35,805 research outputs found
Waiting times of entangled electrons in normal-superconducting junctions
We consider a normal-superconducting junction in order to investigate the
effect of new physical ingredients on waiting times. First, we study the
interplay between Andreev and specular scattering at the interface on the
distribution of waiting times of electrons or holes separately. In that case
the distribution is not altered dramatically compared to the case of a single
quantum channel with a quantum point contact since the interface acts as an
Andreev mirror for holes. We then consider a fully entangled state originating
from spliting of Cooper pairs at the interface and demonstrate a significant
enhancement of the probability to detect two consecutive electrons in a short
time interval. Finally, we discuss the electronic waiting time distribution in
the more realistic situation of partial entanglement
Quantum heat fluctuations of single particle sources
Optimal single electron sources emit regular streams of particles, displaying
no low frequency charge current noise. Due to the wavepacket nature of the
emitted particles, the energy is however fluctuating, giving rise to heat
current noise. We investigate theoretically this quantum source of heat noise
for an emitter coupled to an electronic probe in the hot-electron regime. The
distribution of temperature and potential fluctuations induced in the probe is
shown to provide direct information on the single particle wavefunction
properties and display strong non-classical features.Comment: 5 pages, 2 figure
Experiment Definition Using the Space Laboratory, Long Duration Exposure Facility, and Space Transportation System Shuttle
Candidate experiments designed for the space shuttle transportation system and the long duration exposure facility are summarized. The data format covers: experiment title, Experimenter, technical abstract, benefits/justification, technical discussion of experiment approach and objectives, related work and experience, experiment facts space properties used, environmental constraints, shielding requirements, if any, physical description, and sketch of major elements. Information was also included on experiment hardware, research required to develop experiment, special requirements, cost estimate, safety considerations, and interactions with spacecraft and other experiments
Non-invasive vibrational mode spectroscopy of ion Coulomb crystals through resonant collective coupling to an optical cavity field
We report on a novel non-invasive method to determine the normal mode
frequencies of ion Coulomb crystals in traps based on the resonance enhanced
collective coupling between the electronic states of the ions and an optical
cavity field at the single photon level. Excitations of the normal modes are
observed through a Doppler broadening of the resonance. An excellent agreement
with the predictions of a zero-temperature uniformly charged liquid plasma
model is found. The technique opens up for investigations of the heating and
damping of cold plasma modes, as well as the coupling between them.Comment: 4 pages, 4 figure
On the Wilf-Stanley limit of 4231-avoiding permutations and a conjecture of Arratia
We construct a sequence of finite automata that accept subclasses of the
class of 4231-avoiding permutations. We thereby show that the Wilf-Stanley
limit for the class of 4231-avoiding permutations is bounded below by 9.35.
This bound shows that this class has the largest such limit among all classes
of permutations avoiding a single permutation of length 4 and refutes the
conjecture that the Wilf-Stanley limit of a class of permutations avoiding a
single permutation of length k cannot exceed (k-1)^2.Comment: Submitted to Advances in Applied Mathematic
Dipole Oscillations of a Bose-Einstein Condensate in Presence of Defects and Disorder
We consider dipole oscillations of a trapped dilute Bose-Einstein condensate
in the presence of a scattering potential consisting either in a localized
defect or in an extended disordered potential. In both cases the breaking of
superfluidity and the damping of the oscillations are shown to be related to
the appearance of a nonlinear dissipative flow. At supersonic velocities the
flow becomes asymptotically dissipationless.Comment: 4 pages, 4 figure
Collective strong coupling between ion Coulomb crystals and an optical cavity field: Theory and experiment
A detailed description and theoretical analysis of experiments achieving
coherent coupling between an ion Coulomb crystal and an optical cavity field
are presented. The various methods used to measure the coherent coupling rate
between large ion Coulomb crystals in a linear quadrupole radiofrequency ion
trap and a single field mode of a moderately high-finesse cavity are described
in detail. Theoretical models based on a semiclassical approach are applied in
assessment of the experimental results of [P. F. Herskind et al., Nature Phys.
5, 494 (2009)] and of complementary new measurements. Generally, a very good
agreement between theory and experiments is obtained.Comment: 15 pages, 15 figure
Recommended from our members
Applying Graph Theory to Examine the Dynamics of Student Discussions in Small-Group Learning.
Group work in science, technology, engineering, and mathematics courses is an effective means of improving student outcomes, and many different factors can influence the dynamics of student discussions and, ultimately, the success of collaboration. The substance and dynamics of group discussions are commonly examined using qualitative methods such as discourse analysis. To complement existing work in the literature, we developed a quantitative methodology that uses graph theory to map the progression of talk-turns of discussions within a group. We observed groups of students working with peer facilitators to solve problems in biological sciences, with three iterations of data collection and two major refinements of graph theory calculations. Results include general behaviors based on the turns in which different individuals talk and graph theory parameters to quantify group characteristics. To demonstrate the potential utility of the methodology, we present case studies with distinct patterns: a centralized group in which the peer facilitator behaves like an authority figure, a decentralized group in which most students talk their fair share of turns, and a larger group with subgroups that have implications for equity, diversity, and inclusion. Together, these results demonstrate that our adaptation of graph theory is a viable quantitative methodology to examine group discussions
The anomalous accretion disk of the Cataclysmic Variable RW Sextantis
Synthetic spectra covering the wavelength range 900\AA~to 3000\AA~provide an
accurate fit, established by a analysis, to a combined
observed spectrum of RW Sextantis. Two separately calibrated distances to the
system establish the synthetic spectrum comparison on an absolute flux basis
but with two alternative scaling factors, requiring alternative values of
for final models. Based on comparisons for a range of
values, the observed spectrum does not follow the standard model. Rather than
the exponent 0.25 in the expression for the radial temperature profile, a value
close to 0.125 produces a synthetic spectrum with an accurate fit to the
combined spectrum. A study of time-series spectra shows that a proposed
warped or tilted disk is not supported by the data; an alternative proposal is
that an observed non-axisymmetric wind results from an interaction with the
mass transfer stream debris.Comment: 56 pages, 15 figures, 11 tables. Accepted for The Astrophysical
Journa
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