The discovery of artificial gauge fields controlling the dynamics of uncharged particles that otherwise elude the influence of standard electromagnetic fields has revolutionised the field of quantum simulation. Hence, developing new techniques to induce these fields is essential to boost quantum simulation of photonic structures. Here, we experimentally demonstrate the generation of an artificial gauge field in a photonic lattice by modifying the topological charge of a light beam, overcoming the need to modify the geometry along the evolution or impose external fields. In particular, we show that an effective magnetic flux naturally appears when a light beam carrying orbital angular momentum is injected into a waveguide lattice with a diamond chain configuration. To demonstrate the existence of this flux, we measure an effect that derives solely from the presence of a magnetic flux, the Aharonov-Bohm caging effect, which is a localisation phenomenon of wavepackets due to destructive interference. Therefore, we prove the possibility of switching on and off artificial gauge fields just by changing the topological charge of the input state, paving the way to accessing different topological regimes in a single structure, which represents an important step forward for optical quantum simulation.

}, isbn = {2047-7538}, doi = {https://doi.org/10.1038/s41377-020-00385-6}, url = {https://www.nature.com/articles/s41377-020-00385-6}, author = {C. J{\"o}rg and G. Queralt{\'o} and M. Kremer and G. Pelegr{\'\i} and J. Schulz and A. Szameit and G. von Freymann and J. Mompart and V. Ahufinger} } @article {338, title = {Effective triangular ladders with staggered flux from spin-orbit coupling in 1D optical lattices}, journal = {The European Physical Journal D}, volume = {74}, year = {2020}, chapter = {123}, abstract = {Light-induced spin-orbit coupling is a flexible tool to study quantum magnetism with ultracold atoms. In this work we show that spin-orbit coupled Bose gases in a one-dimensional optical lattice can be mapped into a two-leg triangular ladder with staggered flux following a lowest-band truncation of the Hamiltonian. The effective flux and the ratio of the tunneling strengths can be independently adjusted to a wide range of values. We identify a certain regime of parameters where a hard-core boson approximation holds and the system realizes a frustrated triangular spin ladder with tunable flux. We study the properties of the effective spin Hamiltonian using the density-matrix renormalization-group method and determine the phase diagram at half-filling. It displays two phases: a uniform superfluid and a bond-ordered insulator. The latter can be stabilized only for low Raman detuning. Finally, we provide experimentally feasible trajectories across the parameter space of the SOC system that cross the predicted phase transition.

}, doi = {10.1140/epjd/e2020-10129-1}, url = {https://link.springer.com/article/10.1140/epjd/e2020-10129-1}, author = {J. Cabedo and J. Claramunt and J. Mompart and V. Ahufinger and A. Celi} } @article {337, title = {Orbital angular momentum dynamics of Bose-Einstein condensates trapped in two stacked rings}, journal = {Physical Review A}, volume = {102}, year = {2020}, chapter = {023331 }, abstract = {We investigate the stability and dynamics of the orbital angular momentum modes of a repulsive Bose-Einstein condensate trapped in two tunnel-coupled rings in a stack configuration. Within mean-field theory, we derive a two-state model for the system in the case in which we populate both rings equally with a single orbital angular momentum mode and include small perturbations in other modes. Analyzing the fixed-point solutions of the model and the associated classical Hamiltonian, we characterize the destabilization of the stationary states and the subsequent dynamics. By populating a single orbital angular momentum mode with an arbitrary population imbalance between the rings, we derive analytically the boundary between the regimes of Josephson oscillations and macroscopic quantum self-trapping and study numerically the stability of these solutions.

}, doi = {10.1103/PhysRevA.102.023331}, url = {https://link.aps.org/doi/10.1103/PhysRevA.102.023331}, author = {N. Eul{\`a}lia and J. Mompart and B. Juli{\'a}-D{\'\i}az and V. Ahufinger} } @article {333, title = {Topological state engineering via supersymmetric transformations}, journal = {Communication Physics}, volume = {3}, year = {2020}, chapter = {49}, abstract = {The quest to explore new techniques for the manipulation of topological states simultaneously promotes a deeper understanding of topological physics and is essential in identifying new ways to harness their unique features. Here, we examine the potential of supersymmetric transformations to systematically address, alter and reconfigure the topological properties of a system. To this end, we theoretically and experimentally study the changes that topologically protected states in photonic lattices undergo as supersymmetric\ transformations are applied to their host system. In particular, we show how supersymmetry-induced phase transitions can selectively suspend and re-establish the\ topological protection of specific states. Furthermore, we reveal how understanding the interplay between internal symmetries and the symmetry constraints of supersymmetric transformations provides a roadmap to directly access the desirable topological properties of a system. Our findings pave the way for establishing supersymmetry-inspired techniques as a powerful and versatile tool for topological state engineering.

}, doi = {https://doi.org/10.1038/s42005-020-0316-4}, url = {https://www.nature.com/articles/s42005-020-0316-4$\#$citeas}, author = {G. Queralt{\'o} and M. Kremer and L. J. Maczewsky and M. Heinrich and J. Mompart and V. Ahufinger and A. Szameit} } @article {322, title = {Coherent spin mixing via spin-orbit coupling in Bose gases}, journal = {Phys. Rev. A}, volume = {100}, year = {2019}, month = {Dec}, pages = {063633}, abstract = {We study beyond-mean-field properties of interacting spin-1 Bose gases with synthetic Rashba-Dresselhaus spin-orbit coupling at low energies. We derive a many-body Hamiltonian following a tight-binding approximation in quasimomentum space, where the effective spin dependence of the collisions that emerge from spin-orbit coupling leads to dominant correlated tunneling processes that couple the different bound states. We discuss the properties of the spectrum of the derived Hamiltonian and its experimental signatures. In a certain region of the parameter space, the system becomes integrable, and its dynamics becomes analogous to that of a spin-1 condensate with spin-dependent collisions. Remarkably, we find that such dynamics can be observed in existing experimental setups through quench experiments that are robust against magnetic fluctuations.

}, doi = {10.1103/PhysRevA.100.063633}, url = {https://link.aps.org/doi/10.1103/PhysRevA.100.063633}, author = {J. Cabedo and J. Claramunt and A. Celi and Y. Zhang and V. Ahufinger and J. Mompart} } @article {318, title = {Diffusion Through a Network of Compartments Separated by Partially-Transmitting Boundaries}, journal = {Frontiers in Physics}, volume = {7}, year = {2019}, pages = {31}, abstract = {We study the random walk of a particle in a compartmentalized environment, as realized in biological samples or solid state compounds. Each compartment is characterized by its length L and the boundaries transmittance T. We identify two relevant spatio-temporal scales that provide alternative descriptions of the dynamics: (i) the microscale, in which the particle position is monitored at constant time intervals; and (ii) the mesoscale, in which it is monitored only when the particle crosses a boundary between compartments. Both descriptions provide{\textemdash}by construction{\textemdash}the same long time behavior. The analytical description obtained at the proposed mesoscale allows for a complete characterization of the complex movement at the microscale, thus representing a fruitful approach for this kind of systems. We show that the presence of disorder in the transmittance is a necessary condition to induce anomalous diffusion, whereas the spatial heterogeneity reduces the degree of subdiffusion and, in some cases, can even compensate for the disorder induced by the stochastic transmittance.

}, issn = {2296-424X}, doi = {10.3389/fphy.2019.00031}, url = {https://www.frontiersin.org/article/10.3389/fphy.2019.00031}, author = {G. Mu{\~n}oz-Gil and M. A. Garcia-March and C. Manzo and A. Celi and M. Lewenstein} } @article {319, title = {Knotting fractional-order knots with the polarization state of light}, journal = {Nature Photonics }, volume = {13}, year = {2019}, chapter = {569}, abstract = {The fundamental polarization singularities of monochromatic light are normally associated with invariance under coordinated rotations: symmetry operations that rotate the spatial dependence of an electromagnetic field by an angle\ *θ*\ and its polarization by a multiple\ *γθ*\ of that angle. These symmetries are generated by mixed angular momenta of the form\ *J*_{γ} = *L* + *γS*, and they generally induce M{\"o}bius-strip topologies, with the coordination parameter\ *γ*\ restricted to integer and half-integer values. In this work we construct beams of light that are invariant under coordinated rotations for arbitrary rational\ *γ*, by exploiting the higher internal symmetry of {\textquoteleft}bicircular{\textquoteright} superpositions of counter-rotating circularly polarized beams at different frequencies. We show that these beams have the topology of a torus knot, which reflects the subgroup generated by the torus-knot angular momentum\ *J*_{γ}, and we characterize the resulting optical polarization singularity using third- and higher-order field moment tensors, which we experimentally observe using nonlinear polarization tomography.

STIRAP (stimulated Raman adiabatic passage) is a powerful laser-based method, usually involving two photons, for efficient and selective transfer of populations between quantum states. A particularly interesting feature is the fact that the coupling between the initial and the final quantum states is via an intermediate state, even though the lifetime of the latter can be much shorter than the interaction time with the laser radiation. Nevertheless, spontaneous emission from the intermediate state is prevented by quantum interference. Maintaining the coherence between the initial and final state throughout the transfer process is crucial. STIRAP was initially developed with applications in chemical dynamics in mind. That is why the original paper of 1990 was published in The Journal of Chemical Physics. However, from about the year 2000, the unique capabilities of STIRAP and its robustness with respect to small variations in some experimental parameters stimulated many researchers to apply the scheme to a variety of other fields of physics. The successes of these efforts are documented in this collection of articles. In Part A the experimental success of STIRAP in manipulating or controlling molecules, photons, ions or even quantum systems in a solid-state environment is documented. After a brief introduction to the basic physics of STIRAP, the central role of the method in the formation of ultracold molecules is discussed, followed by a presentation of how precision experiments (measurement of the upper limit of the electric dipole moment of the electron or detecting the consequences of parity violation in chiral molecules) or chemical dynamics studies at ultralow temperatures benefit from STIRAP. Next comes the STIRAP-based control of photons in cavities followed by a group of three contributions which highlight the potential of the STIRAP concept in classical physics by presenting data on the transfer of waves (photonic, magnonic and phononic) between respective waveguides. The works on ions or ion strings discuss options for applications, e.g. in quantum information. Finally, the success of STIRAP in the controlled manipulation of quantum states in solid-state systems, which are usually hostile towards coherent processes, is presented, dealing with data storage in rare-earth ion doped crystals and in nitrogen vacancy (NV) centers or even in superconducting quantum circuits. The works on ions and those involving solid-state systems emphasize the relevance of the results for quantum information protocols. Part B deals with theoretical work, including further concepts relevant to quantum information or invoking STIRAP for the manipulation of matter waves. The subsequent articles discuss the experiments underway to demonstrate the potential of STIRAP for populating otherwise inaccessible high-lying Rydberg states of molecules, or controlling and cooling the translational motion of particles in a molecular beam or the polarization of angular-momentum states. The series of articles concludes with a more speculative application of STIRAP in nuclear physics, which, if suitable radiation fields become available, could lead to spectacular results.

}, doi = {10.1088/1361-6455/ab3995}, url = {https://doi.org/10.1088\%2F1361-6455\%2Fab3995}, author = {K. Bergmann and H. C. N{\"a}gerl and C. Panda and G. Gabrielse and E. Miloglyadov and M. Quack and G. Seyfang and G. Wichmann and S. Ospelkaus and A. Kuhn and S. Longhi and A. Szameit and P. Pirro and B. Hillebrands and X.-F. Zhu and J. Zhu and M. Drewsen and W. K. Hensinger and S. Weidt and T. Halfmann and H.-L. Wang and G. Sorin Paraoanu and N. V. Vitanov and J. Mompart and T. Busch and T. J. Barnum and D. D. Grimes and R. W. Field and M. G. Raizen and E. Narevicius and M. Auzinsh and D. Budker and A. P{\'a}lffy and C. H. Keitel} } @article {323, title = {Second-order topological corner states with ultracold atoms carrying orbital angular momentum in optical lattices}, journal = {Phys. Rev. B}, volume = {100}, year = {2019}, month = {Nov}, pages = {205109}, abstract = {We propose a realization of a two-dimensional higher-order topological insulator with ultracold atoms loaded into orbital angular momentum (OAM) states of an optical lattice. The symmetries of the OAM states induce relative phases in the tunneling amplitudes that allow to describe the system in terms of two decoupled lattice models. Each of these models displays one-dimensional edge states and zero-dimensional corner states that are correlated with the topological properties of the bulk. We show that the topologically nontrivial regime can be explored in a wide range of experimentally feasible values of the parameters of the physical system. Furthermore, we propose an alternative way to characterize the second-order topological corner states based on the computation of the Zak{\textquoteright}s phases of the bands of first-order edge states.

}, doi = {10.1103/PhysRevB.100.205109}, url = {https://link.aps.org/doi/10.1103/PhysRevB.100.205109}, author = {G. Pelegr{\'\i} and A. M. Marques and V. Ahufinger and J. Mompart and R. G. Dias} } @article {302, title = {Topological edge states and Aharanov-Bohm caging with ultracold atoms carrying orbital angular momentum}, journal = {Phys. Rev. A}, volume = {99}, year = {2019}, month = {Feb}, pages = {023613}, abstract = {We show that bosonic atoms loaded into orbital angular momentum\ l=1\ states of a lattice in a diamond-chain geometry provide a flexible and simple platform for exploring a range of topological effects. This system exhibits robust edge states that persist across the gap-closing points, indicating the absence of a topological transition. We discuss how to perform the topological characterization of the model with a generalization of the Zak{\textquoteright}s phase and we show that this system constitutes a realization of a square-root topological insulator. Furthermore, the relative phases arising naturally in the tunneling amplitudes lead to the appearance of Aharanov-Bohm caging in the lattice. We discuss how these properties can be realized and observed in ongoing experiments.

}, doi = {10.1103/PhysRevA.99.023613}, url = {https://link.aps.org/doi/10.1103/PhysRevA.99.023613}, author = {G. Pelegr{\'\i} and A. M. Marques and R. G. Dias and A. J. Daley and J. Mompart and V. Ahufinger} } @article {301, title = {Topological edge states with ultracold atoms carrying orbital angular momentum in a diamond chain}, journal = {Phys. Rev. A}, volume = {99}, year = {2019}, month = {Feb}, pages = {023612}, abstract = {We study the single-particle properties of a system formed by ultracold atoms loaded into the manifold of\ l=1\ orbital angular momentum (OAM) states of an optical lattice with a diamond-chain geometry. Through a series of successive basis rotations, we show that the OAM degree of freedom induces phases in some tunneling amplitudes of the tight-binding model that are equivalent to a net\ π\ flux through the plaquettes. These effects give rise to a topologically nontrivial band structure and protected edge states which persist everywhere in the parameter space of the model, indicating the absence of a topological transition. By taking advantage of these analytical mappings, we also show that this system constitutes a realization of a square-root topological insulator. In addition, we demonstrate that quantum interferences between the different tunneling processes involved in the dynamics may lead to Aharanov-Bohm caging in the system. All these analytical results are confirmed by exact diagonalization numerical calculations.

}, doi = {10.1103/PhysRevA.99.023612}, url = {https://link.aps.org/doi/10.1103/PhysRevA.99.023612}, author = {G. Pelegr{\'\i} and A. M. Marques and R. G. Dias and A. J. Daley and V. Ahufinger and J. Mompart} } @article {280, title = {Atomic-frequency-comb quantum memory via piecewise adiabatic passage}, journal = {Phys. Rev. A}, volume = {98}, year = {2018}, month = {Oct}, pages = {043834}, abstract = {In this paper, we propose a method to create an atomic frequency comb (AFC) in hot atomic vapors using the piecewise adiabatic passage (PAP) technique. Due to the Doppler effect, the trains of pulses used for PAP give rise to a velocity-dependent transfer of the atomic population from the initial state to the target one, thus forming a velocity comb whose periodicity depends not only on the repetition rate of the applied pulses but also on the specific atomic transitions considered. We highlight the advantages of using this transfer technique with respect to standard methods and discuss, in particular, its application to store a single telecom photon in an AFC quantum memory using a high density Ba atomic vapor.

}, doi = {10.1103/PhysRevA.98.043834}, url = {https://link.aps.org/doi/10.1103/PhysRevA.98.043834}, author = {J. L. Rubio and D. Viscor and J. Mompart and V. Ahufinger} } @article {286, title = {Damping of Josephson Oscillations in Strongly Correlated One-Dimensional Atomic Gases}, journal = {Phys. Rev. Lett.}, volume = {121}, year = {2018}, month = {Aug}, pages = {090404}, abstract = {We study Josephson oscillations of two strongly correlated one-dimensional bosonic clouds separated by a localized barrier. Using a quantum-Langevin approach and the exact Tonks-Girardeau solution in the impenetrable-boson limit, we determine the dynamical evolution of the particle-number imbalance, displaying an effective damping of the Josephson oscillations which depends on barrier height, interaction strength, and temperature. We show that the damping originates from the quantum and thermal fluctuations intrinsically present in the strongly correlated gas. Because of the density-phase duality of the model, the same results apply to particle-current oscillations in a one-dimensional ring where a weak barrier couples different angular momentum states.

