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 $13\%$ of the total masked area, the fraction of peaks with SNR $\nu\ge 3$ is $\sim 11\%$ in comparison with $\sim 7\%$ 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 $9\hbox{ deg}^2$, the bias in $(\Omega_m, \sigma_8)$ is already close to $3\sigma$. 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-$z$ error; photo-$z$ 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-$z$ distribution in the range of $z\in[0,4)$. 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$\approx17$ (AliCPT-1 "4 modules*yr") and SNR$\approx26$ (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 $0.6\sigma$ increasement in $\sigma_8$ but without changing the $S_8$ value. For AliCPT-1 first and second stages, the cross-correlation of CSST cosmic shear with CMB lensing give $\sigma_8=0.770\pm 0.034$ and $S_8=0.797\pm 0.028$ and $\sigma_8=0.801\pm 0.023$ and $S_8=0.813\pm 0.016$, respectively.Comment: 17 pages, 10 figure