%0 Journal Article
%J Physical Review B
%D 2014
%T Case study of the uniaxial anisotropic spin-1 bilinear-biquadratic Heisenberg model on a triangular lattice
%A Moreno-Cardoner, M.
%A Perrin, H.
%A Paganelli, S.
%A De Chiara, G.
%A Sanpera, A.
%X We study the spin-1 model on a triangular lattice in the presence of a uniaxial anisotropy field using a cluster mean-field (CMF) approach. The interplay among antiferromagnetic exchange, lattice geometry, and anisotropy forces Gutzwiller mean-field approaches to fail in a certain region of the phase diagram. There, the CMF method yields two supersolid phases compatible with those present in the spin−1/2 XXZ model onto which the spin-1 system maps. Between these two supersolid phases, the three-sublattice order is broken and the results of the CMF approach depend heavily on the geometry and size of the cluster. We discuss the possible presence of a spin liquid in this region.
%B Physical Review B
%V 90
%8 10/2014
%N 14
%! Phys. Rev. B
%R 10.1103/PhysRevB.90.144409
%0 Journal Article
%J Journal of Statistical Mechanics: Theory and Experiment
%D 2014
%T Entanglement properties of spin models in triangular lattices
%A Moreno-Cardoner, M.
%A Paganelli, S.
%A De Chiara, G.
%A Sanpera, A.
%X The different quantum phases appearing in strongly correlated systems as well as their transitions are closely related to the entanglement shared between their constituents. In 1D systems, it is well established that the entanglement spectrum is linked to the symmetries that protect the different quantum phases. This relation extends even further at the phase transitions where a direct link associates the entanglement spectrum to the conformal field theory describing the former. For 2D systems much less is known. The lattice geometry becomes a crucial aspect to consider when studying entanglement and phase transitions. Here, we analyze the entanglement properties of triangular spin lattice models by also considering concepts borrowed from quantum information theory such as geometric entanglement.
%B Journal of Statistical Mechanics: Theory and Experiment
%V 2014
%P P10008
%8 10/2014
%N 10
%! J. Stat. Mech.
%R 10.1088/1742-5468/2014/10/P10008
%0 Journal Article
%J Physical Review A
%D 2014
%T Long-range multipartite entanglement close to a first-order quantum phase transition
%A Stasińska, J.
%A Rogers, B.
%A M. Paternostro
%A De Chiara, G.
%A Sanpera, A.
%X We provide insight into the quantum correlations structure present in strongly correlated systems beyond the standard framework of bipartite entanglement. To this aim we first exploit rotationally invariant states as a test bed to detect genuine tripartite entanglement beyond the nearest neighbor in spin-1/2 models. Then we construct in a closed analytical form a family of entanglement witnesses which provides a sufficient condition to determine if a state of a many-body system formed by an arbitrary number of spin-1/2 particles possesses genuine tripartite entanglement, independently of the details of the model. We illustrate our method by analyzing in detail the anisotropic XXZ spin chain close to its phase transitions, where we demonstrate the presence of long-range multipartite entanglement near the critical point and the breaking of the symmetries associated with the quantum phase transition.
%B Physical Review A
%V 89
%8 3/2014
%N 3
%! Phys. Rev. A
%R 10.1103/PhysRevA.89.032330
%0 Journal Article
%J Physical Review B
%D 2013
%T Scaling of the entanglement spectrum near quantum phase transitions
%A Lepori, L.
%A De Chiara, G.
%A Sanpera, A.
%B Physical Review B
%V 87
%8 6/2013
%N 23
%! Phys. Rev. B
%R 10.1103/PhysRevB.87.235107
%0 Journal Article
%J Physical Review Letters
%D 2012
%T Entanglement Spectrum, Critical Exponents, and Order Parameters in Quantum Spin Chains
%A De Chiara, G.
%A Lepori, L.
%A Lewenstein, M.
%A Sanpera, A.