}, doi = {10.1103/PhysRevLett.121.090404}, url = {https://link.aps.org/doi/10.1103/PhysRevLett.121.090404}, author = {J. Polo and V. Ahufinger and F. W. J. Hekking and A. Minguzzi} } @article {278, title = {Integrated photonic devices based on adiabatic transitions between supersymmetric structures}, journal = {Opt. Express}, volume = {26}, number = {26}, year = {2018}, month = {Dec}, pages = {33797{\textendash}33806}, abstract = {We introduce adiabatic transitions connecting two supersymmetric partner profiles by smoothly modifying the transverse refractive index profile along the propagation direction. With this transformation, one of the transverse electric modes evolves adapting its shape and propagation constant without being coupled to other guided or radiated modes while the rest of the modes are radiated. This technique offers a systematic way to manipulate the modal content in systems of optical waveguides and engineer efficient and robust photonic devices such as tapered waveguides, single-waveguide mode filters, beam splitters and interferometers. Numerical simulations show that very high fidelities and transmitted powers are obtained for a broad range of devices lengths and light{\textquoteright}s\ wavelengths.

}, keywords = {Femtosecond laser writing, Guided wave optics, Optical devices, Optical systems, Refractive index, Waveguide modes}, doi = {10.1364/OE.26.033797}, url = {http://www.opticsexpress.org/abstract.cfm?URI=oe-26-26-33797}, author = {G. Queralt{\'o} and V. Ahufinger and J. Mompart} } @article {279, title = {Quantum sensing using imbalanced counter-rotating Bose-Einstein condensate modes}, journal = {New Journal of Physics}, volume = {20}, number = {10}, year = {2018}, pages = {103001}, abstract = {A quantum device for measuring two-body interactions, scalar magnetic fields and rotations is proposed using a Bose-Einstein condensate (BEC) in a ring trap. We consider an imbalanced superposition of orbital angular momentum modes with opposite winding numbers for which a rotating minimal atomic density line appears. We derive an analytical model relating the angular frequency of the minimal density line rotation to the strength of the nonlinear atom-atom interactions and the difference between the populations of the counter-propagating modes. Additionally, we propose a full experimental protocol based on direct fluorescence imaging of the BEC that allows to measure all the quantities involved in the analytical model and use the system for sensing purposes.

}, url = {http://stacks.iop.org/1367-2630/20/i=10/a=103001}, author = {G. Pelegr{\'\i} and J. Mompart and V. Ahufinger} } @article {277, title = {Engineering of orbital angular momentum supermodes in coupled optical waveguides}, journal = {Scientific Reports}, volume = {7}, year = {2017}, month = {APR 26}, pages = {44057}, type = {Article}, abstract = {In this work we demonstrate the existence of orbital angular momentum (OAM) bright and dark supermodes in a three-evanescently coupled cylindrical waveguides system. Bright and dark supermodes are characterized by their coupling and decoupling from one of the waveguides, respectively. In addition, we demonstrate that complex couplings between modes of different waveguides appear naturally due to the characteristic spiral phase-front of OAM modes in two-dimensional configurations where the waveguides are arranged forming a triangle. Finally, by adding dissipation to the waveguide uncoupled to the dark supermode, we are able to filter this supermode out, allowing for the design of OAM mode cloners and inverters.

}, issn = {2045-2322}, doi = {10.1038/srep44057}, author = {A. Turpin and G. Pelegr{\'\i} and J. Polo and J. Mompart and V. Ahufinger} } @article {276, title = {Mode-division (de)multiplexing using adiabatic passage and supersymmetric waveguides}, journal = {Optics Express}, volume = {25}, number = {22}, year = {2017}, month = {OCT 30}, pages = {27396-27404}, type = {Article}, chapter = {27396}, abstract = {The development of mode-division multiplexing techniques is an important step to increase the information processing capacity. In this context, we design an efficient and robust mode-division (de) multiplexing integrated device based on the combination of spatial adiabatic passage and supersymmetric techniques. It consists of two identical step-index external waveguides coupled to a supersymmetric central one with a specific modal content that prevents the transfer of the fundamental transverse electric spatial mode. The separation between waveguides is engineered along the propagation direction to optimize spatial adiabatic passage for the first excited transverse electric spatial mode of the step-index waveguides. Thus, by injecting a superposition of the two lowest spatial modes into the step-index left waveguide, the fundamental mode remains in the left waveguide while the first excited mode is fully transmitted to the right waveguide. Output fidelities F \> 0.90 are obtained for a broad range of geometrical parameter values and light{\textquoteright}s wavelengths, reaching F = 0.99 for optimized values. (C) 2017 Optical Society of America

}, issn = {{1094-4087}}, doi = {10.1364/OE.25.027396}, author = {G. Queralt{\'o} and V. Ahufinger and J. Mompart} } @article {264, title = {Quantum optics and frontiers of physics: the third quantum revolution}, journal = {Physica Scripta}, volume = {92}, number = {1}, year = {2017}, pages = {013003}, abstract = {The year 2015 was the International Year of Light. However, it also marked, the 20th anniversary of the first observation of Bose{\textendash}Einstein condensation in atomic vapors by Eric Cornell, Carl Wieman and Wolfgang Ketterle. This discovery could be considered as one of the greatest achievements of quantum optics that has triggered an avalanche of further seminal discoveries and achievements. For this reason we devote this essay for the focus issue on {\textquoteleft}Quantum Optics in the International Year of Light{\textquoteright} to the recent revolutionary developments in quantum optics at the frontiers of all physics: atomic physics, molecular physics, condensed matter physics, high energy physics and quantum information science. We follow here the lines of the introduction to our book {\textquoteleft}Ultracold atoms in optical lattices: Simulating quantum many-body systems{\textquoteright} (Lewenstein et al 2012 Ultracold Atoms in Optical Lattices: Simulating Quantum Many-body Systems (Oxford: University Press)), and to a lesser extent the review article M Lewenstein et al (2007 Adv. Phys. 56 [http://https://dx.doi.org/10.1080/00018730701223200] 243 ). The book, however, was published in 2012, and many things has happened since then{\textemdash}the present essay is therefore upgraded to include the latest developments.

}, url = {http://stacks.iop.org/1402-4896/92/i=1/a=013003}, author = {A. Celi and A. Sanpera and V. Ahufinger and M. Lewenstein} } @article {250, title = {Single-atom edgelike states via quantum interference}, journal = {Phys. Rev. A}, volume = {95}, year = {2017}, month = {Jan}, pages = {013614}, abstract = {We demonstrate how quantum interference may lead to the appearance of robust edgelike states of a single ultracold atom in a two-dimensional optical ribbon. We show that these states can be engineered within the manifold of either local ground states of the sites forming the ribbon or states carrying one unit of angular momentum. In the former case, we show that the implementation of edgelike states can be extended to other geometries, such as tilted square lattices. In the latter case, we suggest using the winding number associated to the angular momentum as a synthetic dimension.

}, doi = {10.1103/PhysRevA.95.013614}, url = {http://link.aps.org/doi/10.1103/PhysRevA.95.013614}, author = {G. Pelegr{\'\i} and J. Polo and A. Turpin and M. Lewenstein and J. Mompart and V. Ahufinger} } @article {249, title = {Conical refraction: fundamentals and applications}, journal = {Laser \& Photonics Reviews}, volume = {10}, number = {5}, year = {2016}, month = {SEP}, pages = {750-771}, type = {Review}, abstract = {In 1832 Hamilton predicted that a collimated light beam propagating through a biaxial crystal parallel to one of its optical axes refracts as a slanted cone within the crystal and emerges as a hollow light cylinder, this optical effect being named as conical refraction (CR). The diffractive solution of CR presented by Belsky and Khapalyuk in 1978 and the corresponding re-formulation carried out by Berry in 2004 rekindled this old and almost forgotten phenomenon. In this article, we review the CR phenomenon following different approaches that allow understanding light propagation in biaxial crystals, including the case of multiple crystals in cascade. We then focus on the description of the singular properties of the CR beams, presenting some examples such as optical bottle beams and beams carrying orbital angular momentum. All these features are used to introduce some of the most appealing applications of CR in the fields of optical trapping, free-space optical communications, polarization metrology, super-resolution imaging, two-photon polymerization, and lasers.

}, keywords = {biaxial crystals, conical diffraction, Conical refraction, Crystal optics, optical trapping, Polarization, singular optics}, issn = {1863-8880}, doi = {10.1002/lpor.201600112}, author = {A. Turpin and Yu. V. Loiko and T. K. Kalkandjiev and J. Mompart} } @article {PhysRevA.93.033613, title = {Geometrically induced complex tunnelings for ultracold atoms carrying orbital angular momentum}, journal = {Phys. Rev. A}, volume = {93}, year = {2016}, month = {Mar}, pages = {033613}, publisher = {American Physical Society}, abstract = {We investigate the dynamics of angular momentum states for a single ultracold atom trapped in two-dimensional systems of sided coupled ring potentials. The symmetries of the system show that tunneling amplitudes between different ring states with variation of the winding number are complex. In particular, we demonstrate that in a triangular ring configuration the complex nature of the cross-couplings can be used to geometrically engineer spatial dark states to manipulate the transport of orbital angular momentum states via quantum interference.}, doi = {10.1103/PhysRevA.93.033613}, url = {http://link.aps.org/doi/10.1103/PhysRevA.93.033613}, author = {J. Polo and J. Mompart and V. Ahufinger} } @article {248, title = {Optimal conditions for spatial adiabatic passage of a Bose-Einstein condensate}, journal = {Phys. Rev. A}, volume = {94}, number = {5}, year = {2016}, month = {NOV 8}, type = {Article}, abstract = {We investigate spatial adiabatic passage of a Bose-Einstein condensate in a triple-well potential within the three-mode approximation. By rewriting the dynamics in the so-called time-dependent dark-dressed basis, we analytically derive the optimal conditions for the nonlinear parameter and the on-site energies of each well to achieve a highly efficient condensate transport. We show that the nonlinearity yields a high-efficiency plateau for the condensate transport as a function of the on-site energy difference between the outermost wells, favoring the robustness of the transport. We also analyze the case of different nonlinearities in each well, which, for certain parameter values, leads to an increase of the width of this plateau.

}, issn = {2469-9926}, doi = {10.1103/PhysRevA.94.053606}, author = {J. L. Rubio and V. Ahufinger and T. Busch and J. Mompart} } @article {244, title = {Spatial adiabatic passage: a review of recent progress}, journal = {Reports on Progress in Physics}, volume = {79}, year = {2016}, chapter = {074401}, abstract = {Adiabatic techniques are known to allow for engineering quantum states with high fidelity. This requirement is currently of large interest, as applications in quantum information require the preparation and manipulation of quantum states with minimal errors. Here we review recent progress on developing techniques for the preparation of spatial states through adiabatic passage, particularly focusing on three state systems. These techniques can be applied to matter waves in external potentials, such as cold atoms or electrons, and to classical waves in waveguides, such as light or sound

}, url = {http://stacks.iop.org/0034-4885/79/i=7/a=074401}, author = {R. Menchon-Enrich and A. Benseny and V. Ahufinger and A. D. Greentree and T. Busch and J. Mompart} } @article {1367-2630-18-1-015010, title = {Transport of ultracold atoms between concentric traps via spatial adiabatic passage}, journal = {New Journal of Physics}, volume = {18}, number = {1}, year = {2016}, pages = {015010}, abstract = {Spatial adiabatic passage processes for ultracold atoms trapped in tunnel-coupled cylindrically symmetric concentric potentials are investigated. Specifically, we discuss the matter-wave analog of the rapid adiabatic passage (RAP) technique for a high fidelity and robust loading of a single atom into a harmonic ring potential from a harmonic trap, and for its transport between two concentric rings. We also consider a system of three concentric rings and investigate the transport of a single atom between the innermost and the outermost rings making use of the matter-wave analog of the stimulated Raman adiabatic passage (STIRAP) technique. We describe the RAP-like and STIRAP-like dynamics by means of a two- and a three-state model, respectively, obtaining good agreement with the numerical simulations of the corresponding two-dimensional Schr{\"o}dinger equation.

}, url = {http://stacks.iop.org/1367-2630/18/i=1/a=015010}, author = {J. Polo and A. Benseny and T. Busch and V. Ahufinger and J. Mompart} } @article {PhysRevA.91.053626, title = {Analysis beyond the Thomas-Fermi approximation of the density profiles of a miscible two-component Bose-Einstein condensate}, journal = {Phys. Rev. A}, volume = {91}, year = {2015}, month = {May}, pages = {053626}, publisher = {American Physical Society}, doi = {10.1103/PhysRevA.91.053626}, url = {http://link.aps.org/doi/10.1103/PhysRevA.91.053626}, author = {J. Polo and V. Ahufinger and P. Mason and S. Sridhar and T. P. Billam and S. A. Gardiner} } @article {93, title = {Blue-detuned optical ring trap for Bose-Einstein condensates based on conical refraction}, journal = {Optics Express}, volume = {23}, number = {2}, year = {2015}, chapter = {1638}, abstract = {We present a novel approach for the optical manipulation of neutral atoms in annular light structures produced by the phenomenon of conical refraction occurring in biaxial optical crystals. For a beam focused to a plane behind the crystal, the focal plane exhibits two concentric bright rings enclosing a ring of null intensity called the Poggendorff ring. We demonstrate both theoretically and experimentally that the Poggendorff dark ring of conical refraction is confined in three dimensions by regions of higher intensity. We derive the positions of the confining intensity maxima and minima and discuss the application of the Poggendorff ring for trapping ultra-cold atoms using the repulsive dipole force of blue-detuned light. We give analytical expressions for the trapping frequencies and potential depths along both the radial and the axial directions. Finally, we present realistic numerical simulations of the dynamics of a 87Rb Bose-Einstein condensate trapped inside the Poggendorff ring which are in good agreement with corresponding experimental results.}, keywords = {Atom optics, Birefringence, Crystal optics, Laser trapping}, url = {http://dx.doi.org/10.1364/OE.23.001638}, author = {A. Turpin and J. Polo and Yu. V. Loiko and J. K{\"u}ber and F. Schmaltz and T. K. Kalkandjiev and V. Ahufinger and G. Birkl and J. Mompart} } @article {PhysRevA.92.013802, title = {Conical refraction healing after partially blocking the input beam}, journal = {Phys. Rev. A}, volume = {92}, year = {2015}, month = {Jul}, pages = {013802}, publisher = {American Physical Society}, doi = {10.1103/PhysRevA.92.013802}, url = {http://link.aps.org/doi/10.1103/PhysRevA.92.013802}, author = {A. Turpin and Yu. V. Loiko and T. K. Kalkandjiev and R. Corbal{\'a}n and J. Mompart} } @article {Turpin:15, title = {On the dual-cone nature of the conical refraction phenomenon}, journal = {Optics Letters}, volume = {40}, number = {8}, year = {2015}, month = {Apr}, pages = {1639{\textendash}1642}, publisher = {OSA}, chapter = {1639}, abstract = {In conical refraction (CR), a focused Gaussian input beam passing through a biaxial crystal and parallel to one of the optic axes is transformed into a pair of concentric bright rings split by a dark (Poggendorff) ring at the focal plane. Here, we show the generation of a CR transverse pattern that does not present the Poggendorff fine splitting at the focal plane, i.e., it forms a single light ring. This light ring is generated from a nonhomogeneously polarized input light beam obtained by using a spatially inhomogeneous polarizer that mimics the characteristic CR polarization distribution. This polarizer allows modulating the relative intensity between the two CR light cones in accordance with the recently proposed dual-cone model of the CR phenomenon. We show that the absence of interfering rings at the focal plane is caused by the selection of one of the two CR cones.}, keywords = {Birefringence, Crystal optics, Refraction}, doi = {10.1364/OL.40.001639}, url = {http://ol.osa.org/abstract.cfm?URI=ol-40-8-1639}, author = {A. Turpin and Yu. V. Loiko and T. K. Kalkandjiev and H. Tomizawa and J. Mompart} } @article {Peinado:15, title = {Interferometric characterization of the structured polarized light beam produced by the conical refraction phenomenon}, journal = {Opt. Express}, volume = {23}, number = {14}, year = {2015}, month = {Jul}, pages = {18080{\textendash}18091}, publisher = {OSA}, abstract = {The interest on the conical refraction (CR) phenomenon in biaxial crystals has revived in the last years due to its prospective for generating structured polarized light beams, i.e. vector beams. While the intensity and the polarization structure of the CR beams are well known, an accurate experimental study of their phase structure has not been yet carried out. We investigate the phase structure of the CR rings by means of a Mach-Zehnder interferometer while applying the phase-shifting interferometric technique to measure the phase at the focal plane. In general the two beams interfering correspond to different states of polarization (SOP) which locally vary. To distinguish if there is an additional phase added to the geometrical one we have derived the appropriate theoretical expressions using the Jones matrix formalism. We demonstrate that the phase of the CR rings is equivalent to that one introduced by an azimuthally segmented polarizer with CR-like polarization distribution. Additionally, we obtain direct evidence that the Poggendorff dark ring is an annular singularity, with a \&\#x03C0; phase change between the inner and outer bright rings.

