5,323 research outputs found
Decoherence of Quantum-Enhanced Timing Accuracy
Quantum enhancement of optical pulse timing accuracy is investigated in the
Heisenberg picture. Effects of optical loss, group-velocity dispersion, and
Kerr nonlinearity on the position and momentum of an optical pulse are studied
via Heisenberg equations of motion. Using the developed formalism, the impact
of decoherence by optical loss on the use of adiabatic soliton control for
beating the timing standard quantum limit [Tsang, Phys. Rev. Lett. 97, 023902
(2006)] is analyzed theoretically and numerically. The analysis shows that an
appreciable enhancement can be achieved using current technology, despite an
increase in timing jitter mainly due to the Gordon-Haus effect. The decoherence
effect of optical loss on the transmission of quantum-enhanced timing
information is also studied, in order to identify situations in which the
enhancement is able to survive.Comment: 12 pages, 4 figures, submitte
The relative and absolute timing accuracy of the EPIC-pn camera on XMM-Newton, from X-ray pulsations of the Crab and other pulsars
Reliable timing calibration is essential for the accurate comparison of
XMM-Newton light curves with those from other observatories, to ultimately use
them to derive precise physical quantities. The XMM-Newton timing calibration
is based on pulsar analysis. However, as pulsars show both timing noise and
glitches, it is essential to monitor these calibration sources regularly. To
this end, the XMM-Newton observatory performs observations twice a year of the
Crab pulsar to monitor the absolute timing accuracy of the EPIC-pn camera in
the fast Timing and Burst modes. We present the results of this monitoring
campaign, comparing XMM-Newton data from the Crab pulsar (PSR B0531+21) with
radio measurements. In addition, we use five pulsars (PSR J0537-69, PSR
B0540-69, PSR B0833-45, PSR B1509-58 and PSR B1055-52) with periods ranging
from 16 ms to 197 ms to verify the relative timing accuracy. We analysed 38
XMM-Newton observations (0.2-12.0 keV) of the Crab taken over the first ten
years of the mission and 13 observations from the five complementary pulsars.
All the data were processed with the SAS, the XMM-Newton Scientific Analysis
Software, version 9.0. Epoch folding techniques coupled with \chi^{2} tests
were used to derive relative timing accuracies. The absolute timing accuracy
was determined using the Crab data and comparing the time shift between the
main X-ray and radio peaks in the phase folded light curves. The relative
timing accuracy of XMM-Newton is found to be better than 10^{-8}. The strongest
X-ray pulse peak precedes the corresponding radio peak by 306\pm9 \mus, which
is in agreement with other high energy observatories such as Chandra, INTEGRAL
and RXTE. The derived absolute timing accuracy from our analysis is \pm48 \mus.Comment: 16 pages, 9 figures. Accepted for publication on A&
Timing accuracy of the Swift X-Ray Telescope in WT mode
The X-Ray Telescope (XRT) on board Swift was mainly designed to provide
detailed position, timing and spectroscopic information on Gamma-Ray Burst
(GRB) afterglows. During the mission lifetime the fraction of observing time
allocated to other types of source has been steadily increased. In this paper,
we report on the results of the in-flight calibration of the timing
capabilities of the XRT in Windowed Timing read-out mode. We use observations
of the Crab pulsar to evaluate the accuracy of the pulse period determination
by comparing the values obtained by the XRT timing analysis with the values
derived from radio monitoring. We also check the absolute time reconstruction
measuring the phase position of the main peak in the Crab profile and comparing
it both with the value reported in literature and with the result that we
obtain from a simultaneous Rossi X-Ray Timing Explorer (RXTE) observation. We
find that the accuracy in period determination for the Crab pulsar is of the
order of a few picoseconds for the observation with the largest data time span.
The absolute time reconstruction, measured using the position of the Crab main
peak, shows that the main peak anticipates the phase of the position reported
in literature for RXTE by ~270 microseconds on average (~150 microseconds when
data are reduced with the attitude file corrected with the UVOT data). The
analysis of the simultaneous Swift-XRT and RXTE Proportional Counter Array
(PCA) observations confirms that the XRT Crab profile leads the PCA profile by
~200 microseconds. The analysis of XRT Photodiode mode data and BAT event data
shows a main peak position in good agreement with the RXTE, suggesting the
discrepancy observed in XRT data in Windowed Timing mode is likely due to a
systematic offset in the time assignment for this XRT read out mode.Comment: 6 pages, 4 figures. Accepted for publication on
Astronomy&Astrophysic
Analysis of short pulse laser altimetry data obtained over horizontal path
Recent pulsed measurements of atmospheric delay obtained by ranging to the more realistic targets including a simulated ocean target and an extended plate target are discussed. These measurements are used to estimate the expected timing accuracy of a correlation receiver system. The experimental work was conducted using a pulsed two color laser altimeter
The ballistic acceleration of a supercurrent in a superconductor
One of the most primitive but elusive current-voltage (I-V) responses of a
superconductor is when its supercurrent grows steadily after a voltage is first
applied. The present work employed a measurement system that could
simultaneously track and correlate I(t) and V(t) with sub-nanosecond timing
accuracy, resulting in the first clear time-domain measurement of this
transient phase where the quantum system displays a Newtonian like response.
The technique opens doors for the controlled investigation of other time
dependent transport phenomena in condensed-matter systems.Comment: 4 pages, 3 figure
An improved solar wind electron-density model for pulsar timing
Variations in the solar wind density introduce variable delays into pulsar
timing observations. Current pulsar timing analysis programs only implement
simple models of the solar wind, which not only limit the timing accuracy, but
can also affect measurements of pulsar rotational, astrometric and orbital
parameters. We describe a new model of the solar wind electron density content
which uses observations from the Wilcox Solar Observatory of the solar magnetic
field. We have implemented this model into the tempo2 pulsar timing package. We
show that this model is more accurate than previous models and that these
corrections are necessary for high precision pulsar timing applications.Comment: Accepted by ApJ, 13 pages, 4 figure
Detecting massive gravitons using pulsar timing arrays
Massive gravitons are features of some alternatives to general relativity.
This has motivated experiments and observations that, so far, have been
consistent with the zero mass graviton of general relativity, but further tests
will be valuable. A basis for new tests may be the high sensitivity
gravitational wave experiments that are now being performed, and the higher
sensitivity experiments that are being planned. In these experiments it should
be feasible to detect low levels of dispersion due to nonzero graviton mass.
One of the most promising techniques for such a detection may be the pulsar
timing program that is sensitive to nano-Hertz gravitational waves.
Here we present some details of such a detection scheme. The pulsar timing
response to a gravitational wave background with the massive graviton is
calculated, and the algorithm to detect the massive graviton is presented. We
conclude that, with 90% probability, massles gravitons can be distinguished
from gravitons heavier than eV (Compton wave length
km), if biweekly observation of 60 pulsars
are performed for 5 years with pulsar RMS timing accuracy of 100 ns. If 60
pulsars are observed for 10 years with the same accuracy, the detectable
graviton mass is reduced to eV ( km); for 5-year observations of 100 or 300 pulsars, the sensitivity is
respectively ( km) and
eV ( km). Finally, a 10-year
observation of 300 pulsars with 100 ns timing accuracy would probe graviton
masses down to eV ( km).Comment: 13 pages, 5 figures, Accepted by Ap
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