分类： 物理学 >> 核物理学 提交时间： 2023-09-13
摘要： Abstract: In this experimental study, involving deuteriumdeuterium fusion neutron emission spectroscopy (NES) measurement on the experimental advanced superconducting tokamak (EAST), a liquid scintillator detector (BC501A) was employed. This decision was based on the detector's superior sensitivity, optimal time-response, and its exceptional n- discrimination capability. This detector emits fast pulse signals that are as narrow as 100 ns, with high count rates that can peak at several Mcps. However, conventional nuclear circuits faced challenges in performing pulse height analysis, n pulse shape discrimination (PSD), and in recording the entire pulse waveform under such high-count-rate conditions. To address these challenges, a high-speed digital pulse signal acquisition and processing system was designed. The system was developed around a micro-telecommunications computing architecture (MTCA). Within this structure, a signal acquisition and processing (SAQP) module communicated through PCI Express (PCIe) links, achieving a bandwidth of up to 1.6 GB/s. To accurately capture the detailed shape of the pulses, four channels of analog-to-digital converters (ADCs) were used, each with a 500-MSPS sampling rate and a 14-bit resolution, ensuring an accuracy that surpassed 11 bits. An n- discrimination algorithm, based on the two-gate integral method, was also developed. Implemented within field programmable gate arrays (FPGA), this algorithm provided a real-time n- discrimination spectrum for pulse height analysis. The system underwent rigorous testing in a laboratory setting and during an EAST experiment. The results confirmed that the innovative SAQP system can satisfy the demanding requirements of high-parameter experiments, manage count rates of up to 2 Mcps, execute real-time n- discrimination algorithms, and record entire pulse waveforms without any data loss.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We present a method by using the phase characteristics of radio observation data for pulsar search and candidate identification. The phase characteristics are relations between the pulsar signal and the phase correction in the frequency-domain, and we regard it as a new search diagnostic characteristic. Based on the phase characteristics, a search method is presented: calculating DM (dispersion measure) -- frequency data to select candidate frequencies, and then confirming of candidates by using the broadband characteristics of pulsar signals. Based on this method, we performed a search test on short observation data of M15 and M71, which were observed by Five-hundred-meter Aperture spherical radio Telescope (FAST), and some of the Galactic Plane Pulsar Snapshot survey (GPPS) data. Results show that it can get similar search results to PRESTO (PulsaR Exploration and Search TOolkit) while having a faster processing speed.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We present a method by using the phase characteristics of radio observation data for pulsar search and candidate identification. The phase characteristics are relations between the pulsar signal and the phase correction in the frequency-domain, and we regard it as a new search diagnostic characteristic. Based on the phase characteristics, a search method is presented: calculating DM (dispersion measure) -- frequency data to select candidate frequencies, and then confirming of candidates by using the broadband characteristics of pulsar signals. Based on this method, we performed a search test on short observation data of M15 and M71, which were observed by Five-hundred-meter Aperture spherical radio Telescope (FAST), and some of the Galactic Plane Pulsar Snapshot survey (GPPS) data. Results show that it can get similar search results to PRESTO (PulsaR Exploration and Search TOolkit) while having a faster processing speed.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The Starobinsky inflation model is one of the simplest inflation models that is consistent with the cosmic microwave background observations. In order to explain dark matter of the universe, we consider a minimal extension of the Starobinsky inflation model with introducing the dark sector which communicates with the visible sector only via the gravitational interaction. In Starobinsky inflation model, a sizable amount of dark-sector particle may be produced by the inflaton decay. Thus, a scalar, a fermion or a vector boson in the dark sector may become dark matter. We pay particular attention to the case with dark non-Abelian gauge interaction to make a dark glueball a dark matter candidate. In the minimal setup, we show that it is difficult to explain the observed dark matter abundance without conflicting observational constraints on the coldness and the self-interaction of dark matter. We propose scenarios in which the dark glueball, as well as other dark-sector particles, from the inflaton decay become viable dark matter candidates. We also discuss possibilities to test such scenarios.