}, keywords = {Anisotropic optical materials, Birefringence, Crystal optics}, doi = {10.1364/OE.23.018080}, url = {http://www.opticsexpress.org/abstract.cfm?URI=oe-23-14-18080}, author = {A. Peinado and A. Turpin and C. Iemmi and A. M{\'a}rquez and T. K. Kalkandjiev and J. Mompart and J. Campos} } @article {2040-8986-17-6-065603, title = {Light propagation in biaxial crystals}, journal = {Journal of Optics}, volume = {17}, number = {6}, year = {2015}, pages = {065603}, abstract = {We present a formalism able to predict the transformation of light beams passing through biaxial crystals. We use this formalism to show both theoretically and experimentally the transition from double refraction to conical refraction, which is found when light propagates along one of the optic axes of a biaxial crystal. Additionally, we demonstrate that the theory is applicable both to non-cylindrically symmetric and non-homogeneously polarized beams by predicting the transformation of input beams passing through a cascade of biaxial crystals.}, url = {http://stacks.iop.org/2040-8986/17/i=6/a=065603}, author = {A. Turpin and Yu. V. Loiko and T. K. Kalkandjiev and J. Mompart} } @article {95, title = {Optimization, tolerance analysis and implementation of a Stokes polarimeter based on the conical refraction phenomenon}, journal = {Optics Express}, volume = {23}, number = {5}, year = {2015}, chapter = {5636}, abstract = {Recently, we introduced the basic concepts behind a new polarimeter device based on conical refraction (CR), which presents several appealing features compared to standard polarimeters. To name some of them, CR polarimeters retrieve the polarization state of an input light beam with a snapshot measurement, allow for substantially enhancing the data redundancy without increasing the measuring time, and avoid instrumental errors owing to rotating elements or phase-to-voltage calibration typical from dynamic devices. In this article, we present a comprehensive study of the optimization, robustness and parameters tolerance of CR based polarimeters. In addition, a particular CR based polarimetric architecture is experimentally implemented, and some concerns and recommendations are provided. Finally, the implemented polarimeter is experimentally tested by measuring different states of polarization, including fully and partially polarized light.}, keywords = {Birefringence., Ellipsometry and polarimetry, Polarimetry, Polarization}, url = {http://dx.doi.org/10.1364/OE.23.005636}, author = {A. Peinado and A. Lizana and A. Turpin and C. Iemmi and T. K. Kalkandjiev and J. Mompart and J. Campos} } @article {94, title = {Polarization tailored novel vector beams based on conical refraction}, journal = {Optics Express}, volume = {23}, number = {5}, year = {2015}, chapter = {5704}, abstract = {Coherent vector beams with involved states of polarization (SOP) are widespread in the literature, having applications in laser processing, super-resolution imaging and particle trapping. We report novel vector beams obtained by transforming a Gaussian beam passing through a biaxial crystal, by means of the conical refraction phenomenon. We analyze both experimentally and theoretically the SOP of the different vector beams generated and demonstrate that the SOP of the input beam can be used to control both the shape and the SOP of the transformed beam. We also identify polarization singularities of such beams for the first time and demonstrate their control by the SOP of the input beam.}, keywords = {Birefringence, Crystal optics, Polarization}, url = {http://dx.doi.org/10.1364/OE.23.005704}, author = {A. Turpin and Yu. V. Loiko and A. Peinado and A. Lizana and T. K. Kalkandjiev and J. Campos and J. Mompart} } @booklet {doi:10.1117/12.2184788, title = {Snapshot polarimeter based on the conical refraction phenomenon}, howpublished = {Proc. SPIE}, volume = {9526}, year = {2015}, pages = {952616-952616-8}, abstract = {A complete and punctual Stokes polarimeter based on the conical refraction (CR) phenomenon is presented. The CR phenomenon occurs when light travels along one of the optical axes of a biaxial crystal (BC), leading to a bright ring of light at the focal plane of the system. We propose using the connection between the intensity pattern of the CR ring and the state of polarization (SOP) of the incident beam as a new tool for polarization metrology. In order to implement a complete polarimeter, the instrument is designed with a beam splitter and two BCs, one BC for each sub-beam. In the second sub-beam, a retarder is introduced before the BC, allowing us to measure the ellipticity content of the input SOP. The CR-based polarimeter presents several appealing features compared to standard polarimeters. To name some of them, CR polarimeters retrieve the SOP of an input beam with a single snapshot measurement, allow for substantially enhancing the data redundancy without increasing measuring time, and avoid instrumental errors related to rotating elements or active polarization devices. This work shows the instrument design, in particular the parameters of the set-up have been optimized in order to reduce the amplification of noise. Then, the experimental implementation of the instrument is detailed, including the experimental calibration of the system. Finally, the implemented polarimeter is experimentally tested by measuring different SOPs, including fully and partially polarized light.

}, doi = {10.1117/12.2184788}, url = {http://dx.doi.org/10.1117/12.2184788}, author = {A. Peinado and A. Lizana and A. Turpin and I. Est{\'e}vez and C. Iemmi and T. K. Kalkandjiev and J. Mompart and J. Campos} } @article {1367-2630-17-8-083038, title = {Stimulated Raman adiabatic passage with two-color x-ray pulses}, journal = {New Journal of Physics}, volume = {17}, number = {8}, year = {2015}, pages = {083038}, abstract = {Recent techniques in x-ray free electron lasers allow the generation of highly coherent, intense x-ray pulses with time lengths on the order of femtoseconds. Here we explore the possibilities of using such x-ray pulses to control matter based on coherence. In particular we propose a theoretical scheme to perform stimulated Raman adiabatic passage in the x-ray regime by using inner-hole excited states. Numerical results in two well-known systems, the neon atom and the carbon monoxide molecule, show a robust control of population transfer. In the molecule, vibrational selectivity is achieved with femtosecond x-ray pulses. This work supports the possibility of using two-color x-ray pulses for coherent control.}, url = {http://stacks.iop.org/1367-2630/17/i=8/a=083038}, author = {A. Pic{\'o}n and J. Mompart and S. H Southworth} } @article {Turpin:15, title = {Transformation of vector beams with radial and azimuthal polarizations in biaxial crystals}, journal = {J. Opt. Soc. Am. A}, volume = {32}, number = {5}, year = {2015}, month = {May}, pages = {1012{\textendash}1016}, publisher = {OSA}, abstract = {We present both experimentally and theoretically the transformation of radially and azimuthally polarized vector beams when they propagate through a biaxial crystal and are transformed by the conical refraction phenomenon. We show that, at the focal plane, the transverse pattern is formed by a ring-like light structure with an azimuthal node, this node being found at diametrically opposite points of the ring for radial/azimuthal polarizations. We also prove that the state of polarization of the transformed beams is conical refraction-like, i.e., that every two diametrically opposite points of the light ring are linearly orthogonally polarized.

