Berlin 2001 – wissenschaftliches Programm

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Q: Quantenoptik

Q 17: Poster: Cooling and Trapping

Q 17.12: Poster

Mittwoch, 4. April 2001, 12:30–15:00, AT2

Wave Packet Echoes in the Motion of Trapped Atoms — •Felix B.J. Buchkremer, Rainer Dumke, Gerhard Birkl, and Wolfgang Ertmer — Institut für Quantenoptik, Universität Hannover, Welfengarten 1, 30167 Hannover, Germany

We experimentally demonstrate and systematically study the stimulated revival (echo) of motional wave packets [1]. For this purpose, we prepare wave packets in an optical lattice by nonadiabatically shifting the potential and observe the resulting oscillations and their decay. By a second shift after a variable time delay Δt we stimulate the reocurrence of the oscillations (echo) after 2Δt. This technique, which is analogous to the well known spin or photon echo techniques in nuclear magnetic or optical resonance, enables one for the first time to determine the coherence time of the atom motion even in the presence of strong dephasing. We find that it is about twice as long as the cooling time and, for strongly bound atoms, is much longer than the inverse of the photon scattering rate. This result implies that the coherence time of the motion of trapped atoms in general can be determined by measuring the cooling time.

In order to gain a qualitative and quantitative understanding of the echo mechanism, we have performed a full quantum Monte Carlo wave-function simulation, which we compare with our experimental findings and use to further study the echo effect. Supported by the SFB 407 of the DFG.

[1] F.B.J. Buchkremer, R. Dumke, H. Levsen, G.Birkl, and W. Ertmer, PRL 85, 3121 (2000).