Entanglement in shape phase transitions of coupled molecular benders

10 pags. ; 7 figs. ; PACS number(s): 03.65.Fd, 33.20.Vq, 05.30.Rt, 03.65.UdWe study the entanglement properties of the shape phase transitions between different geometric limits of two coupled equivalent molecular benders modeled with the two-dimensional limit of the vibron model. This system has four possible geometric configurations: linear, cis-bent, trans-bent, and nonplanar. We show how the entanglement, accessed through the calculation of the linear entropy, between benders and between rotational and vibrational degrees of freedom changes sensitively in the critical regions of this two-fluid bosonic model. The numeric calculation is complemented with a variational approach to the ground-state wave function in terms of symmetry-adapted coherent states. © 2014 American Physical Society.Work was partially supported by the Spanish MINECO under projects FIS2011-29813-C02-01 and FIS2011-28738-C02-02 and by the University of Granada under project PP2012-PI04.Peer Reviewe

Entanglement in shape phase transitions of coupled molecular benders

We study the entanglement properties of the shape phase transitions between different geometric limits of two coupled equivalent molecular benders modeled with the two-dimensional limit of the vibron model. This system has four possible geometric configurations: linear, cis-bent, trans-bent, and nonplanar. We show how the entanglement, accessed through the calculation of the linear entropy, between benders and between rotational and vibrational degrees of freedom changes sensitively in the critical regions of this two-fluid bosonic model. The numeric calculation is complemented with a variational approach to the ground-state wave function in terms of symmetry-adapted coherent states.info:eu-repo/grantAgreement/The authors thank J. M. Arias and F. Iachello for discussions and valuable comments. Work was partially supported by the Spanish MINECO under projects FIS2011-29813-C02-01 and FIS2011-28738-C02-02 and by the University of Granada under project PP2012-PI04

Probing excited-state quantum phase transition in a quantum many body system via out-of-time-ordered correlator

As a measure of information scrambling and quantum chaos, out-of-time-ordered correlator (OTOC) plays more and more important role in many different fields of physics. In this work, we verify that the OTOC can also be used as a prober of the excited-state quantum phase transi- tion (ESQPT) in a quantum many body system. By using the exact diagonalization method, we examine the dynamical properties of OTOC in the Lipkin model, which undergoes an ESQPT. We demonstrate that the OTOC exhibits a remarkable distinct evolution behaviors in different phases of ESQPT. Therefore, the presence of an ESQPT in the quantum many body system can be clearly signaled by the different dynamical behaviors of the OTOC. In particular, we show that the steady state value of the OTOC serves as the order parameter of the ESQPT. Our results highlight the connections between the OTOC and ESQPT, which enable one to use OTOC for experimental tests ESQPTs in quantum many body systems

Probing excited-state quantum phase transition in a quantum many body system via out-of-time-ordered correlator

As a measure of information scrambling and quantum chaos, out-of-time-ordered correlator (OTOC) plays more and more important role in many different fields of physics. In this work, we verify that the OTOC can also be used as a prober of the excited-state quantum phase transition (ESQPT) in a quantum many body system. By using the exact diagonalization method, we examine the dynamical properties of OTOC in the Lipkin model, which undergoes an ESQPT. We demonstrate that the OTOC exhibits a remarkable distinct evolution behaviors in different phases of ESQPT. Therefore, the presence of an ESQPT in the quantum many body system can be clearly signaled by the different dynamical behaviors of the OTOC. In particular, we show that the steady state value of the OTOC serves as the order parameter of the ESQPT. Our results highlight the connections between the OTOC and ESQPT, which enable one to use OTOC for experimental tests ESQPTs in quantum many body systems.Comment: 7pages, 4figures. Accepted for publication in Physical Review

Characterizing the Lipkin-Meshkov-Glick model excited state quantum phase transition using dynamical and statistical properties of the diagonal entropy

Using the diagonal entropy, we analyze the dynamical signatures of the Lipkin-Meshkov-Glick (LMG) model excited-state quantum phase transition (ESQPT). We first show that the time evolution of the diagonal entropy behaves as an efficient indicator of the presence of an ESQPT. We also compute the probability distribution of the diagonal entropy values over a certain time interval and we find that the resulting distribution provides a clear distinction between the different phases of ESQPT. Moreover, we observe that the probability distribution of the diagonal entropy at the ESQPT critical point has a universal form, well described by a beta distribution, and that a reliable detection of the ESQPT can be obtained from the diagonal entropy central moments

