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.
Agency: European Commission | Branch: FP7 | Program: CP | Phase: ICT-2007.8.0 | Award Amount: 2.77M | Year: 2009
The Project investigates ultra-cold atom/molecule quantum matter technology for quantum information computational tasks. Our efforts concentrate on atoms/molecules confined in periodic nanostructures, either externally imposed by optical lattices, or self-generated by atomic/molecular interactions. Parallel quantum processing in periodic nanostructures is expected to lead to significant advances in different areas of quantum information. The Project aims at developing novel techniques for quantum engineering and quantum control of ultra-cold atoms and molecules confined in the periodic nanostructures. An innovative aspect is the development of appropriate tools for achieving quantum control of strongly correlated many body systems at the nanoscale by exploiting moderate- and long-range quantum mechanical interactions. Strongly correlated interacting systems offer a level of computational power that cannot be reached with traditional qubits based on spin, or hyperfine atomic states. Moderate and long, range interactions will be exploited in few body quantum systems in order to produce fast quantum gates using novel robust qubit and/or qudit concepts and using quantum states with topological order, all of them highly relevant for next generation quantum information implementations. The objectives rely on the nano-design of atomic/molecular quantum matter at the mesoscopic scale of few-body systems. Generation and detection of multiparticle quantum entanglement, robustness of non-traditional qubits, quantum memories characterise our investigation. The Project will implement new quantum information technologies by achieving the following breakthroughs: characterizing long range interacting systems for optimal quantum information; realizing individual manipulation integrated in proper algorithms; designing new protected qubits or quantum information processors based on long range interactions; developing techniques for topological quantum computation; creating multi-partimulti-particle entanglement for quantum simulation investigations. At the present stage of the quantum information development our objectives are unique for the optical lattice quantum matter technology. As far as the visionary aspects are concerned, the technological and conceptual advances resulting from the planned investigations on multi-particle entanglement, topological structures and nano-optical engineering may lead to the identification of new directions and alternative approaches towards scalable and miniaturisable quantum information processing.
Agency: European Commission | Branch: FP7 | Program: CP | Phase: ICT-2007.3.5 | Award Amount: 3.92M | Year: 2008
The goal of this proposal is to develop advanced table-top solid-state photonic sources for a specific wavelength in the mid-IR spectral range, as a practical, reliable and cost-effective alternative to large-scale free-electron lasers (FELs), for an important application in biomedicine (health): minimally invasive surgery. Recent experiments have verified that the use of mid-IR FEL at wavelengths near 6.45 m, with a focused beam penetration depth comparable to the cell size and coupled both into the spectral wing of the water bending mode and the amide-II vibrational mode, results in tissue ablation with minimal collateral damage and very effective ablation rate. This finding is extremely important as a useful tool for minimally invasive human surgery. However, the clinical use of FEL is ultimately not viable due to large size, high cost, operational complexity and restricted access at a few million-dollar accelerator-based facilities worldwide. Several attempts to develop non-FEL alternatives have largely failed to meet the necessary requirements in terms of pulse energy and repetition rate. The main strategy in this project will be to exploit nonlinear optical techniques (OPO) in combination with novel near-IR laser pump sources (near 1 and 2 m) and new materials (e.g. orientation patterned GaAs) to obtain an unprecedented energy level (10 mJ) near 6.45 m at a repetition rate of 100 Hz (an average power of 1 W). Two basic approaches, differing in the time structure, will provide less than few s (macro) pulse duration. The project encompasses four distinct elements: (1) Material research; (2) Pump laser development; (3) OPO development; and (4) Validation in tissue ablation experiments. The partners, 4 companies and 5 institutes from 7 member states, with proven track record, extensive expertise, and complementary skills provide the critical mass and strong cohesion to achieve the goals of the project in the most successful, effective and timely manner.
Agency: European Commission | Branch: FP7 | Program: CP | Phase: ICT-2007.8.0 | Award Amount: 2.09M | Year: 2008
In the recent years, continuous variables (CV) have emerged as a viable and very promising alternative to the traditional quantum bit-based approaches to quantum information processing. Encoding CV information onto mesoscopic carriers such as the quadratures of light modes or the collective spin of atoms offers several distinct advantages, such as the deterministic generation and manipulation of entangled states of light and atomic ensembles, or the interface between light and atoms allowing the implementation of a quantum memory. This toolbox of available operations has recently been significantly extended by conditional photon subtraction, which allows the generation of highly non-classical states with negative Wigner functions. This opens access to the realm of non-Gaussian operations, which are essential to several critical applications such as CV entanglement distillation or CV quantum computing. By building on these recent spectacular achievements, the present project aims at carrying out exploratory research on mesoscopic CV quantum information systems, with the ambitious ultimate objective of designing the first small-scale quantum processor using this CV toolbox. In an interplay between theory and experimental research, the consortium will investigate the hitherto unexplored potential of CV quantum computing and will address all necessary steps on the way to mesoscopic CV processors. This includes the engineering of non-Gaussian operations on photonic and atomic states exploiting the measurement-induced or actual nonlinearities between light and atoms, CV quantum computing with cat states or cluster states, CV entanglement distillation, error correction, and quantum repeaters. It is anticipated that the present project will have a strong impact on the future of ICT-related technologies and further strengthen the pan-European cooperation in a research area where Europe has started to establish itself at the leading edge.
