15,777 research outputs found
On the stability of quantum holonomic gates
We provide a unified geometrical description for analyzing the stability of
holonomic quantum gates in the presence of imprecise driving controls
(parametric noise). We consider the situation in which these fluctuations do
not affect the adiabatic evolution but can reduce the logical gate performance.
Using the intrinsic geometric properties of the holonomic gates, we show under
which conditions on noise's correlation time and strength, the fluctuations in
the driving field cancel out. In this way, we provide theoretical support to
previous numerical simulations. We also briefly comment on the error due to the
mismatch between real and nominal time of the period of the driving fields and
show that it can be reduced by suitably increasing the adiabatic time.Comment: 7 page
Multi-Domain Walls in Massive Supersymmetric Sigma-Models
Massive maximally-supersymmetric sigma models are shown to exhibit multiple
static kink-domain wall solutions that preserve 1/2 of the supersymmetry. The
kink moduli space admits a natural Kahler metric. We examine in some detail the
case when the target of the sigma model is given by the co-tangent bundle of
CP^n equipped with the Calabi metric, and we show that there exist BPS
solutions corresponding to n kinks at arbitrary separation. We also describe
how 1/4-BPS charged and intersecting domain walls are described in the
low-energy dynamics on the kink moduli space. We comment on the similarity of
these results to monopole dynamics.Comment: 15 pages, 3 figures, Latex. Introduction extended with discussion of
complex central charge
Kraus representation for density operator of arbitrary open qubit system
We show that the time evolution of density operator of open qubit system can
always be described in terms of the Kraus representation. A general scheme on
how to construct the Kraus operators for an open qubit system is proposed,
which can be generalized to open higher dimensional quantum systems.Comment: 5 pages, no figures. Some words are rephrase
Inelastic Collapse of Three Particles
A system of three particles undergoing inelastic collisions in arbitrary
spatial dimensions is studied with the aim of establishing the domain of
``inelastic collapse''---an infinite number of collisions which take place in a
finite time. Analytic and simulation results show that for a sufficiently small
restitution coefficient, , collapse can
occur. In one dimension, such a collapse is stable against small perturbations
within this entire range. In higher dimensions, the collapse can be stable
against small variations of initial conditions, within a smaller range,
.Comment: 6 pages, figures on request, accepted by PR
Rank 3 permutation characters and maximal subgroups
In this paper we classify all maximal subgroups M of a nearly simple
primitive rank 3 group G of type L=Omega_{2m+1}(3), m > 3; acting on an L-orbit
E of non-singular points of the natural module for L such that 1_P^G <=1_M^G
where P is a stabilizer of a point in E. This result has an application to the
study of minimal genera of algebraic curves which admit group actions.Comment: 41 pages, to appear in Forum Mathematicu
Twist-3 Contributions in Semi-Inclusive DIS in the Target Fragmentation Region
We present the complete results up to twist-3 for hadron production in the
target fragmentation region of semi-inclusive deep inelastic scattering with a
polarized lepton beam and polarized nucleon target. The non-perturbative
effects are factorized into fracture functions. The calculation up to twist-3
is non-trivial since one has to keep gauge invariance. By applying collinear
expansion, we show that the hadronic tensor can be expressed by gauge-invariant
fracture functions. We also present the results for the structure functions and
azimuthal asymmetries.Comment: 11 pages, 2 figure
Topological engineering of interfacial optical Tamm states for highly-sensitive near-singular-phase optical detection
We developed planar multilayered photonic-plasmonic structures, which support
topologically protected optical states on the interface between metal and
dielectric materials, known as optical Tamm states. Coupling of incident light
to the Tamm states can result in perfect absorption within one of several
narrow frequency bands, which is accompanied by a singular behavior of the
phase of electromagnetic field. In the case of near-perfect absorptance, very
fast local variation of the phase can still be engineered. In this work, we
theoretically and experimentally demonstrate how these drastic phase changes
can improve sensitivity of optical sensors. A planar Tamm absorber was
fabricated and used to demonstrate remote near-singular-phase temperature
sensing with an over an order of magnitude improvement in sensor sensitivity
and over two orders of magnitude improvement in the figure of merit over the
standard approach of measuring shifts of resonant features in the reflectance
spectra of the same absorber. Our experimentally demonstrated
phase-to-amplitude detection sensitivity improvement nearly doubles that of
state-of-the-art nano-patterned plasmonic singular-phase detectors, with
further improvements possible via more precise fabrication. Tamm perfect
absorbers form the basis for robust planar sensing platforms with tunable
spectral characteristics, which do not rely on low-throughput nano-patterning
techniques.Comment: 31 pages; 6 main text figures and 10 supplementary figure
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