Coherent control of trapped Rydberg ions
Prof. Dr. Markus Hennrich (Department of Physics, Stockholm University, Sweden)

Trapped Rydberg ions are a novel quantum system [1,2]. Fast entanglement gates may be realized in large ion crystals [1,3] by combining the high degree of control of trapped ion systems with the long-range dipole-dipole interactions of Rydberg atoms.
Quantum information processing in this system is envisaged to use low-lying electronic states for storage of qubits and strongly interacting Rydberg states for entanglement operations [4]. This requires the Rydberg excitation to be coherently controlled.
In our experiment we have observed the first coherent Rydberg excitations of an ion [5,6] via a two-photon excitation to Rydberg S states. Coherent effects observed include Rabi oscillations, EIT and STIRAP. We also report the realization of microwave-dressed Rydberg ions driving the transition between S and P Rydberg states. This marks an important step towards realizing entanglement operations between Rydberg ions, which are envisaged to strongly interact with each other via the large oscillating dipole moments of microwave-dressed Rydberg states.
[1] M. Müller, et al., New J. Phys. 10, 093009 (2008).
[2] T. Feldker, et al., Phys. Rev. Lett. 115, 173001 (2015).
[3] F. Schmidt-Kaler, et al., New J. Phys. 13, 075014 (2011).
[4] P. Bachor, et al., J. Phys. B 49, 154004 (2016).
[5] G. Higgins, et al., Phys. Rev. X 7, 021038 (2017).
[6] G. Higgins, et al., arXiv:1708.06387.