Atomic Physics

Faculty of Engineering, LTH

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Single ion quantum state readout

Rare earth ions at low temperatures can remain in a superposition state over extended time. Consequently they also have very long lifetimes. While the weak interaction with the surroundings is ideal for reliable quantum operations, the other side of the coin is that state detection is very difficult, because since it stays for a long time in the excited state the ion transmits at a very low photon rate. Further, most ions have no transition that can be repeatedly cycled for readout. However, the Ce ion has an effectively closed and also short-lived 4f-5d transition in most hosts. Using the dipole blockade effect discussed in the qubit-qubit interaction project in a crystal doped with both Ce and qubit ions of another kind, e.g. Pr, it is possible to device schemes by which it should be possible to reliably readout the state of a qubit ion. We are trying to develop such a scheme.


  • A confocal optical microscope for detection of single impurities in a bulk crystal at cryogenic temperatures
    J Karlsson, L Rippe and S Kröll
    Rev Sci Instr 87, 033701 (2016)
  • Measurement of line-widths and permanent electric dipole moment change of the Ce 4f-5d transition in Y2SiO5 for a qubit readout scheme in rare-earth ion based quantum computing
    Ying Yan, J Karlsson, L Rippe, A Walther, D Serrano, S Kröll, P Goldner, D Lindgren, M-E Pistol,    Lihe Zheng & Jun Xu
    Phys Rev B 87, 184205 (2013)
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