Fully integrated InGaAs/InP single-photon detector module with gigahertz sine wave gating

InGaAs/InP single-photon avalanche diodes (SPADs) working in the regime of GHz clock rates are crucial components for the high-speed quantum key distribution (QKD). We have developed for the first time a compact, stable and user-friendly tabletop InGaAs/InP single-photon detector system operating at a 1.25 GHz gate rate that fully integrates functions for controlling and optimizing SPAD performance. We characterize the key parameters of the detector system and test the long-term stability of the system for continuous operation of 75 hours. The detector system can substantially enhance QKD performance and our present work paves the way for practical high-speed QKD applications.Comment: 11 pages, 6 figures. Accepted for publication in Review of Scientific Instrument

Asymptotic Analysis on Binned Likelihood and Neutrino Floor

Observations of suspected coherent elastic neutrino-nucleus scatterings by dark matter direct detection experiments highlight the need for an investigation into the so-called ``neutrino floor". We focus on the discovery limit, a statistical concept to identify the neutrino floor, and analyze the asymptotic behaviour of the profile binned likelihood ratio test statistic where the likelihood is constructed by variate from events in each bin and pull terms from neutrino fluxes. To achieve the asymptotic result, we propose two novel methods: i) Asymptotic-Analytic method, which furnishes the analytic result for large statistics, is applicable for more extra nuisance parameters, and enables the identification of the most relevant parameters in the statistical analysis; ii) Quasi-Asimov dataset, which is analogous to Asimov dataset but with improved speed. Applying our methods to the neutrino floor, we significantly accelerate the computation procedure compared to the previous literature, and successfully address cases where Asimov dataset fails. Our derivation on the asymptotic behavior of the test statistic not only facilitates research into the impact of neutrinos on the search for dark matter, but may also prove relevant in similar application scenarios.Comment: 24 pages, 7 figures, github repository: https://github.com/zhangblong/AsymptoticAnalysisAndNeutrinoFo

Value-added Evaluation System for Vocational School Students Construction and Practice Research

Student evaluation in the new era should be rooted in the educational macro background of "cultivating people by virtue" and comply with the overall policy orientation of educational evaluation reform. This research focuses on the construction and implementation of value-added evaluation system. Combined with the characteristics of vocational school students, this paper constructs a four-level index system and refines the student evaluation standards. The evaluation subjects are students, head teachers, teachers, parents and enterprise managers. Through the development of the related APP, it is convenient for each evaluation subject to input information, and finally use K-line chart to visually present the change process of the appreciation in students' literacy. A value-added evaluation system with strong timeliness, objectivity, motivation and operability is constructed

Strongly lensed repeating Fast Radio Bursts as precision probes of the universe

Fast Radio bursts (FRBs), bright transients with millisecond durations at $\sim$ GHz and typical redshifts probably $>0.8$, are likely to be gravitationally lensed by intervening galaxies. Since the time delay between images of strongly lensed FRB can be measured to extremely high precision because of the large ratio $\sim10^9$ between the typical galaxy-lensing delay time $\sim\mathcal{O}$(10 days) and the width of bursts $\sim\mathcal{O}$(ms), we propose strongly lensed FRBs as precision probes of the universe. We show that, within the flat $\Lambda$CDM model, the Hubble constant $H_0$ can be constrained with a $\sim0.91\%$ uncertainty from 10 such systems probably observed with the Square Kilometer Array (SKA) in $<$ 30 years. More importantly, the cosmic curvature can be model-independently constrained to a precision of $\sim0.076$. This constraint can directly test the validity of the cosmological principle and break the intractable degeneracy between the cosmic curvature and dark energy.Comment: 8 pages, 6 figure

Static and Dynamic Response Analysis of a High Rock-Fill Dam with a Clay Core

Stress strain analysis based on Biot’s consolidation theory is performed for Nuozhadu dam, which is a high rock-fill clay-core dam located in the Langcangjiang River in Yunnan province, China. Attention is mainly focused on arching effect and possibility of hydraulic fracturing of the core. Equivalent linear approach is employed to evaluate the seismic response of the dam under design earthquakes, and two empirical formulas relating residual shear and volumetric strain to cyclic stress and strain history are proposed to evaluate the permanent deformation. It is found that: 1) the modulus ratio of the clay in the core to rockfills around is the main factor controlling the severity of arching effect, 2) hydraulic fracture would not occur according to the criterion of effective stress, and 3) the permanent deformation that is likely to occur is acceptable under the condition of design earthquakes

Generation of Narrow-Band Polarization-Entangled Photon Pairs for Atomic Quantum Memories

We report an experimental realization of a narrow-band polarization-entangled photon source with a linewidth of 9.6 MHz through cavity-enhanced spontaneous parametric down-conversion. This linewidth is comparable to the typical linewidth of atomic ensemble based quantum memories. Single-mode output is realized by setting a reasonable cavity length difference between different polarizations, using of temperature controlled etalons and actively stabilizing the cavity. The entangled property is characterized with quantum state tomography, giving a fidelity of 94% between our state and a maximally entangled state. The coherence length is directly measured to be 32 m through two-photon interference.Comment: 4 pages, 4 figure