Spectral kissing and its dynamical consequences in the squeeze-driven Kerr oscillator

Transmon qubits are the predominant element in circuit-based quantum information processing, such as existing quantum computers, due to their controllability and ease of engineering implementation. But more than qubits, transmons are multilevel nonlinear oscillators that can be used to investigate fundamental physics questions. Here, they are explored as simulators of excited state quantum phase transitions (ESQPTs), which are generalizations of quantum phase transitions to excited states. We show that the spectral kissing (coalescence of pairs of energy levels) experimentally observed in the effective Hamiltonian of a driven SNAIL-transmon is an ESQPT precursor. We explore the dynamical consequences of the ESQPT, which include the exponential growth of out-of-time-ordered correlators, followed by periodic revivals, and the slow evolution of the survival probability due to localization. These signatures of ESQPT are within reach for current superconducting circuits platforms and are of interest to experiments with cold atoms and ion traps.NSF CCI grant (Award Number 2124511)NSF grant No. DMR-1936006I+D+i project PID2019-104002GB-C21 (MCIN/AEI/10.13039/501100-011033)The Consejería de Conocimiento, Investigación y Universidad, Junta de AndalucíaEuropean Regional Development Fund (ERDF), ref. UHU-1262561The CEAFMC and Universidad de Huelva High Performance Computer (HPC@UHU)The Campus Universitario el Carmen and funded by FEDER/MINECO project UNHU-15CE-2848The MPS Simons Foundation Award ID: 67858

Quantum tunneling and level crossings in the squeeze-driven Kerr oscillator

This research was supported by the NSF CCI grant (Award No. 2124511). F.P.-B. is grateful for funding from the European Union's Horizon 2020 research and innovation program under Grant No. PID2019-104002GB-C21 funded by MCIN/AEI/10.13039/501100011033 and, as appropriate, by ERDF A way of making Europe, by the European Union, or by the European Union Next Generation EU/PRTR. Computing resources supporting this work were partially provided by the CEAFMC and Universidad de Huelva High Performance Computer located on the Campus Universitario el Carmen and funded by FEDER/MINECO Project No. UNHU-15CE-2848.The quasienergy spectrum recently measured in experiments with a squeeze-driven superconducting Kerr oscillator showed good agreement with the energy spectrum of its corresponding static effective Hamiltonian. The experiments also demonstrated that the dynamics of low-energy states can be explained with the same emergent static effective model. The spectrum exhibits real (avoided) level crossings for specific values of the Hamiltonian parameters, which can then be chosen to suppress (enhance) quantum tunneling. Here we analyze the spectrum and the dynamics of the effective model up to high energies, which should soon be within experimental reach. We show that the parameter values for the crossings, which can be obtained from a semiclassical approach, can also be identified directly from the dynamics. Our analysis of quantum tunneling is done with the effective flux of the Husimi volume of the evolved states between different regions of the phase space. Both initial coherent states and quench dynamics are considered. We argue that the level crossings and their consequences on the dynamics are typical to any quantum system with one degree of freedom, whose density of states presents a local logarithmic divergence and a local step discontinuity.CEAFMCEuropean Union Next Generation EU/PRTRUniversidad de Huelva High Performance ComputerNational Science Foundation 2124511 NSFEuropean Commission ECMinisterio de Economía y Competitividad UNHU-15CE-2848 MINECOHorizon 2020 MCIN/AEI/10.13039/501100011033, PID2019-104002GB-C21European Regional Development Fund ERD

Excited state quantum phase transitions in the bending spectra of molecules

We present an extension of the Hamiltonian of the two dimensional limit of the vibron model encompassing all possible interactions up to four-body operators. We apply this Hamiltonian to the modeling of the experimental bending spectrum of fourteen molecules. The bending degrees of freedom of the selected molecular species include all possible situations: linear, bent, and nonrigid equilibrium structures; demonstrating the flexibility of the algebraic approach, that allows for the consideration of utterly different physical cases with a general formalism and a single Hamiltonian. For each case, we compute predicted term values used to depict the quantum monodromy diagram, the Birge-Sponer plot, the participation ratio. We also show the bending energy functional obtained using the coherent --or intrinsic-- state formalism.Comment: 67 pages, 18 tables and 15 figure