We show that microwave shielding on the rotational transition $n=1\rightarrow 2$ can be effective in preventing destructive collisions between ultracold polar molecules. It is slightly less efficient than shielding on the transition $0\rightarrow 1$, but has some important advantages. In particular, it does not produce 2-molecule bound states under the conditions needed for shielding, so it will not enhance 3-body recombination. It thus obviates the need for double-field microwave shielding using a second field of different polarization.
我们用微波来设计超冷极性分子之间的排斥性长程相互作用。所得到的屏蔽抑制了各种损耗机制并提供了大的弹性截面。超精细相互作用限制了实际条件下的屏蔽，但磁场允许将损耗抑制到10-14 cm 3 s-1以下。屏蔽的机制和最佳条件与Gorshkov等人[Phys. Rev. Lett. 101，073201（2008）]，并且不需要消除对于许多应用至关重要的长程偶极-偶极相互作用。
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…
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.
We propose a method to suppress the chemical reactions between ultracold bosonic ground-state $^{23}$Na$^{87}$Rb molecules based on optical shielding. By applying a laser with a frequency blue-detuned from the transition between the lowest rovibrational level of the electronic ground state $X^1Σ^+ (v_X=0, j_X=0)$, and the long-lived excited level $b^3Π_0 (v_b=0, j_b=1)$, the long-range dipole-dipole interaction between the colliding molecules can be engineered, leading to a dramatic suppression of reactive and photoinduced inelastic collisions, for both linear and circular laser polarizations.…
Ultracold polar molecules can be shielded from fast collisional losses using microwaves, but achieving the required polarization purity is technically challenging. Here, we propose a scheme for shielding using microwaves with polarization that is far from circular. The setup relies on a modest static electric field, and is robust against imperfections in its orientation.
We study polar alkali dimer scattering in a quasi-1D geometry for both reactive and non-reactive species. Elastic and reactive rates are computed as a function of the amplitude of a static electric field within a purely long-range model with suitable boundary conditions at shorter range. We describe the diatomic molecules as rigid rotors and results are compared to the fixed-dipole approximation. We show in particular that for molecules with a sufficiently strong induced dipole moment oriented perpendicular to the trap axis, the long-range repulsive interaction leads to the suppression of shor…
We theoretically study collisions between ultracold polar molecules that are polarized by microwave or static electric fields. We systematically study the dependence on field strength, microwave polarization, and detuning from rotational transitions. We calculate the loss in two-body collisions that is observable experimentally and compare to the results expected for purely first-order dipolar interactions. For ground state molecules polarized by a static electric field, the dynamics are accurately described by first-order dipolar interactions. For microwave dressing, instead, resonant dipolar…
Controlled symmetry breaking of the Fermi surface in ultracold polar molecules
Max-Planck-Institut für Quantenoptik（马克斯·普朗克量子光学研究所）；Munich Center for Quantum Science and Technology（慕尼黑量子科学与技术中心）；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）；Fakultät für Physik, Ludwig-Maximilians-Universität（慕尼黑大学物理学院）
Full control of molecular interactions, including reactive losses, would open new frontiers in quantum science. Here, we demonstrate extreme tunability of chemical reaction rates by using an external electric field to shift excited collision channels of ultracold molecules into degeneracy with the initial collision channel. In this situation, resonant dipolar interactions mix the channels at long range, dramatically altering the intermolecular potential. We prepare fermionic potassium-rubidium (KRb) molecules in their first excited rotational state and observe a three orders-of-magnitude modul…
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）
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…
