Coherence and entanglement in the ground state of a bosonic Josephson junction: From macroscopic Schroedinger cat states to separable Fock states
Abstract
We consider a bosonic Josephson junction made of N ultracold and dilute atoms confined by a quasionedimensional doublewell potential within the twosite BoseHubbard model framework. The behavior of the system is investigated at zero temperature by varying the interatomic interaction from the strongly attractive regime to the repulsive one. We show that the ground state exhibits a crossover from a macroscopic Schroedingercat state to a separable Fock state through an atomic coherent regime. By diagonalizing the BoseHubbard Hamiltonian we characterize the emergence of the macroscopic cat states by calculating the Fisher information F, the coherence by means of the visibility {alpha} of the interference fringes in the momentum distribution, and the quantum correlations by using the entanglement entropy S. Both Fisher information and visibility are shown to be related to the groundstate energy by employing the HellmannFeynman theorem. This result, together with a perturbative calculation of the groundstate energy, allows simple analytical formulas for F and {alpha} to be obtained over a range of interactions, in excellent agreement with the exact diagonalization of the BoseHubbard Hamiltonian. In the attractive regime the entanglement entropy attains values very close to its upper limit for a specific interaction strength lying in the regionmore »
 Authors:
 Dipartimento di Fisica 'Galileo Galilei' and Consorzio Nazionale Interuniversitario per la Scienze Fisiche della Materia (CNISM), Universita di Padova, Via Marzolo 8, I35122 Padova (Italy)
 (INO) del Consiglio Nazionale delle Ricerche (CNR), via G. Sansone 1, I50019 Sesto Fiorentino (Italy)
 Dipartimento di Fisica e Matematica and CNISM, Universita dell'Insubria, Via Valleggio 11, I22100 Como (Italy)
 Publication Date:
 OSTI Identifier:
 21546820
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Physical Review. A; Journal Volume: 83; Journal Issue: 5; Other Information: DOI: 10.1103/PhysRevA.83.053607; (c) 2011 American Institute of Physics
 Country of Publication:
 United States
 Language:
 English
 Subject:
 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 74 ATOMIC AND MOLECULAR PHYSICS; BOSONS; CORRELATIONS; ENTROPY; FOCK REPRESENTATION; GROUND STATES; HAMILTONIANS; HUBBARD MODEL; INFORMATION; INTERACTIONS; INTERFERENCE; JOSEPHSON JUNCTIONS; MANYBODY PROBLEM; ONEDIMENSIONAL CALCULATIONS; POTENTIALS; QUANTUM ENTANGLEMENT; QUANTUM STATES; QUANTUM WELLS; SCHROEDINGER PICTURE; TRAPPING; CRYSTAL MODELS; ENERGY LEVELS; MATHEMATICAL MODELS; MATHEMATICAL OPERATORS; NANOSTRUCTURES; PHYSICAL PROPERTIES; QUANTUM OPERATORS; SUPERCONDUCTING JUNCTIONS; THERMODYNAMIC PROPERTIES
Citation Formats
Mazzarella, G., Toigo, F., Salasnich, L., Istituto Nazionale di Ottica, and Parola, A.. Coherence and entanglement in the ground state of a bosonic Josephson junction: From macroscopic Schroedinger cat states to separable Fock states. United States: N. p., 2011.
Web. doi:10.1103/PHYSREVA.83.053607.
Mazzarella, G., Toigo, F., Salasnich, L., Istituto Nazionale di Ottica, & Parola, A.. Coherence and entanglement in the ground state of a bosonic Josephson junction: From macroscopic Schroedinger cat states to separable Fock states. United States. doi:10.1103/PHYSREVA.83.053607.
Mazzarella, G., Toigo, F., Salasnich, L., Istituto Nazionale di Ottica, and Parola, A.. 2011.
"Coherence and entanglement in the ground state of a bosonic Josephson junction: From macroscopic Schroedinger cat states to separable Fock states". United States.
doi:10.1103/PHYSREVA.83.053607.
@article{osti_21546820,
title = {Coherence and entanglement in the ground state of a bosonic Josephson junction: From macroscopic Schroedinger cat states to separable Fock states},
author = {Mazzarella, G. and Toigo, F. and Salasnich, L. and Istituto Nazionale di Ottica and Parola, A.},
abstractNote = {We consider a bosonic Josephson junction made of N ultracold and dilute atoms confined by a quasionedimensional doublewell potential within the twosite BoseHubbard model framework. The behavior of the system is investigated at zero temperature by varying the interatomic interaction from the strongly attractive regime to the repulsive one. We show that the ground state exhibits a crossover from a macroscopic Schroedingercat state to a separable Fock state through an atomic coherent regime. By diagonalizing the BoseHubbard Hamiltonian we characterize the emergence of the macroscopic cat states by calculating the Fisher information F, the coherence by means of the visibility {alpha} of the interference fringes in the momentum distribution, and the quantum correlations by using the entanglement entropy S. Both Fisher information and visibility are shown to be related to the groundstate energy by employing the HellmannFeynman theorem. This result, together with a perturbative calculation of the groundstate energy, allows simple analytical formulas for F and {alpha} to be obtained over a range of interactions, in excellent agreement with the exact diagonalization of the BoseHubbard Hamiltonian. In the attractive regime the entanglement entropy attains values very close to its upper limit for a specific interaction strength lying in the region where coherence is lost and selftrapping sets in.},
doi = {10.1103/PHYSREVA.83.053607},
journal = {Physical Review. A},
number = 5,
volume = 83,
place = {United States},
year = 2011,
month = 5
}

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A Comment on the Letter by M. H. Devoret, J. M. Martinis, and J. Clarke, Phys. Rev. Lett. 55, 1908 (1985). 
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