QUROPE Quantum Information Processing and Communication in Europe

We have fabricated and tested an atom chip that operates as a matter wave interferometer. In this communication we describe the fabrication of the chip by ion-beam milling of gold evaporated onto a silicon substrate. We present data on the quality of the wires, on the current density that can be reached in the wires and on the smoothness of the magnetic traps that are formed. We demonstrate the operation of the interferometer, showing that we can coherently split and recombine a Bose–Einstein condensate with good phase stability.

We present a versatile and compact electron beam driven source for alkali metal atoms which can operate even with a heat dissipation of less than 1mW, and can therefore be implemented inside a closed cycle cryostat. Atoms are loaded into a Magneto-Optical Trap (MOT) and at a given thermal input power, loading rates three orders of magnitude higher than in a typical MOT loaded by an alkali metal dispenser are achieved.

Physicists in Israel are the first to entangle five photons in a NOON state – the superposition of two extreme quantum states. Unlike previous schemes for creating such states, the researchers claim that their new technique can entangle an arbitrarily large number of photons – so called "high-NOON states". This could be good news for those developing quantum metrology techniques because high-NOON states could be used to improve the precision of a range of different measurements.

Physicists in the US have created an ultracold gas of molecules with "adjustable" dipole moments. The experiment, which is the first to study the effect of long-range dipole interactions in an ultracold gas, could lead to new ways of using trapped molecules to simulate quantum effects that occur in solids.

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The optical properties of an atomic medium can be changed dramatically by the coherent interaction with a near-resonant control light field: An optically dense medium can be rendered transparent and group velocities can be strongly reduced. So far the demonstration of this electromagnetically induced transparency (EIT) has relied on macroscopic ensembles of atoms probed by relatively intense light fields. Here we demonstrate the most elementary case, where the medium is formed by a single atom inside an optical cavity, probed by single photons.

The aim of the workshop is to explore how experiments with ultracold gases can address key open problems in many-body quantum physics. Among other things it will focus on the following topics: fundamental limitations and new ideas in quantum simulation of unsolved models such as the Hubbard model; novel cooling schemes based on ideas from quantum information as well as atomic and many-body physics; emergent phenomena in non-equilibrium quantum dynamics; novel quantum magnetism in Bose and Fermi systems; realizing and probing topologically ordered states.

Optical nonlinearities offer unique possibilities for the control of light with light. A prominent example is electromagnetically induced transparency (EIT) where the transmission of a probe beam through an optically dense medium is manipulated by means of a control beam. Scaling such experiments into the quantum domain with one, or just a few particles of both light and matter will allow for the implementation of quantum computing protocols with atoms and photons or the realisation of strongly interacting photon gases exhibiting quantum phase transitions of light.