Quantum state engineering of naturally trapped ions for quantum information and quantum optics

Rare earth ions in inorganic crystals have free-atom like properties. Optical transitions can be sub-kHz and hyperfine state lifetimes may be days. Using optical-pumping techniques these remarkable properties enable accurate tailoring of the ion absorption profiles. In this way artificial spectral structures are created for targeted purposes. 

In an optical cavity made of a rare earth crystal it is straight-forward to create semi-permanent structures that slow down the light propagation by several orders of magnitude. Such intra-cavity modifications of the light propagation change the cavity free spectral width and cavity line-width by equally many orders of magnitude. Using these engineered materials, highly efficient (>50%) quantum memories as well as narrow-band optical filters acting as temporal delay lines for medical and other applications are created. 

The talk will describe key properties of rare-earth-ion-doped inorganic crystals. Demonstrate how their absorption is modified through irradiation of suitable laser pulses. Give examples of opportunities (slow light applications, simultaneous spectral and temporal filtering, high efficiency quantum memories) that may open up using such quantum-state-engineering-based spectral-tailoring techniques, including applications by implementing ion absorption tailoring in whispering gallery mode cavities.