Nonlinear Quantum Optics
Our group explores novel approaches to controlling and processing quantum systems - atoms, photons, mechanical resonators - on the level of single quanta. In particular, we develop new schemes to realize strong (effective) interaction between individual quanta, for example photons. With this approach, the fundamentally new regime of nonlinear quantum optics (NQO) becomes accessible, where the response of the constructed quantum system depends on the exact number of input photons (or phonons). Employing these tools for deterministic generation of few-particle quantum states, we open the possibility of assembling large, complex systems "brick by brick" from the bottom up to gain new insights into strongly interacting many-body quantum systems. Ultimately, we aim to achieve full control over light photon by photon or quantized mechanical motion phonon by phonon.
Rubidium Rydberg NQO
This project explores nonlinear quantum optics in an ultracold gas of Rubidium atoms. The simple level structure of the alkalis and the established techniques for cooling and trapping Rb make this element a natural choice for exploring Rydberg EIT and nonlinear quantum optics. We first demonstrated the manipulation of the quantum statistics of light via Rydberg interaction in 2013 with this setup. Since then, we managed to implement a single-photon transistor and multiple single-photon absorbers, and we have performed detailed studies of the Rydberg-mediated photon-photon interactions.
Ytterbium Rydberg NQO
The YQO project explores few-photon Rydberg excitation and nonlinear quantum optics using ultra-cold Ytterbium atoms. The core goal of this project is to exploit the advantages provided by Yb for realizing large systems of strongly interacting Rydberg polaritons beyond what is currently achieved in alkali gas experiments. Beyond the NQO applications enabled by this new system, we also plan to study in detail the Rydberg physics of this earth-alkaline-like atomic species.
Fiber Cavity Optomechanics
The FCO project focuses on the development of a highly integrated platform for cavity optomechanical experiments. It is based on fiber Fabry-Perot cavities that are formed by two opposing fiber tips with highly reflective coatings and a central depression created via laser ablation. The mechanical resonator element is formed by polymer structures that can be fabricated directly on the fiber mirrors via 3D laser-writing. Vibrational modes of these structures are interacting with light in the optical resonator through the radiation pressure force.
Hybrid Quantum Optics
The HQO project is a new project which will interface ensembles of ultracold atoms excited to Rydberg states with on-chip optical and microwave-waveguides to bring Rydberg-mediated single-photon non-linearities closer to practical applications. We are currently planning and building a new cryogenic ultracold atom setup which will allow to exchange samples and reconfigure the experiment on time-scales much faster compared to traditional ultracold atom setups.