}, keywords = {Birefringence, Crystal optics, Polarization}, doi = {10.1364/JOSAA.32.001012}, url = {http://josaa.osa.org/abstract.cfm?URI=josaa-32-5-1012}, author = {A. Turpin and A. Vargas and A. Lizana and F. A. Torres-Ruiz and I. Est{\'e}vez and I. Moreno and J. Campos and J. Mompart} } @article {102, title = {Applied Bohmian mechanics}, journal = {European Physical Journal D}, volume = {68}, year = {2014}, month = {10/2014}, pages = {1-42}, type = {Topical Review}, chapter = {286}, abstract = {Bohmian mechanics provides an explanation of quantum phenomena in terms of point-like particles guided by wave functions. This review focuses on the use of nonrelativistic Bohmian mechanics to address practical problems, rather than on its interpretation. Although the Bohmian and standard quantum theories have different formalisms, both give exactly the same predictions for all phenomena. Fifteen years ago, the quantum chemistry community began to study the practical usefulness of Bohmian mechanics. Since then, the scientific community has mainly applied it to study the (unitary) evolution of single-particle wave functions, either by developing efficient quantum trajectory algorithms or by providing a trajectorybased explanation of complicated quantum phenomena. Here we present a large list of examples showing how the Bohmian formalism provides a useful solution in different forefront research fields for this kind of problems (where the Bohmian and the quantum hydrodynamic formalisms coincide). In addition, this work also emphasizes that the Bohmian formalism can be a useful tool in other types of (nonunitary and nonlinear) quantum problems where the influence of the environment or the nonsimulated degrees of freedom are relevant. This review contains also examples on the use of the Bohmian formalism for the many-body problem, decoherence and measurement processes. The ability of the Bohmian formalism to analyze this last type of problems for (open) quantum systems remains mainly unexplored by the scientific community. The authors of this review are convinced that the final status of the Bohmian theory among the scientific community will be greatly influenced by its potential success in those types of problems that present nonunitary and/or nonlinear quantum evolutions. A brief introduction of the Bohmian formalism and some of its extensions are presented in the last part of this review.}, doi = {10.1140/epjd/e2014-50222-4}, url = {http://link.springer.com/article/10.1140\%2Fepjd\%2Fe2014-50222-4}, author = {A. Benseny and G. Albareda and A. S. Sanz and J. Mompart and X. Oriols} } @article {97, title = {Coherent injecting, extracting, and velocity filtering of neutral atoms in a ring trap via spatial adiabatic passage}, journal = {European Physical Journal D}, volume = {69}, number = {6}, year = {2014}, month = {06/2014}, chapter = {147}, abstract = {We introduce a coherent technique to inject, extract, and velocity filter neutral atoms in a ring trap coupled via tunneling to two additional waveguides. By adiabatically following the transverse spatial dark state, the proposed technique allows for an efficient and robust velocity dependent atomic population transfer between the ring and the input/output waveguides. We have derived explicit conditions for the spatial adiabatic passage that depend on the atomic velocity along the input waveguide as well as on the initial population distribution among the transverse vibrational states. The validity of our proposal has been checked by numerical integration of the corresponding two-dimensional Schrodinger equation with state-of-the-art parameter values for Rb-87 atoms and an optical dipole ring trap.}, keywords = {Optics, Toroidal traps}, doi = {10.1140/epjd/e2014-40696-3}, url = {http://link.springer.com/article/10.1140/epjd/e2014-40696-3}, author = {Yu. V. Loiko and V. Ahufinger and R. Menchon-Enrich and G. Birkl and J. Mompart} } @proceedings {101, title = {Laser beams with conical refraction patterns}, volume = {8960}, year = {2014}, month = {02/2014}, publisher = {SPIE}, address = {San Francisco, CA}, abstract = {Laser beams with cone-refracted output from the plane mirror is demonstrated for the first time in lasers based on intracavity conical refraction (CR) phenomenon. Transverse profile of such lasers comprises a crescent ring of CR-like distribution, where any opposite points are of orthogonal linear polarizations. We confirm the existence of such mode of CR lasers by two observations. First, cascaded CR in reflection geometry has been demonstrated for first time and it provides experimental prove that a light beam passed along optic axis of a biaxial crystal, reflected back from a plane mirror and passed again through the crystal is restored. Second, CR cavity mode with CR-like pattern through the plane mirror is experimentally and theoretically demonstrated for the first time.}, keywords = {Conical refraction, Laser, Light polarization, Optical resonator, Transverse profile}, doi = {10.1117/12.2039893}, url = {http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=1840891}, author = {Yu. V. Loiko and G. S. Sokolovskii and D. Carnegie and A. Turpin and J. Mompart and E. U. Rafailov} } @article {98, title = {Single-atom interferometer based on two-dimensional spatial adiabatic passage}, journal = {Physical Review A}, volume = {89}, number = {5}, year = {2014}, month = {05/2014}, chapter = {053611}, abstract = {In this work, we propose a single-atom interferometer based on a fully two-dimensional spatial adiabatic passage process using a system of three identical harmonic traps in a triangular geometry. While the transfer of a single atom from the ground state of one trap to the ground state of the most distant one can successfully be achieved in a robust way for a broad range of parameter values, we point out the existence of a specific geometrical configuration of the traps for which a crossing of two energy eigenvalues occurs and the transfer of the atom fails. Instead, the wave function is robustly split into a coherent superposition between two of the traps. We show that this process can be used to construct a single-atom interferometer and discuss its performance in terms of the final population distribution among the asymptotic eigenstates of the individual traps. This interferometric scheme could be used to study space-dependent fields from ultrashort to relatively large distances, or the decay of the coherence of superposition states as a function of the distance.}, doi = {10.1103/PhysRevA.89.053611}, url = {http://dx.doi.org/10.1103/PhysRevA.89.053611}, author = {R. Menchon-Enrich and S. McEndoo and T. Busch and V. Ahufinger and J. Mompart} } @article {99, title = {Spatial adiabatic passage processes in sonic crystals with linear defects}, journal = {Physical Review B}, volume = {89}, number = {9}, year = {2014}, month = {03/2014}, chapter = {094304}, abstract = {We investigate spatial adiabatic passage processes for sound wave propagation in sonic crystals, consisting of steel cylinders embedded in a water host medium, that present two linear defects. This work constitutes an extension of the well-known quantum optical rapid adiabatic passage technique to the field of sound propagation. Several spatial adiabatic passage devices are proposed by appropriately designing the geometry of the two linear defects along the propagation direction to work as a coherent multifrequency adiabatic splitter, a phase difference analyzer, and a coherent multifrequency adiabatic coupler. These devices are robust in front of fluctuations of the geometric parameter values.}, doi = {10.1103/PhysRevB.89.094304}, url = {http://dx.doi.org/10.1103/PhysRevB.89.094304}, author = {R. Menchon-Enrich and J. Mompart and V. Ahufinger} } @article {96, title = {Super-Gaussian conical refraction beam}, journal = {Optics Letters}, volume = {39}, number = {15}, year = {2014}, pages = {4349-4352}, chapter = {4349}, abstract = {We demonstrate the transformation of Gaussian input beams into super-Gaussian beams with a quasi flat-top transverse profile by means of the conical refraction phenomenon by adjusting the ratio between the ring radius and the waist radius of the input beam to 0.445. We discuss the beam propagation of the super-Gaussian beam and show that it has a confocal parameter three times larger than the one that would be obtained from a Gaussian beam. The experiments performed with a KGd(WO4)2 biaxial crystal are in good agreement with the theoretical predictions.}, keywords = {Birefringence, Crystal optics, Laser beam shaping, Laser materials processing}, url = {http://dx.doi.org/10.1364/OL.39.004349}, author = {A. Turpin and Yu. V. Loiko and T. K. Kalkandjiev and H. Tomizawa and J. Mompart} } @article {100, title = {Tunneling-induced angular momentum for single cold atoms}, journal = {Physical Review A}, volume = {89}, number = {1}, year = {2014}, month = {01/2014}, chapter = {013626}, abstract = {We study the generation of angular momentum carrying states for a single cold particle by breaking the symmetry of a spatial adiabatic passage process in a two-dimensional system consisting of three harmonic potential wells. By following a superposition of two eigenstates of the system, a single cold particle is completely transferred to the degenerate first excited states of the final trap, which are resonantly coupled via tunneling to the ground states of the initial and middle traps. Depending on the total time of the process, angular momentum is generated in the final trap, with values that oscillate between +/-(h) over bar. This process is discussed in terms of the asymptotic eigenstates of the individual wells and the results are checked by simulations of the full twodimensional Schrodinger equation.}, doi = {10.1103/PhysRevA.89.013626}, url = {http://dx.doi.org/10.1103/PhysRevA.89.013626}, author = {R. Menchon-Enrich and S. McEndoo and J. Mompart and V. Ahufinger and T. Busch} } @article {Peinado:13, title = {Conical refraction as a tool for polarization metrology}, journal = {Optics Letters}, volume = {38}, number = {20}, year = {2013}, month = {08/2013}, pages = {4100{\textendash}4103}, publisher = {OSA}, chapter = {4100}, abstract = {A method for polarization metrology based on the conical refraction (CR) phenomenon, occurring in biaxial crystals, is reported. CR transforms an input Gaussian beam into a light ring whose intensity distribution is linked to the incoming polarization. We present the design of a division-of-amplitude complete polarimeter composed of two biaxial crystals, whose measurement principle is based on the CR phenomenon. This design corresponds to a static polarimeter, that is, without mechanical movements or electrical signal addressing. Only one division-of-amplitude device is required, besides the two biaxial crystals, to completely characterize any state of polarization, including partially polarized and unpolarized states. In addition, a mathematical model describing the system is included. Experimental images of the intensity distribution related to different input polarization states are provided. These intensity patterns are compared with simulated values, proving the potential of polarimeters based on biaxial crystals.}, keywords = {Anisotropic optical materials, Birefringence, Crystal optics, Ellipsometry and polarimetry, Polarimetry}, issn = {0146-9592}, doi = {10.1364/OL.38.004100}, url = {http://ol.osa.org/abstract.cfm?URI=ol-38-20-4100}, author = {A. Peinado and A. Turpin and A. Lizana and E. Fern{\'a}ndez and J. Mompart and J. Campos} } @article {Loiko:13, title = {Generating a three-dimensional dark focus from a single conically refracted light beam}, journal = {Optics Letters}, volume = {38}, number = {22}, year = {2013}, month = {11/2013}, pages = {4648{\textendash}4651}, publisher = {OSA}, chapter = {4648}, abstract = {We report here the generation of a three-dimensional (3D) dark focus from a single focused monochromatic Gaussian beam that undergoes conical refraction when it propagates along one of the optic axes of a biaxial crystal. We study the resulting ring intensity pattern behind the crystal as a function of the ratio between the ring radius and the beam waist and derive the particular parameter values for which a 3D dark focus with null intensity at the ring center is formed. We have performed experiments with a KGd(WO4)2 biaxial crystal, reporting the generation of a bottle beam in full agreement with our theoretical investigations.}, keywords = {Birefringence, Laser cooling, Laser materials processing, Laser trapping}, issn = {0146-9592}, doi = {10.1364/OL.38.004648}, url = {http://ol.osa.org/abstract.cfm?URI=ol-38-22-4648}, author = {Yu. V. Loiko and A. Turpin and T. K. Kalkandjiev and E. U. Rafailov and J. Mompart} } @article {134, title = {Light spectral filtering based on spatial adiabatic passage}, journal = {Light: Science \& Applications}, volume = {2}, year = {2013}, month = {08/2013}, chapter = {e90}, abstract = {We present the first experimental realization of a light spectral filter based on the spatial adiabatic passage technique. We demonstrate that a fully integrable CMOS-compatible system of three coupled identical total internal reflection silicon oxide waveguides with variable separation along their propagation direction can be used simultaneously as a low- and high-pass spectral filter within the visible range of wavelengths. Light is injected into the right waveguide, and after propagating along the system, long wavelengths are transferred into the left output, whereas short wavelengths propagate to the right and central outputs. The stopband reaches values up to 11 dB for the left output and approximately 20 dB for the right plus central outputs. The passband values are close to 0 dB for both cases. We also demonstrate that the filtering characteristics of the device can be controlled by modifying the parameter values, which define the geometry of the triple-waveguide system. However, the general filtering behavior of the system does not critically depend on technological variations. Thus, the spatial adiabatic passage filtering approach constitutes an alternative to other integrated filtering devices, such as interference or absorbance-based filters.}, keywords = {CMOS-compatible technology, integrated optics devices, spatial adiabatic passage, wavelength filtering devices}, doi = {doi:10.1038/lsa.2013.46}, url = {http://www.nature.com/lsa/journal/v2/n8/full/lsa201346a.html}, author = {R. Menchon-Enrich and A. Llobera and J. Vila-Planas and V. J Cadarso and J. Mompart and V. Ahufinger} } @article {Turpin:13, title = {Multiple rings formation in cascaded conical refraction}, journal = {Optics Letters}, volume = {38}, number = {9}, year = {2013}, month = {05/2013}, pages = {1455{\textendash}1457}, publisher = {OSA}, chapter = {1455}, abstract = {When a light beam passes through a cascade of biaxial crystals (BCs) with aligned optic axes, the resulting transverse intensity pattern consists of multiple concentric rings. We provide a simple formulation for the pattern formation for both circularly and linearly polarized input beams, that could be applied for a cascade of an arbitrary number of BCs. We have experimentally investigated multiple ring formation with up to three cascade BCs, showing that the theoretical formulation is in full agreement with the experimental results.}, keywords = {Anisotropic optical materials, Birefringence, Crystal optics}, issn = {0146-9592}, doi = {10.1364/OL.38.001455}, url = {http://ol.osa.org/abstract.cfm?URI=ol-38-9-1455}, author = {A. Turpin and Yu. V. Loiko and T. K. Kalkandjiev and J. Mompart} } @article {126, title = {Nanoscale resolution for fluorescence microscopy via adiabatic passage}, journal = {Optics Express}, volume = {21}, number = {19}, year = {2013}, chapter = {22139}, abstract = {We propose the use of the subwavelength localization via adiabatic passage technique for fluorescence microscopy with nanoscale resolution in the far field. This technique uses a Λ-type medium coherently coupled to two laser pulses: the pump, with a node in its spatial profile, and the Stokes. The population of the Λ system is adiabatically transferred from one ground state to the other except at the node position, yielding a narrow population peak. This coherent localization allows fluorescence imaging with nanometer lateral resolution. We derive an analytical expression to asses the resolution and perform a comparison with the coherent population trapping and the stimulated-emission-depletion techniques.}, keywords = {Atomic and molecular physics, Microscopy, Quantum optics}, issn = {1094-4087}, doi = {10.1364/OE.21.022139}, url = {http://dx.doi.org/10.1364/OE.21.022139}, author = {J. L. Rubio and D. Viscor and V. Ahufinger and J. Mompart} } @article {127, title = {Optical vault: A reconfigurable bottle beam based on conical refraction of light}, journal = {Optics Express}, volume = {21}, number = {22}, year = {2013}, chapter = {26335}, abstract = {We employ conical refraction of light in a biaxial crystal to create an optical bottle for photophoretic trapping and manipulation of particles in gaseous media. We show that by only varying the polarization state of the input light beam the optical bottle can be opened and closed in order to load and unload particles in a highly controllable manner.}, keywords = {Diffraction, Laser beam shaping., Laser trapping, Optical tweezers or optical manipulation}, issn = {1094-4087}, doi = {10.1364/OE.21.026335}, url = {http://dx.doi.org/10.1364/OE.21.026335}, author = {A. Turpin and V. Shvedov and C. Hnatovsky and Yu. V. Loiko and J. Mompart and W. Krolikowski} } @article {PhysRevA.88.053628, title = {Soliton-based matter-wave interferometer}, journal = {Phys. Rev. A}, volume = {88}, year = {2013}, month = {11/2013}, pages = {053628}, publisher = {American Physical Society}, abstract = {We consider a matter-wave bright soliton interferometer composed of a harmonic potential trap with a Rosen-Morse barrier at its center on which an incident soliton collides and splits into two solitons. These two solitons recombine after a dipole oscillation in the trap at the position of the barrier. We focus on the characterization of the splitting process in the case in which the reflected and transmitted solitons have the same number of atoms. We obtain that the velocity of the split solitons strongly depends on the nonlinearity and on the width of the barrier and that the reflected soliton is in general slower than the transmitted one. Also, we study the phase difference acquired between the two solitons during the splitting and we fit semianalytically the main dependences with the velocity of the incident soliton, the nonlinearity, and the width of the barrier. The implementation of the full interferometer sequence is tested by means of the phase imprinting method.}, doi = {10.1103/PhysRevA.88.053628}, url = {http://link.aps.org/doi/10.1103/PhysRevA.88.053628}, author = {J. Polo and V. Ahufinger} } @article {136, title = {Speeding up the spatial adiabatic passage of matter waves in optical microtraps by optimal control}, journal = {Quantum Information Processing}, volume = {12}, number = {3}, year = {2013}, month = {03/2013}, pages = {1439-1467}, chapter = {1439}, keywords = {Atomic molecular and optical physics, Control of matter waves, Numerical optimization methods, Quantum optimal control}, issn = {1570-0755}, doi = {10.1007/s11128-012-0357-z}, url = {http://link.springer.com/article/10.1007\%2Fs11128-012-0357-z}, author = {A. Negretti and A. Benseny and J. Mompart and T. Calarco} } @article {Turpin:13, title = {Type I and type II second harmonic generation of conically refracted beams}, journal = {Optics Letters}, volume = {38}, number = {14}, year = {2013}, month = {07/2013}, pages = {2484{\textendash}2486}, publisher = {OSA}, chapter = {2484}, abstract = {Type I and type II second harmonic generation (SHG) of a beam transformed by the conical refraction phenomenon are presented. We show that, for type I, the second harmonic intensity pattern is a light ring with a point of null intensity while, for type II, the light ring possesses two dark regions. Taking into account the different two-photon processes involved in SHG, we have derived analytical expressions for the resulting transverse intensity patterns that are in good agreement with the experimental data. Finally, we have investigated the spatial evolution of the second harmonic signals, showing that they behave as conically refracted beams.}, keywords = {Birefringence, Crystal optics, Diffraction theory, Harmonic generation and mixing}, issn = {0146-9592}, doi = {10.1364/OL.38.002484}, url = {http://ol.osa.org/abstract.cfm?URI=ol-38-14-2484}, author = {A. Turpin and Yu. V. Loiko and T. K. Kalkandjiev and J. Trull and C. Cojocaru and J. Mompart} } @article {125, title = {Wave-vector and polarization dependence of conical refraction}, journal = {Optics Express}, volume = {21}, number = {4}, year = {2013}, chapter = {4503}, abstract = {We experimentally address the wave-vector and polarization dependence of the internal conical refraction phenomenon by demonstrating that an input light beam of elliptical transverse profile refracts into two beams after passing along one of the optic axes of a biaxial crystal, i.e. it exhibits double refraction instead of refracting conically. Such double refraction is investigated by the independent rotation of a linear polarizer and a cylindrical lens. Expressions to describe the position and the intensity pattern of the refracted beams are presented and applied to predict the intensity pattern for an axicon beam propagating along the optic axis of a biaxial crystal.}, keywords = {Anisotropic optical materials, Birefringence, Crystal optics}, issn = {1094-4087}, doi = {10.1364/OE.21.004503}, url = {http://dx.doi.org/10.1364/OE.21.004503}, author = {A. Turpin and Yu. V. Loiko and T. K. Kalkandjiev and H. Tomizawa and J. Mompart} } @article {140, title = {Adiabatic Passage of Light in CMOS-Compatible Silicon Oxide Integrated Rib Waveguides}, journal = {IEEE Photonics Technolopgy Letters}, volume = {24}, number = {7}, year = {2012}, month = {04/2012}, pages = {536-538}, chapter = {536}, abstract = {A fully complementary metal-oxide-semiconductor-compatible adiabatic passage of light in the visible range is presented in this letter. We experimentally show that a system of three total internal reflection waveguides, which has been defined by using non-stoichiometric silicon oxide, allows a highly efficient transfer of light between the outermost waveguides by adiabatically following one eigenmode of the system. Furthermore, we demonstrate that such transfer of light is very robust against small variations of the system parameters.}, keywords = {Adiabatic passage of light, integrated optical circuits, silicon technology, total internal reflection (TIR) waveguides}, issn = {1041-1135}, doi = {10.1109/LPT.2011.2180519}, url = {Adiabatic Passage of Light in CMOS-Compatible Silicon Oxide Integrated Rib Waveguides}, author = {R. Menchon-Enrich and A. Llobera and V. J Cadarso and J. Mompart and V. Ahufinger} } @conference { ISI:000302637400022, title = {Conical refraction multiplexing for free space optical communications}, booktitle = {FREE-SPACE LASER COMMUNICATION TECHNOLOGIES XXIV}, series = {{Proceedings of SPIE}}, volume = {{8246}}, year = {2012}, note = {{Conference on Free-Space Laser Communication Technologies XXIV, San Francisco, CA, JAN 24-26, 2012}}, publisher = {SPIE}, organization = {SPIE}, type = {{Proceedings Paper}}, address = {1000 20TH ST, PO BOX 10, BELLINGHAM, WA 98227-0010 USA}, abstract = {Conical refraction (CR) is proposed to increase the channel capacity for free space optical communication applications. We present the first investigations of cascaded CR with a linearly polarized input beam and experimentally prove that two oppositely oriented consecutive identical biaxial crystals perform a forward-backward transformation of the incident light beam. This forward-backward transformation is reported for different input beams with Gaussian, elliptical and angularly modulated transverse intensity profiles and is the basis for our novel proposal on multiplexing and demultiplexing of optical beams. We present experimental proof of usefulness and perspective of the CR multiplexing technique by increasing in one order of magnitude the channel capacity at optical frequencies. The technique is applicable to any wavelength in optical and telecommunication bands. It can be also properly upgraded with the WDM technique.}, keywords = {channel capacity, Conical refraction, Free space optics, laser links, optical multiplexing/demultiplexing}}, isbn = {978-0-8194-8889-3}, issn = {{0277-786X}}, doi = {10.1117/12.909257}, url = {http://spie.org/Publications/Proceedings/Paper/10.1117/12.909257}, author = {Yu. V. Loiko and A. Turpin and T. K. Kalkandjiev and J. Mompart}, editor = {H. Hemmati and D. M. Boroson} } @article {Turpin:12, title = {Free-space optical polarization demultiplexing and multiplexing by means of conical refraction}, journal = {Optics Letters}, volume = {37}, number = {20}, year = {2012}, month = {09/2012}, pages = {4197{\textendash}4199}, publisher = {OSA}, chapter = {4197}, abstract = {Polarization demultiplexing and multiplexing by means of conical refraction is proposed to increase the channel capacity for free-space optical communication applications. The proposed technique is based on the forward-backward optical transform occurring when a light beam propagates consecutively along the optic axes of two identical biaxial crystals with opposite orientations of their conical refraction characteristic vectors. We present an experimental proof of usefulness of the conical refraction demultiplexing and multiplexing technique by increasing in one order of magnitude the channel capacity at optical frequencies in a propagation distance of 4 m.}, keywords = {Anisotropic optical materials, Free-space optical communication, Multiplexing}, issn = {0146-9592}, doi = {10.1364/OL.37.004197}, url = {http://ol.osa.org/abstract.cfm?URI=ol-37-20-4197}, author = {A. Turpin and Yu. V. Loiko and T. K. Kalkandjiev and J. Mompart} } @article {PhysRevA.85.053619, title = {Need for relativistic corrections in the analysis of spatial adiabatic passage of matter waves}, journal = {Phys. Rev. A}, volume = {85}, year = {2012}, month = {05/2012}, pages = {053619}, publisher = {American Physical Society}, abstract = {We investigate the coherent transport of a single particle and a Bose-Einstein condensate between the two extreme traps of a triple-well potential by means of the spatial adiabatic passage technique. This matter wave transport technique consists of adiabatically following an energy eigenstate of the system that only populates the vibrational ground states of the two extreme wells and presents at all times a node in the central region. Unraveling the (nonlinear) time-dependent Schr{\"o}dinger equation in terms of Bohmian quantum trajectories, we show that by slowing down the total time duration of the transport process, Bohmian velocities in the central region are orders of magnitude larger than the mean atomic velocities. This leads to a very counterintuitive effect: in the regime of almost perfect adiabaticity, these velocities require relativistic corrections to properly address the transfer process and avoid superluminal propagation.}, doi = {10.1103/PhysRevA.85.053619}, url = {http://link.aps.org/doi/10.1103/PhysRevA.85.053619}, author = {A. Benseny and J. Bagud{\`a} and X. Oriols and J. Mompart} } @article {PhysRevA.86.063409, title = {Single-site addressing of ultracold atoms beyond the diffraction limit via position-dependent adiabatic passage}, journal = {Phys. Rev. A}, volume = {86}, year = {2012}, month = {12/2012}, pages = {063409}, publisher = {American Physical Society}, abstract = {We propose a single-site addressing implementation based on the subwavelength localization via adiabatic passage (SLAP) technique. We consider a sample of ultracold neutral atoms loaded into a two-dimensional optical lattice with one atom per site. Each atom is modeled by a three-level Λ system in interaction with a pump and a Stokes laser pulse. Using a pump field with a node in its spatial profile, the atoms at all sites are transferred from one ground state of the system to the other via stimulated Raman adiabatic passage, except the one at the position of the node that remains in the initial ground state. This technique allows for the preparation, manipulation, and detection of atoms with a spatial resolution better than the diffraction limit, which either relaxes the requirements on the optical setup used or extends the achievable spatial resolution to lattice spacings smaller than accessible to date. In comparison to techniques based on coherent population trapping, SLAP gives a higher addressing resolution and has additional advantages such as robustness against parameter variations, coherence of the transfer process, and the absence of photon induced recoil. Additionally, the advantages of our proposal with respect to adiabatic spin-flip techniques are highlighted. Analytic expressions for the achievable addressing resolution and efficiency are derived and compared to numerical simulations for 87Rb atoms in state-of-the-art optical lattices.}, doi = {10.1103/PhysRevA.86.063409}, url = {http://link.aps.org/doi/10.1103/PhysRevA.86.063409}, author = {D. Viscor and J. L. Rubio and G. Birkl and J. Mompart and V. Ahufinger} } @article {PhysRevA.86.053827, title = {Two-color quantum memory in double-Λ media}, journal = {Phys. Rev. A}, volume = {86}, year = {2012}, month = {11/2012}, pages = {053827}, publisher = {American Physical Society}, abstract = {We propose a quantum memory for a single-photon wave packet in a superposition of two different colors, i.e., two different frequency components, using the electromagnetically induced transparency technique in a double-Λ system. We examine a specific configuration in which the two frequency components are able to exchange energy through a four-wave mixing process as they propagate, so the state of the incident photon is recovered periodically at certain positions in the medium. We investigate the propagation dynamics as a function of the relative phase between the coupling beams and the input single-photon frequency components. Moreover, by considering time-dependent coupling beams, we numerically simulate the storage and retrieval of a two-frequency-component single-photon qubit.}, doi = {10.1103/PhysRevA.86.053827}, url = {http://link.aps.org/doi/10.1103/PhysRevA.86.053827}, author = {D. Viscor and V. Ahufinger and J. Mompart and A. Zavatta and G. C. La Rocca and M. Artoni} } @article {PhysRevA.83.013605, title = {Disordered spinor Bose-Hubbard model}, journal = {Phys. Rev. A}, volume = {83}, year = {2011}, month = {Jan}, pages = {013605}, publisher = {American Physical Society}, abstract = {We study the zero-temperature phase diagram of the disordered spin-1 Bose-Hubbard model in a two-dimensional square lattice. To this aim, we use a mean-field Gutzwiller ansatz and a probabilistic mean-field perturbation theory. The spin interaction induces two different regimes, corresponding to a ferromagnetic and antiferromagnetic order. In the ferromagnetic case, the introduction of disorder reproduces analogous features of the disordered scalar Bose-Hubbard model, consisting in the formation of a Bose glass phase between Mott insulator lobes. In the antiferromagnetic regime, the phase diagram differs more from the scalar case. Disorder in the chemical potential can lead to the disappearance of Mott insulator lobes with an odd-integer filling factor and, for sufficiently strong spin coupling, to Bose glass of singlets between even-filling Mott insulator lobes. Disorder in the spinor coupling parameter results in the appearance of a Bose glass phase only between the n and the n+1 lobes for n odd. Disorder in the scalar Hubbard interaction inhibits Mott insulator regions for occupation larger than a critical value.}, doi = {10.1103/PhysRevA.83.013605}, url = {http://link.aps.org/doi/10.1103/PhysRevA.83.013605}, author = {M. Lacki and S. Paganelli and V. Ahufinger and A. Sanpera and J. Zakrzewski} } @booklet {doi:10.1117/12.874602, title = {Fermionic transformation rules for spatially filtered light beams in conical refraction}, howpublished = {Proc. SPIE}, volume = {7950}, year = {2011}, pages = {79500D-79500D-9}, abstract = {In conical refraction, when a collimated light beam passes along the optic axis of a biaxial crystal it refracts conically giving rise to a characteristic conical refraction (CR) ring. At each point of the CR ring the light electric field is linearly polarized with the polarization plane rotating along the ring such that every two opposite points of the ring present orthogonal linear polarizations. With a pinhole we have spatially filtered a small part of the CR ring and experimentally reported that this filtered light does not yield a ring pattern when it refracts along the optic axis of a second biaxial crystal, called the CR-analyzer in what follows. Instead, after crossing the CR-analyzer the filtered beam splits into two beams with orthogonal linear polarizations that correspond to two opposite points of the otherwise expected CR ring. We have experimentally derived the transformation rules of the filtered beam. For a CR-analyzer rotated by an angle ω around the optic axis, the filtered beam splits in two beams with intensities following the fermionic transformation rule cos2 (ω / 2) , in contrast to the Malus law of cos 2ω followed by double refraction.}, doi = {10.1117/12.874602}, url = {http://dx.doi.org/10.1117/12.874602}, author = {Yu. V. Loiko and M. A. Bursukova and T. K. Kalkandjiev and E. U. Rafailov and J. Mompart} } @article {PhysRevA.83.033629, title = {Filtering of matter-wave vibrational states via spatial adiabatic passage}, journal = {Phys. Rev. A}, volume = {83}, year = {2011}, month = {Mar}, pages = {033629}, publisher = {American Physical Society}, abstract = {We discuss the filtering of the vibrational states of a cold atom in an optical trap by chaining this trap with two empty ones and adiabatically controlling the tunneling. Matter-wave filtering is performed by selectively transferring the population of the highest populated vibrational state to the most distant trap while the population of the rest of the states remains in the initial trap. Analytical conditions for two-state filtering are derived and then applied to an arbitrary number of populated bound states. Realistic numerical simulations close to state-of-the-art experimental arrangements are performed by modeling the triple well with time-dependent P{\"o}schl-Teller potentials. In addition to filtering of vibrational states, we discuss applications for quantum tomography of the initial population distribution and engineering of atomic Fock states that, eventually, could be used for tunneling-assisted evaporative cooling.}, doi = {10.1103/PhysRevA.83.033629}, url = {http://link.aps.org/doi/10.1103/PhysRevA.83.033629}, author = {Yu. V. Loiko and V. Ahufinger and R. Corbal{\'a}n and G. Birkl and J. Mompart} } @article {0953-4075-44-19-195504, title = {Optical quantum memory for polarization qubits with V -type three-level atoms}, journal = {Journal of Physics B: Atomic, Molecular and Optical Physics}, volume = {44}, number = {19}, year = {2011}, pages = {195504}, abstract = {We investigate an optical quantum memory scheme with V -type three-level atoms based on the controlled reversible inhomogeneous broadening technique. We theoretically show the possibility of storing and retrieving a weak light pulse interacting with the two optical transitions of the system. This scheme implements a quantum memory for a polarization qubit{\textemdash}a single photon in an arbitrary polarization state{\textemdash}without the need of two spatially separated two-level media, thus offering the advantage of experimental compactness overcoming the limitations due to mismatching and unequal efficiencies that can arise in spatially separated memories. The effects of a relative phase change between the atomic levels, as well as of phase noise due to, for example, the presence of spurious electric and magnetic fields are analysed.}, url = {http://stacks.iop.org/0953-4075/44/i=19/a=195504}, author = {D. Viscor and A. Ferraro and Yu. V. Loiko and R. Corbal{\'a}n and J. Mompart and V. Ahufinger} } @article {PhysRevA.84.042314, title = {Quantum-state storage and processing for polarization qubits in an inhomogeneously broadened Λ-type three-level medium}, journal = {Phys. Rev. A}, volume = {84}, year = {2011}, month = {Oct}, pages = {042314}, publisher = {American Physical Society}, abstract = {We address the propagation of a single-photon pulse with two polarization components, i.e., a polarization qubit, in an inhomogeneously broadened {\textquotedblleft}phaseonium{\textquotedblright} Λ-type three-level medium. We combine some of the nontrivial propagation effects characteristic for this kind of coherently prepared systems and the controlled reversible inhomogeneous broadening technique to propose several quantum information-processing applications, such as a protocol for polarization qubit filtering and sieving as well as a tunable polarization beam splitter. Moreover, we show that by imposing a spatial variation of the atomic coherence phase, an efficient quantum memory for the incident polarization qubit can be also implemented in Λ-type three-level systems.}, doi = {10.1103/PhysRevA.84.042314}, url = {http://link.aps.org/doi/10.1103/PhysRevA.84.042314}, author = {D. Viscor and A. Ferraro and Yu. V. Loiko and J. Mompart and V. Ahufinger} } @article {2040-8986-13-6-064019, title = {Spin and orbital angular momentum propagation in anisotropic media: theory}, journal = {Journal of Optics}, volume = {13}, number = {6}, year = {2011}, pages = {064019}, abstract = {This paper is devoted to a study of the propagation of light beams carrying orbital angular momentum in optically anisotropic media. We first review some properties of homogeneous anisotropic media, and describe how the paraxial formalism is modified in order to proceed with a new approach dealing with the general setting of paraxial propagation along uniaxial inhomogeneous media. This approach is suitable for describing space-variant optical-axis phase plates.}, url = {http://stacks.iop.org/2040-8986/13/i=6/a=064019}, author = {A. Pic{\'o}n and A. Benseny and J. Mompart and G F Calvo} } @article { ISI:000298333500005, title = {Spin Effects in Bose-Glass Phases}, journal = {Journal of Low Temperature Physics}, volume = {165}, number = {{5-6, SI}}, year = {2011}, month = {DEC}, pages = {227-238}, publisher = {{SPRINGER/PLENUM PUBLISHERS}}, address = {{233 SPRING ST, NEW YORK, NY 10013 USA}}, abstract = {We study the mechanism of formation of Bose glass (BG) phases in the spin-1 Bose Hubbard model when diagonal disorder is introduced. To this aim, we analyze first the phase diagram in the zero-hopping limit, there disorder induces superposition between Mott insulator (MI) phases with different filling numbers. Then BG appears as a compressible insulating phase (its compressibility marking the distinction with respect to a more common Mott insulator). The phase diagram for finite hopping is also calculated with the Gutzwiller approximation. The bosons{\textquoteright} spin degrees of freedom introduce another scattering channel in the two-body interaction modifying the stability of MI regions with respect to the action of disorder. This leads to some peculiar phenomena such as the creation of BG of singlets, for very strong spin correlation, or the disappearance of BG phase in some particular cases where fluctuations are not able to mix different MI regions.}, keywords = {Bose glass, Spin-1 Bose Hubbard model, Ultracold atoms}, issn = {0022-2291}, doi = {10.1007/s10909-011-0392-7}, author = {S. Paganelli and M. Lacki and V. Ahufinger and J. Zakrzewski and A. Sanpera} } @article {PhysRevA.81.043621, title = {Adiabatic splitting, transport, and self-trapping of a Bose-Einstein condensate in a double-well potential}, journal = {Phys. Rev. A}, volume = {81}, year = {2010}, month = {Apr}, pages = {043621}, publisher = {American Physical Society}, abstract = {We show that the adiabatic dynamics of a Bose-Einstein condensate (BEC) in a double-well potential can be described in terms of a dark variable resulting from the combination of the population imbalance and the spatial atomic coherence between the two wells. By means of this dark variable, we extend, to the nonlinear matter-wave case, the recent proposal by Vitanov and Shore [Phys. Rev. A 73, 053402 (2006)] on adiabatic passage techniques to coherently control the population of two internal levels of an atom or molecule. We investigate the conditions to adiabatically split or transport a BEC as well as to prepare an adiabatic self-trapping state by the optimal delayed temporal variation of the tunneling rate via either the energy bias between the two wells or the BEC nonlinearity. The emergence of nonlinear eigenstates and unstable stationary solutions of the system as well as their role in the breaking down of the adiabatic dynamics is investigated in detail.}, doi = {10.1103/PhysRevA.81.043621}, url = {http://link.aps.org/doi/10.1103/PhysRevA.81.043621}, author = {C. Ottaviani and V. Ahufinger and R. Corbal{\'a}n and J. Mompart} } @article {PhysRevA.82.013604, title = {Atomtronics with holes: Coherent transport of an empty site in a triple-well potential}, journal = {Phys. Rev. A}, volume = {82}, year = {2010}, month = {Jul}, pages = {013604}, publisher = {American Physical Society}, abstract = {We investigate arrays of three traps with two fermionic or bosonic atoms. The tunneling interaction between neighboring sites is used to prepare multisite dark states for the empty site (i.e., the hole) which allows for the coherent manipulation of its external degrees of freedom. By means of an ab initio integration of the Schr{\"o}dinger equation, we investigate the adiabatic transport of a hole between the two extreme traps of a triple-well potential. Furthermore, a quantum-trajectory approach based on the de Broglie{\textendash}Bohm formulation of quantum mechanics is used to get physical insight into the transport process. Finally, we discuss the use of the hole for the construction of a coherent single hole diode and a coherent single hole transistor.}, doi = {10.1103/PhysRevA.82.013604}, url = {http://link.aps.org/doi/10.1103/PhysRevA.82.013604}, author = {A. Benseny and S. Fern{\'a}ndez-Vidal and J. Bagud{\`a} and R. Corbal{\'a}n and A. Pic{\'o}n and L. Roso and G. Birkl and J. Mompart} } @article {PhysRevA.81.033420, title = {Dipole spectrum structure of nonresonant nonpertubative driven two-level atoms}, journal = {Phys. Rev. A}, volume = {81}, year = {2010}, month = {Mar}, pages = {033420}, publisher = {American Physical Society}, abstract = {We analyze the dipole spectrum of a two-level atom excited by a nonresonant intense monochromatic field under the electric dipole approximation and beyond the rotating wave approximation. We show that the apparently complex spectral structure can be completely described by two families: harmonic frequencies of the driving field and field-induced nonlinear fluorescence. Our formulation of the problem provides quantitative laws for the most relevant spectral features: harmonic ratios and phases, nonperturbative Stark shift, and frequency limits of the harmonic plateau. In particular, we demonstrate the locking of the harmonic phases at the wings of the plateau opening the possibility of ultrashort pulse generation through harmonic filtering.}, doi = {10.1103/PhysRevA.81.033420}, url = {http://link.aps.org/doi/10.1103/PhysRevA.81.033420}, author = {A. Pic{\'o}n and L. Roso and J. Mompart and O. Varela and V. Ahufinger and R. Corbal{\'a}n and L. Plaja} } @article {1367-2630-12-8-083053, title = {Transferring orbital and spin angular momenta of light to atoms}, journal = {New Journal of Physics}, volume = {12}, number = {8}, year = {2010}, pages = {083053}, abstract = {Light beams carrying orbital angular momentum (OAM), such as Laguerre{\textendash}Gaussian (LG) beams, give rise to the violation of the standard dipolar selection rules during interaction with matter, yielding, in general, an exchange of angular momentum larger than $\#$$\#$IMG$\#$$\#$ [http://ej.iop.org/icons/Entities/planck.gif] {planck} per absorbed photon. By means of ab initio three-dimensional (3D) numerical simulations, we investigate in detail the interaction of a hydrogen atom with intense Gaussian and LG light pulses. We analyze the dependence of the angular momentum exchange with the polarization, the OAM and the carrier-envelope phase of light, as well as with the relative position between the atom and the light vortex. In addition, a quantum-trajectory approach based on the de Broglie{\textendash}Bohm formulation of quantum mechanics is used to gain physical insight into the absorption of angular momentum by the hydrogen atom.}, url = {http://stacks.iop.org/1367-2630/12/i=8/a=083053}, author = {A. Pic{\'o}n and A. Benseny and J. Mompart and J R V{\'a}zquez de Aldana and L. Plaja and G F Calvo and L. Roso} } @article {PhysRevA.79.053638, title = {Coherent patterning of matter waves with subwavelength localization}, journal = {Phys. Rev. A}, volume = {79}, year = {2009}, month = {May}, pages = {053638}, publisher = {American Physical Society}, abstract = {We propose the subwavelength localization via adiabatic passage (SLAP) technique to coherently achieve state-selective patterning of matter waves well beyond the diffraction limit. The SLAP technique consists in coupling two partially overlapping and spatially structured laser fields to three internal levels of the matter wave yielding state-selective localization at those positions where the adiabatic passage process does not occur. We show that by means of this technique matter wave localization down to the single nanometer scale can be achieved. We analyze in detail the potential implementation of the SLAP technique for nanolithography with an atomic beam of metastable Ne* and for coherent patterning of a two-component R87b Bose-Einstein condensate.}, doi = {10.1103/PhysRevA.79.053638}, url = {http://link.aps.org/doi/10.1103/PhysRevA.79.053638}, author = {J. Mompart and V. Ahufinger and G. Birkl} } @article {PhysRevA.79.053809, title = {Doppler-free adiabatic self-induced transparency}, journal = {Phys. Rev. A}, volume = {79}, year = {2009}, month = {May}, pages = {053809}, publisher = {American Physical Society}, abstract = {We demonstrate that a Doppler-broadened two-level medium can be made transparent to a laser pulse by an appropriate adiabatic variation in the laser field amplitude and its nominal detuning. This technique of adiabatic self-induced transparency (ASIT) is compared with the well-known self-induced transparency phenomenon, showing that the adiabatic method is much more robust against variations in the system parameters. We also discuss a possible experimental implementation of ASIT using R87b atoms.}, doi = {10.1103/PhysRevA.79.053809}, url = {http://link.aps.org/doi/10.1103/PhysRevA.79.053809}, author = {Yu. V. Loiko and C. Serrat and R. Vilaseca and V. Ahufinger and J. Mompart and R. Corbal{\'a}n} } @article {PhysRevA.78.013608, title = {Double-barrier potentials for matter-wave gap solitons}, journal = {Phys. Rev. A}, volume = {78}, year = {2008}, month = {Jul}, pages = {013608}, publisher = {American Physical Society}, abstract = {We investigate collisions of solitons of the gap type, supported by a lattice potential in repulsive Bose-Einstein condensates, with an effective double-barrier potential that resembles a Fabry-Perot cavity. We identify conditions under which the trapping of the entire incident soliton in the cavity is possible. Collisions of the incident soliton with an earlier trapped one are considered too. In the latter case, many outcomes of the collisions are identified, including merging, release of the trapped soliton with or without being replaced by the incoming one, and trapping of both solitons.}, doi = {10.1103/PhysRevA.78.013608}, url = {http://link.aps.org/doi/10.1103/PhysRevA.78.013608}, author = {V. Ahufinger and B. A. Malomed and G. Birkl and R. Corbal{\'a}n and A. Sanpera} } @article {0953-4075-41-4-045505, title = {Generation of entangled photon pairs in optical cavity-QED: operating in the bad cavity limit}, journal = {Journal of Physics B: Atomic, Molecular and Optical Physics}, volume = {41}, number = {4}, year = {2008}, pages = {045505}, abstract = {We propose an optical cavity-QED scheme for the deterministic generation of polarization-entangled photon pairs that operates with high fidelity even in the bad cavity limit. The scheme is based on the interaction of an excited four-level atom with two empty optical cavity modes via an adiabatic passage process. Monte Carlo wavefunction simulations are used to evaluate the fidelity of the cavity-QED source and its entanglement capability in the presence of decoherence. In the bad cavity limit, fidelities close to one are predicted for state-of-the-art experimental parameter values.

