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Magnetic trapping of ultracold molecules at high density

Nature Physics volume 19, pages 1567–1572 (2023)Cite this article

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Abstract

Trapping ultracold molecules in conservative traps is essential for multiple applications, including quantum-state-controlled chemistry, quantum simulations and quantum information processing. The study of molecular collisions, in particular, requires samples at high densities, which have been challenging to achieve so far with established cooling and trapping techniques. Here we report the magnetic trapping of molecules in the triplet ground state at high density and ultralow temperature. We measure the inelastic loss rates in a single-spin sample and spin mixtures of fermionic molecules and spin-stretched atom–molecule mixtures. We demonstrate the sympathetic cooling of molecules in the magnetic trap by the radio-frequency evaporation of co-trapped atoms and observe an increase in the molecules’ phase-space density by a factor of 16. Magnetic trapping at these densities allows the study of both atom–molecule and molecule–molecule collisions in the ultracold regime in the absence of trapping light, which often leads to undesired photochemistry effects.

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Fig. 1: Illustration of the experimental sequence.
Fig. 2: Ground-state hyperfine structure of triplet NaLi and decay of spin-stretched molecules.
Fig. 3: Inelastic loss of molecular spin mixtures.
Fig. 4: Sympathetic cooling of NaLi by Na atoms.

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Code availability

The codes used to generate the results are available from the corresponding author upon reasonable request.

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Acknowledgements

We thank J. Doyle for valuable discussions. We acknowledge support from the National Science Foundation through grant no. PHY-1734011 for the Center for Ultracold Atoms and through grant no. 1506369, and from the Air Force Office of Scientific Research (MURI, grant no. FA9550-21-1-0069). Some of the analysis was performed by W.K. at the Aspen Center for Physics, which is supported by the National Science Foundation grant PHY-1607611. J.J.P. acknowledges additional support from the Samsung Scholarship.

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Authors and Affiliations

  1. Research Laboratory of Electronics, MIT-Harvard Center for Ultracold Atoms, Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA

    Juliana J. Park, Yu-Kun Lu & Wolfgang Ketterle

  2. Institute for Quantum Computing and Department of Physics & Astronomy, University of Waterloo, Waterloo, Ontario, Canada

    Alan O. Jamison

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  1. Juliana J. Park
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J.J.P. and Y.-K.L. carried out the experimental work. All authors contributed to the development of models, data analysis and writing of the manuscript.

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Correspondence to Juliana J. Park.

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Park, J.J., Lu, YK., Jamison, A.O. et al. Magnetic trapping of ultracold molecules at high density. Nat. Phys. 19, 1567–1572 (2023). https://doi.org/10.1038/s41567-023-02141-0

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