308 research outputs found
Quantum emulsion: a glassy phase of bosonic mixtures in optical lattices
We numerically investigate mixtures of two interacting bosonic species with
unequal parameters in one-dimensional optical lattices. In large parameter
regions full phase segregation is seen to minimize the energy of the system,
but the true ground state is masked by an exponentially large number of
metastable states characterized by microscopic phase separation. The ensemble
of these quantum emulsion states, reminiscent of emulsions of immiscible
fluids, has macroscopic properties analogous to those of a Bose glass, namely a
finite compressibility in absence of superfluidity. Their metastability is
probed by extensive quantum Monte Carlo simulations generating a rich
correlated stochastic dynamics. The tuning of the repulsion of one of the two
species via a Feshbach resonance drives the system through a quantum phase
transition to the superfluid state.Comment: 4 pages, 3 figure
Time-dependent study of disordered models with infinite projected entangled pair states
Infinite projected entangled pair states (iPEPS), the tensor network ansatz
for two-dimensional systems in the thermodynamic limit, already provide
excellent results on ground-state quantities using either imaginary-time
evolution or variational optimisation. Here, we show (i) the feasibility of
real-time evolution in iPEPS to simulate the dynamics of an infinite system
after a global quench and (ii) the application of disorder-averaging to obtain
translationally invariant systems in the presence of disorder. To illustrate
the approach, we study the short-time dynamics of the square lattice Heisenberg
model in the presence of a bi-valued disorder field
Continuous Tensor Network States for Quantum Fields
We introduce a new class of states for bosonic quantum fields which extend
tensor network states to the continuum and generalize continuous matrix product
states (cMPS) to spatial dimensions . By construction, they are
Euclidean invariant, and are genuine continuum limits of discrete tensor
network states. Admitting both a functional integral and an operator
representation, they share the important properties of their discrete
counterparts: expressiveness, invariance under gauge transformations, simple
rescaling flow, and compact expressions for the -point functions of local
observables. While we discuss mostly the continuous tensor network states
extending Projected Entangled Pair States (PEPS), we propose a generalization
bearing similarities with the continuum Multi-scale Entanglement
Renormalization Ansatz (cMERA).Comment: 16 pages, 5 figures, close to published versio
Combining Tensor Networks with Monte Carlo Methods for Lattice Gauge Theories
Gauged gaussian Projected Entangled Pair States are particular tensor network
constructions that describe lattice states of fermionic matter interacting with
dynamical gauge fields. We show how one can efficiently compute, using
Monte-Carlo techniques, expectation values of physical observables in that
class of states. This opens up the possibility of using tensor network
techniques to investigate lattice gauge theories in two and three spatial
dimensions
Discrete entanglement distribution with squeezed light
We show how one can entangle distant atoms by using squeezed light.
Entanglement is obtained in steady state, and can be increased by manipulating
the atoms locally. We study the effects of imperfections, and show how to scale
up the scheme to build a quantum network.Comment: 5 pages, 4 figure
Quantum Simulations of Lattice Gauge Theories using Ultracold Atoms in Optical Lattices
Can high energy physics be simulated by low-energy, non-relativistic,
many-body systems, such as ultracold atoms? Such ultracold atomic systems lack
the type of symmetries and dynamical properties of high energy physics models:
in particular, they manifest neither local gauge invariance nor Lorentz
invariance, which are crucial properties of the quantum field theories which
are the building blocks of the standard model of elementary particles.
However, it turns out, surprisingly, that there are ways to configure atomic
system to manifest both local gauge invariance and Lorentz invariance. In
particular, local gauge invariance can arise either as an effective, low
energy, symmetry, or as an "exact" symmetry, following from the conservation
laws in atomic interactions. Hence, one could hope that such quantum simulators
may lead to new type of (table-top) experiments, that shall be used to study
various QCD phenomena, as the confinement of dynamical quarks, phase
transitions, and other effects, which are inaccessible using the currently
known computational methods.
In this report, we review the Hamiltonian formulation of lattice gauge
theories, and then describe our recent progress in constructing quantum
simulation of Abelian and non-Abelian lattice gauge theories in 1+1 and 2+1
dimensions using ultracold atoms in optical lattices.Comment: A review; 55 pages, 14 figure
Chiral topological spin liquids with projected entangled pair states
Topological chiral phases are ubiquitous in the physics of the Fractional
Quantum Hall Effect. Non-chiral topological spin liquids are also well known.
Here, using the framework of projected entangled pair states (PEPS), we
construct a family of chiral spin liquids on the square lattice which are
generalized spin-1/2 Resonating Valence Bond (RVB) states obtained from
deformed local tensors with symmetry. On a cylinder, we construct
four topological sectors with even or odd number of spinons on the boundary and
even or odd number of () fluxes penetrating the cylinder which,
we argue, remain orthogonal in the limit of infinite perimeter. The analysis of
the transfer matrix provides evidence of short-range (long-range) triplet
(singlet) correlations as for the critical (non-chiral) RVB state. The
Entanglement Spectrum exhibits chiral edge modes, which we confront to
predictions of Conformal Field Theory, and the corresponding Entanglement
Hamiltonian is shown to be long ranged.Comment: 7 pages, 6 figures, Final version (small changes
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