Molecular quantum gases (that is, ultracold and dense molecular gases) have many potential applications, including quantum control of chemical reactions, precision measurements, quantum simulation and quantum information processing^1,2,3. For molecules, to reach the quantum regime usually requires efficient cooling at high densities, which is frequently hindered by fast inelastic collisions that heat and deplete the population of molecules^4,5. Here we report the preparation of two-dimensional Bose–Einstein condensates (BECs) of spinning molecules by inducing pairing interactions in an atomic condensate near a g-wave Feshbach resonance⁶. The trap geometry and the low temperature of the molecules help to reduce inelastic loss, ensuring thermal equilibrium. From the equation-of-state measurement, we determine the molecular scattering length to be + 220(±30) Bohr radii (95% confidence interval). We also investigate the unpairing dynamics in the strong coupling regime and find that near the Feshbach resonance the dynamical timescale is consistent with the unitarity limit. Our work demonstrates the long-sought transition between atomic and molecular condensates, the bosonic analogue of the crossover from a BEC to a Bardeen−Cooper−Schrieffer (BCS) superfluid in a Fermi gas^7,8,9. In addition, our experiment may shed light on condensed pairs with orbital angular momentum, where a novel anisotropic superfluid with non-zero surface current is predicted^10,11, such as the A phase of ³He.

分子量子气体（即超冷和致密分子气体）具有许多潜在的应用，包括化学反应的量子控制、精密测量、量子模拟和量子信息处理^1,2,3。对于分子来说，要达到量子状态通常需要在高密度下进行有效冷却，这经常受到快速非弹性碰撞的阻碍，这种碰撞会加热并耗尽分子^4,5的数量。在这里，我们报告了通过在g波 Feshbach 共振⁶附近的原子凝聚物中诱导配对相互作用来制备旋转分子的二维玻色 - 爱因斯坦凝聚物 (BEC). 陷阱的几何形状和分子的低温有助于减少非弹性损失，确保热平衡。根据状态方程测量，我们确定分子散射长度为 + 220(±30) 玻尔半径（95% 置信区间）。我们还研究了强耦合机制中的不成对动力学，发现在 Feshbach 共振附近，动力学时间尺度与单一性极限一致。我们的工作证明了原子和分子凝聚物之间长期寻求的过渡，这是费米气体中从 BEC 到 Bardeen-Cooper-Schrieffer (BCS) 超流体的交叉的玻色子类似物^7,8,9. 此外，我们的实验可能会揭示具有轨道角动量的凝聚对，其中预测了具有非零表面电流的新型各向异性超流体^10,11，例如³ He 的 A 相。