Quasi-Adiabatic External State Preparation of Ultracold Atoms in Microgravity
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ORIGINAL ARTICLE
Quasi-Adiabatic External State Preparation of Ultracold Atoms in Microgravity A. R. Pollard1 · E. R. Moan1
· C. A. Sackett1
· E. R. Elliott2 · R. J. Thompson2
Received: 30 July 2020 / Accepted: 30 September 2020 © Springer Nature B.V. 2020
Abstract The Cold Atom Laboratory on the International Space Station produces ultracold gases of rubidium and potassium in a tight magnetic trap near the surface of a magnetic chip. In order to use these samples in long-duration field-free experiments, the atoms must be moved away from the chip, expanded to larger volume, and released from the trap. We describe how these goals can be achieved using quasi-adiabatic techniques. For rubidium atoms, we demonstrate a displacement of 0.6 mm and expansion into a trap with a mean oscillation frequency of 6.4 Hz. The center-of-mass release velocity and the condensate expansion velocity are about 0.2 mm/s each. An unexpectedly large background magnetic field gradient is observed, which limits the usable interaction time for the released atoms. Keywords Ultracold atoms · Cold atom laboratory · Adiabatic cooling
Introduction A microgravity environment offers significant benefits for ultracold atom experiments and applications (M¨untinga et al. 2013; Becker et al. 2018; Condon et al. 2019; Aveline et al. 2020). It allows for long interaction times with atoms in a localized volume, without the need for an external field to support against gravity. This is advantageous for precision measurements which work best in zero field, and for experiments investigating Feshbach studies (D’Incao et al. 2017; Mossman et al. 2016) and ‘bubble’ geometry traps (Lundblad et al. 2019) where gravitational support would be impossible or add complexity. Microgravity is also an ideal environment for atom interferometry, which encompasses a broad range of applications such as inertial navigation, gravity gradient mapping, equivalence principle tests, and recoil frequency measurements (Cronin et al. 2009). Finally, it should be possible to attain extremely Supported by NASA, grant number 1640951. C. A. Sackett
[email protected] 1
Physics Department, University of Virginia, Charlottesville, VA 22904 USA
2
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
low temperatures in microgravity, since an atomic gas can be expanded to larger volumes than possible in terrestrial gravity (M¨untinga et al. 2013; Ammann and Christensen 1997; Leanhardt et al. 2003; Sackett et al. 2018). The Cold Atom Laboratory (CAL) is an ultracold atom apparatus installed on the International Space Station (Aveline et al. 2020; Elliott et al. 2018). It uses atom chip technology to produce Bose-Einstein condensates of 87 Rb (Fortagh and Zimmermann 2007), and also has the capability to produce cold gases of 39 K. It can be operated remotely in real time by staff at the Jet Propulsion Laboratory, who work with a group of principal investigators to develop and run experimental sequences. Resulting data are collated and forwarded to
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