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Considering a Schwarzschild black hole surrounded by a fully ionized hydrogen plasma, we study the refractive effect and the pure gravitational effect of the plasma on the shadow. The effects are treated in a unified formalism but characterized by two independent parameters. For semi-realistic values of parameters, we find their corrections to the shadow radius are both negligible, and the gravitational correction can overtake the refractive correction for active galactic nuclei of masses larger than $10^9M_{\odot}$. Since the refractive effect is induced by the electromagnetic interaction, this result is in sharp contrast to the textbook knowledge that the ratio of the gravitational force to the electromagnetic force is $Gm_em_p/e^2=4.4\times10^{-40}$ in a hydrogen atom. With unrealistically large values of parameters, we illustrate the two effects on the light trajectories and the intensity map.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We study the stability of the electroweak vacuum during and after the Starobinsky inflation, assuming the existence of the non-minimal Higgs coupling to the Ricci scalar. In the Starobinsky inflation, there exists $R^2$ term (with $R$ being the Ricci scalar), which modifies the evolution equation of the Higgs field. We consider the case that the non-minimal coupling is sizable so that the quantum fluctuation of the Higgs field is suppressed and that the Higgs amplitude is settled near the origin during the inflation. In such a case, the Higgs amplitude may be amplified in the preheating epoch after inflation because of the parametric resonance due to the non-minimal coupling. We perform a detailed analysis of the evolution of the Higgs field in the preheating epoch by a numerical lattice simulation and derive an upper bound on the non-minimal coupling constant $\xi$ in order to realize the electroweak vacuum in the present universe. We find that the upper bound on $\xi$ in the Starobinsky inflation model is more stringent than that in conventional inflation models without the $R^2$ term.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Li-Yun Chen
Cheng-Cheng Guo
Ming-Ming Pan
Chen Lai
Yun-Xia Wang
Guo-Cai Liao
Zi-Wei Ma
Fan-Wei Zhang
Jagadeesh Suriyaprakash
Lijing Guo
Eser Akinoglu
Qiang Li
Li-Jun Wu
摘要： Laser-induced periodic surface structures (LIPSSs) on various materials have been extensively investigated because of their wide applications. The combination of different materials allows for greater freedom in tailoring their functions and achieving responses not possible in a homogeneous material. By utilizing a femtosecond (fs) laser to irradiate the Fe-doped Polyvinyl Pyrrolidone (PVP) composite film, highly regular ultrafine nanogratings (U-nanogratings) with a period as small as 35.0 ($\pm$ 2.0) nm can be self-organized on the surface with extremely high efficiency. The period of the U-nanogratings can be controlled by varying the scanning speed of the laser beam (deposited energy) and the thickness of the composite film. Based on the experimental, theoretical, and simulation results, we propose a two-step formation mechanism: composite film excitation and two sequent grating-splitting. The high photosensitivity and low glass transition temperature of the composite film facilitate the fabrication of the ultrafine nanostructures. The proposed design method for the composite material and fabrication process could not only provide a strategy for obtaining highly regular U-nanogratings, but also offer a platform to explore the interaction physics between ultra-short pulses and matter under extreme conditions.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Quantum contextuality is one of the most perplexing and peculiar features of quantum mechanics. Concisely, it refers to the observation that the result of a single measurement in quantum mechanics depends on the set of joint measurements actually performed. The study of contextuality has a long history at University of Science and Technology of China (USTC). Here we review the theoretical and experimental advances in this direction achieved at USTC over the last 20 years. We start by introducing the renowned simplest proof of state-independent contextuality. We then present several experimental tests of quantum versus noncontextual theories with photons. Finally, we discuss the investigation on the role of contextuality in general quantum information science and its application in quantum computation.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Yuan-Ze Yang
Tian-Xiang Zhu
Zhi-Peng Li
Xiao-Dong Zeng
Nai-Jie Guo
Shang Yu
Yu Meng
Zhao-An Wang
Lin-Ke Xie
Zong-Quan Zhou
Qiang Li
Jin-Shi Xu
Wei Liu
Yi-Tao Wang
Jian-Shun Tang
Chuan-Feng Li
Guang-Can Guo