}, url = {http://stacks.iop.org/0953-4075/41/i=4/a=045505}, author = {R. Garc{\'\i}a-Maraver and K. Eckert and R. Corbal{\'a}n and J. Mompart} } @article {1742-6596-84-1-012008, title = {Cavity-QED-based entangled photon pair gun}, journal = {Journal of Physics: Conference Series}, volume = {84}, number = {1}, year = {2007}, pages = {012008}, abstract = {We describe a cavity-QED scheme to deterministically generate polarization entangled photon pairs by using a single atom successively coupled to two single longitudinal mode cavities presenting polarization degeneracy. The cavities are initially prepared either in the vacuum state or in a single photon Fock state for each orthogonal polarization. Sharing the same basic elements, the source can operate on different physical processes. For a V -type three-level atom initially prepared in the ground state two implementations of the source are possible using either: i) two truncated Rabi Oscillations, or ii) a counterintuitive Stimulated Raman Adiabatic Passage process. Although slower than the former implementation, this second one is very efficient and robust under fluctuations of the experimental parameters and, particularly interesting, almost insensitive to atomic decay. For a four-level atom in a diamond configuration initially prepared in the upper state, the source can produce entangled photon pairs even in the bad cavity limit via an adiabatic passage process. We have performed Monte Carlo wave function simulations to characterize these sources by means of: i) the success probability P of producing the desired entangled state, ii) the fidelity F in the reduced space of two emitted cavity photons, and iii) the S parameter of the Clauser-Horne-Shimony-Holt (CHSH) inequality to quantify the entanglement capability.

