QUROPE Quantum Information Processing and Communication in Europe

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.

We measure the two-point density correlation function of freely expanding quasicondensates in the weakly interacting quasi-one-dimensional (1D) regime. While initially suppressed in the trap, density fluctuations emerge gradually during expansion as a result of initial phase fluctuations present in the trapped quasicondensate. Asymptotically, they are governed by the thermal coherence length of the system.

Quantum many-body systems

Bell inequalities, non-locality and communication complexity

Quantum channels

- Cooling techniques for molecular ions

- Quantum-state control of single ultracold molecular ions

- Coherent manipulation of state-selected molecular ions

- State-controlled, ultracold ion-neutral collisions

Ultracold atoms on atom chips, Bose-Einstein condensation, quantum metrology, spin-squeezing, chip-based atomic clocks, quantum information processing, hybrid quantum systems, micro- and nanomechanical oscillators

We report heating rate measurements in a microfabricated gold-on-sapphire surface electrode ion trap with trapping height of approximately 240 micron. Using the Doppler recooling method, we characterize the trap heating rates over an extended region of the trap. The noise spectral density of the trap falls in the range of noise spectra reported in ion traps at room temperature. We find that during the first months of operation the heating rates increase by approximately one order of magnitude.

Researchers in Switzerland have demonstrated an innovative way of trapping tiny objects using electrostatic fields. The device could allow scientists to scrutinize much smaller biological molecules than is possible with the more established trapping technique known as "optical tweezers".

Full story available at physicsworld.com

A group of researchers in the UK has shown that it is possible to build a refrigerator using just two quantum particles (or even just one) in order to cool another quantum particle. They believe that such a device could be exploited in nanotechnology and that versions of it may even exist in nature.

Full story available at physicsworld.com

One of the challenges of adiabatic control theory is the proper inclusion of the effects of dissipation. Here we study the adiabatic dynamics of an open two-level quantum system deriving a generalized master equation to consistently account for the combined action of the driving and dissipation. We demonstrate that in the zero-temperature limit the ground state dynamics is not affected by environment. As an example, we apply our theory to Cooper pair pumping, which demonstrates the robustness of ground state adiabatic evolution.