186 research outputs found
Mask Effects on Cosmological Studies with Weak Lensing Peak Statistics
In this paper, we analyze in detail with numerical simulations how the mask
effect can influence the weak lensing peak statistics reconstructed from the
shear measurement of background galaxies. It is found that high peak fractions
are systematically enhanced due to masks, the larger the masked area, the
higher the enhancement. In the case with about of the total masked area,
the fraction of peaks with SNR is in comparison with
of the mask-free case in our considered cosmological model. This can
induce a large bias on cosmological studies with weak lensing peak statistics.
Even for a survey area of , the bias in
is already close to . It is noted that most of the affected peaks are
close to the masked regions. Therefore excluding peaks in those regions can
reduce the bias but at the expense of loosing usable survey areas. Further
investigations find that the enhancement of high peaks number can be largely
attributed to higher noise led by the fewer number of galaxies usable in the
reconstruction. Based on Fan et al. (2010), we develop a model in which we
exclude only those large masks with radius larger than $3\arcmin. For the
remained part, we treat the areas close to and away from the masked regions
separately with different noise levels. It is shown that this two-noise-level
model can account for the mask effect on peak statistics very well and the
cosmological bias is significantly reduced.Comment: 18 pages, 16 figures, ApJ in pres
Coherence-protected Quantum Gate by Continuous Dynamical Decoupling in Diamond
To implement reliable quantum information processing, quantum gates have to
be protected together with the qubits from decoherence. Here we demonstrate
experimentally on nitrogen-vacancy system that by using continuous wave
dynamical decoupling method, not only the coherence time is prolonged by about
20 times, but also the quantum gates is protected for the duration of
controlling time. This protocol shares the merits of retaining the superiority
of prolonging the coherence time and at the same time easily combining with
quantum logic tasks. It is expected to be useful in task where duration of
quantum controlling exceeds far beyond the dephasing time.Comment: 5 pages, 4 figure
Forecast of cross-correlation of CSST cosmic shear tomography with AliCPT-1 CMB lensing
We present a forecast study on the cross-correlation between cosmic shear
tomography from the Chinese Survey Space Telescope (CSST), and CMB lensing from
Ali CMB Polarization Telescope (AliCPT-1) in Tibet. We generate the correlated
galaxy lensing and CMB lensing signals from the Gaussian realizations based on
the inputted auto- and cross-spectra. As for the error budget, we consider the
CMB lensing reconstruction noise based on the AliCPT-1 lensing reconstruction
pipeline; the shape noise of the galaxy lensing measurement; CSST photo-
error; photo- bias; intrinsic alignment effect. The AliCPT-1 CMB lensing
mock data are generated according to two experimental stages, namely the "4
modules*yr" and "48 modules*yr" cases. We estimate the cross-spectra in 4
tomographic bins according to the CSST photo- distribution in the range of
. After reconstructing the pseudo-cross-spectra from the
realizations, we calculate the signal-to-noise ratio (SNR). By combining the 4
photo-z bins, the total cross-correlation SNR (AliCPT-1 "4
modules*yr") and SNR (AliCPT-1 "48 modules*yr"). Finally, we study
the cosmological application of this cross-correlation signal. Due to the
negative contribution to the galaxy lensing data, the exclusion of intrinsic
alignment in the template fitting will lead to roughly a
increasement in but without changing the value. For AliCPT-1
first and second stages, the cross-correlation of CSST cosmic shear with CMB
lensing give and and
and , respectively.Comment: 17 pages, 10 figure
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