Ultracold Atoms in Multiple - Radiofrequency Adiabatic Potentials

Our understanding of quantum systems has been shaped by the ability to study ultracold atoms in a range of trapping geometries, from single wells to lattice potentials and box traps. The application of a radiofrequency (RF) field to a static magnetic trap, to form an RF adiabatic potential, dramatically extends the versatility of magnetic trapping techniques [1]. By applying multiple independently-generated dressing frequencies, we have extended the scope of the RF dressing method, and demonstrated the application of three frequencies to create a precisely configurable multiple-RF (MRF) double well. In a scheme that can be extended by the application of additional dressing frequencies, we load cold Rb-87 atoms into a double well potential with an adjustable barrier height, formed by three independently-generated frequencies.

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Above: a) Array of current-carrying coils used to produce AC and DC magnetic fields. b) Atoms are initially loaded into a time-averaged adiabatic potential, which combines a TOP AC field and a RF field. c) The amplitude of the TOP field is reduced. d) The TOP field is fully removed, leaving only the RF field, forming an adiabatic potential or 'shell' trap. e) Applying multiple RF frequencies can form double wells.

Our multiple-radiofrequency approach allows for precise control over the double well potential, including the depth of individual wells and the height of the barrier, and enables reliable transfer of atoms between the available trapping geometries. We are currently investigating double well physics and transitions in this MRF dressed scheme.

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Above: We can load atoms selectively into the upper or lower well by varying the barrier height and changing the depths of each well. Upper image: atoms loaded mostly into lower well. Lower image: atoms loaded equally.

[1] Techniques to cool and rotate Bose-Einstein condensates in time-averaged adiabatic potentials. M. Gildemeister, B.E. Sherlock and C.J. Foot. Phys. Rev. A 85, 053401 (2012)

[2] Ultracold atoms in multiple-radiofrequency dressed adiabatic potentials. T.L. Harte, E. Bentine, K. Luksch, A.J. Barker, D. Trypogeorgos, B. Yuen and C.J. Foot. Under review