Non-conditioned generation of Schroedinger cat states in a cavity

We investigate the dynamics of a two-level atom in a cavity filled with a nonlinear medium. We show that the atom-field detuning $\delta$ and the nonlinear parameter $\chi^{(3)}$ may be combined to yield a periodic dynamics and allowing the generation of almost exact superpositions of coherent states ({\sl Schr\"odinger} cats). By analysing the atomic inversion and the field purity, we verify that any initial atom-field state is recovered at each revival time, and that a coherent field interacting with an excited atom evolves to a superposition of coherent states at each collapse time. We show that a mixed field state (statistical mixture of two coherent states) evolves towards a pure field state ({\sl Schr\"odinger} cat) as well. We discuss the validity of those results by using the field fidelity and the {\sl Wigner} function.Comment: REVTeX4, 8 pages, 7 figures, link to an external animation fil

Nonlinear Jaynes-Cummings model of atom-field interaction

Interaction of a two-level atom with a single mode of electromagnetic field including Kerr nonlinearity for the field and intensity-dependent atom-field coupling is discussed. The Hamiltonian for the atom-field system is written in terms of the elements of a closed algebra, which has SU(1,1) and Heisenberg-Weyl algebras as limiting cases. Eigenstates and eigenvalues of the Hamiltonian are constructed. With the field being in a coherent state initially, the dynamical behaviour of atomic-inversion, field-statistics and uncertainties in the field quadratures are studied. The appearance of nonclassical features during the evolution of the field is shown. Further, we explore the overlap of initial and time-evolved field states.Comment: 14 pages, 6 figures is PS forma

Quantum statistical properties of the Jaynes-Cummings model in the presence of a classical homogeneous gravitational field

The temporal evolution of quantum statistical properties of an interacting atom-radiation field system in the presence of a classical homogeneous gravitational field is investigated within the framework of the Jaynes-Cummings model. To analyse the dynamical evolution of the atom-radiation system a quantum treatment of the internal and external dynamics of the atom is presented based on an alternative su(2) dynamical algebraic structure. By solving the Schr\"{o}dinger equation in the interaction picture, the evolving state of the system is found by which the influence of the gravitational field on the dynamical behavior of the atom-radiation system is explored. Assuming that initially the radiation field is prepared in a coherent state and the two-level atom is in a coherent superposition of the excited and ground states, the influence of gravity on the collapses and revivals of the atomic population inversion, atomic dipole squeezing, atomic momentum diffusion, photon counting statistics and quadrature squeezing of the radiation field is studied.Comment: 21 page

An algebraic approach to the Tavis-Cummings problem

An algebraic method is introduced for an analytical solution of the eigenvalue problem of the Tavis-Cummings (TC) Hamiltonian, based on polynomially deformed su(2), i.e. su_n(2), algebras. In this method the eigenvalue problem is solved in terms of a specific perturbation theory, developed here up to third order. Generalization to the N-atom case of the Rabi frequency and dressed states is also provided. A remarkable enhancement of spontaneous emission of N atoms in a resonator is found to result from collective effects.Comment: 13 pages, 7 figure

The dynamics of a four-level three-mode system. Operator solution

In the dipole and rotating wave approximation the operator solutions for the level populations and photon numbers are found. The numerical results for the time-evolution of the level populations for the case of initially coherent pumping modes 1 and 3 (mode 2 initially in vacuum) are reported and compared with those for a three-level atom in the ladder and lambda configurations.Dans l'approximation dipolaire et dans l'approximation du champ tournant, on donne les solutions pour les opérateurs correspondant aux populations des niveaux et aux nombres de photons. Les résultats numériques pour l'évolution dans le temps des populations des niveaux, dans le cas de modes de pompage 1 et 3 initialement cohérents (le mode 2 étant initialement vide), sont donnés et comparés aux résultats pour un atome à trois niveaux dans les configurations en échelle et en lambda

Second-harmonic elastic light scattering by molecular liquid mixtures

Second-harmonic light scattering (SHS) studies of liquid mixtures are shown to provide valuable information regarding correlations between non-centrosymmetric (e. g. dipolar) molecules and centrosymmetric (e. g. quadrupolar) ones, between dipolar molecules and tetrahedral ones, as well as between the components of atomic media. Such studies moreover permit determination of nonlinear second-order and third-order molecular polarizabilities as to sign and value.Nous montrons que l'étude de la diffusion bi-harmonique élastique de la lumière dans les mélanges liquides est une source de données sur les corrélations entre molécules non-centrosymétriques (par ex. dipolaires) et centrosymétriques (par ex. quadrupolaires), entre molécules dipolaires et tétraédriques, et entre les composantes des milieux polyatomiques, et qu'elle permet de déterminer les polarisabilités moléculaires d'ordres 2 et 3 quant à leur signe et leur valeur