%0 Journal Article
%J PHYSICAL REVIEW B
%D 2017
%T Magnetic phases of spin-1 lattice gases with random interactions
%A McAlpine, Kenneth D.
%A Paganelli, Simone
%A Ciuchi, Sergio
%A Sanpera, Anna
%A De Chiara, Gabriele
%X A spin-1 atomic gas in an optical lattice, in the unit-filling Mott insulator (MI) phase and in the presence of disordered spin-dependent interaction, is considered. In this regime, at zero temperature, the system is well described by a disordered rotationally invariant spin-1 bilinear-biquadratic model. We study, via the density matrix renormalization group algorithm, a bounded disorder model such that the spin interactions can be locally either ferromagnetic or antiferromagnetic. Random interactions induce the appearance of a disordered ferromagnetic phase characterized by a nonvanishing value of the spin glass order parameter across the boundary between a ferromagnetic phase and a dimer phase exhibiting random singlet order. We also study the distribution of the block entanglement entropy in the different regions.
%B PHYSICAL REVIEW B
%V 95
%8 jun
%R 10.1103/PhysRevB.95.235128
%0 Journal Article
%J Physical Review Letters
%D 2013
%T Bose-Glass Phases of Ultracold Atoms due to Cavity Backaction
%A Hessam Habibian
%A André Winter
%A Paganelli, Simone
%A Heiko Rieger
%A Giovanna Morigi
%X We determine the quantum ground-state properties of ultracold bosonic atoms interacting with the mode of a high-finesse resonator. The atoms are confined by an external optical lattice, whose period is incommensurate with the cavity mode wavelength, and are driven by a transverse laser, which is resonant with the cavity mode. While for pointlike atoms photon scattering into the cavity is suppressed, for sufficiently strong lasers quantum fluctuations can support the buildup of an intracavity field, which in turn amplifies quantum fluctuations. The dynamics is described by a Bose-Hubbard model where the coefficients due to the cavity field depend on the atomic density at all lattice sites. Quantum Monte Carlo simulations and mean-field calculations show that, for large parameter regions, cavity backaction forces the atoms into clusters with a checkerboard density distribution. Here, the ground state lacks superfluidity and possesses finite compressibility, typical of a Bose glass. This system constitutes a novel setting where quantum fluctuations give rise to effects usually associated with disorder.
%B Physical Review Letters
%V 110
%8 2/2013
%U http://prl.aps.org/abstract/PRL/v110/i7/e075304
%N 7
%! Phys. Rev. Lett.
%R 10.1103/PhysRevLett.110.075304
%0 Journal Article
%J Phyiscal Review A
%D 2013
%T Quantum phases of incommensurate optical lattices due to cavity backaction
%A Hessam Habibian
%A André Winter
%A Paganelli, Simone
%A Heiko Rieger
%A Giovanna Morigi
%B Phyiscal Review A
%V 88
%P 043618
%0 Journal Article
%J Physical Review A
%D 2013
%T Routing quantum information in spin chains
%A Paganelli, Simone
%A Lorenzo, Salvatore
%A Apollaro, Tony J. G.
%A Plastina, Francesco
%A Giorgi, Gian Luca
%B Physical Review A
%V 87
%8 6/2013
%N 6
%! Phys. Rev. A
%R 10.1103/PhysRevA.87.062309
%0 Journal Article
%J New Journal of Physics
%D 2012
%T Beyond pure state entanglement for atomic ensembles
%A Julia Stasińska
%A Paganelli, Simone
%A Sanpera, Anna
%X We analyze multipartite entanglement between atomic ensembles within quantum matter–light interfaces. In our proposal, a polarized light beam crosses sequentially several polarized atomic ensembles impinging on each of them at a given angle $\alpha$ i . These angles are crucial parameters for shaping the entanglement since they are directly connected to the appropriate combinations of the collective atomic spins that are squeezed. We exploit such a scheme to go beyond the pure state paradigm proposing realistic experimental settings to address multipartite mixed state entanglement in continuous variables.
%B New Journal of Physics
%V 14
%P 033034
%U http://stacks.iop.org/1367-2630/14/i=3/a=033034
%R 10.1088/1367-2630/14/3/033034
%0 Journal Article
%J Physical Review A
%D 2012
%T Spin-driven spatial symmetry breaking of spinor condensates in a double well
%A Melé-Messeguer, M.
%A Paganelli, Simone
%A Juliá-Díaz, B.
%A Ann Sanpera
%A Polls, A.
%B Physical Review A
%I American Physical Society
%V 86
%P 053626 -
%8 2012/11/26/
%G eng
%U http://link.aps.org/doi/10.1103/PhysRevA.86.053626
%N 5
%0 Journal Article
%J ArXiv e-prints
%D 2011
%T A continuous-variable formalism for the Faraday atom-light interface
%A Stasińska, J.
%A Paganelli, Simone
%A Rodó, C.
%A Sanpera, A.
