Research in quantum optics and atomic physics has revolutionized our ability to isolate quantum systems from their environment, engineer their properties and steer their dynamics with astonishing precision. Cold atoms and ions, as well as photons thus play a major role in the so-called second quantum revolution, by enabling foundational investigations of quantum physics, and offering candidate platforms for future technologies, from quantum computing, and quantum simulations, to quantum communication and sensing. At the heart of these developments lies the ability to generate and control interactions between different quantum mechanical components and to probe and observe quantum states and their dynamics. 

The Center of Excellence for Complex Quantum Systems (CCQ) aims to expand these capabilities by designing, exploring and exploiting hybrid quantum platforms in which atoms, ions and photons blend together and may thereby acquire new emergent properties. In particular, we perform experiments with laser-cooled trapped ion crystals and multi-component quantum gases of ultracold atoms, and we develop techniques to hybridize such distinct quantum systems or to couple them to quantum light fields, confined inside optical resonators. The theoretical and experimental investigation of these platforms aims to deepen our understanding of emergent interactions at the quantum level, and seeks to provide new principles and tools for the probing and steering of complex quantum systems. These developments will also lay a foundation for the advancement of new quantum technologies, mentioned above.