Publications (7)18.96 Total impact
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ABSTRACT: Recent progress in quantum optics and quantum information has brought the longstanding dreams of quantum simulators and even quantum computers (almost) within reach. Here, we review some current theoretical pathways supporting experimental progress towards quantum simulators. In this, we focus mainly on topological aspects and numerical studies of quantum computation.  [Show abstract] [Hide abstract]
ABSTRACT: We present a systematic study of the generation of the array of optical or matterwave kinks (dark solitons) in the ground state (GS) of binary systems. We consider quasionedimensional systems described by a pair of nonlinear Schrödinger (NLSE’s) or GrossPitaevskii equations (GPE’s), which are coupled by the linear mixing, with local strength Ω, and by nonlinear interactions. We assume the selfrepulsive nonlinearity in both components, and include the effects of a harmonic trapping potential, while the nonlinear interaction between the components may be both repulsive and attractive. The model may be realized in terms of periodically modulated slab waveguides in nonlinear optics and also in BoseEinstein condensates. Depending on the sign and strengths of the linear and nonlinear couplings between the components, the ground states in such binary systems may be symmetric, antisymmetric, or asymmetric. In this work, we introduce a periodic spatial modulation of the linear coupling, making Ω an odd or even function of the coordinate (x). The sign flips of Ω(x) strongly modify the structure of the GS in the binary system, as the relative sign of its components tends to lock to the local sign of Ω. Using a systematic numerical analysis and an analytic approximation, we demonstrate that the GS of the trapped system contains one or several kinks (dark solitons) in one component, while the other component does not change its sign. The final results are presented in the form of maps showing the number of kinks in the GS as a function of the system’s parameters, with the odd (even) modulation function giving rise to the odd (even) number of the kinks. The modulation of Ω(x) also produces a strong effect on the transition between states with nearly equal and strongly unequal amplitudes of the two components.  [Show abstract] [Hide abstract]
ABSTRACT: We observe signatures of disorderinduced order in onedimensional XY spin chains with an external sitedependent uniaxial random field within the XY plane. We numerically investigate signatures of a quantum phase transition at T=0, in particular, an upsurge of the magnetization in the direction orthogonal to the external magnetic field and the scaling of the block entropy with the amplitude of this field. Also, we discuss possible realizations of this effect in ultracold atomic experiments.  [Show abstract] [Hide abstract]
ABSTRACT: We consider a mixture of a superfluid Fermi gas of ultracold atoms and a BoseEinstein condensate of molecules possessing a continuous U(1) (relative phase) symmetry. We study the effects that a spatially random photoassociativedissociative symmetry breaking coupling of the systems. Such coupling allows to control the relative phase between a superfluid order parameter of the Fermi system and the condensate wavefunction of molecules for temperatures below the BCS critical temperature. The presented mechanism of phase control belongs to the general class of disorderinduced order phenomena that rely on breaking of continuous symmetry.  [Show abstract] [Hide abstract]
ABSTRACT: We propose and analyze a general mechanism of disorderinduced order in twocomponent BoseEinstein condensates, analogous to corresponding effects established for $XY$ spin models. We show that a random Raman coupling induces a relative phase of $$\pi${}/2$ between the two BECs and that the effect is robust. We demonstrate it in one, two, and three dimensions at $T=0$ and present evidence that it persists at small $T>0$. Applications to phase control in ultracold spinor condensates are discussed. 
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ABSTRACT: We propose a general mechanism of randomfieldinduced order (RFIO), in which longrange order is induced by a random field that breaks the continuous symmetry of the model. We particularly focus on the case of the classical ferromagnetic XY model on a twodimensional lattice, in a uniaxial random field. We prove rigorously that the system has spontaneous magnetization at temperature T=0, and we present strong evidence that this is also the case for small T>0. We discuss generalizations of this mechanism to various classical and quantum systems. In addition, we propose possible realizations of the RFIO mechanism, using ultracold atoms in an optical lattice. Our results shed new light on controversies in existing literature, and open a way to realize RFIO with ultracold atomic systems.
Publication Stats
88  Citations  
18.96  Total Impact Points  
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Institutions

20062010

ICFO Institute of Photonic Sciences
Barcino, Catalonia, Spain
