arXiv subjects

Veronica Ahufinger

Publications and source records attributed to Veronica Ahufinger.

13 recordsLinked to original sources

arXiv2022

Spatially strongly confined atomic excitation via two dimensional stimulated Raman adiabatic passage

We consider a method of sub-wavelength superlocalization and patterning of atomic matter waves via a two dimensional stimulated Raman adiabatic passage (2D STIRAP) process. An atom initially prepared in its ground level interacts with a doughnut-shaped optical vortex pump beam and a traveling wave Stokes laser beam with a constant (top-hat) intensity profile in space. The beams are sent in a counter-intuitive temporal sequence, in which the Stokes pulse precedes the pump pulse. The atoms interacting with both the traveling wave and the vortex beam are transferred to a final state through the 2D STIRAP, while those located at the core of the vortex beam remain in the initial state, creating a super-narrow nanometer scale atomic spot in the spatial distribution of ground state atoms. By numerical simulations we show that the 2D STIRAP approach outperforms the established method of coherent population trapping, yielding much stronger confinement of atomic excitation. Numerical simulations of the Gross-Pitaevskii equation show that using such a method one can create 2D bright and dark solitonic structures in trapped Bose-Einstein condensates (BECs). The method allows one to circumvent the restriction set by the diffraction limit inherent to conventional methods for formation of localized solitons, with a full control over the position and size of nanometer resolution defects.

quant-ph↗

arXiv2019

Topological state engineering via supersymmetric transformations

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 (SUSY) 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 SUSY transformations are applied to their host system. In particular, we show how SUSY-induced phase transitions can selectively suspend and re-establish 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 SUSY-inspired techniques as a powerful and versatile tool for topological state engineering.

physics.optics↗

arXiv2016

Quantum optics and frontiers of physics: The third quantum revolution

The year 2015 was the International Year of Light. It marked, however, also the 20th anniversary of the first observation of Bose-Einstein condensation in atomic vapors by Eric Cornell, Carl Wieman and Wolfgang Ketterle. This discovery can 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 focus issue on "Quantum Optics in the International Year of Light" 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 "Ultracold atoms in optical lattices: Simulating quantum many-body systems" [1]. The book, however, was published in 2012, and many things has happened since then -- the present essay is therefore upgraded to include the latest developments.

cond-mat.quant-gas↗

arXiv2014

Coherent injecting, extracting, and velocity filtering of neutral atoms in a ring trap via spatial adiabatic passage

We introduce here 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 Schrödinger equation with state-of-the-art parameter values for $^{87}$Rb atoms and an optical dipole ring trap.

physics.atom-ph↗

arXiv2014

Single-atom interferometer based on two-dimensional spatial adiabatic passage

In this work we propose a novel 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 wavefunction 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.

quant-ph↗

arXiv2014

Spatial adiabatic passage processes in sonic crystals with linear defects

We investigate spatial adiabatic passage processes for sound waves 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.

cond-mat.mtrl-sci↗

arXiv2014

Tunneling-induced angular momentum for single cold atoms

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 $\pm\hbar$. This process is discussed in terms of the asymptotic eigenstates of the individual wells and the results have been checked by simulations of the full two-dimensional Schrödinger equation.

quant-ph↗

arXiv2011

Spin effects in Bose-Glass phases

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 but still insulating phase. The phase diagram for finite hopping is also calculated with the Gutzwiller approximation. The bosons' spin degree of freedom introduces 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.

cond-mat.quant-gas↗

arXiv2011

Disordered spinor Bose-Hubbard model

We study the zero temperature phase diagram of the disordered spin-1 Bose-Hubbard model in a 2-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 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 n+1 lobes for n odd. Disorder in the scalar Hubbard interaction inhibits Mott insulator regions for occupation larger than a critical value.

cond-mat.other↗

arXiv2007

Ultracold atomic gases in optical lattices: mimicking condensed matter physics and beyond

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 "artificial" 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.

cond-mat.other↗

arXiv2005

Trapped ion chain as a neural network

We demonstrate the possibility of realizing a neural network in a chain of trapped ions with induced long range interactions. Such models permit to store information distributed over the whole system. The storage capacity of such network, which depends on the phonon spectrum of the system, can be controlled by changing the external trapping potential and/or by applying longitudinal local magnetic fields. The system properties suggest the possibility of implementing robust distributed realizations of quantum logic.

cond-mat.dis-nn↗

arXiv2005

Disordered complex systems using cold gases and trapped ions

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 revisited here. 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.

quant-ph↗

arXiv2005

Quantum Information Processing in Disordered and Complex Quantum Systems

We investigate quantum information processing and manipulations in disordered systems of ultracold atoms and trapped ions. First, we demonstrate generation of entanglement and local realization of quantum gates in a quantum spin glass system. Entanglement in such systems attains significantly high values, after quenched averaging, and has a stable positive value for arbitrary times. Complex systems with long range interactions, such as ion chains or dipolar atomic gases, can be modeled by neural network Hamiltonians. In such systems, we find the characteristic time of persistence of quenched averaged entanglement, and also find the time of its revival.

quant-ph↗