64,514 research outputs found
Observations of nonlinear run-up patterns on plane and rhythmic beach morphology
Application of non-linear forecasting and bispectral analysis to video observations of run-up over cuspate topography shows that these alongshore patterns in the morphology are accompanied by changes to the fundamental behaviour of the run-up timeseries. Nonlinear forecasting indicates that at beach cusp horns, the behaviour of swash flow is more predictable and global (meaning that characteristics of individual swash events are well represented by the behaviour of the timeseries as a whole). Conversely, at beach cusp bays, the behaviour of swash flow is less predictable and more local (meaning that the characteristics of individual swash events are best represented by the behaviour of a small fraction of the timeseries). Bispectral analysis indicates that there is a nonlinear transfer of energy from the incident wave frequency f to infragravity frequency ~f/2 which only occurs in the bay, suggesting that the local behaviour is caused by interactions between successive swash cycles which are magnified by channelling caused by the beach cusp geometry. The local behaviour and the bispectral signatures are not present in offshore measurements, and are not present in runup timeseries collected when the beach was planar. These results provide evidence that interactions between successive run-ups are a fundamental characteristic of beach cusp bays. Ultimately, these interactions could lead to the growth of an infragravity wave with an alongshore wavelength forced by the presence of beach cusps
A linear construction for certain Kerdock and Preparata codes
The Nordstrom-Robinson, Kerdock, and (slightly modified) Pre\- parata codes
are shown to be linear over \ZZ_4, the integers . The Kerdock and
Preparata codes are duals over \ZZ_4, and the Nordstrom-Robinson code is
self-dual. All these codes are just extended cyclic codes over \ZZ_4. This
provides a simple definition for these codes and explains why their Hamming
weight distributions are dual to each other. First- and second-order
Reed-Muller codes are also linear codes over \ZZ_4, but Hamming codes in
general are not, nor is the Golay code.Comment: 5 page
High-sensitivity diamond magnetometer with nanoscale resolution
We present a novel approach to the detection of weak magnetic fields that
takes advantage of recently developed techniques for the coherent control of
solid-state electron spin quantum bits. Specifically, we investigate a magnetic
sensor based on Nitrogen-Vacancy centers in room-temperature diamond. We
discuss two important applications of this technique: a nanoscale magnetometer
that could potentially detect precession of single nuclear spins and an optical
magnetic field imager combining spatial resolution ranging from micrometers to
millimeters with a sensitivity approaching few femtotesla/Hz.Comment: 29 pages, 4 figure
A reconfigurable optical header recognition system for optical packet routing applications
We demonstrate a reconfigurable all-optical packet processing system. The key device is a code-reconfigurable header decoder based on a fiber Bragg grating. The performance of the system is tested for different packet headers, and error-free operation is confirmed
Temporally and spectrally multiplexed single photon source using quantum feedback control for scalable photonic quantum technologies
Current proposals for scalable photonic quantum technologies require
on-demand sources of indistinguishable single photons with very high efficiency
(having unheralded loss below ). Even with recent progress in the field
there is still a significant gap between the requirements and state of the art
performance. Here, we propose an on-chip source of multiplexed, heralded
photons. Using quantum feedback control on a photon storage cavity with an
optimized driving protocol, we estimate an on-demand efficiency of and
unheralded loss of order , assuming high efficiency detectors and
intrinsic cavity quality factors of order . We further explain how
temporal- and frequency-multiplexing can be used in parallel to significantly
reduce device requirements if single photon frequency conversion is possible
with efficiency in the same range of
Investigation and analysis of time codes Final report
Optimal time code system using correlation detection technique
Lagrangian quantum turbulence model based on alternating superfluid/ normal fluid stochastic dynamics
Inpired by recent measurements of the velocity and acceleration statistics of
Lagrangian tracer particles embedded in a turbulent quantum liquid we propose a
new superstatistical model for the dynamics of tracer particles in quantum
turbulence. Our model consists of random sequences S/N/S/... where the particle
spends some time in the superfluid (S) and some time in the normal fluid (N).
This model leads to a superposition of power law distributions generated in the
superfluid and Gaussian distributions in the normal liquid, in excellent
agreement with experimental measurements. We include memory effects into our
analysis and present analytic predictions for probability densities and
correlation functions.Comment: 6 pages, 4 figure
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