Nonlinear Quantum Optics
Our group explores novel approaches to controlling and processing quantum systems - atoms, photons, mechanical resonators - on the level of single quanta. For example, we develop new schemes to realize strong (effective) interaction between individual 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 quanta. These tools enable deterministic generation of few-particle quantum states and 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
The RQO project explores nonlinear quantum optics in an ultracold gas of Rubidium atoms. The well-explored level structure of the Rb and the established techniques for cooling and trapping alkali atoms make this element a natural choice for realizing 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 have demonstrated photonic quantum devices such as a single-photon transistor and N-photon absorbers. We have performed detailed studies of the Rydberg-mediated photon-photon interactions and continue to apply it to realize systems of strongly interacting photons.
Ytterbium Rydberg NQO
The YQO project explores few-photon Rydberg excitation and nonlinear quantum optics using ultracold 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 study in detail the unique 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 novel mechanical resonator element in our system ares polymer structures fabricated directly on the fiber mirrors via 3D laser-writing. The mechanical motion of these structures interact with light in the optical resonator through the radiation pressure force. We explore this optomechanical platform for sensing applications as well as for scaling mechanical oscillator networks.
Hybrid Quantum Optics
The HQO project interfaces ensembles of ultracold atoms excited to Rydberg states with on-chip microwave and mechanical oscillators to realize a quantum system combining quanta in the optical and microwave domain. This challenging goal requires a custom cryogenic setup combining 4K on chip devices with laser cooled Rb atoms and Rydberg excitation. In this novel hybrid system we aim to show optical cooling of a mechanical mode and ultimately the coherent coupling of single photons to single phonons.
Molecule Quantum Optics
The MQO project is building a new experimental platform to trap, cool, and control individual polar molecules, with the long-term goal of turning them into a programmable tweezer array for quantum science. Single molecules offer distinct degrees of freedom, namely vibrational and rotational quantum states, which provide new options for quantum information encoding and processing. This project is a collaborative effort between three research groups in Bonn - Quantum Metrology, Nonlinear Quantum Optics and Nanophysics and Quantum Photonics.
Waveguide QED
How do you build a large, strongly interacting quantum system one atom at a time?
In our lab, we aim to do so by combining three powerful ingredients:
1. Long-range interactions mediated by nanophotonic interfaces for cold atoms
2. Single-atom control offered by optical tweezer arrays
3. Strong atom–photon coupling that can be achieved in an optical cavity
By bringing these ingredients together, we seek to create and investigate novel quantum systems that are simply impossible to realize using conventional approaches.