3,262 research outputs found
Surface Acoustic Wave induced Transport in a Double Quantum Dot
We report on non-adiabatic transport through a double quantum dot under
irradiation of surface acoustic waves generated on-chip. At low excitation
powers, absorption and emission of single and multiple phonons is observed. At
higher power, sequential phonon assisted tunneling processes excite the double
dot in a highly non-equilibrium state. The present system is attractive for
studying electron-phonon interaction with piezoelectric coupling.Comment: 4 pages, 3 figure
Monitoring Networked Applications With Incremental Quantile Estimation
Networked applications have software components that reside on different
computers. Email, for example, has database, processing, and user interface
components that can be distributed across a network and shared by users in
different locations or work groups. End-to-end performance and reliability
metrics describe the software quality experienced by these groups of users,
taking into account all the software components in the pipeline. Each user
produces only some of the data needed to understand the quality of the
application for the group, so group performance metrics are obtained by
combining summary statistics that each end computer periodically (and
automatically) sends to a central server. The group quality metrics usually
focus on medians and tail quantiles rather than on averages. Distributed
quantile estimation is challenging, though, especially when passing large
amounts of data around the network solely to compute quality metrics is
undesirable. This paper describes an Incremental Quantile (IQ) estimation
method that is designed for performance monitoring at arbitrary levels of
network aggregation and time resolution when only a limited amount of data can
be transferred. Applications to both real and simulated data are provided.Comment: This paper commented in: [arXiv:0708.0317], [arXiv:0708.0336],
[arXiv:0708.0338]. Rejoinder in [arXiv:0708.0339]. Published at
http://dx.doi.org/10.1214/088342306000000583 in the Statistical Science
(http://www.imstat.org/sts/) by the Institute of Mathematical Statistics
(http://www.imstat.org
Rejoinder: Monitoring Networked Applications With Incremental Quantile Estimation
Rejoinder: Monitoring Networked Applications With Incremental Quantile
Estimation [arXiv:0708.0302]Comment: Published at http://dx.doi.org/10.1214/088342306000000592 in the
Statistical Science (http://www.imstat.org/sts/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Entanglement distillation by adiabatic passage in coupled quantum dots
Adiabatic passage of two correlated electrons in three coupled quantum dots
is shown to provide a robust and controlled way of distilling, transporting and
detecting spin entanglement, as well as of measuring the rate of spin
disentanglement. Employing tunable interdot coupling the scheme creates, from
an unentangled two-electron state, a superposition of spatially separated
singlet and triplet states. A single measurement of a dot population (charge)
collapses the wave function to either of these states, realizing entanglement
to charge conversion. The scheme is robust, with the efficiency close to 100%,
for a large range of realistic spectral parameters.Comment: 5 pages, 4 figure
Exchange-controlled single-electron-spin rotations in quantum dots
We show theoretically that arbitrary coherent rotations can be performed
quickly (with a gating time ~1 ns) and with high fidelity on the spin of a
single confined electron using control of exchange only, without the need for
spin-orbit coupling or ac fields. We expect that implementations of this scheme
would achieve gate error rates on the order of \eta ~ 10^{-3} in GaAs quantum
dots, within reach of several known error-correction protocolsComment: 4+ pages, 3 figures; v2: Streamlined presentation, final version
published in PRB (Rapid Comm.
Gas signatures of Herbig Ae/Be disks probed with Herschel SPIRE spectroscopy
Herbig Ae/Be objects, like their lower mass counterparts T Tauri stars, are
seen to form a stable circumstellar disk which is initially gas-rich and could
ultimately form a planetary system. We present Herschel SPIRE 460-1540 GHz
spectra of five targets out of a sample of 13 young disk sources, showing line
detections mainly due to warm CO gas.Comment: to be published in proceedings of IAU symposium 299 (Victoria, BC,
Canada, June 2013
Implementing a Class of Permutation Tests: The coin Package
The R package coin implements a unified approach to permutation tests providing a huge class of independence tests for nominal, ordered, numeric, and censored data as well as multivariate data at mixed scales. Based on a rich and flexible conceptual framework that embeds different permutation test procedures into a common theory, a computational framework is established in coin that likewise embeds the corresponding R functionality in a common S4 class structure with associated generic functions. As a consequence, the computational tools in coin inherit the flexibility of the underlying theory and conditional inference functions for important special cases can be set up easily. Conditional versions of classical tests---such as tests for location and scale problems in two or more samples, independence in two- or three-way contingency tables, or association problems for censored, ordered categorical or multivariate data---can easily be implemented as special cases using this computational toolbox by choosing appropriate transformations of the observations. The paper gives a detailed exposition of both the internal structure of the package and the provided user interfaces along with examples on how to extend the implemented functionality.
Nonadiabatic Electron Manipulation in Quantum-Dot Arrays
A novel method of coherent manipulation of the electron tunneling in
quantum-dots is proposed, which utilizes the quantum interference in
nonadiabatic double-crossing of the discrete energy levels. In this method, we
need only a smoothly varying gate voltage to manipulate electrons, without a
sudden switching-on and off. A systematic design of a smooth gate-pulse is
presented with a simple analytic formula to drive the two-level electronic
state to essentially arbitrary target state, and numerical simulations for
complete transfer of an electron is shown for a coupled double quantum-dots and
an array of quantum-dots. Estimation of the manipulation-time shows that the
present method can be employed in realistic quantum-dots
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