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Double Microwave Shielding

Tijs Karman1,*, Niccolò Bigagli2, Weijun Yuan2, Siwei Zhang2, Ian Stevenson2, and Sebastian Will2,†

  • *Contact author: t.karman@science.ru.nl
  • †Contact author: sebastian.will@columbia.edu
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PRX Quantum 6, 020358 – Published 25 June, 2025

DOI: https://doi.org/10.1103/b8pm-3prn

Abstract

We develop double microwave shielding, which has recently enabled evaporative cooling to the first Bose-Einstein condensate of polar molecules [Bigagli et al., Nature 631, 289 (2024)]. Two microwave fields of different frequency and polarization are employed to effectively shield polar molecules from inelastic collisions and three-body recombination. Here, we describe in detail the theory of double microwave shielding. We demonstrate that double microwave shielding effectively suppresses two- and three-body losses. Simultaneously, dipolar interactions and the scattering length can be flexibly tuned, enabling comprehensive control over interactions in ultracold gases of polar molecules. We show that this approach works universally for a wide range of molecules. This opens the door to studying many-body physics with strongly interacting dipolar quantum matter.

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Popular Summary

Ultracold molecules offer a platform for artificial quantum matter, akin to ultracold atoms, but with strong tunable long-ranged dipolar interactions. The first Bose-Einstein condensate of polar molecules was realized recently by suppressing collisional loss by “shielding” and compensating the dipolar interaction to prevent three-body recombination. In this paper, we introduce “double microwave shielding” and show that it enables simultaneous tuning of dipolar interactions and the scattering length, while preserving collisional stability.

Specifically, we theoretically study collisional shielding of polar molecules dressed with two microwave fields, which cause their dipoles to oscillate and rotate along with the fields. This dressing induces repulsive shielding interactions that prevent collisional loss. Outside the shield, the molecules experience dipolar interactions between their rapidly oscillating and perpendicularly rotating moments that can compensate one another. The presented method is universal, and we show that it works for a wide range of polar molecules.

Double microwave shielding opens the door to studying many-body physics with strongly interacting dipolar quantum matter, which could enable quantum simulation of extended Hubbard models in new regimes and realize new supersolid states of matter and support the preparation of quantum information platforms based on polar molecules.

Article Text

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PRX Quantum 6, 020358– Published 25 June, 2025
  • Received 17 January 2025
  • Revised 7 April 2025
  • Accepted 20 May 2025
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