme can also be generalized to the two-mode case.     

Scattering spectrum and lifetimes of the excited states of an atom in an electric field

We examine the problem of the interaction between a monochromatic electromagnetic wave and a two-level atom. The four-level compound-system model is used for the calculations. An asymmetric scattering spectrum is obtained. It is shown that, when resonance is exact, the integral intensities of the scattering spectrum components and lifetimes of the compound system at the excited levels are independent of the initial state of the atom. Elabuzh State Pedagogical Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 99–102, May, 1998.     

The kapitsa-dirac resonance effect

The effectiveness of atom scattering by the field of a standing light wave with arbitrary interaction times is calculated in a quasiclassical approximation. The influence of spontaneous emission and the non-monochromatic nature of the field on the effective potential of an atom is discussed. The conclusions of theory are compared with the results of a recent experiment.