379 research outputs found
Soft versus Hard Dynamics for Field-driven Solid-on-Solid Interfaces
Analytical arguments and dynamic Monte Carlo simulations show that the
microstructure of field-driven Solid-on-Solid interfaces depends strongly on
the dynamics. For nonconservative dynamics with transition rates that factorize
into parts dependent only on the changes in interaction energy and field
energy, respectively (soft dynamics), the intrinsic interface width is
field-independent. For non-factorizing rates, such as the standard Glauber and
Metropolis algorithms (hard dynamics), it increases with the field.
Consequences for the interface velocity and its anisotropy are discussed.Comment: 9 pages LaTex with imbedded .eps figs. Minor revision
Entropy production and fluctuation relations for a KPZ interface
We study entropy production and fluctuation relations in the restricted
solid-on-solid growth model, which is a microscopic realization of the KPZ
equation. Solving the one dimensional model exactly on a particular line of the
phase diagram we demonstrate that entropy production quantifies the distance
from equilibrium. Moreover, as an example of a physically relevant current
different from the entropy, we study the symmetry of the large deviation
function associated with the interface height. In a special case of a system of
length L=4 we find that the probability distribution of the variation of height
has a symmetric large deviation function, displaying a symmetry different from
the Gallavotti-Cohen symmetry.Comment: 21 pages, 5 figure
Facet ridge end points in crystal shapes
Equilibrium crystal shapes (ECS) near facet ridge end points (FRE) are
generically complex. We study the body-centered solid-on-solid model on a
square lattice with an enhanced uniaxial interaction range to test the
stability of the so-called stochastic FRE point where the model maps exactly
onto one dimensional Kardar-Parisi-Zhang type growth and the local ECS is
simple. The latter is unstable. The generic ECS contains first-order ridges
extending into the rounded part of the ECS, where two rough orientations
coexist and first-order faceted to rough boundaries terminating in
Pokrovsky-Talapov type end points.Comment: Contains 4 pages, 5 eps figures. Uses RevTe
Chiral phase properties of finite size quark droplets in the Nambu--Jona-Lasinio model
Chiral phase properties of finite size hadronic systems are investigated
within the Nambu--Jona-Lasinio model. Finite size effects are taken into
account by making use of the multiple reflection expansion. We find that, for
droplets with relatively small baryon numbers, chiral symmetry restoration is
enhanced by the finite size effects. However the radius of the stable droplet
does not change much, as compared to that without the multiple reflection
expansion.Comment: RevTex4, 9 pages, 6 figures, to be published in Phys. Rev.
Spin chirality induced by the Dzyaloshinskii-Moriya interaction and the polarized neutron scattering
We discuss the influence of the Dzyaloshinskii-Moriya (DM) interaction in the
Heizenberg spin chain model for the observables in the polarized neutron
scattering experiments. We show that different choices of the parameters of DM
interaction may leave the spectrum of the problem unchanged, while the
observable spin-spin correlation functions may differ qualitatively.
Particularly, for the uniform DM interaction one has the incommensurate
fluctuations and polarization-dependent neutron scattering in the paramagnetic
phase. We sketch the possible generalization of our treatment to higher
dimensions.Comment: 4 pages, REVTEX, no figures, references added, to appear in PR
Universality class of the restricted solid-on-solid model with hopping
We study the restricted solid-on-solid (RSOS) model with finite hopping
distance , using both analytical and numerical methods. Analytically, we
use the hard-core bosonic field theory developed by the authors [Phys. Rev. E
{\bf 62}, 7642 (2000)] and derive the Villain-Lai-Das Sarma (VLD) equation for
the case which corresponds to the conserved RSOS (CRSOS) model
and the Kardar-Parisi-Zhang (KPZ) equation for all finite values of .
