QUROPE Quantum Information Processing and Communication in Europe

G. Morigi (P8 USAAR), seminar, Wigner crystals of trapped ions.

G. Morigi (P8 USAAR), seminar, Cavity Quantum Electrodynamics with Ultracold Atoms,

G. Morigi, seminar, Ion Coulomb Crystals: An unusual form of condensed matter.

G. Morigi, seminar, Quantenstrukturen in Materie und Licht.

S. Rist and G. Morigi, poster presentation, Atom counting via photon counting

M. Rizzi, invited talk, Pfaffian state generation by strong 3-body dissipation
 

P. Treutlein, invited talk, 06.09.2010, Observation of bi-directional coupling between ultracold atoms and a mechanical oscillator,

An optical microcavity with small mode radius is used to measure the local density of a cold atom cloud. Atom densities below 1 per cavity mode volume are measured with signals near the photon shot-noise limit. Atom detection is fast and efficient, reaching fidelities in excess of 97% after 10 us and 99.9% after 30 us. Notably, the fluctuations of the detected photon counts are smaller than expected for Poissonian distributions of atoms probed with Poissonian light fields.

We investigate the use of a Bose-Einstein condensate trapped on an atom chip for making interferometric measurements of small forces. A fundamental limit on sensitivity is imposed by the noise in the energy difference of the split condensates, which we measure and explain. We also consider systematic errors. A leading effect is the variation of rf magnetic field in the trap with distance from the wires on the chip surface. This can produce energy differences that are comparable with those due to gravity.

We study the nonlinear dynamics of an ensemble of cold trapped atoms with a hyperfine transition magnetically coupled to a resonant microwave cavity mode. Despite the minute single atom coupling one obtains strong coupling between collective hyperfine qubits and microwave photons enabling coherent transfer of an excitation between the long lived atomic qubit state and the mode. Evidence of strong coupling can be obtained from the cavity transmission spectrum even at finite thermal photon number.