04. ENTANGLEMENT IN MANY-BODY SYSTEMS

Measuring multipartite entanglement via dynamic susceptibilities

Date: 
2015-09-05 - 2016-06-07
Author(s): 

Philipp Hauke, Markus Heyl, Luca Tagliacozzo, Peter Zoller

Reference: 

Nature Physics, advance online pubication

Entanglement plays a central role in our understanding of quantum many body physics, and is fundamental in characterising quantum phases and quantum phase transitions. Developing protocols to detect and quantify entanglement of many-particle quantum states is thus a key challenge for present experiments. Here, we show that the quantum Fisher information, representing a witness for genuinely multipartite entanglement, becomes measurable for thermal ensembles via the dynamic susceptibility, i.e., with resources readily available in present cold atomic gas and condensed-matter experiments.

One-dimensional Bose gas in optical lattices of arbitrary strength

Date: 
2015-09-15 - 2016-02-08
Author(s): 

Grigory E. Astrakharchik, Konstantin V. Krutitsky, Maciej Lewenstein, and Ferran Mazzanti

Reference: 

Phys. Rev. A 93, 021605(R)

One-dimensional Bose gas with contact interaction in optical lattices at zero temperature is investigated by means of the exact diffusion Monte Carlo algorithm. The results obtained from the fundamental continuous model are compared with those obtained from the lattice (discrete) Bose-Hubbard model, using exact diagonalization, and from the quantum sine-Gordon model.

Topological phases of lattice bosons with a dynamical gauge field

Date: 
2015-12-14 - 2016-03-02
Author(s): 

David Raventós, Tobias Graß, Bruno Juliá-Díaz, Luis Santos, Maciej Lewenstein

Reference: 

Phys. Rev. A 93, 033605

Optical lattices with a complex-valued tunneling term have become a standard way of studying gauge-field physics with cold atoms. If the complex phase of the tunneling is made density dependent, such a system features even a self-interacting or dynamical magnetic field. In this paper we study the scenario of a few bosons in either a static or a dynamical gauge field by means of exact diagonalization.

Entanglement of an impurity in a few-body one-dimensional ideal Bose system

Date: 
2015-12-10 - 2016-03-17
Author(s): 

M. A. García-March, A. S. Dehkharghani, N. T. Zinner

Reference: 

Journal of Physics B: Atomic, Molecular and Optical Physics, Volume 49, Number 7

We study the correlation between an impurity and a small ensemble of bosonic particles in one dimension. Our study analyzes the one-body density matrix and calculates the corresponding von Neumann entanglement entropy as a function of the interaction strength between the impurity and the bosons when all particles have the same mass.

Nonlocality in many-body quantum systems detected with two-body correlators

Date: 
2015-06-22 - 2015-07-24
Author(s): 

Jordi Tura, Remigiusz Augusiak, Ana Belén Sainz, Bernd Lücke, Carsten Klempt, Maciej Lewenstein, Antonio Acín

Reference: 

Annals of Physics, Volume 362, November 2015, Pages 370–423

Contemporary understanding of correlations in quantum many-body systems and in quantum phase transitions is based to a large extent on the recent intensive studies of entanglement in many-body systems.

Splitting a critical spin chain

Date: 
2014-01-30 - 2014-04-23
Author(s): 

Alejandro Zamora, Javier Rodriguez-Laguna, Maciej Lewenstein, Luca Tagliacozzo

Reference: 

arXiv:1401.7916

Constrained dynamics via the Zeno effect in quantum simulation: Implementing non-Abelian lattice gauge theories with cold atoms

Date: 
2013-10-16 - 2014-01-22
Author(s): 

K. Stannigel, P. Hauke, D. Marcos, M. Hafezi, S. Diehl, M. Dalmonte, P. Zoller

Reference: 

ArXiv:1308.0528

We show how engineered classical noise can be used to generate constrained Hamiltonian dynamics in atomic quantum simulators of many-body systems, taking advantage of the continuous Zeno effect. After discussing the general theoretical framework, we focus on applications in the context of lattice gauge theories, where imposing exotic, quasi-local constraints is usually challenging.

Tensor networks for Lattice Gauge Theories and Atomic Quantum Simulation

Date: 
2013-12-11 - 2014-01-22
Author(s): 

E. Rico, T. Pichler, M. Dalmonte, P. Zoller, S. Montangero

Reference: 

ArXiv:1312:3127

We show that gauge invariant quantum link models, Abelian and non-Abelian, can be exactly described in terms of tensor networks states. Quantum link models represent an ideal bridge between high-energy to cold atom physics, as they can be used in cold-atoms in optical lattices to study lattice gauge theories.

Hybrid Topological Quantum Computation with Majorana Fermions: A Cold Atom Setup

Date: 
2013-12-23 - 2014-01-22
Author(s): 

C. Laflamme, M. A. Baranov, P. Zoller, C. V. Kraus

Reference: 

ArXiv:1312.6583

In this paper we present a hybrid scheme for topological quantum computation in a system of cold atoms trapped in an atomic lattice. A topological qubit subspace is defined using Majorana fermions which emerge in a network of atomic Kitaev one-dimensional wires. We show how braiding can be efficiently implemented in this setup and propose a direct way to demonstrate the non-Abelian nature of Majorana fermions via a single parity measurement.

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