Ultracold Atoms and Quantum Measurement Processes

Sydney Schreppler, Nicolas Spethmann, Jonathan Kohler +1 more

Yvan Castin, Jean Dalibard, Claude N. Cohen-Tannoudji

Johannes Deiglmayr, A. Göritz, Th. Best +2 more

We present a scheme to embed molecular anions in a gas of ultracold rubidium atoms as a route towards the preparation of cold molecular ions by collisional cooling with ultracold atoms. Associative detachment as an important loss process in collisions between OH${}^{\ensuremath{-}}$ molecules and rubidium atoms is studied. The density distribution of trapped negative ions in the multipole radio frequency trap is measured by photodetachment tomography, which allows us to derive absolute rate coefficients for the process. We define a regime where translational and internal cooling of molecular ions embedded into the ultracold atomic cloud can be achieved.

Sebastiano Anderloni, Fabio Benatti, Roberto Floreanini B +1 more

The standard experimental techniques usually adopted in the study of the behaviour of ultracold atoms in optical lattices involve extracting the atom density profile from absorption images of the atomic sample after trap release. Quantum mechanically this procedure is described by a generalized measure (POVM); interference patterns found in absorption images suggest a generalized measure based on fixed-phase, coherent-like states. We show that this leads to an average atomic density which differs from the usually adopted one, obtained as the expectation value of the atom density operator in the many-body state.

Ivan Deutsch

Ahmed Abdelrahman, T. Mukai, Hartmut Häffner +1 more

We propose a hybrid architecture for quantum information processing based on magnetically trapped ultracold atoms coupled via optical fields. The ultracold atoms, which can be either Bose-Einstein condensates or ensembles, are trapped in permanent magnetic traps and are placed in microcavities, connected by silica based waveguides on an atom chip structure. At each trapping center, the ultracold atoms form spin coherent states, serving as a quantum memory. An all-optical scheme is used to initialize, measure and perform a universal set of quantum gates on the single and two spin-coherent states where entanglement can be generated addressably between spatially separated trapped ultracold atoms. This allows for universal quantum operations on the spin coherent state quantum memories. We give detailed derivations of the composite cavity system mediated by a silica waveguide as well as the control scheme. Estimates for the necessary experimental conditions for a working hybrid device are given.