}, url = {http://stacks.iop.org/1742-6596/84/i=1/a=012008}, author = {R. Garc{\'\i}a-Maraver and K. Eckert and R. Corbal{\'a}n and J. Mompart} } @article {Garcia-Maraver:07, title = {Cavity-quantum-electrodynamics entangled photon source based on two truncated Rabi oscillations}, journal = {J. Opt. Soc. Am. B}, volume = {24}, number = {2}, year = {2007}, month = {Feb}, pages = {257{\textendash}265}, publisher = {OSA}, abstract = {We discuss a cavity-QED scheme to deterministically generate entangled photons pairs by using a three-level atom successively coupled to two single longitudinal mode high-Q cavities presenting polarization degeneracy. The first cavity is prepared in a well-defined Fock state with two photons with opposite circular polarizations while the second cavity remains in the vacuum state. Half of a resonant Rabi oscillation in each cavity transfers one photon from the first to the second cavity, leaving the photons entangled in their polarization degree of freedom. The feasibility of this implementation and some practical considerations are discussed for both microwave and optical regimes. In particular, Monte Carlo wave-function simulations have been performed with state-of-the-art parameter values to evaluate the success probability of the cavity-QED source in producing entangled photon pairs as well as its entanglement capability.

}, keywords = {Photon statistics, Quantum electrodynamics}, doi = {10.1364/JOSAB.24.000257}, url = {http://josab.osa.org/abstract.cfm?URI=josab-24-2-257}, author = {R. Garc{\'\i}a-Maraver and K. Eckert and R. Corbal{\'a}n and J. Mompart} } @article {1367-2630-9-1-004, title = {Quantum switches and quantum memories for matter-wave lattice solitons}, journal = {New Journal of Physics}, volume = {9}, number = {1}, year = {2007}, pages = {4}, abstract = {We study the possibility of implementing a quantum switch and a quantum memory using matter-wave lattice solitons and making them interact with {\textquoteright}effective{\textquoteright} potentials (barrier/well) corresponding to defects of the optical lattice. In the case of interaction with an {\textquoteright}effective{\textquoteright} potential barrier, the bright lattice soliton experiences an abrupt transition from complete transmission to complete reflection (quantum switch) for a critical height of the barrier. The trapping of the soliton in an {\textquoteright}effective{\textquoteright} potential well and its release on demand, without losses, shows the feasibility of using the system as a quantum memory. The inclusion of defects as a way of controlling the interactions between two solitons is also reported.}, url = {http://stacks.iop.org/1367-2630/9/i=1/a=004}, author = {V. Ahufinger and A Mebrahtu and R. Corbal{\'a}n and A. Sanpera} } @article {PhysRevLett.98.023003, title = {Trapped Ion Chain as a Neural Network: Error Resistant Quantum Computation}, journal = {Phys. Rev. Lett.}, volume = {98}, year = {2007}, month = {Jan}, pages = {023003}, publisher = {American Physical Society}, abstract = {We demonstrate the possibility of realizing a neural network in a chain of trapped ions with induced long range interactions. Such models permit one to store information distributed over the whole system. The storage capacity of such a network, which depends on the phonon spectrum of the system, can be controlled by changing the external trapping potential. We analyze the implementation of error resistant universal quantum information processing in such systems.}, doi = {10.1103/PhysRevLett.98.023003}, url = {http://link.aps.org/doi/10.1103/PhysRevLett.98.023003}, author = {M. Pons and V. Ahufinger and C. Wunderlich and A. Sanpera and S. Braungardt and A. Sen(De) and U. Sen and M. Lewenstein} } @article { ISI:000246721000001, title = {Ultracold atomic gases in optical lattices: mimicking condensed matter physics and beyond}, journal = {Advances in Physics}, volume = {56}, number = {2}, year = {2007}, pages = {243-379}, publisher = {{TAYLOR \& FRANCIS LTD}}, address = {{4 PARK SQUARE, MILTON PARK, ABINGDON OX14 4RN, OXON, ENGLAND}}, abstract = {We review recent developments in the physics of ultracold atomic and molecular gases in optical lattices. Such systems are nearly perfect realisations of various kinds of Hubbard models, and as such may very well serve to mimic condensed matter phenomena. We show how these systems may be employed as quantum simulators to answer some challenging open questions of condensed matter, and even high energy physics. After a short presentation of the models and the methods of treatment of such systems, we discuss in detail, which challenges of condensed matter physics can be addressed with (i) disordered ultracold lattice gases, (ii) frustrated ultracold gases, (iii) spinor lattice gases, (iv) lattice gases in {\textquoteleft}{\textquoteleft}artificial{\textquoteright}{\textquoteright} magnetic fields, and, last but not least, (v) quantum information processing in lattice gases. For completeness, also some recent progress related to the above topics with trapped cold gases will be discussed.}, keywords = {disordered systems, frustrated systems, Hubbard models, quantum information, spinor gases, Ultracold atomic and molecular gases}, issn = {0001-8732}, doi = {10.1080/00018730701223200}, author = {M. Lewenstein and A. Sanpera and V. Ahufinger and B. Damski and A. Sen(De) and U. Sen} } @article {PhysRevA.75.023801, title = {Ultrashort pulse control of space-dependent excitations in a three-level system}, journal = {Phys. Rev. A}, volume = {75}, year = {2007}, month = {Feb}, pages = {023801}, publisher = {American Physical Society}, abstract = {Coherent control of regions with spatial excitation of populations and coherence between two lower states in three-level Λ-type quantum systems mediated by the self-induced transparency (SIT) phenomenon is theoretically investigated with one- and two-color ultrashort pulses and with pulse sequences beyond the slowly varying envelope (SVEA) and rotating wave (RWA) approximations. The effects of different parameters characterizing the pulses and the medium on the location as well as the width of such excited regions have been studied numerically by means of the finite-difference time-domain (FDTD) method. It has been determined that with a scheme of two-pulse excitation one can effectively control the position at which the region is written and its width. In particular, the position of the excited region can be controlled by the area of the pulses. We find that the maximum value of the population transferred to the lower excited state depends on the detuning of the pulses with respect to the one-photon resonances, and that both position and width of the region also depend on the temporal duration of the pulses. We show how after the excited region is written, its position can be shifted by additional pulses. On the basis of numerical results, scaling laws are formulated for the reported phenomena. With such control, the width of the region excited inside the medium can be reduced to the order of the wavelength of the light.}, doi = {10.1103/PhysRevA.75.023801}, url = {http://link.aps.org/doi/10.1103/PhysRevA.75.023801}, author = {Yu. V. Loiko and C. Serrat and R. Vilaseca and V. Ahufinger and J. Mompart and R. Corbal{\'a}n} } @article {PhysRevA.74.031801, title = {Deterministic cavity-QED source of polarization-entangled photon pairs}, journal = {Phys. Rev. A}, volume = {74}, year = {2006}, month = {Sep}, pages = {031801}, publisher = {American Physical Society}, abstract = {We present two cavity quantum electrodynamics proposals that, sharing the same basic elements, allow for the deterministic generation of entangled photon pairs by means of a three-level atom successively coupled to two single longitudinal mode high-Q optical resonators presenting polarization degeneracy. In the faster proposal, the three-level atom yields a polarization-entangled photon pair via two truncated Rabi oscillations, whereas in the adiabatic proposal, a counterintuitive stimulated Raman adiabatic passage process is considered. Although slower than the former process, this second method is very efficient and robust under fluctuations of the experimental parameters and, particularly interesting, almost completely insensitive to atomic decay.

}, doi = {10.1103/PhysRevA.74.031801}, url = {http://link.aps.org/doi/10.1103/PhysRevA.74.031801}, author = {R. Garc{\'\i}a-Maraver and K. Eckert and R. Corbal{\'a}n and J. Mompart} } @article {PhysRevA.74.062309, title = {Quantum-information processing in disordered and complex quantum systems}, journal = {Phys. Rev. A}, volume = {74}, year = {2006}, month = {Dec}, pages = {062309}, publisher = {American Physical Society}, abstract = {We study quantum information processing in complex disordered many body systems that can be implemented by using lattices of ultracold atomic gases and trapped ions. We demonstrate, first in the short range case, the generation of entanglement and the local realization of quantum gates in a disordered magnetic model describing a quantum spin glass. We show that in this case it is possible to achieve fidelities of quantum gates higher than in the classical case. Complex systems with long range interactions, such as ions chains or dipolar atomic gases, can be used to model neural network Hamiltonians. For such systems, where both long range interactions and disorder appear, it is possible to generate long range bipartite entanglement. We provide an efficient analytical method to calculate the time evolution of a given initial state, which in turn allows us to calculate its quantum correlations.}, doi = {10.1103/PhysRevA.74.062309}, url = {http://link.aps.org/doi/10.1103/PhysRevA.74.062309}, author = {A. Sen(De) and U. Sen and V. Ahufinger and H. J. Briegel and A. Sanpera and M. Lewenstein} } @article {0953-4075-39-10-S12, title = {Strongly correlated Fermi{\textendash}Bose mixtures in disordered optical lattices}, journal = {Journal of Physics B: Atomic, Molecular and Optical Physics}, volume = {39}, number = {10}, year = {2006}, pages = {S121}, abstract = {We investigate theoretically the low-temperature physics of a two-component ultracold mixture of bosons and fermions in disordered optical lattices. We focus on the strongly correlated regime. We show that, under specific conditions, composite fermions, made of one fermion plus one bosonic hole, form. The composite picture is used to derive an effective Hamiltonian whose parameters can be controlled via the boson{\textendash}boson and the boson{\textendash}fermion interactions, the tunnelling terms and the inhomogeneities. We finally investigate the quantum phase diagram of the composite fermions and show that it corresponds to the formation of Fermi glasses, spin glasses and quantum percolation regimes.}, url = {http://stacks.iop.org/0953-4075/39/i=10/a=S12}, author = {L. Sanchez-Palencia and V. Ahufinger and A. Kantian and J. Zakrzewski and A. Sanpera and M. Lewenstein} } @article {Eckert2006264, title = {Three level atom optics in dipole traps and waveguides}, journal = {Optics Communications}, volume = {264}, number = {2}, year = {2006}, note = {Quantum Control of Light and Matter In honor of the 70th birthday of Bruce Shore}, pages = {264 - 270}, abstract = {An analogy is explored between a setup of three atomic traps coupled via tunneling and an internal atomic three-level system interacting with two laser fields. Within this scenario we describe a \{STIRAP\} like process which allows to move an atom between the ground states of two trapping potentials and analyze its robustness. This analogy is extended to other robust and coherent transport schemes and to systems of more than a single atom. Finally it is applied to manipulate external degrees of freedom of atomic wave packets propagating in waveguides.}, issn = {0030-4018}, doi = {http://dx.doi.org/10.1016/j.optcom.2006.02.056}, url = {http://www.sciencedirect.com/science/article/pii/S003040180600486X}, author = {K. Eckert and J. Mompart and R. Corbal{\'a}n and M. Lewenstein and G. Birkl} } @conference { ISI:000236853300016, title = {Disordered complex systems using cold gases and trapped ions}, booktitle = {Laser Spectroscopy}, year = {2005}, note = {{17th International Conference on Laser Spectroscopy, Aviemore, SCOTLAND, JUN 19-24, 2005}}, pages = {{158-166}}, type = {{Proceedings Paper}}, address = {PO BOX 128 FARRER RD, SINGAPORE 9128, SINGAPORE}, abstract = {We report our research on disordered complex systems using cold gases and trapped ions and address the possibility of using complex systems for quantum information processing. Two simple paradigmatic models of disordered complex systems are here revisited. The first one corresponds to a short range disordered Ising Hamiltonian (spin glasses) which can be implemented with a bose-fermi (bose-bose) mixture in a disordered optical lattice. The second model we address here is a long range disordered Hamiltonian characteristic of neural networks (Hopfield model) which can be implemented in a chain of trapped ions with appropriately designed interactions.}, isbn = {981-256-659-7}, author = {A. Sen(De) and U. Sen and M. Lewenstein and V. Ahufinger and M. Pons and A. Sanpera}, editor = {E. A. Hinds and A. Ferguson and E. Riis} } @article {PhysRevA.72.063616, title = {Disordered ultracold atomic gases in optical lattices: A case study of Fermi-Bose mixtures}, journal = {Phys. Rev. A}, volume = {72}, year = {2005}, month = {Dec}, pages = {063616}, publisher = {American Physical Society}, abstract = {We present a review of properties of ultracold atomic Fermi-Bose mixtures in inhomogeneous and random optical lattices. In the strong interacting limit and at very low temperatures, fermions form, together with bosons or bosonic holes, composite fermions. Composite fermions behave as a spinless interacting Fermi gas, and in the presence of local disorder they interact via random couplings and feel effective random local potential. This opens a wide variety of possibilities of realizing various kinds of ultracold quantum disordered systems. In this paper we review these possibilities, discuss the accessible quantum disordered phases, and methods for their detection. The discussed quantum phases include Fermi glasses, quantum spin glasses, {\textquotedblleft}dirty{\textquotedblright} superfluids, disordered metallic phases, and phases involving quantum percolation.}, doi = {10.1103/PhysRevA.72.063616}, url = {http://link.aps.org/doi/10.1103/PhysRevA.72.063616}, author = {V. Ahufinger and L. Sanchez-Palencia and A. Kantian and A. Sanpera and M. Lewenstein} } @inbook { ISI:000304603600009, title = {Entanglement Properties of Composite Quantum Systems}, booktitle = {Quantum Information Processing}, year = {2005}, pages = {83-99}, publisher = {BLACKWELL SCIENCE PUBL}, organization = {BLACKWELL SCIENCE PUBL}, type = {{Article; Book Chapter}}, address = {OSNEY MEAD, OXFORD OX2 0EL, ENGLAND}, abstract = {We present here an overview of our work concerning entanglement properties of composite quantum systems. The characterization of entanglement, i.e. the possibility to assert if a given quantum state is entangled with others and how much entangled it is, remains one of the most fundamental open questions in quantum information theory. We discuss our recent results related to the problem of separability and distillability for distinguishable particles, employing the tool of witness operators. Finally, we also state our results concerning quantum correlations for indistinguishable particles.}, isbn = {978-3-52760-600-9}, doi = {10.1002/3527606009.ch7}, author = {K. Eckert and O. Guehne and F. Hulpke and P. Hyllus and J. Korbicz and J. Mompart and D. Bruss and M. Lewenstein and A. Sanpera}, editor = {T. Beth and G. Leuchs} } @article { ISI:000225524900010, title = {Frequency up-conversion He-Ne laser without inversion}, journal = {Applied Physics B-Lasers and Optics}, volume = {80}, number = {1}, year = {2005}, month = {JAN}, pages = {67-72}, publisher = {{SPRINGER}}, address = {{233 SPRING STREET, NEW YORK, NY 10013 USA}}, abstract = {{A scheme for obtaining up-conversion lasing without inversion in the visible range is proposed using a Doppler-broadened He-Ne mixture as active medium. We consider a cascade scheme (2s(2) <{\textendash}{\textendash}> 2p(2) <{\textendash}{\textendash}> 1s(3)) with a frequency upconversion ratio of 1.91. The upper transition is inverted and driven by an external field and lasing without inversion occurs at 616.4 nm provided that the collisional decay rates of the 1s(3) and 1s(5) levels overcome a certain threshold.}}, issn = {0946-2171}, doi = {10.1007/s00340-004-1694-0}, author = {V. Ahufinger and R Shuker and R. Corbal{\'a}n} } @article {PhysRevLett.94.130403, title = {Lattice Solitons in Quasicondensates}, journal = {Phys. Rev. Lett.}, volume = {94}, year = {2005}, month = {Apr}, pages = {130403}, publisher = {American Physical Society}, abstract = {We analyze finite temperature effects in the generation of bright solitons in condensates in optical lattices. We show that even in the presence of strong phase fluctuations solitonic structures with a well defined phase profile can be created. We propose a novel family of variational functions which describe well the properties of these solitons and account for the nonlinear effects in the band structure. We discuss also the mobility and collisions of these localized wave packets.}, doi = {10.1103/PhysRevLett.94.130403}, url = {http://link.aps.org/doi/10.1103/PhysRevLett.94.130403}, author = {V. Ahufinger and A. Sanpera} } @article {PhysRevA.72.012327, title = {One- and two-dimensional quantum walks in arrays of optical traps}, journal = {Phys. Rev. A}, volume = {72}, year = {2005}, month = {Jul}, pages = {012327}, publisher = {American Physical Society}, abstract = {We propose a different implementation of discrete-time quantum walks for a neutral atom in an array of optical microtraps or an optical lattice. We analyze a one-dimensional walk in position space, with the coin, the additional qubit degree of freedom that controls the displacement of the quantum walker, implemented as a spatially delocalized qubit, i.e., the coin is also encoded in position space. We analyze the dependence of the quantum walk on temperature and experimental imperfections such as shaking in the trap positions. Finally, combining a spatially delocalized qubit and a hyperfine qubit, we also give a scheme to realize a quantum walk on a two-dimensional square lattice with the possibility of implementing different coin operators.}, doi = {10.1103/PhysRevA.72.012327}, url = {http://link.aps.org/doi/10.1103/PhysRevA.72.012327}, author = {K. Eckert and J. Mompart and G. Birkl and M. Lewenstein} } @article {PhysRevA.70.062324, title = {Cavity QED quantum phase gates for a single longitudinal mode of the intracavity field}, journal = {Phys. Rev. A}, volume = {70}, year = {2004}, month = {Dec}, pages = {062324}, publisher = {American Physical Society}, abstract = {A single three-level atom driven by a longitudinal mode of a high-Q cavity is used to implement two-qubit quantum phase gates for the intracavity field. The two qubits are associated with the zero- and one-photon Fock states of each of the two opposite circular polarization states of the field. The three-level atom mediates the conditional phase gate provided the two polarization states and the atom interact in a V-type configuration and the two-photon resonance condition is satisfied. Microwave and optical implementations are discussed with gate fidelities being evaluated against several decoherence mechanisms such as atomic velocity fluctuations or the presence of a weak magnetic field. The use of coherent states for both polarization states is investigated to assess the entanglement capability of the proposed quantum gates.

