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Castelldefels, Spain

Struck J.,University of Hamburg | Weinberg M.,University of Hamburg | Olschlager C.,University of Hamburg | Windpassinger P.,University of Hamburg | And 9 more authors.
Nature Physics | Year: 2013

Magnetism plays a key role in modern science and technology, but still many open questions arise from the interplay of magnetic many-body interactions. Deeper insight into complex magnetic behaviour and the nature of magnetic phase transitions can be obtained from, for example, model systems of coupled XY and Ising spins. Here, we report on the experimental realization of such a coupled system with ultracold atoms in triangular optical lattices. This is accomplished by imposing an artificial gauge field on the neutral atoms, which acts on them as a magnetic field does on charged particles. As a result, the atoms show persistent circular currents, the direction of which provides an Ising variable. On this, the tunable staggered gauge field, generated by a periodic driving of the lattice, acts as a longitudinal field. Further, the superfluid ground state presents strong analogies with the paradigm example of the fully frustrated XY model on a triangular lattice. © 2013 Macmillan Publishers Limited. Source

Novotny L.,University of Rochester | Van Hulst N.,Institute Of Ciencies Fotoniques | Van Hulst N.,Catalan Institution for Research and Advanced Studies
Nature Photonics | Year: 2011

Optical antennas are devices that convert freely propagating optical radiation into localized energy, and vice versa. They enable the control and manipulation of optical fields at the nanometre scale, and hold promise for enhancing the performance and efficiency of photodetection, light emission and sensing. Although many of the properties and parameters of optical antennas are similar to their radiowave and microwave counterparts, they have important differences resulting from their small size and the resonant properties of metal nanostructures. This Review summarizes the physical properties of optical antennas, provides a summary of some of the most important recent developments in the field, discusses the potential applications and identifies the future challenges and opportunities. © 2011 Macmillan Publishers Limited. All rights reserved. Source

Hauke P.,Institute For Quantenoptik Und Quanteninformation | Hauke P.,University of Innsbruck | Lewenstein M.,Institute Of Ciencies Fotoniques | Lewenstein M.,Catalan Institution for Research and Advanced Studies | Eckardt A.,Max Planck Institute For Physik Komplexer Systeme
Physical Review Letters | Year: 2014

We propose a simple scheme for tomography of band-insulating states in one- and two-dimensional optical lattices with two sublattice states. In particular, the scheme maps out the Berry curvature in the entire Brillouin zone and extracts topological invariants such as the Chern number. The measurement relies on observing - via time-of-flight imaging - the time evolution of the momentum distribution following a sudden quench in the band structure. We consider two examples of experimental relevance: the Harper model with π flux and the Haldane model on a honeycomb lattice. Moreover, we illustrate the performance of the scheme in the presence of a parabolic trap, noise, and finite measurement resolution. © 2014 American Physical Society. Source

Institute Of Ciencies Fotoniques, Catalan Institution for Research and Advanced Studies | Date: 2011-02-11

An optical parametric oscillator including a nonlinear crystal pumped by a laser source and an optical resonator, including an optical interferometer, which determines a level of output coupling of the oscillator, allowing high stability, broad wavelength tuning, and output power level optimization.

Prettico G.,Institute Of Ciencies Fotoniques | Bae J.,Korea Institute for Advanced Study
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2011

Bound information, a cryptographic classical analog of bound entanglement, is defined as classical secret correlations from which no secret key can be extracted. Its existence was conjectured and shown in a multipartite case. In this work, we provide an example of bound information in a four-partite scenario. Later, using this example, we prove that bound information can be superactivated and moreover unlockable in a finite-copy scenario. We also show that bound entangled states (bound information) can be used to distribute multipartite pure-state entanglements (secret keys). © 2011 American Physical Society. Source

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