Consequently, we find that the CRSOS model belongs to the VLD universality
class and the RSOS models with any finite hopping distance belong to the KPZ
universality class. There is no phase transition at a certain finite hopping
distance contrary to the previous result. We confirm the analytic results using
the Monte Carlo simulations for several values of the finite hopping distance.Comment: 13 pages, 3 figure
Quantum teleportation between light and matter
Quantum teleportation is an important ingredient in distributed quantum
networks, and can also serve as an elementary operation in quantum computers.
Teleportation was first demonstrated as a transfer of a quantum state of light
onto another light beam; later developments used optical relays and
demonstrated entanglement swapping for continuous variables. The teleportation
of a quantum state between two single material particles (trapped ions) has now
also been achieved. Here we demonstrate teleportation between objects of a
different nature - light and matter, which respectively represent 'flying' and
'stationary' media. A quantum state encoded in a light pulse is teleported onto
a macroscopic object (an atomic ensemble containing 10^12 caesium atoms).
Deterministic teleportation is achieved for sets of coherent states with mean
photon number (n) up to a few hundred. The fidelities are 0.58+-0.02 for n=20
and 0.60+-0.02 for n=5 - higher than any classical state transfer can possibly
achieve. Besides being of fundamental interest, teleportation using a
macroscopic atomic ensemble is relevant for the practical implementation of a
quantum repeater. An important factor for the implementation of quantum
networks is the teleportation distance between transmitter and receiver; this
is 0.5 metres in the present experiment. As our experiment uses propagating
light to achieve the entanglement of light and atoms required for
teleportation, the present approach should be scalable to longer distances.Comment: 23 pages, 8 figures, incl. supplementary informatio
Demonstrating various quantum effects with two entangled laser beams
We report on the preparation of entangled two mode squeezed states of yet
unseen quality. Based on a measurement of the covariance matrix we found a
violation of the Reid and Drummond EPR-criterion at a value of only 0.36\pm0.03
compared to the threshold of 1. Furthermore, quantum state tomography was used
to extract a single photon Fock state solely based on homodyne detection,
demonstrating the strong quantum features of this pair of laser-beams. The
probability for a single photon in this ensemble measurement exceeded 2/3
Derivation of continuum stochastic equations for discrete growth models
We present a formalism to derive the stochastic differential equations (SDEs)
for several solid-on-solid growth models. Our formalism begins with a mapping
of the microscopic dynamics of growth models onto the particle systems with
reactions and diffusion. We then write the master equations for these
corresponding particle systems and find the SDEs for the particle densities.
Finally, by connecting the particle densities with the growth heights, we
derive the SDEs for the height variables. Applying this formalism to discrete
growth models, we find the Edwards-Wilkinson equation for the symmetric
body-centered solid-on-solid (BCSOS) model, the Kardar-Parisi-Zhang equation
for the asymmetric BCSOS model and the generalized restricted solid-on-solid
(RSOS) model, and the Villain--Lai--Das Sarma equation for the conserved RSOS
model. In addition to the consistent forms of equations for growth models, we
also obtain the coefficients associated with the SDEs.Comment: 5 pages, no figur
Mapping coherence in measurement via full quantum tomography of a hybrid optical detector
Quantum states and measurements exhibit wave-like --- continuous, or
particle-like --- discrete, character. Hybrid discrete-continuous photonic
systems are key to investigating fundamental quantum phenomena, generating
superpositions of macroscopic states, and form essential resources for
quantum-enhanced applications, e.g. entanglement distillation and quantum
computation, as well as highly efficient optical telecommunications. Realizing
the full potential of these hybrid systems requires quantum-optical
measurements sensitive to complementary observables such as field quadrature
amplitude and photon number. However, a thorough understanding of the practical
performance of an optical detector interpolating between these two regions is
absent. Here, we report the implementation of full quantum detector tomography,
enabling the characterization of the simultaneous wave and photon-number
sensitivities of quantum-optical detectors. This yields the largest
parametrization to-date in quantum tomography experiments, requiring the
development of novel theoretical tools. Our results reveal the role of
coherence in quantum measurements and demonstrate the tunability of hybrid
quantum-optical detectors.Comment: 7 pages, 3 figure
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