However, the model system of a trapped ion crystal may be employed for a wealth of applications: We investigate genuine solid-state effects such as defect formation . We use single ultra-cold ions extracted from the trap to deterministically dope solids or sense structure at the nm-scale . We operate a single ion heat engine  truly at the nano scale,with potential of reaching the quantum regime. We position single trapped ions in vortex light fields with orbital angular momentum and prove novel selection rules . I describe the most recent results from the Mainz ion-trapping group and future perspectives.
Fig: Segment micro ion trap for quantum processing with 40Ca+ ions
Ulm, et al., "Observation of the Kibble-Zurek scaling law for defect
formation in ion crystals", Nat. Comm. 4, 2290 (2013)
 Jacob, et al., "Transmission Microscopy with Nanometer Resolution Using a Deterministic Single Ion Source ", PRL 117, 043001 (2016)
 Roßnagel, et al., "A single-atom heat engine", Science 352, 325 (2016)
 Schmiegelow et al., "Transfer of optical orbital angular momentum to a bound electron", Nat. Comm. 7, 12998 (2016)