Output coupling of a Bose-Einstein condensate formed in a TOP trap

Abstract

Two distinct mechanisms are investigated for transferring a pure 87 Rb Bose-Einstein condensate in the |F = 2, m F = 2〉 state into a mixture of condensates in all the m F states within the F = 2 manifold. Some of these condensates remain trapped whilst others are output coupled in the form of an elementary pulsed atom laser. Here we present details of the condensate preparation and results of the two condensate output coupling schemes. The first scheme is a radio frequency technique which allows controllable transfer into available m F states, and the second makes use of Majorana spin flips to equally populate all the manifold sub-states. More recently, the production of multi-component condensates has revealed intriguing quantum fluid dynamics, and enabled precise measurement of relative quantum phase [9]. Experiments at JILA have focused on mixtures involving atoms in different ground state hyperfine levels (quantum number F), and coupling with a two photon (microwave plus radio frequency) transition. Experiments at MIT have used an optical dipole trap to confine a condensate occupying all magnetic sub-states (quantum number m F ) of the same hyperfine level [10]. Spin exchange processes result in domain formation which exhibits an anti-ferromagnetic interaction [11]. An important aspect of that work is the confinement of condensed atoms in sub-states which cannot be magnetically trapped.In this paper we present the results of two techniques for transforming a single state |F = 2, m F = 2〉 87 Rb Bose condensate into a mixture of all five magnetic sub-states of the F = 2 hyperfine level. Two of these states are magnetically confined (|2, 2〉 and |2, 1〉), with magnetic moments differing by a factor of 2, and the other states are unconfined.Applying an RF field similar to that used in the evaporative cooling stage of the experiment we can couple atoms between adjacent m F states. It is possible to control the number of atoms which are coupled from the |2, 2〉 state into the other m F states: condensates with predetermined sub-state populations can be constructed. For example, we can limit the transfer into untrapped states.

Nonlinear atom-opticalδ-kicked harmonic oscillator using a Bose-Einstein condensate

“…A description of the BEC apparatus was given previously [23], but there have been some modifications. We now use injection-seeded diode lasers to drive the two magneto-optical traps and atoms are transferred continuously between the traps using a focused resonant laser beam.…”

The Theory of Atom Lasers

“…For example the characteristic frequency in the optical case is the frequency of the light, of order 10 15 Hz, while for atoms the de Broglie frequency is closer to that of the trapping potential, of order 10 3 Hz. And, whereas it is so far only practical to get atoms to accumulate into the ground mode of a trap, optical lasers typically operate on high modes of the optical cavity.…”

“…Eventually we expect that atom lasers will provide a convenient source for greatly improved atomic clocks, or for manipulation of the quantum mechanical state of the matter wave, analogous for example to optical squeezing 12 . As of April 2000 five experimental groups have demonstrated atom lasers experimentally, in either pulsed operation 7,14,15 or with quasi-continuous output 16,17 . In each case, the laser mode consists of a Bose-Einstein condensate confined in the ground state of a magnetic trap, gain is achieved by evaporatively cooling a reservoir of thermal atoms, and the output coupling is accomplished by using an external electromagnetic field to transfer the internal state of the atom from a trapped to an untrapped state.…”

Damping and frequency shift in the oscillations of two colliding Bose-Einstein condensates

“…The issue of the interaction between Bose-Einstein condensates in different internal states has deserved much attention in the recent literature, both from the experimental [1][2][3][4][5][6] and theoretical point of view [7][8][9]. The study of these mixtures of quantum fluids includes several important topics, as the characterization of the dynamical behaviour, the response in presence of an external coupling, the phase coherence and the superfluid properties of the system.…”