7,876 research outputs found
Sequential modular position and momentum measurements of a trapped ion mechanical oscillator
The non-commutativity of position and momentum observables is a hallmark
feature of quantum physics. However this incompatibility does not extend to
observables which are periodic in these base variables. Such modular-variable
observables have been suggested as tools for fault-tolerant quantum computing
and enhanced quantum sensing. Here we implement sequential measurements of
modular variables in the oscillatory motion of a single trapped ion, using
state-dependent displacements and a heralded non-destructive readout. We
investigate the commutative nature of modular variable observables by
demonstrating no-signaling-in-time between successive measurements, using a
variety of input states. In the presence of quantum interference, which we
enhance using squeezed input states, measurements of different periodicity show
signaling-in-time. The sequential measurements allow us to extract two-time
correlators for modular variables, which we use to violate a Leggett-Garg
inequality. The experiments involve control and coherence of multi-component
superpositions of up to 8 coherent, squeezed or Fock state wave-packets.
Signaling-in-time as well as Leggett-Garg inequalities serve as efficient
quantum witnesses which we probe here with a mechanical oscillator, a system
which has a natural crossover from the quantum to the classical regime.Comment: 6 pages, 3 figures and supplemental informatio
Orbital magnetism in axially deformed sodium clusters: From scissors mode to dia-para magnetic anisotropy
Low-energy orbital magnetic dipole excitations, known as scissors mode (SM),
are studied in alkali metal clusters. Subsequent dynamic and static effects are
explored. The treatment is based on a self-consistent microscopic approach
using the jellium approximation for the ionic background and the Kohn-Sham mean
field for the electrons. The microscopic origin of SM and its main features
(structure of the mode in light and medium clusters, separation into low- and
high-energy plasmons, coupling high-energy M1 scissors and E2 quadrupole
plasmons, contributions of shape isomers, etc) are discussed. The scissors M1
strength acquires large values with increasing cluster size. The mode is
responsible for the van Vleck paramagnetism of spin-saturated clusters. Quantum
shell effects induce a fragile interplay between Langevin diamagnetism and van
Vleck paramagnetism and lead to a remarkable dia-para anisotropy in magnetic
susceptibility of particular light clusters. Finally, several routes for
observing the SM experimentally are discussed.Comment: 21 pages, 7 figure
Eigenvalue distributions for some correlated complex sample covariance matrices
The distributions of the smallest and largest eigenvalues for the matrix
product , where is an complex Gaussian matrix
with correlations both along rows and down columns, are expressed as determinants. In the case of correlation along rows, these expressions are
computationally more efficient than those involving sums over partitions and
Schur polynomials reported recently for the same distributions.Comment: 11 page
Barrier, converting, and tray-forming properties of paperboard packaging materials coated with waterborne dispersions
In this work, different food-contact experimental and commercial aqueous polymeric dispersions were applied to paperboard via rod coating technology to achieve <5% non-cellulosic content. Barrier (water, moisture and grease), mechanical (tensile and bending) and converting (heat-sealing and creasing) properties were analysed before tray formation trials on pilot-scale equipment. Dispersion-coated samples were compared against polyethylene terephthalate (PET) extrusion-coated paperboard, the principal industrial material used for food trays. Results show that, within the investigated properties, waterborne dispersions can achieve similar barrier properties compared with PET, yet at lower dry coat grammage (12 g/m(2) vs. 40 g/m(2 )of PET-coated paperboard). Additionally, the investigated coatings heat-sealed at temperatures as low as 80-90(degrees)C, almost 100(degrees)C less than PET; however, lower seal forces could be achieved (15-20 N/(25 mm) vs. 23 N/(25 mm) of PET-coated paperboard). Paperboard delamination occurred at the highest seal forces. Dispersion-coated trays were obtained at 4.5-5.0% blank moisture content. Formed trays at industrial processing parameters showed critical coating damage during converting due to tensile stresses. This work shows that milder processing conditions allow a reduction in coat defects
Time-dependent Hamiltonian estimation for Doppler velocimetry of trapped ions
The time evolution of a closed quantum system is connected to its Hamiltonian
through Schroedinger's equation. The ability to estimate the Hamiltonian is
critical to our understanding of quantum systems, and allows optimization of
control. Though spectroscopic methods allow time-independent Hamiltonians to be
recovered, for time-dependent Hamiltonians this task is more challenging. Here,
using a single trapped ion, we experimentally demonstrate a method for
estimating a time-dependent Hamiltonian of a single qubit. The method involves
measuring the time evolution of the qubit in a fixed basis as a function of a
time-independent offset term added to the Hamiltonian. In our system the
initially unknown Hamiltonian arises from transporting an ion through a static,
near-resonant laser beam. Hamiltonian estimation allows us to estimate the
spatial dependence of the laser beam intensity and the ion's velocity as a
function of time. This work is of direct value in optimizing transport
operations and transport-based gates in scalable trapped ion quantum
information processing, while the estimation technique is general enough that
it can be applied to other quantum systems, aiding the pursuit of high
operational fidelities in quantum control.Comment: 10 pages, 8 figure
The pasta phase within density dependent hadronic models
In the present paper we investigate the onset of the pasta phase with
different parametrisations of the density dependent hadronic model and compare
the results with one of the usual parametrisation of the non-linear Walecka
model. The influence of the scalar-isovector virtual delta meson is shown. At
zero temperature two different methods are used, one based on coexistent phases
and the other on the Thomas-Fermi approximation. At finite temperature only the
coexistence phases method is used. npe matter with fixed proton fractions and
in beta-equilibrium are studied. We compare our results with restrictions
imposed on the the values of the density and pressure at the inner edge of the
crust, obtained from observations of the Vela pulsar and recent isospin
diffusion data from heavy-ion reactions, and with predictions from spinodal
calculations.Comment: 15 pages, 11 figures and 7 table
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