}, doi = {10.1103/PhysRevA.70.062324}, url = {http://link.aps.org/doi/10.1103/PhysRevA.70.062324}, author = {R. Garc{\'\i}a-Maraver and R. Corbal{\'a}n and K. Eckert and S. Rebic and M. Artoni and J. Mompart} } @article {PhysRevA.69.053604, title = {Creation and mobility of discrete solitons in Bose-Einstein condensates}, journal = {Phys. Rev. A}, volume = {69}, year = {2004}, month = {May}, pages = {053604}, publisher = {American Physical Society}, abstract = {We analyze the generation and mobility of discrete solitons in Bose-Einstein condensates confined in an optical lattice under realistic experimental conditions. We discuss first the creation of one-dimensional discrete solitons, for both attractive and repulsive interatomic interactions. We then address the issue of their mobility, focusing our attention on the conditions for the experimental observability of the Peierls-Nabarro barrier. Finally we report on the generation of self-trapped structures in two and three dimensions. Discrete solitons may open alternative routes for the manipulation and transport of Bose-Einstein condensates.}, doi = {10.1103/PhysRevA.69.053604}, url = {http://link.aps.org/doi/10.1103/PhysRevA.69.053604}, author = {V. Ahufinger and A. Sanpera and P. Pedri and L. Santos and M. Lewenstein} } @booklet {doi:10.1117/12.589360, title = {Single three-level atoms for quantum information}, howpublished = {Proc. SPIE}, volume = {5622}, year = {2004}, pages = {430-434}, abstract = {A single three-level atom in interaction with a single longitudinal mode of a high-Q cavity is used to quantum engineer the intracavity field. In our proposal the quantum bit states correspond to the vacuum and single photon Fock states of each of two circular polarization states of the longitudinal mode. We show that for particular velocities of the three-level atom crossing the cavity it is possible to implement in one single step a two-qubit quantum phase gate between the two circular polarization states. Fidelity against several decoherence mechanisms such as atomc velocity fluctuations or the presence of a weak magnetic field along the cavity axis is analyzed.

