标题： 时间反演对称性保护的超冷分子碰撞相干控制 显示英文标题

标题： Time-Reversal Symmetry-Protected Coherent Control of Ultracold Molecular Collisions

摘要： 原子和分子散射的相干控制依赖于将碰撞粒子制备在内部状态的叠加态，建立可以用来调节散射过程结果的干涉路径。 然而，在具有复杂碰撞动力学的系统中，不同部分波贡献对积分截面的非相干叠加（部分波混乱）是一个重大挑战，通常会限制控制能力。 这项工作表明，时间反演对称性可以通过约束S矩阵元素的相对相位来克服这些限制，从而保护相干控制免受部分波混乱的影响，即使是在由高度各向异性相互作用介导的碰撞中也是如此。 以超冷O$_2$-O$_2$散射为例，我们展示了相干控制对短程动力学复杂性具有鲁棒性。 此外，时间反演对称性还能保护控制不受碰撞能量分布的影响。 这些发现表明，超冷散射到时间反演不变的最终态（如J = 0, M = 0的旋转态）总是可以通过使用时间反演不变的初始叠加态进行最优控制。 超越超冷范围，我们观察到交叉分子束实验与陷阱实验在可控性方面的显著差异，前者更容易控制，强调了时间反演和排列对称性在任何温度下维持控制中的协同作用。 这些结果为在超冷范围内外复杂非弹性碰撞和化学反应的相干控制开辟了新的途径。 显示英文摘要

摘要： Coherent control of atomic and molecular scattering relies on the preparation of colliding particles in superpositions of internal states, establishing interfering pathways that can be used to tune the outcome of a scattering process. However, incoherent addition of different partial wave contributions to the integral cross sections (partial wave scrambling), commonly encountered in systems with complex collisional dynamics, poses a significant challenge, often limiting control. This work demonstrates that time-reversal symmetry can overcome these limitations by constraining the relative phases of S-matrix elements, thereby protecting coherent control against partial wave scrambling, even for collisions mediated by highly anisotropic interactions. Using the example of ultracold O$_2$-O$_2$ scattering, we show that coherent control is robust against short-range dynamical complexity. Furthermore, the time-reversal symmetry also protects the control against a distribution of collisional energy. These findings show that ultracold scattering into the final states that are time-reversal-invariant, such as the J = 0, M = 0 rotational state, can always be optimally controlled by using time-reversal-invariant initial superpositions. Beyond the ultracold regime, we observe significant differences in the controllability of crossed-molecular beam vs. trap experiments with the former being easier to control, emphasizing the cooperative role of time-reversal and permutation symmetries in maintaining control at any temperature. These results open new avenues for the coherent control of complex inelastic collisions and chemical reactions both in and outside of the ultracold regime.