arXiv subjects

J. Mompart

Publications and source records attributed to J. Mompart.

At least 19 recordsLinked to original sources

arXiv2020

Roadmap on Atomtronics: State of the art and perspective

Atomtronics deals with matter-wave circuits of ultra-cold atoms manipulated through magnetic or laser-generated guides with different shapes and intensities. In this way, new types of quantum networks can be constructed, in which coherent fluids are controlled with the know-how developed in the atomic and molecular physics community. In particular, quantum devices with enhanced precision, control and flexibility of their operating conditions can be accessed. Concomitantly, new quantum simulators and emulators harnessing on the coherent current flows can also be developed. Here, we survey the landscape of atomtronics-enabled quantum technology and draw a roadmap for the field in the near future. We review some of the latest progresses achieved in matter-wave circuits design and atom-chips. Atomtronic networks are deployed as promising platforms for probing many-body physics with a new angle and a new twist. The latter can be done both at the level of equilibrium and non-equilibrium situations. Numerous relevant problems in mesoscopic physics, like persistent currents and quantum transport in circuits of fermionic or bosonic atoms, are studied through a new lens. We summarize some of the atomtronics quantum devices and sensors. Finally, we discuss alkali-earth and Rydberg atoms as potential platforms for the realization of atomtronic circuits with special features.

cond-mat.quant-gas↗

arXiv2020

Interaction-induced topological properties of two bosons in flat-band systems

In flat-band systems, destructive interference leads to the localization of non-interacting particles and forbids their motion through the lattice. However, in the presence of interactions the overlap between neighbouring single-particle localized eigenstates may enable the propagation of bound pairs of particles. In this work, we show how these interaction-induced hoppings can be tuned to obtain a variety of two-body topological states. In particular, we consider two interacting bosons loaded into the orbital angular momentum $l=1$ states of a diamond-chain lattice, wherein an effective $\pi$ flux may yield a completely flat single-particle energy landscape. In the weakly-interacting limit, we derive effective single-particle models for the two-boson quasiparticles which provide an intuitive picture of how the topological states arise. By means of exact diagonalization calculations, we benchmark these states and we show that they are also present for strong interactions and away from the strict flat-band limit. Furthermore, we identify a set of doubly localized two-boson flat-band states that give rise to a special instance of Aharonov-Bohm cages for arbitrary interactions.

cond-mat.quant-gas↗

arXiv2020

Experimental observation of Aharonov-Bohm caging using orbital angular momentum modes in optical waveguides

The discovery of artificial gauge fields, controlling the dynamics of uncharged particles that otherwise elude the influence of standard electric or magnetic fields, has revolutionized the field of quantum simulation. Hence, developing new techniques to induce those fields is essential to boost quantum simulation in photonic structures. Here, we experimentally demonstrate in a photonic lattice the generation of an artificial gauge field by modifying the input state, overcoming the need to modify the geometry along the evolution or imposing the presence of external fields. In particular, we show that an effective magnetic flux naturally appears when light beams carrying orbital angular momentum are injected into waveguide lattices with certain configurations. To demonstrate the existence of that flux, we measure the resulting Aharonov-Bohm caging effect. Therefore, we prove the possibility of switching on and off artificial gauge fields by changing the topological charge of the input state, paving the way to access different topological regimes in one single structure, which represents an important step forward for optical quantum simulation.

physics.optics↗

arXiv2019

Coherent spin mixing via spin-orbit coupling in Bose gases

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 quasi-momentum space, where the effective spin dependence of the collisions that emerges 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.

cond-mat.quant-gas↗

arXiv2019

Second-order topological corner states with ultracold atoms carrying orbital angular momentum in optical lattices

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 non-trivial 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's phases of the bands of first-order edge states.

cond-mat.quant-gas↗

arXiv2019

Roadmap on STIRAP applications

STIRAP (Stimulated Raman Adiabatic Passage) is a powerful laser-based method, usually involving two photons, for efficient and selective transfer of population 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, as of about the year 2000, the unique capabilities of STIRAP and its robustness with respect to small variations of some experimental parameters stimulated many researchers to apply the scheme in a variety of other fields of physics. The successes of these efforts are documented in this collection of articles.

