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.
We investigate the use of microwave radiation to produce a repulsive shield between pairs of ultracold polar molecules and prevent collisional losses that occur when molecular pairs reach short range. We carry out coupled-channels calculations on RbCs+RbCs and CaF+CaF collisions in microwave fields. We show that effective shielding requires predominantly circular polarization, but can still be achieved with elliptical polarization that is around 90% circular.
Harnessing the potential wide-ranging quantum science applications of molecules will require control of their interactions. Here, we use microwave radiation to directly engineer and tune the interaction potentials between ultracold calcium monofluoride (CaF) molecules. By merging two optical tweezers, each containing a single molecule, we probe collisions in three dimensions. The correct combination of microwave frequency and power creates an effective repulsive shield, which suppresses the inelastic loss rate by a factor of six, in agreement with theoretical calculations. The demonstrated mic…
Mapping the parameter space of double microwave shielding
Institute for Molecules and Materials, Radboud University（分子与材料研究所，拉德堡德大学）；Department of Physics, Columbia University（物理系，哥伦比亚大学）；Department of Physics, University of Virginia（物理系，弗吉尼亚大学）
Effective potentials for polar molecules under non-orthogonal dual microwave fields
Institute of Theoretical Physics, Chinese Academy of Sciences（中国科学院理论物理研究所）；School of Physical Sciences, University of Chinese Academy of Sciences（中国科学院大学物理科学学院）；Institute of Fundamental Physics and Quantum Technology and School of Physics Science and Technology, Ningbo University（宁波大学基础物理与量子技术研究院及物理科学与技术学院）
Tuning interactions between static-field-shielded polar molecules with microwaves
Imperial College London（帝国理工学院）；Durham University（杜伦大学）；National Institute of Science Education and Research (NISER)（国家科学教育研究中心）；University of Warsaw（华沙大学）
Ultracold polar molecules offer strong electric dipole moments and rich internal structure, which makes them ideal building blocks to explore exotic quantum matter, implement novel quantum information schemes, or test fundamental symmetries of nature. Realizing their full potential requires cooling interacting molecular gases deeply into the quantum degenerate regime. However, the complexity of molecules which makes their collisions intrinsically unstable at the short range, even for nonreactive molecules, has so far prevented the cooling to quantum degeneracy in three dimensions. Here, we dem…
Engineering SU($N$)-Symmetric Hubbard Models with Microwave-Shielded Dipolar Molecules
Institute of Science and Technology Austria (ISTA)（奥地利科学技术研究院）；Vienna Center for Quantum Science and Technology, Atominstitut, TU Wien（维也纳量子科学与技术中心，原子物理研究所，维也纳工业大学）；Department of Physics and Astronomy, Rice University（莱斯大学物理与天文学系）；Smalley-Curl Institute, Rice University（莱斯大学斯马利-柯尔研究所）
Tunable state-dependent interactions in collisionally stable mixtures of polar molecules
Institute for Molecules and Materials, Radboud University（分子与材料研究所，拉德堡德大学）；Institut für Theoretische Physik, Universität Heidelberg（理论物理研究所，海德堡大学）；Institute for Quantum Electronics, ETH Zürich（量子电子学研究所，苏黎世联邦理工学院）
We propose a novel and robust technique to realize a beam splitter for trapped Bose-Einstein condensates (BECs). The scheme relies on the possibility of producing different potentials simultaneously for two internal atomic states. The atoms are coherently transferred, via a Rabi coupling between the two long-lived internal states, from a single well potential to a double-well. We present numerical simulations supporting our proposal and confirming excellent efficiency and fidelity of the transfer process with realistic numbers for a BEC of $^{87}$Rb. We discuss the experimental implementation …
