Quantum control of chemical reactivity at ultralow temperatures: Insights from quantum dynamical calculations

Ultracold molecules offer unique opportunities for probing molecular collisions and chemical reactivity at the most fundamental level, where rovibrational degrees of freedom of the reactants, and even those of reaction complexes, can be precisely controlled. Quantum scattering calculations play an essential role in exploring and leveraging these opportunities by providing a connection between the collision observables and the underlying microscopic interactions within the reaction complex. Significant progress has been achieved in recent years, with field-free quantum dynamics of ultracold three-atom reactions now amenable to rigorous computational studies [1]. I will discuss how the quantum dynamics of ultracold barrierless chemical reactions (such as NaLi + Na $\to$ Na$_2$ + Li) can be controlled by spin polarizing the reactants in an external magnetic field [2,3]. I will then introduce quantum interference-based coherent control as an efficient tool to tune ultracold molecular collisions by varying the relative populations and phases of initial coherent superpositions of degenerate molecular states [4,5]. I will conclude by arguing that rapid development of efficient theoretical methodologies [1,6] will soon make it possible to perform numerically exact quantum dynamical simulations of a wide variety of triatomic chemical reactions in the absence or presence of external electromagnetic fields, enabling full exploration of ultracold controlled reaction dynamics.