1,104 research outputs found
Corner wetting in a far-from-equilibrium magnetic growth model
The irreversible growth of magnetic films is studied in three-dimensional
confined geometries of size , where is the growing
direction. Competing surface magnetic fields, applied to opposite corners of
the growing system, lead to the observation of a localization-delocalization
(weakly rounded) transition of the interface between domains of up and down
spins on the planes transverse to the growing direction. This effective
transition is the precursor of a true far-from-equilibrium corner wetting
transition that takes place in the thermodynamic limit. The phenomenon is
characterized quantitatively by drawing a magnetic field-temperature phase
diagram, firstly for a confined sample of finite size, and then by
extrapolating results, obtained with samples of different size, to the
thermodynamic limit. The results of this work are a nonequilibrium realization
of analogous phenomena recently investigated in equilibrium systems, such as
corner wetting transitions in the Ising model.Comment: 14 pages, 8 figures. EPJ styl
Series compensation investigation on the hydro-quebec and NYPA 765 kV transmission system : modeling and stability analysis
This thesis presents a mathematical approach for raising the power steady state stability limit by adding series capacitive compensation to a transmission line. The effect of series capacitive compensation and degree of compensation were investigated in detail. The power system studied includes an automatically controlled power system, IEEE Type I.
The results of the actual and theoretical steady state stability limits for a given series capacitance location and degree of compensation were obtained by applying the frequency domain technique. The natural frequencies of each compensated power network were examined.
The best location for series capacitive compensation is proposed which is the midpoint of the MSU-1 and MSC-7040 lines. At this location, the actual and theoretical power steady state stability limits were obtained and compared for different degrees of compensation and system operating voltages
Quantum Simulations of Relativistic Quantum Physics in Circuit QED
We present a scheme for simulating relativistic quantum physics in circuit
quantum electrodynamics. By using three classical microwave drives, we show
that a superconducting qubit strongly-coupled to a resonator field mode can be
used to simulate the dynamics of the Dirac equation and Klein paradox in all
regimes. Using the same setup we also propose the implementation of the
Foldy-Wouthuysen canonical transformation, after which the time derivative of
the position operator becomes a constant of the motion.Comment: 13 pages, 3 figure
Quantum Simulation of Dissipative Processes without Reservoir Engineering
We present a quantum algorithm to simulate general finite dimensional
Lindblad master equations without the requirement of engineering the
system-environment interactions. The proposed method is able to simulate both
Markovian and non-Markovian quantum dynamics. It consists in the quantum
computation of the dissipative corrections to the unitary evolution of the
system of interest, via the reconstruction of the response functions associated
with the Lindblad operators. Our approach is equally applicable to dynamics
generated by effectively non-Hermitian Hamiltonians. We confirm the quality of
our method providing specific error bounds that quantify itss accuracy.Comment: 7 pages + Supplemental Material (6 pages
Dynamic heterogeneities in attractive colloids
We study the formation of a colloidal gel by means of Molecular Dynamics
simulations of a model for colloidal suspensions. A slowing down with gel-like
features is observed at low temperatures and low volume fractions, due to the
formation of persistent structures. We show that at low volume fraction the
dynamic susceptibility, which describes dynamic heterogeneities, exhibits a
large plateau, dominated by clusters of long living bonds. At higher volume
fraction, where the effect of the crowding of the particles starts to be
present, it crosses over towards a regime characterized by a peak. We introduce
a suitable mean cluster size of clusters of monomers connected by "persistent"
bonds which well describes the dynamic susceptibility.Comment: 4 pages, 4 figure
Quantum Estimation Methods for Quantum Illumination
Quantum illumination consists in shining quantum light on a target region
immersed in a bright thermal bath, with the aim of detecting the presence of a
possible low-reflective object. If the signal is entangled with the receiver,
then a suitable choice of the measurement offers a gain with respect to the
optimal classical protocol employing coherent states. Here, we tackle this
detection problem by using quantum estimation techniques to measure the
reflectivity parameter of the object, showing an enhancement in the
signal-to-noise ratio up to 3 dB with respect to the classical case when
implementing only local measurements. Our approach employs the quantum Fisher
information to provide an upper bound for the error probability, supplies the
concrete estimator saturating the bound, and extends the quantum illumination
protocol to non-Gaussian states. As an example, we show how Schrodinger's cat
states may be used for quantum illumination.Comment: Published versio
Algorithmic quantum simulation of memory effects
We propose a method for the algorithmic quantum simulation of memory effects
described by integrodifferential evolution equations. It consists in the
systematic use of perturbation theory techniques and a Markovian quantum
simulator. Our method aims to efficiently simulate both completely positive and
nonpositive dynamics without the requirement of engineering non-Markovian
environments. Finally, we find that small error bounds can be reached with
polynomially scaling resources, evaluated as the time required for the
simulation
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