QUROPE Quantum Information Processing and Communication in Europe

We report a technique that uses clouds of ultracold atoms as sensitive, tunable, and non-invasive probes for microwave field imaging with micrometer spatial resolution. The microwave magnetic field components drive Rabi oscillations on atomic hyperfine transitions whose frequency can be tuned with a static magnetic field. Readout is accomplished using state-selective absorption imaging. Quantitative data extraction is simple and it is possible to reconstruct the distribution of microwave magnetic field amplitudes and phases.

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.

The formulation of massless relativistic fermions in lattice gauge theories is hampered by the fundamental problem of species doubling, namely, the rise of spurious fermions modifying the underlying physics. A suitable tailoring of the fermion masses prevents such abundance of species, and leads to the so-called Wilson fermions. Here we show that ultracold atoms provide us with the first controllable realization of these paradigmatic fermions, thus generating a quantum simulator of fermionic lattice gauge theories. We describe a novel scheme that exploits laser-assisted tunneling in a cubic optical superlattice to design the Wilson fermion masses. The high versatility of this proposal allows us to explore a variety of interesting phases in three-dimensional topological insulators, and to test the remarkable predictions of axion electrodynamics.

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.

We introduce lossless state detection of trapped neutral atoms based on cavity-enhanced fluorescence. In an experiment with a single 87-Rb atom, a hyperfine-state detection fidelity of 99.4% is achieved in 85 microseconds. The quantum bit is interrogated many hundred times without loss of the atom while a result is obtained in every read-out attempt. The fidelity proves robust against atomic frequency shifts induced by the trapping potential.

The purpose of this first CHIST-ERA conference will be to bring together personalities and scientists from the community of the call topics (Quantum Information Foundations and Technologies and Self-Awareness & Self-Consciousness) preliminarily chosen by the CHIST-ERA Consortium and that will be called for in the first CHIST-ERA transnational call for projects.