QUROPE Quantum Information Processing and Communication in Europe

The generation of entangled photon pairs is usually a complex process involving optically driven schemes and nonlinear optics. The recent demonstration of an electrically powered light-emitting diode that is capable of this task looks set to greatly simplify experiments in the field of quantum information processing.

Controlling the interaction of a single quantum system with its environment is a fundamental challenge in quantum science and technology. We strongly suppressed the coupling of a single spin in diamond with the surrounding spin bath by using double-axis dynamical decoupling. The coherence was preserved for arbitrary quantum states, as verified by quantum process tomography. The resulting coherence time enhancement followed a general scaling with the number of decoupling pulses.

 We propose a scheme involving cold atoms trapped in optical lattices to observe different phenomena traditionally linked to quantum–optical systems. The basic idea consists of connecting the trapped atomic state to a non-trapped state through a Raman scheme. The coupling between these two types of atoms (trapped and free) turns out to be similar to that describing light–matter interaction within the rotating–wave approximation, the role of matter and photons being played by the trapped and free atoms, respectively.

We report transport operations with linear crystals of 40Ca+ ions performed by applying complex electric time-dependent potentials. For their control we use the information obtained from the ions’ fluorescence. We demonstrate that by means of this feedback technique, we can transport a predefined number of ions and also split and unify ion crystals.

We describe a versatile planar Penning trap structure, which allows to dynamically modify the trapping configuration almost arbitrarily. The trap consists of 37 hexagonal electrodes, each of 300 mikron diameter, fabricated in a gold-on-sapphire lithographic technique. Every hexagon can be addressed individually, thus shaping the electric potential. The fabrication of such a device with clean room methods is demonstrated.

Atom optics employs the modern techniques of quantum optics and laser cooling to enable applications which often outperform current standard technologies. Atomic matter wave interferometers allow for ultra-precise sensors; metrology and clocks are pushed to an extraordinary accuracy of 17 digits using single atoms. Miniaturization and integration are driven forward for both atomic clocks and atom optical circuits.