Two — Photon Rydberg excitation of trapped strontium ions

A trapped ion quantum computer usually uses the motional modes of the ion crystal to exchange quantum information and to generate entanglement. As the number of ions in a trap is increased, the motional modes become progressively more complicated and their energy spacing is reduced. This makes the entangling operation increasingly difficult. An alternative method for a trapped-ion quantum computer may be realised by exciting some of the ions to Rydberg states. The large polarizability of Rydberg ions modifies the trapping potential thus allows tailoring the motional modes for entanglement operations [1]. Additionally entangling gates may be realised using the dipole interaction between Rydberg ions, without using motional modes at all [2,3].