Photons interacting with Rydberg super atoms

• Applicant: Professor Dr. Hans Peter Büchler
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 428455952

In this project, we study the interaction of propagating photons with small atomic clouds giving rise to so-called Rydberg superatoms. The main idea is, that the photons couple the atomic ground state to a highly excited Rydberg state either in a setup with electromagnetic induced transparency or in the regime, where an intermediate p-level can be adiabatically eliminated. The strong interaction between the Rydberg atoms leads to the blockade phenomenon, which suppressed the second excitation of a Rydberg state in an atomic cloud smaller than the blockade radius, and therefore leads to the formation of Rydberg superatoms. The main focus of this collaboration between the experimental group of Prof. S. Hofferberth and the theoretical group of Prof. H.P. Büchler is on the quantum phenomena induced by such superatoms and their potential application for quantum information processing. One important aspect are the correlations induced onto the propagating photons for several Rydberg superatoms: The consortium has previously successfully observed the behavior of a single superatom by the appearance of Rabi oscillations in the outgoing light field. An interesting research question is then on the behavior and the modifications on the correlations for photons interacting with several superatoms. On the theoretical side, a fundamental question is whether the correlations can be determined using the quantum regression theorem. Therefore, a main goal is the derivation of the validity of the quantum regression theorem in this regime and probe experimentally either its validity or probe corrections in a suitable experimental setup. Another important aspect is the behavior of electromagnetic induced transparency for a single superatom. The focus is on the appearance of photonic bound states in such a setup. In all these studies, the dephasing of a superatom is crucial and might lead to a fundamental limit on the correlations, which can be experimental achieved. Therefore, the theory group will study the behavior and the dephasing by virtual exchange of photons in a three-dimensional setting. Finally, we study theoretically the propagation of Rydberg polaritons in a microscopic setting, where the discrete and random distribution of the atoms is taken into account. This approach allows us to study the influence of back scattering as well as provide an intrinsic bound on the efficiency of photon storage in a EIT setting and schemes for realization of photonic quantum gates.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1929: Giant Interactions in Rydberg Systems (GiRyd)
• International Connection: Denmark
• Cooperation Partner: Professor Dr. Sebastian Hofferberth