%0 Journal Article
%J Phys. Rev. B
%D 2019
%T Frustrated quantum spin systems in small triangular lattices studied with a numerical method
%A Castells-Graells, D.
%A Yuste, A.
%A Sanpera, A.
%B Phys. Rev. B
%V 100
%P 155119
%8 Oct
%U https://link.aps.org/doi/10.1103/PhysRevB.100.155119
%R 10.1103/PhysRevB.100.155119
%0 Journal Article
%J New Journal of Physics
%D 2015
%T Thermometry precision in strongly correlated ultracold lattice gases
%A Mehboudi, M
%A Moreno-Cardoner, M.
%A Chiara, G De
%A Sanpera, A.
%B New Journal of Physics
%V 17
%P 055020
%8 05/2015
%N 5
%! New J. Phys.
%R 10.1088/1367-2630/17/5/055020
%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 Letters
%D 2012
%T Quantum Memory Assisted Probing of Dynamical Spin Correlations
%A O. Romero-Isart
%A Rizzi, M.
%A Muschik, C. A.
%A Polzik, E. S.
%A Lewenstein, M.
%A Sanpera, A.
%X We propose a method to probe time-dependent correlations of nontrivial observables in many-body ultracold lattice gases. The scheme uses a quantum nondemolition matter-light interface, first to map the observable of interest on the many-body system into the light and then to store coherently such information into an external system acting as a quantum memory. Correlations of the observable at two (or more) instances of time are retrieved with a single final measurement that includes the readout of the quantum memory. Such a method brings to reach the study of dynamics of many-body systems in and out of equilibrium by means of quantum memories in the field of quantum simulators.
%B Physical Review Letters
%V 108
%8 2/2012
%N 6
%! Phys. Rev. Lett.
%R 10.1103/PhysRevLett.108.065302
%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 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 Journal of Low Temperature Physics
%D 2011
%T Detection of Entanglement in Ultracold Lattice Gases
%A Chiara, G.
%A Sanpera, A.
%X Probing non trivial magnetic ordering in quantum magnets realized with ultracold lattice gases demands detection methods with some spatial resolution built on it. Here we demonstrate that the Faraday matter-light interface provides an experimentally feasible tool to distinguish indubitably different quantum phases of a given many-body system in a non-demolishing way. We illustrate our approach by focussing on the Heisenberg chain for spin-1 bosons in the presence of a SU(2) symmetry breaking field. We explain how using the light signal obtained via homodyne detection one can reconstruct the phase diagram of the model. Further we show that the very same technique that provides a direct experimentally measurable signal of different order parameters can be extended to detect also the presence of multipartite entanglement in such systems.
%B Journal of Low Temperature Physics
%V 165
%P 292 - 305
%8 12/2011
%U link.springer.com/article/10.1007%2Fs10909-011-0403-8
%N 5-6
%! J Low Temp Phys
%R 10.1007/s10909-011-0403-8
%0 Journal Article
%J Phys. Rev. A
%D 2011
%T Probing magnetic order in ultracold lattice gases
%A De Chiara, Gabriele
%A O. Romero-Isart
%A Sanpera, A.
%X A forthcoming challenge in ultracold lattice gases is the simulation of quantum magnetism. That involves both the preparation of the lattice atomic gas in the desired spin state and the probing of the state. Here we demonstrate how a probing scheme based on atom-light interfaces gives access to the order parameters of nontrivial quantum magnetic phases, allowing us to characterize univocally strongly correlated magnetic systems produced in ultracold gases. This method, which is also nondemolishing, yields spatially resolved spin correlations and can be applied to bosons or fermions. As a proof of principle, we apply this method to detect the complete phase diagram displayed by a chain of (rotationally invariant) spin-1 bosons.
