Numerically exact quantum dynamics and control of ultracold atom-molecule collisions: Magnetic Feshbach resonances

Despite its relevance to ultracold controlled chemistry and quantum information science, the quantum dynamics of ultracold molecular collisions is far from completely understood due to the rapidly proliferating rotational, vibrational, fine, and hyperfine states coupled by highly anisotropic intermolecular interactions and external electromagnetic fields. I will review our efforts aimed at better understanding the physics of ultracold atom-molecule collisions, which include (i) an efficient total rotational angular momentum (TRAM) basis for incorporating the effects of hyperfine structure and external magnetic fields in molecular quantum scattering calculations and (ii) multichannel quantum defect theory with a frame transformation (MQDT-FT) [2]. These improvements allow for a substantial reduction in basis size and computational effort, making it possible to obtain the first numerically converged spectra of magnetic Feshbach resonances in highly anisotropic Rb + SrF collisions in the rigid-rotor approximation. Applications to quantum interference-based coherent control of ultracold atom-molecule collisions will be discussed.

[1] T. V. Tscherbul and J. P. D’Incao, Phys. Rev. A 108, 053317 (2023); [2] M. Morita, P. Brumer, and T. V. Tscherbul, arXiv:2309.00263.