}, doi = {10.1117/12.589360}, url = {http://dx.doi.org/10.1117/12.589360}, author = {J. Mompart and R. Garc{\'\i}a-Maraver and R. Corbal{\'a}n} } @article {PhysRevA.70.023606, title = {Three-level atom optics via the tunneling interaction}, journal = {Phys. Rev. A}, volume = {70}, year = {2004}, month = {Aug}, pages = {023606}, publisher = {American Physical Society}, abstract = {Three-level atom optics is introduced as a simple, efficient, and robust method to coherently manipulate and transport neutral atoms. The tunneling interaction among three trapped states allows us to realize the spatial analog of the stimulated Raman adiabatic passage, coherent population trapping, and electromagnetically induced transparency techniques and offers a wide range of possible applications. We investigate an implementation in optical microtrap arrays and show that under realistic parameters the coherent manipulation and transfer of neutral atoms among dipole traps could be realized in the millisecond range.}, doi = {10.1103/PhysRevA.70.023606}, url = {http://link.aps.org/doi/10.1103/PhysRevA.70.023606}, author = {K. Eckert and M. Lewenstein and R. Corbal{\'a}n and G. Birkl and W. Ertmer and J. Mompart} } @article {PhysRevLett.91.083901, title = {Cavity Solitons in Two-Level Lasers with Dense Amplifying Medium}, journal = {Phys. Rev. Lett.}, volume = {91}, year = {2003}, month = {Aug}, pages = {083901}, publisher = {American Physical Society}, abstract = {Local-field effects are known to induce bistability in dense optical media. We examine theoretically whether this property is preserved in broad-area cavities, and show that bistability between the homogeneous lasing and nonlasing states of the system persists provided a Fourier filtering technique is used to prevent off-axis emission. The resulting bistability gives rise to spatial light localization in the form of cavity solitons, which exhibit a particularly large degree of plasticity as a function of the characteristics of the addressing beam. This is the simplest laser able to sustain cavity solitons.}, doi = {10.1103/PhysRevLett.91.083901}, url = {http://link.aps.org/doi/10.1103/PhysRevLett.91.083901}, author = {V. Ahufinger and J. Garc{\'\i}a-Ojalvo and J. Mompart and M. C. Torrent and R. Corbal{\'a}n and R. Vilaseca} } @article {1464-4266-5-3-301, title = {Enlargement of the inversionless lasing domain by using broad-area cavities}, journal = {Journal of Optics B: Quantum and Semiclassical Optics}, volume = {5}, number = {3}, year = {2003}, pages = {201}, abstract = {We investigate analytically and numerically the role of diffraction in the operation of a broad-area inversionless laser in a cascade three-level configuration. Through a linear stability analysis of the trivial non-lasing solution and numerical integration of the corresponding Maxwell{\textendash}Schr{\"o}dinger equations, we show that off-axis emission allows stationary inversionless lasing over a cavity detuning range much larger than in small-aspect-ratio cavities and in conventionally inverted three-level lasers. In addition, we investigate inversionless lasing in a self-pulsing regime in the presence of diffraction, which leads to rich spatiotemporal dynamics.}, url = {http://stacks.iop.org/1464-4266/5/i=3/a=301}, author = {J. Mompart and M. C. Torrent and V. Ahufinger and J. Garc{\'\i}a-Ojalvo and R. Corbal{\'a}n and R. Vilaseca} } @article {1464-4266-5-3-311, title = {Gain without inversion at two symmetrical sidebands of resonance in cold free 87 Rb atoms: an experimental proposal}, journal = {Journal of Optics B: Quantum and Semiclassical Optics}, volume = {5}, number = {3}, year = {2003}, pages = {268}, abstract = {We propose an experiment for obtaining about 0.4\% inversionless gain at the sidebands of resonance in cold free 87 Rb atoms. This gain is of the same order of magnitude as the one already observed near resonance (Kitching and Hollberg 1999 Phys. Rev. A 59 4685).}, url = {http://stacks.iop.org/1464-4266/5/i=3/a=311}, author = {V. Ahufinger and R. Corbal{\'a}n} } @article {PhysRevLett.90.147901, title = {Quantum Computing with Spatially Delocalized Qubits}, journal = {Phys. Rev. Lett.}, volume = {90}, year = {2003}, month = {Apr}, pages = {147901}, publisher = {American Physical Society}, abstract = {We analyze the operation of quantum gates for neutral atoms with qubits that are delocalized in space, i.e., the computational basis states are defined by the presence of a neutral atom in the ground state of one out of two trapping potentials. The implementation of single-qubit gates as well as a controlled phase gate between two qubits is discussed and explicit calculations are presented for rubidium atoms in optical microtraps. Furthermore, we show how multiqubit highly entangled states can be created in this scheme.}, doi = {10.1103/PhysRevLett.90.147901}, url = {http://link.aps.org/doi/10.1103/PhysRevLett.90.147901}, author = {J. Mompart and K. Eckert and W. Ertmer and G. Birkl and M. Lewenstein} } @article {Mompart:03, title = {Quantum-jump statistical analysis of three-level systems with arbitrary coupling laser intensities and detunings}, journal = {J. Opt. Soc. Am. B}, volume = {20}, number = {11}, year = {2003}, month = {Nov}, pages = {2368{\textendash}2376}, publisher = {OSA}, abstract = {We develop the quantum-jump statistical tools required to analyze the probe response in three-level systems where the probe and driving lasers have arbitrary intensities and detunings. We apply these tools to investigate the appearance of two inversionless amplification sidebands in the probe spectrum as the driving laser intensity increases.}, keywords = {Coherent optical effects, Laser theory, Multiphoton processes}, doi = {10.1364/JOSAB.20.002368}, url = {http://josab.osa.org/abstract.cfm?URI=josab-20-11-2368}, author = {J. Mompart and R. Corbal{\'a}n} } @article {Ahufinger2002159, title = {Electromagnetically induced transparency in a Bose{\textendash}Einstein condensate}, journal = {Optics Communications}, volume = {211}, number = {1{\textendash}6}, year = {2002}, pages = {159 - 165}, abstract = {We report on the direct observation of the electromagnetically induced transparency (EIT) lineshape of cold 87Rb atoms above and below the transition temperature for Bose{\textendash}Einstein condensation (BEC). Similar results are observed in both temperature regimes, with an absorption reduction of about 60\%. Good agreement with a theoretical model is discussed.}, issn = {0030-4018}, doi = {http://dx.doi.org/10.1016/S0030-4018(02)01826-6}, url = {http://www.sciencedirect.com/science/article/pii/S0030401802018266}, author = {V. Ahufinger and R. Corbal{\'a}n and F. Cataliotti and S. Burger and F. Minardi and C. Fort} } @article {PhysRevA.66.042317, title = {Quantum computing in optical microtraps based on the motional states of neutral atoms}, journal = {Phys. Rev. A}, volume = {66}, year = {2002}, month = {Oct}, pages = {042317}, publisher = {American Physical Society}, abstract = {We investigate quantum computation with neutral atoms in optical microtraps where the qubit is implemented in the motional states of the atoms, i.e., in the two lowest vibrational states of each trap. The quantum gate operation is performed by adiabatically approaching two traps and allowing tunneling and cold collisions to take place. We demonstrate the capability of this scheme to realize a square root of swap gate, and address the problem of double occupation and excitation to other unwanted states. We expand the two-particle wave function in an orthonormal basis and analyze quantum correlations throughout the whole gate process. Fidelity of the gate operation is evaluated as a function of the degree of adiabaticity in moving the traps. Simulations are based on rubidium atoms in state-of-the-art optical microtraps with quantum gate realizations in the few tens of milliseconds duration range.}, doi = {10.1103/PhysRevA.66.042317}, url = {http://link.aps.org/doi/10.1103/PhysRevA.66.042317}, author = {K. Eckert and J. Mompart and X. X. Yi and J. Schliemann and D. Bruss and G. Birkl and M. Lewenstein} } @article {PhysRevLett.88.023603, title = {Coherent Population Trapping in Two-Electron Three-Level Systems with Aligned Spins}, journal = {Phys. Rev. Lett.}, volume = {88}, year = {2001}, month = {Dec}, pages = {023603}, publisher = {American Physical Society}, abstract = {The possibility of coherent population trapping in two electron states with aligned spins (orthosystem) is evidenced. From the analysis of a three-level atomic system containing two electrons, and driven by the two laser fields needed for coherent population trapping, a conceptually new kind of dark state appears. The properties of this trapping are physically interpreted in terms of a dark hole, instead of a dark two-electron state. This technique, among many other applications, offers the possibility of measuring, with subnatural resolution, some superposition-state matrix elements of the electron-electron correlation that due to their time dependent nature are inaccessible by standard measuring procedures.}, doi = {10.1103/PhysRevLett.88.023603}, url = {http://link.aps.org/doi/10.1103/PhysRevLett.88.023603}, author = {J. Mompart and R. Corbal{\'a}n and L. Roso} } @article {PhysRevA.64.033802, title = {Electromagnetically induced transparency with a standing-wave drive in the frequency up-conversion regime}, journal = {Phys. Rev. A}, volume = {64}, year = {2001}, month = {Aug}, pages = {033802}, publisher = {American Physical Society}, abstract = {We study electromagnetically induced transparency for a probe traveling-wave (TW) laser field in closed Doppler-broadened three-level systems driven by a standing-wave (SW) laser field of moderate intensity (its Rabi frequencies are smaller than the Doppler width of the driven transition). We show that probe windows of transparency occur for values of the probe to drive field frequency ratio R close to half-integer values. For optical transitions and typical values of Doppler broadening for atoms in a vapor cell, we show that for R>1 a SW drive field is appreciably more efficient than a TW drive in inducing probe transparency. As examples, we consider parameters for real cascade schemes in barium atoms with R≈1.5 and in beryllium atoms with R≈3.5 showing that probe transmission values well above 50\% are possible for conditions in which it is almost negligible either without driving field or with only one of the TW components of the drive. We show that a strongly asymmetric drive having two TW components with unequal intensities is even more eficient than a symmetric SW drive in inducing probe transparency. The case of arbitrary probe intensity is also considered.}, doi = {10.1103/PhysRevA.64.033802}, url = {http://link.aps.org/doi/10.1103/PhysRevA.64.033802}, author = {F. Silva and J. Mompart and V. Ahufinger and R. Corbal{\'a}n} } @article {PhysRevA.63.063810, title = {Generalized Einstein B coefficients for coherently driven three-level systems}, journal = {Phys. Rev. A}, volume = {63}, year = {2001}, month = {May}, pages = {063810}, publisher = {American Physical Society}, abstract = {Generalized Einstein B coefficients for coherently driven closed three-level systems are introduced by means of the quantum-jump technique. The nonreciprocity between stimulated emission and absorption for both one-photon and two-photon gain and loss processes has been studied and quantified in terms of the rates of the particular incoherent processes present in each three-level system. Some general properties of these generalized Einstein B coefficients have been found. In particular, whenever the generalized Einstein B coefficient for one-photon gain overcomes that for one-photon loss then the generalized Einstein B coefficient for two-photon loss overcomes that for two-photon gain, and vice versa. Finally, we have obtained simple analytical expressions indicating the way to maximize the asymmetry between stimulated emission and absorption coefficients either for one-photon or for two-photon processes.}, doi = {10.1103/PhysRevA.63.063810}, url = {http://link.aps.org/doi/10.1103/PhysRevA.63.063810}, author = {J. Mompart and R. Corbal{\'a}n} } @article {0295-5075-51-3-286, title = {Electromagnetically induced transparency in Doppler-broadened three-level systems with resonant standing-wave drive}, journal = {EPL (Europhysics Letters)}, volume = {51}, number = {3}, year = {2000}, pages = {286}, abstract = {We study electromagnetically induced transparency for a probe travelling-wave (TW) laser field in closed Doppler-broadened three-level systems driven by a resonant standing-wave (SW) laser field of moderate intensity (its Rabi frequencies are smaller than the Doppler width of the driven transition). We show that probe windows of transparency occur only for values of the probe-to-drive field frequency ratio R close to half-integer values. For optical transitions and typical values of Doppler broadening for atoms in a vapor cell, we show that for R > 1 a SW drive field is appreciably more efficient than a TW driving in inducing probe transparency. As an example, we consider parameters for a real closed cascade scheme in barium atoms with R $\#$$\#$IMG$\#$$\#$ [http://ej.iop.org/icons/Entities/simeq.gif] {simeq} 1.5 showing that probe transmission values of 50\% are possible for cases in which the transmission is almost negligible either without driving field or with only one of the TW components of the drive.}, url = {http://stacks.iop.org/0295-5075/51/i=3/a=286}, author = {F. Silva and J. Mompart and V. Ahufinger and R. Corbal{\'a}n} } @article {1464-4266-2-3-201, title = {Lasing without inversion}, journal = {Journal of Optics B: Quantum and Semiclassical Optics}, volume = {2}, number = {3}, year = {2000}, pages = {R7}, abstract = {This review paper is devoted to amplification and lasing without population inversion involving atomic transitions in gas media. We start by discussing the main motivation in inversionless lasing research, namely, the generation of short-wavelength laser light. Then, we review the basic physics of inversionless lasing in two-level and, eventually, in three- and multilevel atomic configurations. Finally, we summarize the current state of the art of LWI experiments and indicate the main difficulties with respect to short-wavelength laser generation.}, url = {http://stacks.iop.org/1464-4266/2/i=3/a=201}, author = {J. Mompart and R. Corbal{\'a}n} } @article {PhysRevA.61.053814, title = {Lasing without inversion in three-level systems without external coherent driving}, journal = {Phys. Rev. A}, volume = {61}, year = {2000}, month = {Apr}, pages = {053814}, publisher = {American Physical Society}, abstract = {We have studied an incoherently pumped laser operating with a Doppler-broadened three-level system placed in a doubly resonant cavity. This system generates two laser fields, one of them without population inversion. Both ladder and V-type three-level schemes are considered with a ratio R=ωα/ωβ of inversionless laser frequency ωα to ordinary laser frequency ωβ of R=0.67 and R=1.88, respectively. Dual-wavelength lasing extends up to Doppler-broadening values for optical transitions of atoms in a vapor cell. Some considerations for the practical realization of this dual-wavelength laser are discussed.}, doi = {10.1103/PhysRevA.61.053814}, url = {http://link.aps.org/doi/10.1103/PhysRevA.61.053814}, author = {V. Ahufinger and J. Mompart and R. Corbal{\'a}n} } @article {1464-4266-2-3-321, title = {Propagation effects on lasing without population inversion}, journal = {Journal of Optics B: Quantum and Semiclassical Optics}, volume = {2}, number = {3}, year = {2000}, pages = {359}, abstract = {We study propagation effects on lasing without population inversion in a Doppler-broadened V -type three-level system. In particular, we focus our analysis on frequency up-conversion lasing without inversion in atomic rubidium. In an atomic beam configuration, we show that it is possible to increase notably the probe gain per single pass through the active medium by detuning driving and probe fields out of one-photon resonance but maintaining the two-photon resonance condition. In a vapour cell configuration, we show that due to propagation effects the probe gain per single pass depends strongly on the driving field intensity at the entrance of the active medium. In fact, for appropriate parameter values, it is possible to reach values of the probe gain per single pass of around 40\%. For this last case, we have considered the feedback of a ring laser cavity.}, url = {http://stacks.iop.org/1464-4266/2/i=3/a=321}, author = {J. Mompart and V. Ahufinger and R. Corbal{\'a}n and F Prati} } @article {PhysRevA.59.3038, title = {Giant pulse lasing in three-level systems}, journal = {Phys. Rev. A}, volume = {59}, year = {1999}, month = {Apr}, pages = {3038{\textendash}3043}, publisher = {American Physical Society}, abstract = {We propose an alternative method to Q switching for generating giant pulses of laser light in three-level media. This mehod is based on the presence of an external coherent field driving one transition to allow the accumulation of a large population inversion in the other transition without laser oscillation even in a cavity with high-Q factor. The switching off of the external coherent field causes the development of the giant pulse. Different time profiles for the switching off of the external field have been investigated.}, doi = {10.1103/PhysRevA.59.3038}, url = {http://link.aps.org/doi/10.1103/PhysRevA.59.3038}, author = {J. Mompart and R. Corbal{\'a}n and R. Vilaseca} } @article { ISI:000082230000013, title = {Inversionless amplification with standing-wave drive}, journal = {Laser Physics}, volume = {9}, number = {4}, year = {1999}, month = {JUL-AUG}, pages = {858-865}, publisher = {{INTERPERIODICA}}, address = {{PO BOX 1831, BIRMINGHAM, AL 35201-1831 USA}}, abstract = {We study amplification without inversion in closed Doppler-broadened three-level systems driven by a standing-wave (SW) laser field. Our results are compared to those of the well-known case of a traveling-wave drive. A distinguishing feature of the SW case is the contribution to probe the gain of multiphoton processes involving one probe photon and several pump photons, with alternating absorption and emission from the two counterpropagating pump components. These processes are only weakly affected by Doppler broadening for probe to drive frequency ratios R equal to integer numbers. Examples of inversionless amplification with frequency up-conversion ratios R = 3 and R = 4 are presented.}, issn = {1054-660X}, author = {F. Silva and V. Ahufinger and J. Mompart and R. Corbal{\'a}n} } @booklet {doi:10.1117/12.358396, title = {Lasing without inversion: realities and prospects}, howpublished = {Proc. SPIE}, volume = {3572}, year = {1999}, pages = {33-44}, abstract = {We review amplification and lasing without inversion (AWI and LWI) in homogeneously broadened closed three-level systems in the framework of both density-matrix and quantum- jump formalisms. With the density-matrix formalism: (1) we study the nature of quantum interference in these systems; (2) determine analytically the conditions for AWI and locate the position of maxima and minima in the probe absorption spectrum; and (3) study various regimes of lasing, namely, continuous wave, self-pulsing and giant pulse lasing. Within the quantum-jump formalism we calculate the relative probabilities of the various physical processes responsible for probe field amplification and absorption.}, doi = {10.1117/12.358396}, url = {http://dx.doi.org/10.1117/12.358396}, author = {J. Mompart and R. Corbal{\'a}n} } @article {PhysRevA.60.614, title = {Lasing without inversion with frequency up-conversion in a Doppler-broadened V-type three-level system}, journal = {Phys. Rev. A}, volume = {60}, year = {1999}, month = {Jul}, pages = {614{\textendash}620}, publisher = {American Physical Society}, abstract = {We study lasing without inversion in a Doppler-broadened V-type three-level system in the frequency up-conversion regime. We show that the ratio R=ωl/ωd of generated laser frequency to driving laser frequency that can be achieved using a vapor cell is modest (R<~2). Our analysis demonstrates that using an atomic beam the frequency of the generated field can be substantially larger than that of the driving field R\~{}10. Two different configurations are considered: (a) copropagating driving and laser beams orthogonal to the atomic beam, and (b) counterpropagating driving and atomic beams and laser beam at a determined angle with the driving beam.}, doi = {10.1103/PhysRevA.60.614}, url = {http://link.aps.org/doi/10.1103/PhysRevA.60.614}, author = {V. Ahufinger and J. Mompart and R. Corbal{\'a}n} } @article { ISI:000082230000012, title = {Quantum interference and quantum-Zeno effect in amplification without inversion}, journal = {Laser Physics}, volume = {9}, number = {9}, year = {1999}, month = {JUL-AUG}, pages = {844-857}, publisher = {{INTERPERIODICA}}, address = {{PO BOX 1831, BIRMINGHAM, AL 35201-1831 USA}}, abstract = {We analyze amplification without inversion (AWI) in different homogeneously broadened closed three-level systems in the framework of both density-matrix and quantum-jump formalisms. With the density-matrix formalism we study the nature of quantum interference in these systems; determine analytically the condition for AWI and locate the position of maxima and minima in the probe absorption spectrum. Within the quantum-jump formalism we calculate the relative probabilities of the various physical processes responsible for probe field amplification and absorption, and analyze the role of the quantum-Zeno effect in AWI. The result is that AWI in the h and p schemes is due to one-photon processes while for V and Lambda schemes are due to two-photon processes. We also show that AWI in V and h schemes always occurs in the quantum-Zeno regime, while this regime is not necessary for AWI in the Lambda and p schemes.}, issn = {1054-660X}, author = {J. Mompart and V. Ahufinger and F. Silva and R. Corbal{\'a}n and R. Vilaseca} } @article {198, title = {Quantum-jump approach to dipole dephasing: Application to inversionless amplification}, journal = {The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics}, volume = {5}, number = {3}, year = {1999}, pages = {351-356}, publisher = {EDP Sciences, Springer-Verlag}, abstract = {We present a model for simulating atomic dipole dephasing within the Monte-Carlo wave function formalism which leads to the same results as the standard density-matrix formalism. In this model dipole dephasing processes are accounted by quantum-jumps into one of the atomic energy eigenstates. This fact allows us to obtain analytical expressions for the effects of elastic collisions on the various physical processes responsible for amplification without population inversion in a cascade three-level atomic configuration.}, keywords = {Monte-Carlo and statistical methods, Photon interactions with atoms, Quantum optics}, issn = {1434-6060}, doi = {10.1007/PL00021600}, url = {http://dx.doi.org/10.1007/PL00021600}, author = {J. Mompart and R. Corbal{\'a}n} } @article {1464-4266-1-1-026, title = {Transverse profile effects on lasing without population inversion}, journal = {Journal of Optics B: Quantum and Semiclassical Optics}, volume = {1}, number = {1}, year = {1999}, pages = {146}, abstract = {We analyse the effects of a Gaussian transverse profile for the driving and laser fields on lasing without population inversion, in four different three-level schemes. We show that the lasing domains can be considerably reduced with respect to the plane-wave case in the V and in the cascade configuration driven in the upper transition, while in the $\#$$\#$IMG$\#$$\#$ [http://ej.iop.org/icons/common/Lambda.gif] {Lambda} and in the cascade configuration driven in the lower transition such domains are always larger in the Gaussian case.}, url = {http://stacks.iop.org/1464-4266/1/i=1/a=026}, author = {F Prati and J. Mompart and R. Corbal{\'a}n} } @article {1355-5111-10-2-009, title = {Interpretation of transient V scheme amplification without inversion}, journal = {Quantum and Semiclassical Optics: Journal of the European Optical Society Part B}, volume = {10}, number = {2}, year = {1998}, pages = {355}, abstract = {Amplification without inversion (AWI) in a resonant V-type system is studied using a dressed basis which reduces the coherent interaction of both involved optical transitions to that of a single two-level system. The transient AWI recently reported through a numerical analysis of the density matrix equations of the V-system in the bare atom basis (Zhu Y 1996 Phys. Rev . A 53 2742) is damped Rabi nutation with transient population inversion in this dressed basis. Although the transient AWI in the bare state basis occurs both with and without an incoherent pump field, the integrated probe gain is positive only in the first case.}, url = {http://stacks.iop.org/1355-5111/10/i=2/a=009}, author = {J. Mompart and C. Peters and R. Corbal{\'a}n} } @article {Mompart1998133, title = {Inversionless amplification in three-level systems: dressed states quantum interference and quantum-jump analyses}, journal = {Optics Communications}, volume = {156}, number = {1{\textendash}3}, year = {1998}, pages = {133 - 144}, abstract = {We investigate amplification without inversion (AWI) in different three-level systems driven by an on-resonance coherent field and identify the elements that contribute to destructive or constructive dressed states quantum interference in the probe field absorption spectrum. We determine analytically the conditions for \{AWI\} at the probe field line center and at the wings of the resonance region. For this latter case, we explicitly locate the position of the maximum gain as a function of the probe field detuning. Finally, through a quantum-jump analysis, we find that \{AWI\} at the wings of the resonance region is due to an asymmetry between one-photon-stimulated emission and absorption processes, in contrast with \{AWI\} at the line center which arises from the contribution of two-photon gain.}, keywords = {Quantum jumps}, issn = {0030-4018}, doi = {http://dx.doi.org/10.1016/S0030-4018(98)00433-7}, url = {http://www.sciencedirect.com/science/article/pii/S0030401898004337}, author = {J. Mompart and R. Corbal{\'a}n} } @article {Mompart1998299, title = {Lasing without inversion in the V-type three-level system under the two-photon resonance condition}, journal = {Optics Communications}, volume = {147}, number = {4{\textendash}6}, year = {1998}, pages = {299 - 304}, abstract = {We investigate lasing without inversion in the closed V-type three-level system with off-resonant driving and laser fields by using both density-matrix and quantum-jump approaches. We demonstrate analytically and numerically that, under the two-photon resonance condition, it is possible to relax the severe conditions between spontaneous population decay and incoherent pump rates needed in the resonant case. We extend the same analysis to the remaining three-level systems.}, keywords = {atomic coherence}, issn = {0030-4018}, doi = {http://dx.doi.org/10.1016/S0030-4018(97)00490-2}, url = {http://www.sciencedirect.com/science/article/pii/S0030401897004902}, author = {J. Mompart and R. Corbal{\'a}n and R. Vilaseca} } @article {PhysRevA.57.2163, title = {Lasing without inversion in three-level systems: Self-pulsing in the cascade schemes}, journal = {Phys. Rev. A}, volume = {57}, year = {1998}, month = {Mar}, pages = {2163{\textendash}2168}, publisher = {American Physical Society}, abstract = {Lasing without inversion (LWI) in specific models of closed three-level systems is analyzed in terms of nonlinear dynamics. From a linear stability analysis of the trivial nonlasing solution of the homogeneously broadened systems with on-resonance driving and laser fields, we find that, near lasing threshold, resonant closed Λ and V schemes yield continuous-wave LWI while resonant cascade schemes can give rise to self-pulsing LWI. The origin of this different behavior is discussed. For parameters of a real cascade system in atomic 138Ba we check numerically that the self-pulsing solution is stable in a broad range of nonzero detunings. It is shown that the self-pulsing emission can still be observed when the typical residual Doppler broadening of an atomic beam is taken into account.}, doi = {10.1103/PhysRevA.57.2163}, url = {http://link.aps.org/doi/10.1103/PhysRevA.57.2163}, author = {J. Mompart and C. Peters and R. Corbal{\'a}n} } @article {1355-5111-10-2-005, title = {Self-pulsing lasing without inversion in the double-Λ scheme}, journal = {Quantum and Semiclassical Optics: Journal of the European Optical Society Part B}, volume = {10}, number = {2}, year = {1998}, pages = {309}, abstract = {Lasing without inversion (LWI) is investigated from a nonlinear dynamics point of view for an atomic system with three coupled J = 0-1 transitions. The driving and generated fields couple two of these transitions defining a double- $\#$$\#$IMG$\#$$\#$ [http://ej.iop.org/images/1355-5111/10/2/005/img7.gif] scheme. In addition, two incoherent pump fields are acting on the system. We find that LWI can occur not only in a continuous wave regime but also in a self-pulsing regime. A clear physical interpretation of the origin of this self-pulsing LWI is given. We obtain analytically the threshold driving field intensity needed to achieve both continuous wave and self-pulsing LWI emission. For large enough cavity losses, the system can reach either continuous wave or self-pulsing regimes by only changing the driving field intensity.}, url = {http://stacks.iop.org/1355-5111/10/i=2/a=005}, author = {R. Corbal{\'a}n and J. Mompart and R. Vilaseca and E Arimondo} } @article {1355-5111-10-4-009, title = {Self-pulsing lasing without inversion in the double-Λ scheme}, journal = {Quantum and Semiclassical Optics: Journal of the European Optical Society Part B}, volume = {10}, number = {4}, year = {1998}, pages = {661}, abstract = {In this recently published article the address of the fourth author of this article was incorrectly stated. The correction affiliation for Professor Arimondo should read; Dipartimento di Fisica and Istituto Nazionale di Fisica della Materia, Unit{\'a} di Pisa, Universit{\'a} di Pisa, I-56100 Pisa, Italy.}, url = {http://stacks.iop.org/1355-5111/10/i=4/a=009}, author = {R. Corbal{\'a}n and J. Mompart and R. Vilaseca and E Arimondo} }