Periodic Reporting for period 4 - RYD-QNLO (Quantum nonlinear optics through Rydberg interaction)
Berichtszeitraum: 2022-04-01 bis 2023-10-31
More specifically, the project employs a combination of state-of-the-art experimental techniques from atomic physics and quantum optics, including ultracold atomic gases, strongly interacting Rydberg atoms, and coherent optical control methods such as electromagnetically induced transparency to realize an optical medium inside which individual photons behave like interacting particles. Building on this novel concept, the project explores both fundamental aspects of the quanta of light as well as technological applications in quantum information.
One part of the project has investigated the fundamental processes of absorption and stimulated emission at the level of single photons. Towards this end, we have realized so-called Rydberg superatoms, ensembles of many thousand laser-cooled atoms which collectively behave like a single quantum emitter strongly coupled to a single light mode. So far, we have observed in this setup how a single superatom can mediate correlations between two or even three individual photons. As planned, we have extended our experimental capabilities to produce multiple separated superatoms all coupled to the same probe mode. Currently, we are studying the superradiance of two simultaneously excited superatoms.
The second part of the project is concentrated on building up a new apparatus employing ultracold Ytterbium atoms for mediating photon-photon interactions. Here, the construction of the setup is proceeding, in September 2019 we observed the first magneto-optical trap loading the different bosonic isotopes of Yb. At the moment, the work is focused on implementing the probe/control setup required for excitation of Ytterbium Rydberg atoms with single photons. In parallel, we have constructed the full laser system including the Rydberg and probe lasers, all of which are now stabilized to linewidths of a few Hz.
The Yb experiment is well on track to be the world-first setup using Ytterbium (or any other 2-valence electron system) for single-photon interaction. While various questions stated in the initial proposal about this new system remain - such as how high the optical depth can be pushed by exploiting the unique features of Yb - so far, the designed apparatus has fulfilled all design criteria and seems well suited to carry out the proposed research in the next periods. In particular, we hope to perform Rydberg polariton experiments with up to 10 strongly interacting polaritons in the next period, which would exceed current experiments and push beyond the limits of current theory.