Quantum information processing and communication can be regarded as one of today’s most important challenges in the basic science underlying the field of computing and communication. The LLC Quantum Information Group develops quantum hardware based on inorganic crystals doped with rare-earth ions, for use in quantum computing and quantum memories. Controlling and mastering the phase of the quantum mechanical wave function is a key requirement for quantum information applications. Consequently quantum systems with long coherence times enable the development of high fidelity quantum information techniques. Rare-earth-doped solid state systems offer unique opportunities in this respect as they have coherence times that range from milliseconds up to minutes. The group also actively works with strong slow light effects in these materials, where the speed of light is reduced by several orders of magnitude. This includes applications in medical imaging and laser frequency stabilization.