## Topological insulators with arbitrarily tunable entanglement

Date:
2014-05-15
Author(s):

J. C. Budich, J. Eisert, and E. J. Bergholtz

Reference:

Phys. Rev. B 89, 195120 (2014); DOI: http://dx.doi.org/10.1103/PhysRevB.89.195120

## Quantifying entanglement with scattering experiments

Date:
2013-10-03
Author(s):

O. Marty, M. Epping, H. Kampermann, D. Bruß, M.B. Plenio and M. Cramer

Reference:

Physical Review B 89, 125117 (2014)

We show how the entanglement contained in states of spins arranged on a lattice may be quantified with observables arising in scattering experiments. We focus on the partial differential cross-section obtained in neutron scattering from magnetic materials but our results are sufficiently general such that they may also be applied to, e.g., optical Bragg scattering from ultracold atoms in optical lattices or from ion chains.

## Density-dependent tunneling in the extended Bose–Hubbard model

Date:
2013-06-26 - 2013-12-05
Author(s):

M. Maik, P. Hauke, O. Dutta, M. Lewenstein, J. Zakrzewski

Reference:

New J. Phys. 15, 113041 (2013)

Recently, it has become apparent that when the interactions between polar molecules in optical lattices become strong, the conventional description using the extended Hubbard model has to be modified by additional terms, in particular a density-dependent tunneling term. We investigate here the influence of this term on the ground-state phase diagrams of the two-dimensional extended Bose–Hubbard model.

## Spin liquid phases of alkaline-earth-metal atoms at finite temperature

Date:
2013-10-11 - 2013-12-05
Author(s):

P. Sinkovicz, A. Zamora, E. Szirmai, M. Lewenstein, G. Szirmai

Reference:

Phys. Rev. A 88, 043619 (2013)

We study spin liquid phases of spin-5/2 alkaline-earth-metal atoms on a honeycomb lattice at finite temperatures. Our analysis is based on a Gutzwiller projection variational approach recast to a path-integral formalism. In the framework of a saddle-point approximation we determine spin liquid phases with lowest free energy and study their temperature dependence.

## Ground States of Fermionic lattice Hamiltonians with Permutation Symmetry

Date:
2013-12-05
Author(s):

Christina V. Kraus, Maciej Lewenstein, J. Ignacio Cirac

Reference:

Phys. Rev. A. 88, 022335 (2013)

We study the ground states of lattice Hamiltonians that are invariant under permutations, in the limit where the number of lattice sites N

## Momentum polarization: an entanglement measure of topological spin and chiral central charge

Date:
2012-12-31
Author(s):

Hong-Hao Tu, Yi Zhang, Xiao-Liang Qi

Reference:

arXiv:1212.6951v1

Topologically ordered states are quantum states of matter with topological ground state degeneracy and quasi-particles carrying fractional quantum numbers and fractional statistics. The topological spin $\theta_a=2\pi h_a$ is an important property of a topological quasi-particle, which is the Berry phase obtained in the adiabatic self-rotation of the quasi-particle by $2\pi$.

## Projected BCS states and spin Hamiltonians for the SO(n)1 Wess-Zumino-Witten model

Date:
2013-01-14
Author(s):

Hong-Hao Tu

Reference:

DOI: 10.1103/PhysRevB.87.041103
PACS: 75.10.Pq, 03.65.Fd, 11.25.Hf

We propose a class of projected BCS wave functions and derive their parent spin Hamiltonians. These wave functions can be formulated as infinite matrix product states constructed by chiral correlators of Majorana fermions. In one dimension, the spin Hamiltonians can be viewed as SO(n) generalizations of Haldane-Shastry models. We numerically compute the spin-spin correlation functions and Rényi entropies for n=5 and 6. Together with the results for n=3 and 4, we conclude that these states are critical and their low-energy effective theory is the SO(n)1 Wess-Zumino-Witten model.

## Critical properties and Renyi entropies of the spin-3/2 XXZ chain

Date:
2012-04-06
Author(s):

M. Dalmonte, E. Ercolessi and L. Taddia

Reference:

Phys. Rev. B 85, 165112 (2012)
doi:10.1103/PhysRevB.85.165112

We discuss entanglement and critical properties of the spin-3/2 XXZ chain in its entire gapless region. Employing density-matrix renormalization-group calculations combined with different methods based on level spectroscopy, correlation functions, and entanglement entropies, we determine the sound velocity and the Luttinger parameter of the model as a function of the anisotropy parameter.

## Two-photon quantum interference from separate nitrogen vacancy centers in diamond

Date:
2011-10-14
Author(s):

H. Bernien, L. Childress, L. Robledo, M. Markham, D. Twitchen, R. Hanson

Reference:

Physical Review Letters 108, 043604 (2012)

We report on the observation of quantum interference of the emission from two separate nitrogen vacancy (NV) centers in diamond. Taking advantage of optically induced spin polarization in combination with polarization filtering, we isolate a single transition within the zero-phonon line of the non-resonantly excited NV centers. The time-resolved two-photon interference contrast of this filtered emission reaches 66%. Furthermore, we observe quantum interference from dissimilar NV centers tuned into resonance through the dc Stark effect.

## Generating Entanglement and Squeezed States of Nuclear Spins in Quantum Dots

Date:
2011-11-08
Author(s):

M. S. Rudner, L. M. K. Vandersypen, V. Vuletić, and L. S. Levitov

Reference:

Physical Review Letters 107, 206806

We present a scheme for achieving coherent spin squeezing of nuclear spin states in semiconductor quantum dots. The nuclear polarization dependence of the electron spin resonance generates a unitary evolution that drives nuclear spins into a collective entangled state. The polarization dependence of the resonance generates an area-preserving, twisting dynamics that squeezes and stretches the nuclear spin Wigner distribution without the need for nuclear spin flips. Our estimates of squeezing times indicate that the entanglement threshold can be reached in current experiments.