Ultracold polar molecules possess long-range, anisotropic and tunable dipolar interactions, providing opportunities to probe quantum phenomena that are inaccessible with existing cold gas platforms. However, experimental progress has been hindered by the dominance of two-body loss over elastic interactions, which prevents efficient evaporative cooling. Although recent work has demonstrated controlled interactions by confining molecules to a two-dimensional geometry, a general approach for tuning molecular interactions in a three-dimensional stable system has been lacking. Here we demonstrate tunable elastic dipolar interactions in a bulk gas of ultracold ⁴⁰K⁸⁷Rb molecules in three dimensions, facilitated by an electric field-induced shielding resonance that suppresses the reactive loss by a factor of 30. This improvement in the ratio of elastic to inelastic collisions enables direct thermalization. The thermalization rate depends on the angle between the collisional axis and the dipole orientation controlled by an external electric field, a direct manifestation of the anisotropic dipolar interaction. We achieve evaporative cooling mediated by the dipolar interactions in three dimensions. This work demonstrates full control of a long-lived bulk quantum gas system with tunable long-range interactions, paving the way for the study of collective quantum many-body physics.

超冷极性分子具有长程、各向异性和可调谐的偶极相互作用，为探索现有冷气体平台无法实现的量子现象提供了机会。然而，实验进展受到了弹性相互作用中两体损失的主导地位的阻碍，这阻碍了有效的蒸发冷却。尽管最近的工作已经通过将分子限制在二维几何结构中证明了受控相互作用，但一直缺乏在三维稳定系统中调整分子相互作用的通用方法。^{在这里，我们展示了超冷40} K ⁸⁷块状气体中的可调谐弹性偶极相互作用三个维度的 Rb 分子，由电场诱导的屏蔽共振促进，将反应损失抑制了 30 倍。弹性与非弹性碰撞比的这种改进实现了直接热化。热化速率取决于碰撞轴与由外部电场控制的偶极子取向之间的角度，这是各向异性偶极子相互作用的直接表现。我们在三个维度上实现了由偶极相互作用介导的蒸发冷却。这项工作展示了对具有可调长程相互作用的长寿命体量子气体系统的完全控制，为集体量子多体物理学的研究铺平了道路。