Andreas research focus is on experimental quantum information and quantum optics, using rare-earth-ion-doped crystals. In order to realize the long-term goal of building a quantum computer, he is working towards demonstrating the benefits of the long-lived rare-earth ion states for storing and processing quantum information. At present, the main challenge is to enable detection and interaction with single rare-earth ions inside a solid host. To make them visible, he leads the work on using micro-sized optical cavities to selectively enhance the spontaneous emission from the ions, using the Purcell effect, to enable higher fluorescence.