Effects of relative phase and interactions on atom-laser outcoupling from a double-well Bose-Einstein condensate: Markovian and non-Markovian dynamics

We investigate aspects of the dynamics of a continuous atom-laser scheme based on the merging of independently formed atomic condensates. Our theoretical analysis covers the Markovian as well as the non-Markovian operational regimes, and is based on a semiclassical (mean-field) two-mode model. The role of the relative phase between the two condensates and the effect of interatomic interactions on the evolution of the trapped populations and the distribution of outcoupled atoms are discussed.Comment: to appear in J. Phys.

Adiabatic cavity QED with pairs of atoms: Atomic entanglement and Quantum teleportation

We study the dynamics of a pair of atoms, resonantly interacting with a single mode cavity, in the situation where the atoms enter the cavity with a time delay between them. Using time dependent coupling functions to represent the spatial profile of the mode, we considered the adiabatic limit of the system. Although the time evolution is mostly adiabatic, energy crossings play an important role in the system dynamics. Following from this, entanglement, and a procedure for cavity state teleportation are considered. We examine the behaviour of the system when we introduce decoherence, a finite detuning, and potential asymmetries in the coupling profiles of the atoms.Comment: 12 pages, 7 figures, To appear in European Physical Journal Special Topic

Entanglement trapping in a non-stationary structured reservoir

We study a single two-level atom interacting with a reservoir of modes defined by a reservoir structure function with a frequency gap. Using the pseudomodes technique, we derive the main features of a trapping state formed in the weak coupling regime. Utilising different entanglement measures we show that strong correlations and entanglement between the atom and the modes are in existence when this state is formed. Furthermore, an unexpected feature for the reservoir is revealed. In the long time limit and for weak coupling the reservoir spectrum is not constant in time.Comment: 10 pages, 16 figure

Entanglement in the adiabatic limit of a two-atom Tavis-Cummings model

We study the adiabatic limit for the sequential passage of atoms through a high-Q cavity, in the presence of frequency chirps. Despite the fact that the adiabatic approximation might be expected to fail, we were able to show that for proper choice of Stark-pulses this is not the case. Instead, a connection to the resonant limit is established, where the robust creation of entanglement is demonstrated. Recent developments in the fabrication of high-Q cavities allow fidelities for a maximally entangled state up to 97%.Comment: 12 pages, 5 figures, Submitted to Physica Scripta as part of the Proceedings of the 15th CEWQO 200

Multiple electron trapping in the fragmentation of strongly driven molecules

We present a theoretical quasiclassical study of the formation, during Coulomb explosion, of two highly excited neutral H atoms (double H$^{*}$) of strongly driven H$_2$. In this process, after the laser field is turned off each electron occupies a Rydberg state of an H atom. We show that two-electron effects are important in order to correctly account for double H$^{*}$ formation. We find that the route to forming two H$^{*}$ atoms is similar to pathway B that was identified in Phys. Rev. A {\bf 85} 011402 (R) as one of the two routes leading to single H$^{*}$ formation. However, instead of one ionization step being "frustrated" as is the case for pathway B, both ionization steps are "frustrated" in double H$^{*}$ formation. Moreover, we compute the screened nuclear charge that drives the explosion of the nuclei during double H$^{*}$ formation.Comment: 4 pages, 6 figure

Molecular heat pump for rotational states

In this work we investigate the theory for three different uni-directional population transfer schemes in trapped multilevel systems which can be utilized to cool molecular ions. The approach we use exploits the laser-induced coupling between the internal and motional degrees of freedom so that the internal state of a molecule can be mapped onto the motion of that molecule in an external trapping potential. By sympathetically cooling the translational motion back into its ground state the mapping process can be employed as part of a cooling scheme for molecular rotational levels. This step is achieved through a common mode involving a laser-cooled atom trapped alongside the molecule. For the coherent mapping we will focus on adiabatic passage techniques which may be expected to provide robust and efficient population transfers. By applying far-detuned chirped adiabatic rapid passage pulses we are able to achieve an efficiency of better than 98% for realistic parameters and including spontaneous emission. Even though our main focus is on cooling molecular states, the analysis of the different adiabatic methods has general features which can be applied to atomic systems

Dephasing effects on stimulated Raman adiabatic passage in tripod configurations

We present an analytic description of the effects of dephasing processes on stimulated Raman adiabatic passage in a tripod quantum system. To this end, we develop an effective two-level model. Our analysis makes use of the adiabatic approximation in the weak dephasing regime. An effective master equation for a two-level system formed by two dark states is derived, where analytic solutions are obtained by utilizing the Demkov-Kunike model. From these, it is found that the fidelity for the final coherent superposition state decreases exponentially for increasing dephasing rates. Depending on the pulse ordering and for adiabatic evolution the pulse delay can have an inverse effect.Comment: 13 pages; 9 figures; Accepted for publication Physical Review