Rydberg Ions

Rydberg excitation of trapped Ions

Our overaching goal is to join control and readout of states of ions, held in a linear Paul trap, with excitation to Rydberg states. This way, we are combining the advantages of trapped ions, e.g. exceptional control over the external and internal states, long range Coulomb interactions, with the exciting prospects of Rydberg physics, especially the long range interaction between two Rydberg ion spins by van-der-Waal or dipole-dipole interaction. The transition to Rydberg states is driven in a single-photon excitation scheme at 122 nm wavelength. The technology for VUV generation has been developed for anti-Hydrogen laser cooling. We investigate pathways for mulit-particle entanglement and non-equilibrium dynamics.



Large dipolar interactions in Rydberg excitations enable designed interactions in linear and planar ion crystals  



rydber exc. Bild1

Rydberg excitation to  51F state: The line is a fit of the model that takes into account the polarizability of the Rydberg state, the electric field of the Paul trap at the ion position and the micro-motion oscillation of the ion in the trap. The figure is from T. Feldker, P. Bachor, M. Stappel, D. Kolbe, R. Gerritsma, J. Walz, F. Schmidt-Kaler"Rydberg excitation of a single trapped ion", Phys. Rev. Lett. 115, 173001 (2015)

We work in collaboration with the team of Jochen Walz, including theory support by the teams of Peter Zoller, Innsbruck and Igor Lesanowski, Nottingham. The project started in late 2010 with a first "blueprint" of the experiment which is published in NJP2011.

Research highlights : 

  • Excitation of a single Ca-ion from the D3/2 state to the 51F Rydberg level. This is the first excitation of a single ion to Rydberg levels ever. The high efficiency of the detection sheme is prooven. We observed narrow resonances, and the line shape is studied in detail. Furthermore, we deduce the giant polarizability of the Rydberg states and demonstrate the interaction with the dynamical Paul trap field for confining ions. The results have been published in PRL2015.
  • Most recently we have been able to coherently initialize Rydberg excitation and address this on single ions out of a linear crystal. This demonstartes key prerequisites for more complex applications of Rydberg ions in quantum simulation or quantum information processing. We have excited the 22F state from the upper qubit state in the metastable D5/2 level, see preprint.
  • We have, in collaboration with the team of Peter Zoller, Innsbruck, worked out a scheme for Rydberg-enabled plaquette interaction of six ion spins. This is a buillding block to realize the Fisher Balents Girvin model. The mode shaping is investigated for the case of a planar ion crystal. Results are published in NJP2015.
  • Mode shaping in linear ion crystals has been realized using doubly ionized calcium. The Ca++ appear as dark sites in the crystal. Using a six-ion linear crystal, we have observed localized eigenmodes and the Ca++ ion enables the separation of radial modes. Furthermore, we observe structural phase transitions from linear to zigzag, depending on the position of the single ion Ca++. Results are found in  Appl. Phys. B. 2013.

We thank for funding by EU within Chist-ERA RydIon and the EU-STREP RYSQ.