In this work, we examine a system for coherent transfer of atoms into a Bose-Einstein condensate. We utilize two spatially separate Bose-Einstein condensates in different hyperfine ground states held in the same dc magnetic trap. By means of a pulsed transfer of atoms, we are able to show a clear resonance in the timing of the transfer, both in temperature and in number, from which we draw conclusions about the underlying physical process. The results are discussed in the context of the recently demonstrated pumped atom laser.
In this work, we examine a system for coherent transfer of atoms into a Bose-Einstein condensate. We utilize two spatially separate Bose-Einstein condensates in different hyperfine ground states held in the same dc magnetic trap. By means of a pulsed transfer of atoms, we are able to show a clear resonance in the timing of the transfer, both in temperature and in number, from which we draw conclusions about the underlying physical process. The results are discussed in the context of the recently demonstrated pumped atom laser.
A pulsed atom laser is experimentally demonstrated by means of outcoupling coherent atoms from 87 Rb Bose–Einstein condensates in magnetic trap via radio-frequency pulses. To study the strong outcoupling dynamics of the atom laser, the original | F = 2, m F = 2⟩ condensate and the coupled | F = 2, m F = 1⟩ component, both of which overlap in space usually, are separated spatially by collective oscillations. The number of atoms in three of the five Zeeman states are measured and compared with the theoretical results.
We propose a scheme that allows us to coherently extract cold atoms from a reservoir in a deterministic way. The transfer is achieved by means of radiation pulses coupling two atomic states which are object to different trapping conditions. A particular realization is proposed, where one state has zero magnetic moment and is confined by a dipole trap, whereas the other state with nonvanishing magnetic moment is confined by a steep microtrap potential. We show that in this setup a predetermined number of atoms can be transferred from a reservoir, a Bose-Einstein condensate, into the collective quantum state of the steep trap with high efficiency in the parameter regime of present experiments.
Considering all the ground-state atom interactions, we investigate the population transfer of two Bose-Einstein condensate (BEC) states, which are trapped in different potential wells, or two ground states of the BEC in the same trap using the stimulated Raman adiabatic process. With a proper choice of pulsed geometric parameters, the dark state exists. By simply choosing ground-state detunings, the effects of the interatomic interaction can be suppressed and a high population transfer rate can be obtained.
We studied the creation of coherent atomic ensembles by various means, allof which are either already demonstrated experimentally or within reach ofcurrent experiments. We investigated the dynamics of the outcoupling of acoherent beam from an atomic Bose-Einstein condensate. Since this problemis well treated in present literature, we focused on another aspect of proposedatom-laser schemes, the pumping. To this end, we investigated the merging ofindependent condensates and paid particular attention to the role of the relativephase. We found that it emerges as a key parameter during the merging process,almost solely defining the resulting dynamics. More concretely, the phasedifference determines the depth of an adiabatically formed soliton as well as thedynamics of a dipole oscillation of the atomic cloud, which builds up during themerging process. Under the assumption of a coherent cooling, such as evaporationof higher energy atoms from the ensemble, we were able to empiricallyfind an analytic formula for the phase of the final condensate. We studied themerging as an independent process, not necessarily linked to the atom laseritself. Our results might shed light onto new, non-destructive ways of readingout phase-differences between condensates as it is necessary in matter-wavespectroscopy. Although not related to our work, it is worth mentioning thatin the mean-time, a different pumping mechanism was demonstrated. It relieson two electronic transitions, with a reservoir condensate and a separate lasingcondensate [74]. We turned towards a different way of producing matter wavepulses altogether, namely superradiance from condensates, which shows otherpromising aspects, such as well defined populations and momenta of the createdpulses. We constructed a quantum treatment for the early stages of the process,which, as we have shown, is not well described within the available mean-fieldmodels. This semi-classical model can, however, produce quantum expectationvalues by means of averaging over randomly seeded trajectories. We used thisrelations to investigate the statistics of delay– and passage-times of superradiantpulses. Beyond the mean-field treatment of the problem, the quantum modelpredicts long range order as well as atomic bunching in the side-modes and enhancedcross-correlations between forward and backwards scattered atoms. Inthe strong pulse regime, the two counter-propagating clouds become entangledand the number difference between them is squeezed.4.6.2 OutlookThe experimental verification of our results is within reach of current experiments,and the tools available to probe Bose-Einstein condensates are advancingat a fast rate. As far as our studies are concerned, there are still open questions.We found that, in general, the merging of condensates is related to the formationof a soliton. The decay of such a structure is a topic of current debate, but theconsensus that this depends highly on the geometry of the trapping potentialsused seems reached.We investigated the early stage of superradiance from condensates and it isnatural to ask what is to expect for later stages, or in other situations wheredepletion of the primary condensate, population of higher order side-modes or120interaction between end-fire modes become relevant. Our results suggest thatthe exotic correlations we found decay with time, but this is not conclusive
We investigate atomic population dynamics of two Bose-Einstein condensate (BEC) states that are in different traps or in the same trap and are optically coupled through a common excited state by Raman laser pulses. For large interatomic interactions, almost all of the atoms that are initially in one of the traps (or one of the internal states) are either completely transferred into the other state or stay in the initially occupied state after the laser pulses, and the atoms (populations) are never distributed to both condensate states at the same time. Applications to the atomic logic gate and to output couplers of the atom laser are pointed out.
We demonstrate that atoms in magnetically insensitive hyperfine states ( m =0) can be trapped efficiently by a Bose-Einstein Condensate of the same atomic species occupying a different hyperfine state. The latter is trapped magnetically. Hyperfine-state–changing collisions, and therefore loss of the trapped ( m =0) atoms, are shown to be strongly inhibited in case of a low density of the confined atomic cloud. We monitor the transition from a "soft" to a "hard" effective potential by studying the backaction of the trapped ( m =0) atoms onto the condensate which provides their confinement. The controlled outcoupling of the trapped atoms by shaping the condensate wave function is explored. We observe a pulsed emission of atoms from the trapping region reminiscent of an atom laser.