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Entanglement Entropy and Quantum Field Theory
 P06002 (2004). [CC05] ———, Evolution of Entanglement Entropy in OneDimensional Systems
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Correlation functions for the open XXZ chain I
"... We consider the XXZ spin chain with diagonal boundary conditions in the framework of algebraic Bethe Ansatz. Using the explicit computation of the scalar products of Bethe states and a revisited version of the bulk inverse problem, we calculate the elementary building blocks for the correlation func ..."
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Cited by 17 (3 self)
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We consider the XXZ spin chain with diagonal boundary conditions in the framework of algebraic Bethe Ansatz. Using the explicit computation of the scalar products of Bethe states and a revisited version of the bulk inverse problem, we calculate the elementary building blocks for the correlation functions. In the limit of halfinfinite chain, they are obtained as multiple integrals of usual functions, similar to the case of periodic boundary conditions. 1
Bipartite entanglement entropy in massive 1+1dimensional quantum field theories
, 2009
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Bipartite entanglement entropy in massive QFT with a boundary: the Ising model
, 2008
"... In this paper we give an exact infiniteseries expression for the bipartite entanglement entropy of the quantum Ising model both with a boundary magnetic field and in infinite volume. This generalizes and extends previous results involving the present authors for the bipartite entanglement entropy ..."
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Cited by 6 (5 self)
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In this paper we give an exact infiniteseries expression for the bipartite entanglement entropy of the quantum Ising model both with a boundary magnetic field and in infinite volume. This generalizes and extends previous results involving the present authors for the bipartite entanglement entropy of integrable quantum field theories, which exploited the generalization of the form factor program to branchpoint twist fields. In the boundary case, we isolate in a universal way the part of the entanglement entropy which is related to the boundary entropy introduced by Affleck and Ludwig, and explain how this relation should hold in more general QFT models. We provide several consistency checks for the validity of our form factor results, notably, the identification of the leading ultraviolet behaviour both of the entanglement entropy and of the twopoint function of twist fields in the bulk theory, to a great degree of precision by including up to 500 form factor contributions.
Quantum Entanglement, Interaction, and the Classical Limit”, Zeit. fur Nat
 A
, 2004
"... Two or more quantum systems are said to be in an entangled or nonfactorisable state if their joint (supposedly pure) wavefunction is not expressible as a product of individual wave functions but is instead a superposition of product states. Only when the systems are in a factorisable state they c ..."
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Two or more quantum systems are said to be in an entangled or nonfactorisable state if their joint (supposedly pure) wavefunction is not expressible as a product of individual wave functions but is instead a superposition of product states. Only when the systems are in a factorisable state they can be considered to be separated (in the sense of Bell). We show that whenever two quantum systems interact with each other, it is impossible that all factorisable states remain factorisable during the interaction unless the full Hamiltonian does not couple these systems so to say unless they do not really interact. We also present certain conditions under which particular factorisable states remain factorisable although they represent a bipartite system whose components mutually interact. We identify certain quasiclassical regimes that satisfy these conditions and show that they correspond to classical, prequantum, paradigms associated to the concept of particle. PACS number: O3.65.Bz
Entanglement and Density Matrix of a Block of Spins in AKLT Model
, 802
"... We study a 1dimensional AKLT spin chain, consisting of spins S in the bulk and S/2 at both ends. The unique ground state of this AKLT model is described by the ValenceBondSolid (VBS) state. We investigate the density matrix of a contiguous block of bulk spins in this ground state. It is shown tha ..."
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Cited by 5 (1 self)
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We study a 1dimensional AKLT spin chain, consisting of spins S in the bulk and S/2 at both ends. The unique ground state of this AKLT model is described by the ValenceBondSolid (VBS) state. We investigate the density matrix of a contiguous block of bulk spins in this ground state. It is shown that the density matrix is a projector onto a subspace of dimension (S + 1) 2. This subspace is described by nonzero eigenvalues and corresponding eigenvectors of the density matrix. We prove that for large block the von Neumann entropy coincides with Renyi entropy and is equal to ln (S + 1) 2.
Higher particle form factors of branch point twist fields in integrable quantum field theories
 JOURNAL OF PHYSICS A: MATHEMATICAL AND GENERAL, 44(25)
, 2011
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BoseEinstein Condensates in Optical Lattices: The Superfluid to Mott Insulator Phase Transition
, 2008
"... 87Rb Bose Einstein Condensate in 3D optical lattice was studied in the regime of weak interaction(the superfluid phase) and strong interaction(the Mott insulating phase). The stability of superfluid currents was studied using a moving optical lattice. The critical momentum for stable superfluid curr ..."
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87Rb Bose Einstein Condensate in 3D optical lattice was studied in the regime of weak interaction(the superfluid phase) and strong interaction(the Mott insulating phase). The stability of superfluid currents was studied using a moving optical lattice. The critical momentum for stable superfluid current varies from 0.5 recoil momentum (shallow lattice) to 0 (the Mott insulator) as the system reaches the Mott insulator transition. The phase diagram for the disappearance of superfluidity was studied as a function of momentum and lattice depth. Our phase diagram boundary extrapolates to the critical lattice depth for the superfluidtoMI transition. When a onedimensional gas was loaded into a moving optical lattice a sudden broadening of the transition between stable and unstable phases was observed. A new auxiliary vacuum chamber, which is called the science chamber, was designed and installed to improve optical lattice experimental performance and imaging resolution power. Atoms are transported from the main chamber to the science chamber. By further evaporation cooling, BECs with N 23 x 104 atoms are produced