%B Phys. Rev. A
%V 83
%P 021604
%U http://pra.aps.org/abstract/PRA/v83/i2/e021604
%R 10.1103/PhysRevA.83.021604
%0 Journal Article
%J Phys. Rev. A
%D 2010
%T Creating p-wave superfluids and topological excitations in optical lattices
%A Massignan, P.
%A Sanpera, A.
%A Lewenstein, M.
%X We propose to realize a p-wave superfluid using bosons mixed with a single species of fermions in a deep optical lattice. We analyze with a self-consistent method its excitation spectrum in presence of a vortex, and we point out the range of interaction strengths in which the zero-energy mode with topological character exists on a finite optical lattice. Lattice effects are strongest close to fermionic half filling: here the linearity of the low-lying spectrum is lost, and a new class of extended zero-energy modes with checkerboard structure and d-wave symmetry appears.
%B Phys. Rev. A
%I American Physical Society
%V 81
%P 031607
%8 Mar/2010
%U http://link.aps.org/doi/10.1103/PhysRevA.81.031607
%R 10.1103/PhysRevA.81.031607
%0 Journal Article
%J Physical Review Letters
%D 2004
%T Atomic Fermi-Bose Mixtures in Inhomogeneous and Random Lattices: From Fermi Glass to Quantum Spin Glass and Quantum Percolation
%A Sanpera, A.
%A Kantian, A.
%A Sanchez-Palencia, L.
%A Zakrzewski, J.
%A Lewenstein, M.
%B Physical Review Letters
%V 93
%G eng
%U http://prl.aps.org/abstract/PRL/v93/i4/e040401
%R 10.1103/PhysRevLett.93.040401
%0 Journal Article
%J Physical Review Letters
%D 2004
%T Coherence Properties of Guided-Atom Interferometers
%A Kreutzmann, H.
%A Poulsen, U.
%A Lewenstein, M.
%A Dumke, R.
%A Ertmer, W.
%A Birkl, G.
%A Sanpera, A.
%B Physical Review Letters
%V 92
%G eng
%U http://prl.aps.org/abstract/PRL/v92/i16/e163201
%R 10.1103/PhysRevLett.92.163201
%0 Journal Article
%J Physical Review A
%D 2002
%T Detection of entanglement with few local measurements
%A Gühne, O.
%A Hyllus, P.
%A Bruß, D.
%A Ekert, A.
%A Lewenstein, M.
%A Macchiavello, C.
%A Sanpera, A.
%B Physical Review A
%V 66
%G eng
%U http://pra.aps.org/abstract/PRA/v66/i6/e062305
%R 10.1103/PhysRevA.66.062305
%0 Journal Article
%J Physical Review Letters
%D 2001
%T Classification of Mixed Three-Qubit States
%A Acín, A.
%A Bruß, D.
%A Lewenstein, M.
%A Sanpera, A.
%B Physical Review Letters
%V 87
%G eng
%U http://prl.aps.org/abstract/PRL/v87/i4/e040401
%R 10.1103/PhysRevLett.87.040401
%0 Journal Article
%J Science (New York, N.Y.)
%D 2001
%T Feynman's path-integral approach for intense-laser-atom interactions
%A Salieres, P.
%A Carre, B.
%A Le Deroff, L.
%A Grasbon, F.
%A Paulus, G. G.
%A Walther, H.
%A Kopold, R.
%A Becker, W.
%A Milosevic, D. B.
%A Sanpera, A.
%A Lewenstein, M.
%X Atoms interacting with intense laser fields can emit electrons and photons of very high energies. An intuitive and quantitative explanation of these highly nonlinear processes can be found in terms of a generalization of classical Newtonian particle trajectories, the so-called quantum orbits. Very few quantum orbits are necessary to reproduce the experimental results. These orbits are clearly identified, thus opening the way for an efficient control as well as previously unknown applications of these processes.
%B Science (New York, N.Y.)
%V 292
%P 902–5
%G eng
%U http://www.sciencemag.org/cgi/content/abstract/292/5518/902
%R 10.1126/science.108836