%X We investigate the entanglement spectrum near criticality in finite quantum spin chains. Using finite size scaling we show that when approaching a quantum phase transition, the Schmidt gap, i.e., the difference between the two largest eigenvalues of the reduced density matrix λ1, λ2, signals the critical point and scales with universal critical exponents related to the relevant operators of the corresponding perturbed conformal field theory describing the critical point. Such scaling behavior allows us to identify explicitly the Schmidt gap as a local order parameter.
%B Physical Review Letters
%V 109
%8 12/2012
%N 23
%! Phys. Rev. Lett.
%R 10.1103/PhysRevLett.109.237208
%0 Journal Article
%J Physical Review B
%D 2011
%T Bilinear-biquadratic spin-1 chain undergoing quadratic Zeeman effect
%A De Chiara, G.
%A Lewenstein, M.
%A Sanpera, A.
%X The Heisenberg model for spin-1 bosons in one dimension presents many different quantum phases, including the famous topological Haldane phase. Here we study the robustness of such phases in front of a SU(2) symmetry-breaking field as well as the emergence of unique phases. Previous studies have analyzed the effect of such uniaxial anisotropy in some restricted relevant points of the phase diagram. Here we extend those studies and present the complete phase diagram of the spin-1 chain with uniaxial anisotropy. To this aim, we employ the density-matrix renormalization group together with analytical approaches. The complete phase diagram can be realized using ultracold spinor gases in the Mott insulator regime under a quadratic Zeeman effect.
%B Physical Review B
%V 84
%8 8/2011
%U http://prb.aps.org/abstract/PRB/v84/i5/e054451
%N 5
%! Phys. Rev. B
%R 10.1103/PhysRevB.84.054451
%0 Journal Article
%J EPL (Europhysics Letters)
%D 2011
%T Entangling two distant oscillators with a quantum reservoir
%A Wolf, A
%A De Chiara, G.
%A Kajari, E
%A Lutz, E
%A G. Morigi
%X The generation of entanglement between two oscillators that interact via a common reservoir is theoretically studied. The reservoir is modeled by a one-dimensional harmonic crystal initially in thermal equilibrium. Starting from a separable state, the oscillators can become entangled after a transient time, that is of the order of the thermalization time scale. This behaviour is observed at finite temperature even when the oscillators are at a distance significantly larger than the crystal's interparticle spacing. The underlying physical mechanisms can be explained by the dynamical properties of the collective variables of the two oscillators which may decouple from or be squeezed by the reservoir. Our predictions can be tested with an ion chain in a linear Paul trap.
%B EPL (Europhysics Letters)
%V 95
%P 60008
%8 09/2011
%U http://epljournal.edpsciences.org/index.php?option=com_article&access=standard&Itemid=129&url=/articles/epl/abs/2011/18/epl13816/epl13816.html
%N 6
%! EPL
%R 10.1209/0295-5075/95/60008
%0 Journal Article
%J Physical Review A
%D 2011
%T Quantifying, characterizing, and controlling information flow in ultracold atomic gases
%A Haikka, P.
%A McEndoo, S.
%A De Chiara, G.
%A G. M. Palma
%A Maniscalco, S.
%X We study quantum information flow in a model comprised of a trapped impurity qubit immersed in a Bose-Einstein-condensed reservoir. We demonstrate how information flux between the qubit and the condensate can be manipulated by engineering the ultracold reservoir within experimentally realistic limits. We show that this system undergoes a transition from Markovian to non-Markovian dynamics, which can be controlled by changing key parameters such as the condensate scattering length. In this way, one can realize a quantum simulator of both Markovian and non-Markovian open quantum systems, the latter ones being characterized by a reverse flow of information from the background gas (reservoir) to the impurity (system).
%B Physical Review A
%V 84
%8 9/2011
%U http://pra.aps.org/abstract/PRA/v84/i3/e031602
%N 3
%! Phys. Rev. A
%R 10.1103/PhysRevA.84.031602