%X Quantum interfaces between polarized atomic ensembles and coherent states of light, applied recently to manipulate bipartite and multipartite entanglement, are revisited by means of a continuous-variable formalism. The explicit use of the continuous-variable formalism facilitates significantly the analysis of entanglement between different modes, reducing it to the study of the properties of a final covariance matrix which can be found analytically. Furthermore, it allows to study matter-light interfaces for mixed states, adapting the formalism to the experimental situations in which the initial prepared Gaussian states are, unavoidably, affected by a certain amount of noise. A multipartite scenario, leading to the generation of macroscopic cluster states is presented and analyzed in detail within this formalism.
%B ArXiv e-prints
%G eng
%U http://arxiv.org/abs/1007.0403
%0 Journal Article
%J Phys. Rev. A
%D 2011
%T Disordered spinor Bose-Hubbard model
%A Ł{\k a}cki, M.
%A Paganelli, Simone
%A Ahufinger, V.
%A Sanpera, Anna
%A Zakrzewski, J.
%K Condensed Matter - Other Condensed Matter
%K Quantum Physics
%X 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.
%B Phys. Rev. A
%V 83
%P 013605
%G eng
%U http://link.aps.org/doi/10.1103/PhysRevA.83.013605
%R 10.1103/PhysRevA.83.013605
%0 Journal Article
%J J Low Temp Phys
%D 2011
%T Spin Effects in Bose-Glass Phases
%A Paganelli, Simone
%A Ła̧cki, Mateusz
%A Ahufinger, Veronica
%A Zakrzewski, Jakub
%A Sanpera, Anna
%B J Low Temp Phys
%V 165
%P 227
%U http://www.springerlink.com/content/10w5036068935773/
%R 10.1007/s10909-011-0392-7
%0 Journal Article
%J Phys. Rev. A
%D 2010
%T Ion-trap simulation of the quantum phase transition in an exactly solvable model of spins coupled to bosons
%A Giorgi, Gian Luca
%A Paganelli, Simone
%A Galve, Fernando
%K Quantum Physics
%X It is known that arrays of trapped ions can be used to efficiently simulate a variety of many-body quantum systems. Here we show how it is possible to build a model representing a spin chain interacting with bosons that is exactly solvable. The exact spectrum of the model at zero temperature and the ground-state properties are studied. We show that a quantum phase transition occurs when the coupling between spins and bosons reaches a critical value, which corresponds to a level crossing in the energy spectrum. Once the critical point is reached, the number of bosonic excitations in the ground state, which can be assumed as an order parameter, starts to be different from zero. The population of the bosonic mode is accompanied by a macroscopic magnetization of the spins. This double effect could represent a useful resource for phase transition detection since a measure of the phonon can give information about the phase of the spin system. A finite-temperature phase diagram is also given in the adiabatic regime.
%B Phys. Rev. A
%V 81
%P 052118
%8 2010
%G eng
%R 10.1103/PhysRevA.81.052118
%0 Journal Article
%J Physical Review A (Atomic, Molecular, and Optical Physics)
%D 2009
%T Manipulating mesoscopic multipartite entanglement with atom-light interfaces
%A Julia Stasińska
%A Rodó, Carles
%A Paganelli, Simone
%A Sanpera, Anna
%A Birkl, G.
%K atom-photon collisions
%K EPR paradox
%K measurement theory
%K mesoscopic entanglement
%K multipartite entanglement
%K quantum entanglement
%K quantum optics
%X Entanglementbetween two macroscopic atomic ensembles induced by measurement on anancillary light system has proven to be a powerful methodfor engineering quantum memories and quantum state transfer. Here weinvestigate the feasibility of such methods for generation, manipulation, anddetection of genuine multipartite entanglement (Greenberger-Horne-Zeilinger and clusterlike states) betweenmesoscopic atomic ensembles without the need of individual addressing ofthe samples. Our results extend in a nontrivial way theEinstein-Podolsky-Rosen entanglement between two macroscopic gas samples reported experimentally in[B. Julsgaard, A. Kozhekin, and E. Polzik, Nature (London) 413,400 (2001)]. We find that under realistic conditions, a secondorthogonal light pulse interacting with the atomic samples, can modifyand even reverse the entangling action of the first oneleaving the samples in a separable state. ©2009 The American Physical Society
%B Physical Review A (Atomic, Molecular, and Optical Physics)
%I APS
%V 80
%P 062304–8
%8 12/2009
%G eng
%U http://link.aps.org/abstract/PRA/v80/e062304
%0 Journal Article
%J Fortschritte der Physik
%D 2009
%T Optimized electron propagation on a quantum chain by a topological phase
%A Paganelli, Simone
%A Giorgi, G. L.
%A de Pasquale, F.
%X We study the quantum diffusion of an electron in a quantum chain starting from an initial state localized around a given site. As the wavepacket diffuses, the probability of reconstructing the initial state on another site diminishes drastically with the distance. In order to optimize the state transmission we find that a topological quantum phase can be introduced. The effect of this phase is the reduction of wavepacket spreading together with almost coherent group propagation. In this regime, the electron has a quasi-linear dispersion and high fidelity can be achieved also over large distances in terms of lattice spacing.
%B Fortschritte der Physik
%V 57
%P 1094–1102
%G eng
%U http://doi.wiley.com/10.1002/prop.200900087
%R 10.1002/prop.200900087