Ground state cooling, quantum state engineering and study of decoherence of ions in Paul traps
Ferdinand Schmidt‐Kaler, Christian F. Roos, Hanns‐Christoph Nägerl, H. J. Rohde, S. Gulde, A.B. Mundt, M. Lederbauer, Gregor Thalhammer, Th. Zeiger, Petr Barton, Liv Hornekær, G. Reymond, Dietrich G. Leibfried, Jürgen Eschner, R. Blatt · Journal of Modern Optics · 2000
We investigate single ions of 40Ca+ in Paul traps for quantum information processing. Superpositions of the S½ electronic ground state and the metastable D5/2; state are used to implement a qubit. Laser light on the S½ ↔ D5/2 transition is used for the manipulation of the ion's quantum state. We apply sideband cooling to the ion and reach the ground state of vibration with up to 99.9% probability. Starting from this Fock state (n = 0), we demonstrate coherent quantum state manipulation. A large number of Rabi oscillations and a ms-coherence time is observed. Motional heating is measured to be as low as one vibrational quantum in 190ms. We also report on ground state cooling of two ions.