In the second part I will talk about giant artificial atoms in quantum optics. The ultra-strong coupling regime in light-matter interactions requires non-perturbative methods, for example, to calculate the radiation emitted from an atom. I will discuss how star-to-chain transformations may be utilised for such tasks, when combined with methods based on matrix product states [2,3]. Being well known in the study of open quantum systems, we demonstrate that the approach allows us to also treat field observables - both in vacuum states and thermal states of the field. As an outlook I will touch upon future experimental realisations.

[1] JK, D. Malz, J. I. Cirac, “Cross-platform verification in quantum networks”, Phys. Rev. A 107, 062424 (2023).

[2] D. D. Noachtar, JK, R. H. Jonsson, “Nonperturbative treatment of giant atoms using chain transformations”, Phys. Rev. A 106, 013702 (2022).

[3] R. H. Jonsson, JK, “Chain-mapping methods for relativistic light-matter interactions”, Quantum 8, 1237 (2024).

Biography

Johannes Knorzer studied physics in Freiburg and Hamburg, Germany. He received his PhD in theoretical physics from the Ludwig Maximilian University of Munich in 2020 under the supervision of Ignacio Cirac. In his PhD he focused on quantum acoustics and solid-state implementations for quantum simulation, in close collaboration with experimental groups. His research interests lie at the intersection of quantum information science, quantum optics and condensed-matter physics. Currently, two of his main research directions are distributed quantum algorithms and analogue quantum simulation for applications in condensed-matter physics. After completing his PhD, he continued as a postdoc in the Cirac group at MPQ. Since 2022 he is a Junior Fellow at the Institute for Theoretical Studies at ETH Zurich, where he is working with the group of Eugene Demler.

Inviter

Tao Shi