分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Pulsar timing arrays (PTAs) consisting of widely distributed and well-timed millisecond pulsars can serve as a galactic interferometer to measure gravitational waves. With the same data acquired for PTAs, we propose to develop pulsar polarization arrays (PPAs), to explore astrophysics and fundamental physics. As in the case of PTAs, PPAs are best suited to reveal temporal and spatial correlations at large scales that are hard to mimic by local noise. To demonstrate the physical potential of PPAs, we consider detection of ultralight axion-like dark matter (ALDM), through cosmic birefringence induced by its Chern-Simon coupling. Because of its tiny mass, the ultralight ALDM can be generated as a Bose-Einstein condensate, characterized by a strong wavy nature. Incorporating both temporal and spatial correlations of the signal, we show that PPAs have a potential to probe the Chern-Simon coupling up to $\sim 10^{-14}-10^{-17}$GeV$^{-1}$, with a mass range $\sim 10^{-27} - 10^{-21}$eV.
分类： 心理学 >> 实验心理学 提交时间： 2021-03-08
摘要： Panum’s limiting case is a typical phenomenon of monocular occlusion in binocular vision. It occurs naturally when one object is occluded by another object for one eye, but in the other eye the two objects are located in different directions. Only recently has it been found that in addition to horizontal disparity, the vertical disparity gradient and cue conflict are two important determinants for double fusion. Therefore, the current study aims to determine the relationship between the two determinants and perceptual learning in Panum’s limiting case. Twenty-six observers were trained for five days. Meanwhile, the RTs and duration of double fusion was measured when the participants viewed several versions of Panum’s configuration. In these stimuli, vertical disparity gradient was varied from 0.1 to 0.6 and cue conflict was manipulated from low to high. The results revealed that for each level of these factors, the RTs of double fusion decreased and the duration of double fusion increased with each training session. Moreover, there were significant differences among different levels of vertical disparity gradient and cue conflict. Lastly, there was also a significant interaction effect between the two determinants in Panum’s limiting case. These results suggest that there is perceptual learning for each level of the two determinants in monocular occlusion and these factors jointly affect the sensitivity and stability of double fusion.
分类： 物理学 >> 电磁学、光学、声学、传热、经典力学和流体动力学 分类： 材料科学 >> 纳米科学和纳米技术 提交时间： 2017-02-23
摘要： The hexagonal boron nitride (h-BN) nanosheets are synthesized by the liquid-phase exfoliation method and transferred onto the microfiber by optical deposition method. The h-BN-deposited microfiber exhibits dual-function, that is, saturable absorption and high-nonlinearity. To check the laser performance by using the proposed h-BN device, it is inserted into an erbium-doped fiber laser (EDFL). In experiment, we demonstrate a tunable, switchable dual-wavelength soliton pulse by properly adjusting the pump power and the polarization state in the EDFL. The dual-wavelength soliton laser has a pump threshold of 50 mW at 976 nm, pulse energy of up to 3.4 nJ, peak power of about 2.62 kW, and pulse duration of about 1.3 ps. Additionally, we also demonstrate switchable operation of single-wavelength soliton pulse located at 1531.5 and 1557.5 nm, respectively. Our finding unambiguously implies that apart from its fantastic electric and thermal property, h-BN nanosheets may also possess attractive optoelectronic property for nonlinear photonics, such as mode-locker, Q-switcher, optical limiter and so on.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Ruo-Jing Ren
Yong-Heng Lu
Ze-Kun Jiang
Jun Gao
Wen-Hao Zhou
Yao Wang
Zhi-Qiang Jiao
Xiao-Wei Wang
Alexander S. Solntsev
Xian-Min Jin
摘要： Squeezed light is a critical resource in quantum sensing and information processing. Due to the inherently weak optical nonlinearity and limited interaction volume, considerable pump power is typically needed to obtain efficient interactions to generate squeezed light in bulk crystals. Integrated photonics offers an elegant way to increase the nonlinearity by confining light strictly inside the waveguide. For the construction of large-scale quantum systems performing many-photon operations, it is essential to integrate various functional modules on a chip. However, fabrication imperfections and transmission crosstalk may add unwanted diffraction and coupling to other photonic elements, reducing the quality of squeezing. Here, by introducing the topological phase, we experimentally demonstrate the topologically protected nonlinear process of spontaneous four-wave mixing enabling the generation of squeezed light on a silica chip. We measure the cross-correlations at different evolution distances for various topological sites and verify the non-classical features with high fidelity. The squeezing parameters are measured to certify the protection of cavity-free, strongly squeezed states. The demonstration of topological protection for squeezed light on a chip brings new opportunities for quantum integrated photonics, opening novel approaches for the design of advanced multi-photon circuits.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Hao Tang
Tian-Yu Wang
Zi-Yu Shi
Zhen Feng
Yao Wang
Xiao-Wen Shang
Jun Gao
Zhi-Qiang Jiao
Zhan-Ming Li
Yi-Jun Chang
Wen-Hao Zhou
Yong-Heng Lu
Yi-Lin Yang
Ruo-Jing Ren
Lu-Feng Qiao
Xian-Min Jin
摘要： Dynamic localization, which originates from the phenomena of particle evolution suppression under an externally applied AC electric field, has been simulated by suppressed light evolution in periodically-curved photonic arrays. However, experimental studies on their quantitative dynamic transport properties and application for quantum information processing are rare. Here we fabricate one-dimensional and hexagonal two-dimensional arrays, both with sinusoidal curvature. We successfully observe the suppressed single-photon evolution patterns, and for the first time measure the variances to study their transport properties. For one-dimensional arrays, the measured variances match both the analytical electric field calculation and the quantum walk Hamiltonian engineering approach. For hexagonal arrays, as anisotropic effective couplings in four directions are mutually dependent, the analytical approach suffers, while quantum walk conveniently incorporates all anisotropic coupling coefficients in the Hamiltonian and solves its exponential as a whole, yielding consistent variances with our experimental results. Furthermore, we implement a nearly complete localization to show that it can preserve both the initial injection and the wave-packet after some evolution, acting as a memory of a flexible time scale in integrated photonics. We demonstrate a useful quantum simulation of dynamic localization for studying their anisotropic transport properties, and a promising application of dynamic localization as a building block for quantum information processing in integrated photonics.
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