%0 Journal Article
%J Reports on Progress in Physics
%D 2018
%T Genuine quantum correlations in quantum many-body systems: a review of recent progress
%A De Chiara, Gabriele
%A Sanpera, Anna
%B Reports on Progress in Physics
%V 81
%P 074002
%8 Jan-07-2018
%! Rep. Prog. Phys.
%R 10.1088/1361-6633/aabf61
%0 Journal Article
%J NEW JOURNAL OF PHYSICS
%D 2017
%T Global and local thermometry schemes in coupled quantum systems
%A Campbell, Steve
%A Mehboudi, Mohammad
%A De Chiara, Gabriele
%A Paternostro, Mauro
%X We study the ultimate bounds on the estimation of temperature for an interacting quantum system. We consider two coupled bosonic modes that are assumed to be thermal and using quantum estimation theory establish the role the Hamiltonian parameters play in thermometry. We show that in the case of a conserved particle number the interaction between the modes leads to a decrease in the overall sensitivity to temperature, while interestingly, if particle exchange is allowed with the thermal bath the converse is true. We explain this dichotomy by examining the energy spectra. Finally, we devise experimentally implementable thermometry schemes that rely only on locally accessible information from the total system, showing that almost Heisenberg limited precision can still be achieved, and we address the (im)possibility for multiparameter estimation in the system.
%B NEW JOURNAL OF PHYSICS
%V 19
%8 oct
%R 10.1088/1367-2630/aa7fac
%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 Phys. Rev. A
%D 2011
%T Entanglement detection in hybrid optomechanical systems
%A De Chiara, Gabriele
%A Paternostro, Mauro
%A Palma, G. Massimo
%X We study a device formed by a Bose Einstein condensate (BEC) coupled to the field of a cavity with a moving end-mirror and find a working point such that the mirror-light entanglement is reproduced by the BEC-light quantum correlations. This provides an experimentally viable tool for inferring mirror-light entanglement with only a limited set of assumptions. We prove the existence of tripartite entanglement in the hybrid device, persisting up to temperatures of a few milli-Kelvin, and discuss a scheme to detect it.
%B Phys. Rev. A
%V 83
%P 052324
%U http://link.aps.org/doi/10.1103/PhysRevA.83.052324
%R 10.1103/PhysRevA.83.052324
%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. Lett.
%D 2010
%T Cold-atom induced control of an opto-mechanical device
%A M. Paternostro
%A De Chiara, Gabriele
%A G. M. Palma
%X We consider a cavity with a vibrating end mirror and coupled to a Bose-Einstein condensate. The cavity field mediates the interplay between mirror and collective oscillations of the atomic density. We study the implications of this dynamics and the possibility of an indirect diagnostic. Our predictions can be observed in a realistic setup that is central to the current quest for mesoscopic quantumness.
%B Phys. Rev. Lett.
%V 104
%P 243602
%8 06/2010
%U http://link.aps.org/doi/10.1103/PhysRevLett.104.243602
%R 10.1103/PhysRevLett.104.243602
%0 Journal Article
%J Phys. Rev. A
%D 2010
%T The quantum ground state of self-organized atomic crystals in optical resonators
%A S. Fernández-Vidal
%A De Chiara, Gabriele
%A J. Larson
%A G. Morigi
%X Cold atoms, driven by a laser and simultaneously coupled to the quantum field of an optical resonator, may self-organize in periodic structures. These structures are supported by the optical lattice, which emerges from the laser light they scatter into the cavity mode and form when the laser intensity exceeds a threshold value. We study theoretically the quantum ground state of these structures above the pump threshold of self-organization by mapping the atomic dynamics of the self-organized crystal to a Bose-Hubbard model. We find that the quantum ground state of the self-organized structure can be the one of a Mott insulator, depending on the pump strength of the driving laser. For very large pump strengths, where the intracavity-field intensity is maximum and one would expect a Mott-insulator state, we find intervals of parameters where the phase is compressible. These states could be realized in existing experimental setups.
%B Phys. Rev. A
%V 81
%P 043407
%8 04/2010
%U http://link.aps.org/doi/10.1103/PhysRevA.81.043407
%R 10.1103/PhysRevA.81.043407
%0 Journal Article
%J New. J. Phys.
%D 2010
%T Spontaneous nucleation of structural defects in inhomogeneous ion chains
%A De Chiara, Gabriele
%A del Campo, Adolfo
%A G. Morigi
%A M. B. Plenio
%A A. Retzker
%X Structural defects in ion crystals can be formed during a linear quench of the transverse trapping frequency across the mechanical instability from a linear chain to the zigzag structure. The density of defects after the sweep can be conveniently described by the Kibble-Zurek mechanism. In particular, the number of kinks in the zigzag ordering can be derived from a time-dependent Ginzburg-Landau equation for the order parameter, here the zigzag transverse size, under the assumption that the ions are continuously laser cooled. In a linear Paul trap the transition becomes inhomogeneous, being the charge density larger in the center and more rarefied at the edges. During the linear quench the mechanical instability is first crossed in the center of the chain, and a front, at which the mechanical instability is crossed during the quench, is identified which propagates along the chain from the center to the edges. If the velocity of this front is smaller than the sound velocity, the dynamics becomes adiabatic even in the thermodynamic limit and no defect is produced. Otherwise, the nucleation of kinks is reduced with respect to the case in which the charges are homogeneously distributed, leading to a new scaling of the density of kinks with the quenching rate. The analytical predictions are verified numerically by integrating the Langevin equations of motion of the ions, in presence of a time-dependent transverse confinement. We argue that the non-equilibrium dynamics of an ion chain in a Paul trap constitutes an ideal scenario to test the inhomogeneous extension of the Kibble-Zurek mechanism, which lacks experimental evidence to date.
%B New. J. Phys.
%V 12
%P 115003
%8 12/2010
%U http://iopscience.iop.org/1367-2630/12/11/115003?fromSearchPage=true
%R 10.1088/1367-2630/12/11/115003
%0 Journal Article
%J Phys. Rev. Lett.
%D 2010
%T Structural defects in ion crystals by quenching the external potential: the inhomogeneous Kibble-Zurek mechanism
%A del Campo, Adolfo
%A De Chiara, Gabriele
%A G. Morigi
%A M. B. Plenio
%A A. Retzker
%B Phys. Rev. Lett.
%V 105
%P 075701
%8 08/2010
%U http://link.aps.org/doi/10.1103/PhysRevLett.105.075701
%R 10.1103/PhysRevLett.105.075701