Berlin 2005 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
Q: Quantenoptik und Photonik
Q 36: Quanteneffekte II
Q 36.8: Vortrag
Dienstag, 8. März 2005, 12:30–12:45, HU 1072
Feedback control of a single ion’s motion — •D. Rotter1, P. Bushev2, A. Wilson1, C. Becher1, J. Eschner1,3, and R. Blatt1,4 — 1Institut für Experimentalphysik, Universität Innsbruck, Austria — 2Laboratory of Physical Chemistry, ETH Zürich — 3Institute for Photonic Sciences (ICFO), Spain — 4Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Austria
We demonstrate feedback cooling of a single trapped ion below the Doppler limit by the method of "cold damping" [1] or homodyne feedback [2]. We also show that the motional phase can be stabilised against the diffusion induced by photon recoils by locking it to an external reference oscillator. In our experiment a single Ba+ ion in a Paul trap is continuously laser-excited at Doppler cooling conditions. A part of the resonance fluorescence is retro-reflected, thus leading to interference fringes of high contrast [3]. Since the interference is sensitive to the ion-mirror distance, amplitude and phase of the ion’s motion are detected with high signal-to-noise ratio in the fluctuation spectrum of the photocurrent. For cold damping, we create an additional friction force proportional to the instantaneous velocity of the ion, by supplying additional electric fields which are -90∘ phase-shifted against the measured amplitude of the motion. Phase-locked operation is achieved by measuring phase deviations between the ion’s motion and the reference oscillator, and feeding them back to the level of the rf trap drive, thus controlling the trap stiffness.
[1] J. M. W. Milatz et al., Physica 19, 181 (1953).
[2] S. Mancini et al., PRL 80, 688 (1998).
[3] J. Eschner et al., Nature 413, 495 (2001).