Title:Quantum control of ultracold atom-ion and atom-molecule collisions

Speaker: Michał Tomza,Univeristy of Warsaw

Time:2024-10-25 10:00am

Venue: C302,New Science Building

Abstract:Experiments at ultralow temperatures provide unprecedented opportunities for preparing reagents in well-defined quantum states and controlling their collisions with external fields. I will present our recent results of ab initio electronic structure and multichannel scattering calculations proposing, guiding, and explaining ultracold experiments. I will start with our efforts related to hybrid systems of laser-cooled trapped ions and ultracold atoms combined in a single experimental setup. In collaboration with experimental groups in Amsterdam and in Freiburg, we reached and explained the quantum regime of ion-atom collisions manifested via shape resonances [1] and their quantum control with an external magnetic field observed with magnetic Feshbach resonances [2]. I will continue by explaining the mechanism of recently observed magnetic Feshbach resonances in ultracold Na+NaLi atom-molecule mixtures [3]. In collaboration with groups at MIT and in Nijmegen, we showed that these Feshbach resonances result from spin-rotation and spin-spin couplings in combination with the anisotropic atom-molecule interaction. I will conclude by discussing hyperfine-to-rotational energy transfer in ultracold Rb+KRb atom-molecule collisions [4]. In collaboration with groups at Harvard and in Reno, we found that electronic spin is strongly coupled with molecular rotation in this system.

[1] T. Feldker, H. Fürst, H. Hirzler, N. V. Ewald, M. Mazzanti, D. Wiater, M. Tomza, R. Gerritsma, Nature Phys. 16, 413 (2020)

[2] P. Weckesser, F. Thielemann, D. Wiater, A. Wojciechowska, L. Karpa, K. Jachymski, M. Tomza, T. Walker, T. Schaetz, Nature 600, 429 (2021)

[3] J. J. Park, H. Son, Y.K. Lu, T. Karman, M. Gronowski, M. Tomza, A. O. Jamison, W. Ketterle, Phys. Rev. X 13, 031018 (2023)

[4] Y.-X. Liu, L. Zhu, J. Luke, M. C. Babin, T. V. Tscherbul, M. Gronowski, H. Ladjimi, M. Tomza, J. L. Bohn, K.-K. Ni, Nature Chem. / arxiv (2024)

Bio:Michał Tomza is a full professor, leader of the Quantum Molecular Systems research group, and head of the Center for Atomic Molecular and Optical Physics at the University of Warsaw. He specializes in the physics of ultracold quantum matter, including the theory of interactions and collisions of ultracold atoms, ions, and molecules controlled with electromagnetic fields and their application in quantum science in close collaboration with experimental groups. He finished his PhD in quantum chemistry and theoretical physics in Warsaw, Poland, and in Kassel, Germany, in 2014. Next, he was a postdoctoral researcher in Vancouver, Canada, and in Barcelona, Spain. Since 2017, he has led his research group at the University of Warsaw. He has also conducted research as a visiting scientist at several institutions in Europe and US.