Symmetric microwave potentials for interferometry with thermal atoms on a chip

Abstract

International audienceA trapped atom interferometer involving state-selective adiabatic potentials with two microwave frequencies on a chip is proposed. We show that this configuration provides a way to achieve a high degree of symmetry between the two arms of the interferometer, which is necessary for coherent splitting and recombination of thermal (i.e., noncondensed) atoms. The resulting interferometer holds promise to achieve high contrast and long coherence time, while avoiding the mean-field interaction issues of interferometers based on trapped Bose-Einstein condensates

Experimental study of the role of trap symmetry in an atom-chip interferometer above the Bose–Einstein condensation threshold

“…The two outputs of the interferometer are measured via absorption imaging [37] and used to normalize the atom number in state bñ | by the total atom number [39] (although only one is shown in figure 3). The highest value of δω we achieved is one the order of 50 mHz, thus the first expected revivals [21] could occur at 1/δω∼20 s, such Ramsey time can not be achieved in our experiment.…”

“…Still, we expect the populations to be approximately conserved (and the above formula to apply up to a numerical factor on the order of unity) as long as the relative asymmetry is small enough (typically smaller than ÿω/kT10 −3 in our experiment). Second, the model of [21,22] is one-dimensional, while in the experiment described here the asymmetry occurs along all three trapping axes (with identical relative asymmetry, as will be seen below). In the three-dimensional harmonic case it can be shown that the contrast C follows [34]:…”

“…| , coupled by a two photon transition. During the whole interferometer sequence both states are maintained trapped, but not necessarily in identical potentials [16,21], leading to inhomogeneous dephasing. We suppose that the traps are harmonic but with slightly different frequencies along one of the trapping axes, namely ω a =ω for state añ…”

“…To date, atom-chip-based interferometers have been successfully demonstrated using Bose-Einstein condensates [15,16], but are subject to dephasing mechanisms resulting from atom-atom interactions [17][18][19][20]. Recently, we proposed a trapped atom interferometer using an ensemble of cold atoms above the Bose-Einstein condensation threshold (referred to as thermal atoms in the following) [21,22]. This proposal is reminiscent of optical white light interferometry because of the necessity of keeping the path length difference between the two arms of the interferometer smaller than the coherence length.…”

Contrast and phase-shift of a trapped atom interferometer using a thermal ensemble with internal state labelling

“…Atom interferometry with trapped atoms is much less well developed although it offers some advantages: interrogation times are not limited by the atoms' flight from the interaction region and one can hope to reduce the overall size of the device using technologies such as atom chips [5][6][7]. These advantages motivated our recent proposal for a trapped atom interferometer using thermal atoms [8], a situation closely analogous to white light interferometry in optics [9]. In it we discussed the importance of maintaining a high degree of symmetry in the two interferometer arms.…”