摘要： Optically addressable spins in two-dimensional hexagonal boron nitride (hBN) attract widespread attention for their potential advantage in on-chip quantum devices, such as quantum sensors and quantum network. A variety of spin defects have been found in hBN, but no convenient and deterministic generation methods have been reported for other defects except negatively charged boron vacancy ($\rm V_B^-$). Here we report that by using femtosecond laser direct writing technology, we can deterministically create spin defect ensembles with spectra range from 550 nm to 800 nm. Positive single-peak optically detected magnetic resonance (ODMR) signals are detected in the presence of longitudinal magnetic field, and the contrast can reach 0.8%. With the appropriate thickness of hBN flakes and femtosecond laser pulse energy, we can deterministically generate bright spin defects in-situ. Our results provide a convenient deterministic method to create spin defects in hBN, which will motivate more endeavors for future researches and applications of spin-based technologies.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Nai-Jie Guo
Yuan-Ze Yang
Xiao-Dong Zeng
Shang Yu
Yu Meng
Zhi-Peng Li
Zhao-An Wang
Lin-Ke Xie
Jin-Shi Xu
Jun-Feng Wang
Qiang Li
Wei Liu
Yi-Tao Wang
Jian-Shun Tang
Chuan-Feng Li
Guang-Can Guo
摘要： Optically addressable spin defects in solid-state materials are the promising platform for quantum information applications, such as quantum network. The two-dimensional (2D) hexagonal boron nitride (hBN) as a carrier of abundant defects is an emerging candidate. While negatively charged boron vacancy (V$_\text{B}^-$) spin defect in hBN is studied intensively, the coherent control of single spin in 2D materials has not been realized yet, which constitutes the cornerstone for applying the 2D spin defect in quantum-information tasks. Here, we report the first coherent control of the single electronic spin in 2D materials at room temperature. Considering both the optical and spin properties, this defect belongs to a new type of spin defects distinguished to all other spin defects observed before. This defect has simultaneously the narrow zero-phonon line, high Debye-Waller factor, high brightness, high polarization of PL photons, low $ g^{(2)}(0) $, moderate spin $ T_{1} $ and $ T_{2} $ comparable to V$ _\text{B}^{-} $. These excellent optical properties and relatively good spin properties of this single spin lay the foundation for the applications of the 2D-material-hosted spin defects in quantum information tasks.
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
摘要： We perform a detailed hadron-level study on the sensitivity of Higgs boson pair production via the WW∗WW∗channel with the final state 3ℓ2j + missing ET at the LHC with the collision energy S√=14 TeV and a future 100 TeV collider. To avoid the huge background from pp→ZW+jets processes, we confine to consider the four lepton patterns: e±e±μ∓ and μ±μ±e∓. We propose a partial reconstruction method to determine the most reliable combination. After that, we examine a few crucial observables which can discriminate efficiently signal and background events, especially we notice that the observable mT2 is very efficient. For the LHC 14 TeV collisions, with an accumulated 3000 fb−1 dataset, we find that the sensitivity of this mode can reach up to 1.5 σ for the Standard Model and the triple coupling of Higgs boson λ3 in the simplest effective theory can be constrained into the range [-1, 8] at 95% confidence level; at a 100 TeV collider with the integrated luminosity 3000 fb−1, the sensitivity can reach up to 13 σ for the Standard Model and we find that all values of λ3 in the effective theory can be covered up to 3σ even without optimising signals. To precisely measure the triple coupling of Higgs boson λ3=1 of the Standard Model at a 100 TeV collider, by using the invariant mass of three leptons which is robust to against the contamination of underlying events and pileup effects and by performing a χ2 analysis, we find that it can be determined into a range [0.8, 1.5] at 95% confidence level.
分类： 物理学 >> 核物理学 提交时间： 2016-09-02
摘要： We explore the discovery potential of Higgs pair production at a 100 TeV collider via full leptonic mode. The same mode can be explored at the LHC when Higgs pair production is enhanced by new physics. We examine two types of fully leptonic final states and propose a partial reconstruction method. The reconstruction method can reconstruct some kinematic observables. It is found that the mT2 variable determined by this reconstruction method and the reconstructed visible Higgs mass are important and crucial to discriminate the signal and background events. It is also noticed that a new variable, denoted as Δm which is defined as the mass difference of two possible combinations, is very useful as a discriminant. We also investigate the interplay between the direct measurements of tt¯h couplings and other related couplings and trilinear Higgs coupling at hadron colliders and electron-positron colliders.
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