Coherence and entanglement in the ground state of a bosonic Josephson junction: From macroscopic Schroedinger cat states to separable Fock states

Journal Article · Sun May 15 00:00:00 EDT 2011 · Physical Review. A

DOI:https://doi.org/10.1103/PHYSREVA.83.053607· OSTI ID:21546820

Mazzarella, G; Toigo, F ^[1]; Salasnich, L ^[1]; Parola, A ^[2]

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1. Dipartimento di Fisica 'Galileo Galilei' and Consorzio Nazionale Interuniversitario per la Scienze Fisiche della Materia (CNISM), Universita di Padova, Via Marzolo 8, I-35122 Padova (Italy)
2. Dipartimento di Fisica e Matematica and CNISM, Universita dell'Insubria, Via Valleggio 11, I-22100 Como (Italy)

We consider a bosonic Josephson junction made of N ultracold and dilute atoms confined by a quasi-one-dimensional double-well potential within the two-site Bose-Hubbard 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 Schroedinger-cat state to a separable Fock state through an atomic coherent regime. By diagonalizing the Bose-Hubbard 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 ground-state energy by employing the Hellmann-Feynman theorem. This result, together with a perturbative calculation of the ground-state 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 Bose-Hubbard 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 self-trapping sets in.

• OSTI ID: 21546820
• Journal Information: Physical Review. A, Vol. 83, Issue 5; Other Information: DOI: 10.1103/PhysRevA.83.053607; (c) 2011 American Institute of Physics; ISSN 1050-2947
• Country of Publication: United States
• Language: English

Related Subjects

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
MANY-BODY PROBLEM
ONE-DIMENSIONAL 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