1,721,107 research outputs found
Phase diagram of the extended Bose-Hubbard model
No full textBy means of the density matrix renormalization group technique, we accurately determine the zero-temperature phase diagram of the one-dimensional extended Bose-Hubbard model with on-site and nearest-neighbor interactions. We analyze the scaling of the charge and of the neutral ground-state energy gaps, as well as of various order parameters. In this way we come to an accurate location of the boundaries between the superfluid and the insulating phases. In this last region, we are able to distinguish between the conventional Mott insulating and density-wave phases and the Haldane insulator phase displaying long-range string ordering, as originally predicted by Dalla Torre et al (2006 Phys. Rev. Lett. 97 260401). © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft
Mott-insulating and glassy phases of polaritons in 1D arrays of coupled cavities
No full textBy means of analytical and numerical methods we analyze the phase diagram of polaritons in one-dimensional coupled cavities. We locate the phase boundary, discuss the behavior of the polariton compressibility and visibility fringes across the critical point, and find a nontrivial scaling of the phase boundary as a function of the number of atoms inside each cavity. We also predict the emergence of a polaritonic glassy phase when the number of atoms fluctuates from cavity to cavity. © 2007 The American Physical Society
Ground-state fidelity at first-order quantum transitions
Full text linkWe analyze the scaling behavior of the fidelity, and the corresponding susceptibility, emerging in finite-size many-body systems whenever a given control parameter λ is varied across a quantum phase transition. For this purpose we consider a finite-size scaling (FSS) framework. Our working hypothesis is based on a scaling assumption of the fidelity in terms of the FSS variables associated with λ and its variation δλ. This framework entails the FSS predictions for continuous transitions and enables one to extend them to first-order transitions, where the FSS becomes qualitatively different. The latter is supported by analytical and numerical analyses of the quantum Ising chain along its first-order quantum transition line, driven by an external longitudinal field
Dynamical chaos and decoherence
No full textFidelity is a convenient tool to study the sensitivity of quantum motion under Hamiltonian perturbations. In this paper we first show that classical chaos can produce the dephasing necessary to suppress quantum interference, even in the absence of any environment. To this end we consider the fidelity of mixed states, which takes into account interference amplitudes, and directly relate its decay to the decay of an appropriate classical correlation function, which is totally unrelated to quantum phases. We then discuss the dephasing in a two-qubit system, induced by the coupling to a single-particle, deterministic chaotic environment. The latter is shown to behave as a pure dephasing many-body object which induces decoherence in the system; memory effects are also taken into account
Information transfer rates in spin quantum channels
No full textWe analyze the communication efficiency of quantum information transfer along unmodulated spin chains by computing the communication rates of various protocols. The effects of temporal correlations are discussed, showing that they can be exploited to boost the transmission efficiency. © 2007 World Scientific Publishing Company
Scaling properties of work fluctuations after quenches near quantum transitions
Full text linkWe study the scaling properties of the statistics of the work done on a generic many-body system at a quantum phase transition of any order and type, arising from quenches of a driving control parameter. For this purpose we exploit a dynamic finite-size scaling framework. Namely, we put forward the existence of a nontrivial finite-size scaling limit for the work distribution, defined as the large-size limit when appropriate scaling variables are kept fixed. The corresponding scaling behaviors are thoroughly verified by means of analytical and numerical calculations in two paradigmatic many-body systems as the quantum Ising model and the Bose–Hubbard model
Erratum: Entanglement transitions in the quantum Ising chain: A comparison between different unravelings of the same Lindbladian [Phys. Rev. B 105, 064305 (2022)]
Full text linkCorrection to https://dx.doi.org/10.1103/PhysRevB.105.064305
Critical crossover phenomena driven by symmetry-breaking defects at quantum transitions
Full text linkWe study the effects of symmetry-breaking defects at continuous quantum
transitions (CQTs), which may arise from localized external fields coupled to
the order-parameter operator. The problem is addressed within
renormalization-group (RG) and finite-size scaling frameworks. We consider the
paradigmatic one-dimensional quantum Ising models at their CQT, in the presence
of defects which break the global symmetry. We show that such
defects can give rise to notable critical crossover regimes where the
ground-state properties experience substantial and rapid changes, from
symmetric conditions to symmetry-breaking boundaries. An effective
characterization of these crossover phenomena driven by defects is achieved by
analyzing the ground-state fidelity associated with small changes of the defect
strength. Within the critical crossover regime, the fidelity susceptibility
shows a power-law divergence when increasing the system size, related to the RG
dimension of the defect strength; in contrast, outside the critical defect
regime, it remains finite. We support the RG scaling arguments with numerical
results.Comment: 13 pages, 11 figure
From Kondo effect to weak-link regime in quantum spin-1/2 spin chains
Full text linkWe analyze the crossover from Kondo to weak-link regime by means of a model of tunable bond impurities in the middle of a spin-1/2 XXZ Heisenberg chain. We study the Kondo screening cloud and estimate the Kondo length by combining perturbative renormalization group approach with the exact numerical calculation of the integrated real-space spin-spin correlation functions. We show that, when the spin impurity is symmetrically coupled to the two parts of the chain with realistic values of the Kondo coupling strengths and spin-parity symmetry is preserved, the Kondo length takes values within the reach of nowadays experimental technology in ultracold-atom setups. In the case of nonsymmetric Kondo couplings and/or spin parity broken by a nonzero magnetic field applied to the impurity, we discuss how Kondo screening redistributes among the chain as a function of the asymmetry in the couplings and map out the shrinking of the Kondo length when the magnetic field induces a crossover from Kondo impurity to weak-link physics
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