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.
Rodrigo D.,Ecole Polytechnique Federale de Lausanne |
Limaj O.,Ecole Polytechnique Federale de Lausanne |
Janner D.,Institute Of Ciencies Fotoniques |
Etezadi D.,Ecole Polytechnique Federale de Lausanne |
And 5 more authors.
Science | Year: 2015
Infrared spectroscopy is the technique of choice for chemical identification of biomolecules through their vibrational fingerprints. However, infrared light interacts poorly with nanometric-size molecules. We exploit the unique electro-optical properties of graphene to demonstrate a high-sensitivity tunable plasmonic biosensor for chemically specific label-free detection of protein monolayers. The plasmon resonance of nanostructured graphene is dynamically tuned to selectively probe the protein at different frequencies and extract its complex refractive index. Additionally, the extreme spatial light confinement in graphene - up to two orders of magnitude higher than in metals - produces an unprecedentedly high overlap with nanometric biomolecules, enabling superior sensitivity in the detection of their refractive index and vibrational fingerprints. The combination of tunable spectral selectivity and enhanced sensitivity of graphene opens exciting prospects for biosensing. © 2015, American Association for the Advancement of Science. All rights reserved.
Austin D.R.,Institute Of Ciencies Fotoniques |
Biegert J.,Institute Of Ciencies Fotoniques |
Biegert J.,Catalan Institution for Research and Advanced Studies
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2012
We derive analytic expressions for the spectral amplitude of high-order harmonic generation from a single atom using the strong-field approximation (SFA). We demonstrate good agreement with time-dependent Schrödinger equation calculations, including the dependence on the drive wavelength across the range 566-2260 nm. Previous claims of a discrepancy in the drive wavelength scaling ignore changes in the timing of trajectories corresponding to a fixed harmonic photon energy. Under this condition, tunnel ionization is shown to play the most important role for the short trajectories. The established agreement enables us to use the SFA to predict that the intensity at the classical cutoff scales inversely with the ninth power of the drive wavelength in the high photon energy limit when the Coulomb singularity dominates the recombination amplitude. © 2012 American Physical Society.
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.
Chaves R.,Institute Of Ciencies Fotoniques |
Fritz T.,Institute Of Ciencies Fotoniques
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2012
For any Bell locality scenario (or Kochen-Specker noncontextuality scenario), the joint Shannon entropies of local (or noncontextual) models define a convex cone for which the nontrivial facets are tight entropic Bell (or contextuality) inequalities. In this paper we explore this entropic approach and derive tight entropic inequalities for various scenarios. One advantage of entropic inequalities is that they easily adapt to situations such as bilocality scenarios, which have additional independence requirements that are nonlinear on the level of probabilities, but linear on the level of entropies. Another advantage is that, despite the nonlinearity, taking detection inefficiencies into account turns out to be very simple. When joint measurements are conducted by a single detector only, the detector efficiency for witnessing quantum contextuality can be arbitrarily low. © 2012 American Physical Society.
Fritz T.,Institute Of Ciencies Fotoniques |
Chaves R.,Institute Of Ciencies Fotoniques
IEEE Transactions on Information Theory | Year: 2013
A marginal problem asks whether a given family of marginal distributions for some set of random variables arises from some joint distribution of these variables. Here, we point out that the existence of such a joint distribution imposes nontrivial conditions already on the level of Shannon entropies of the given marginals. These entropic inequalities are necessary (but not sufficient) criteria for the existence of a joint distribution. For every marginal problem, a list of such Shannon-type entropic inequalities can be calculated by Fourier-Motzkin elimination, and we offer a software interface to a Fourier-Motzkin solver for doing so. For the case that the hypergraph of given marginals is a cycle graph, we provide a complete analytic solution to the problem of classifying all relevant entropic inequalities, and use this result to bound the decay of correlations in stochastic processes. Furthermore, we show that Shannon-type inequalities for differential entropies are not relevant for continuous-variable marginal problems; non-Shannon-type inequalities are both in the discrete and in the continuous case. In contrast to other approaches, our general framework easily adapts to situations where one has additional (conditional) independence requirements on the joint distribution, as in the case of graphical models. We end with a list of open problems. A complementary article discusses applications to quantum nonlocality and contextuality. © 2012 IEEE.