quant-ph↗

arXiv2019

Quantum magnetism with ultracold bosons carrying orbital angular momentum

We show how strongly correlated ultracold bosonic atoms loaded in specific orbital angular momentum states of arrays of cylindrically symmetric potentials can realize a variety of spin-1/2 models of quantum magnetism. We consider explicitly the dependence of the effective couplings on the geometry of the system and demonstrate that several models of interest related to a general $XYZ$ Heisenberg model with external field can be obtained. Furthermore, we discuss how the relative strength of the effective couplings can be tuned and which phases can be explored by doing so in realistic setups. Finally, we address questions concerning the experimental read-out and implementation and we argue that the stability of the system can be enhanced by using ring-shaped trapping potentials.

quant-ph↗

arXiv2018

Quantum sensing using imbalanced counter-rotating Bose--Einstein condensate modes

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 non-linear 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.

quant-ph↗

arXiv2018

Topological edge states and Aharanov-Bohm caging with ultracold atoms carrying orbital angular momentum

We show that bosonic atoms loaded into orbital angular momentum $l=1$ states of a lattice in a diamond-chain geometry provides a flexible and simple platform for exploring a range of topological effects. This system exhibits robust edge states, and the relative phases arising naturally in the tunnelling amplitudes lead to the appearance of Aharanov-Bohm caging in the lattice. We discuss how these properties can be realised and observed in ongoing experiments.

physics.atom-ph↗

arXiv2018

Topological edge states with ultracold atoms carrying orbital angular momentum in a diamond chain

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 and give rise to a topologically non-trivial band structure and protected edge states. 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.

physics.atom-ph↗

arXiv2018

Mode-division (de)multiplexing using adiabatic passage and supersymmetric waveguides

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 $\mathcal{F}>0.90$ are obtained for a broad range of geometrical parameter values and light's wavelengths, reaching $\mathcal{F}=0.99$ for optimized values.

physics.optics↗

arXiv2018

Continuous supersymmetric transformations in optical waveguides

We introduce continuous supersymmetric transformations to manipulate the modal content in systems of optical waveguides, providing a systematic method to design efficient and robust integrated devices such as tapered waveguides, single-waveguide mode filters, beam splitters and interferometers. These transformations connect superpartner profiles by smoothly modifying the transverse index profile along the propagation direction and, if the modification is performed adiabatically, the transverse electric modes evolve adapting their shape and propagation constant without being coupled to other guided or radiated modes. Numerical simulations show that very high fidelities are obtained for a broad range of devices lengths and light's wavelengths.

physics.optics↗

arXiv2017

Trapping of Bose-Einstein condensates in a three-dimensional dark focus generated by conical refraction

We present an efficient three-dimensional dark-focus optical trapping potential for neutral atoms and Bose-Einstein condensates. This "optical bottle" is created by a single blue-detuned light field exploiting the phenomenon of conical refraction occurring in biaxial crystals. The conversion of a Gaussian input beam to the bottle beam has an efficiency of close to 100 % and the optical setup requires the addition of the biaxial crystal and a circular polarizer only. Based on the conical-refraction theory, we derive the general form of the potential, the trapping frequencies, and the potential barrier heights. We present experiments on confining a $^{87}$Rb Bose-Einstein condensate in three dimensions. We determine the trap shape, the vibrational frequencies along the weak axis, as well as the lifetime of ultracold atoms in this type of potential.

cond-mat.quant-gas↗

arXiv2017

Engineering of orbital angular momentum supermodes in coupled optical waveguides

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 it out, allowing for the design of OAM mode clonners and inverters.

physics.optics↗

arXiv2017

Single atom edge-like states via quantum interference

We demonstrate how quantum interference may lead to the appearance of robust edge-like states of a single ultracold atom in a two-dimensional optical ribbon. We show that these states can be engineered either within the manifold of local ground states of the sites forming the ribbon, or of states carrying one unit of angular momentum. In the former case, we show that the implementation of edge-like states can be extended to other geometries, such as tilted square lattices. In the latter case, we suggest to use the winding number associated to the angular momentum as a synthetic dimension.

quant-ph↗

arXiv2016

Geometrically induced complex tunnelings for ultracold atoms carrying orbital angular momentum

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.

cond-mat.quant-gas↗

arXiv2015

Blue-detuned optical ring trap for Bose-Einstein condensates based on conical refraction

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 $^{87}$Rb Bose-Einstein condensate trapped inside the Poggendorff ring which are in good agreement with corresponding experimental results.

physics.atom-ph↗

arXiv2014

Polarization tailored novel vector beams based on conical refraction

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 an input beam.

physics.optics↗