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 {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 {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 {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 {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.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} }