6,110 research outputs found
Opto-mechanical transducers for long-distance quantum communication
We describe a new scheme to interconvert stationary and photonic qubits which
is based on indirect qubit-light interactions mediated by a mechanical
resonator. This approach does not rely on the specific optical response of the
qubit and thereby enables optical quantum interfaces for a wide range of solid
state spin and charge based systems. We discuss the implementation of quantum
state transfer protocols between distant nodes of a large scale network and
evaluate the effect of the main noise sources on the resulting state transfer
fidelities. For the specific examples of electronic spin qubits and
superconducting charge qubits we show that high fidelity quantum communication
protocols can be implemented under realistic experimental conditions.Comment: Version as accepted by PR
Finite Wavelength Instabilities in a Slow Mode Coupled Complex Ginzburg-Landau Equation
In this Letter, we discuss the effect of slow real modes in reaction-diffusion systems close to a supercritical Hopf bifurcation. The spatiotemporal effects of the slow mode cannot be captured by traditional descriptions in terms of a single complex Ginzburg-Landau equation (CGLE). We show that the slow mode coupling to the CGLE introduces a novel set of finite wavelength instabilities not present in the CGLE. For spiral waves, these instabilities highly affect the location of regions for convective and absolute instability. These new instability boundaries are consistent with transitions to spatiotemporal chaos found by simulation of the corresponding coupled amplitude equations
Efficient qubit detection using alkali earth metal ions and a double STIRAP process
We present a scheme for robust and efficient projection measurement of a
qubit consisting of the two magnetic sublevels in the electronic ground state
of alkali earth metal ions. The scheme is based on two stimulated Raman
adiabatic passages (STIRAP) involving four partially coherent laser fields. We
show how the efficiency depends on experimentally relevant parameters: Rabi
frequencies, pulse widths, laser linewidths, one- and two-photon detunings,
residual laser power, laser polarization and ion motion.Comment: 14 pages, 15 figure
Entanglement in Anderson Nanoclusters
We investigate the two-particle spin entanglement in magnetic nanoclusters
described by the periodic Anderson model. An entanglement phase diagram is
obtained, providing a novel perspective on a central property of magnetic
nanoclusters, namely the temperature dependent competition between local Kondo
screening and nonlocal Ruderman-Kittel-Kasuya-Yoshida spin ordering. We find
that multiparticle entangled states are present for finite magnetic field as
well as in the mixed valence regime and away from half filling. Our results
emphasize the role of charge fluctuations.Comment: 5 pages, 3 figure
Dual Geometric Worm Algorithm for Two-Dimensional Discrete Classical Lattice Models
We present a dual geometrical worm algorithm for two-dimensional Ising
models. The existence of such dual algorithms was first pointed out by
Prokof'ev and Svistunov \cite{ProkofevClassical}. The algorithm is defined on
the dual lattice and is formulated in terms of bond-variables and can therefore
be generalized to other two-dimensional models that can be formulated in terms
of bond-variables. We also discuss two related algorithms formulated on the
direct lattice, applicable in any dimension. These latter algorithms turn out
to be less efficient but of considerable intrinsic interest. We show how such
algorithms quite generally can be "directed" by minimizing the probability for
the worms to erase themselves. Explicit proofs of detailed balance are given
for all the algorithms. In terms of computational efficiency the dual
geometrical worm algorithm is comparable to well known cluster algorithms such
as the Swendsen-Wang and Wolff algorithms, however, it is quite different in
structure and allows for a very simple and efficient implementation. The dual
algorithm also allows for a very elegant way of calculating the domain wall
free energy.Comment: 12 pages, 6 figures, Revtex
Demonstration of PLOTs from the EuroPLOT project
The EuroPLOT project (2010-2013) has been funded to explore the concept of persuasive design for learning and teaching. It has developed Persuasive Learn-ing Objects and Technologies (PLOTs), manifested in two tools and a set of learning objects that have been tested and evaluated in four different case studies. These PLOTs will be shown in this demonstration, and the participants can try them out and experience for themselves the impact of persuasive technology that is embedded in these PLOTs. This will be one authoring tool (PLOTMaker) and one delivery tool (PLOTLearner). Furthermore, there will be learning objects shown which have been developed for those four different case studies. All of these PLOTs have already been tested and evaluated during case studies with real learners
Corrections to scaling in entanglement entropy from boundary perturbations
We investigate the corrections to scaling of the Renyi entropies of a region
of size l at the end of a semi-infinite one-dimensional system described by a
conformal field theory when the corrections come from irrelevant boundary
operators. The corrections from irrelevant bulk operators with scaling
dimension x have been studied by Cardy and Calabrese (2010), and they found not
only the expected corrections of the form l^(4-2x) but also unusual corrections
that could not have been anticipated by finite-size scaling arguments alone.
However, for the case of perturbations from irrelevant boundary operators we
find that the only corrections that can occur to leading order are of the form
l^(2-2x_b) for boundary operators with scaling dimension x_b < 3/2, and l^(-1)
when x_b > 3/2. When x_b=3/2 they are of the form l^(-1)log(l). A marginally
irrelevant boundary perturbation will give leading corrections going as
log(l)^(-3). No unusual corrections occur when perturbing with a boundary
operator.Comment: 8 pages. Minor improvements and updated references. Published versio
Exact Results for the Bipartite Entanglement Entropy of the AKLT spin-1 chain
We study the entanglement between two domains of a spin-1 AKLT chain subject
to open boundary conditions. In this case the ground-state manifold is
four-fold degenerate. We summarize known results and present additional exact
analytical results for the von Neumann entanglement entropy, as a function of
both the size of the domains and the total system size for {\it all} four
degenerate ground-states. In the large limit the entanglement entropy
approaches and for the and states,
respectively. In all cases, it is found that this constant is approached
exponentially fast defining a length scale equal to the known
bulk correlation length.Comment: 11 pages, 3 figure
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