Entanglement properties of lattice bosons from a variational wave function
Jérôme Thibaut  1@  , Tommaso Roscilde  2, 3@  
1 : Laboratoire de Physique de l'ENS Lyon  (Phys-ENS)  -  Website
CNRS : UMR5672, École Normale Supérieure (ENS) - Lyon
46 allée d'Italie 69007 Lyon -  France
2 : Institut Universitaire de France  (IUF)
Institut Universitaire de France
103 boulevard Saint-Michel, 75005 Paris, France -  France
3 : Laboratoire de Physique, CNRS UMR 5672, Ecole Normale Supérieure de Lyon, Université de Lyon  (ENS Lyon)
ENS Lyon
46 Alléee d'Italie, Lyon, F-69364, France -  France

Entanglement is a defining characteristic of many-body quantum systems, expressing the degree of non-locality required by the description of the state of the system, and quantifying the amount of classical information demanded to faithfully reproduce the reduced state of any subsystem. The ground states of many-body Hamiltonians with short-range interactions are generically characterized by area-law scaling of entanglement entropies of a subsystem, implying that the classical information required to store the reduced density matrix is exponential in the surface of the subsystem itself — this aspect impairs scalable simulations with methods based on the explicit reconstruction of reduced density matrix, such as DMRG, in dimensions higher than one. A viable alternative is based on variational ground states explicitly exhibiting an area-law scaling of entanglement. Here we explore the entanglement properties of entangled plaquette states (EPS) [F. Mezzacapo et al, New Journal of Physics, 11, 083026 (2009)] representing a systematically improvable variational Ansatz for lattice boson models, and lending itself to an efficient optimization based on variational Monte Carlo. We evaluate the explicit dependence of the entanglement entropy on the number of coefficients in the variational Ansatz, and contrast the entanglement properties of local vs. nonlocal plaquettes in the EPS structure. Applying the EPS approach to a lattice boson model (the spatially anisotropic pi-flux triangular lattice) which bridges 1d and 2d physics, we investigate how the entanglement scaling reveals the effective dimensionality of correlations.


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