Simple Security Proof of Mode-Pairing Quantum Key Distribution

Mode-pairing (MP) quantum key distribution (QKD) eliminates the requirements of phase locking and phase tracking compared with twin-field (TF) QKD while still surpassing the fundamental rate-distance limit of QKD. The complexity of the experimental implementation is reduced while the efficiency is also guaranteed. The security of MP-QKD is proved rigorously by examining the consistency of the states detailly between MP-QKD and the fixed-pairing scheme under all of Eve's possible interference, where the latter is equivalent to measurement-device-independent (MDI) QKD. Here we propose a simple and straightforward method to prove the information-theoretic security of MP-QKD. Specifically, an entanglement scheme for MP-QKD is proposed and its security is proved using entanglement purification. Then the security of MP-QKD can be guaranteed with the equivalence of the entanglement scheme and prepare-and-measure scheme for MP-QKD. With this approach, it is beneficial to analyze and understand the performance and security of MP-QKD. We explain why the pairing rounds in MP-QKD can be decoupled and determined by the measurement results announced by a third party, which is the key difference between MP-QKD and MDI-QKD. Moreover, we analyze the security of MP-QKD with the allowed optimal pairing strategy, which is significant for the secret key rate, under collective and coherent attacks

Single-shot, full characterization of the spatial wavefunction of light fields via Stokes tomography

Since the diffraction behavior of a light field is fully determined by its spatial wavefunction, i.e., its spatial complex amplitude (SCA), full characterization of spatial wavefunction, plays a vital role in modern optics from both the fundamental and applied aspects. In this work, we present a novel complex-amplitude profiler based on spatial Stokes tomography with the capability to fully determine the SCA of a light field in a single shot with high precision and resolution. The SCA slice observed at any propagation plane provides complete information about the light field, thus allowing us to further retrieve the complete beam structure in 3 dimensions space, as well as the exact modal constitution in terms of spatial degrees of freedom. The principle demonstrated here provides an important advancement for the full characterization of light beams with a broad spectrum of potential applications in various areas of optics, especially for the growing field of structured light

Determination of heavy metals in chinese prickly ash from different production areas using inductively coupled plasma-mass spectrometry

Purpose: To determine the heavy metal content of Chinese prickly ash (CPA) produced in various areas of China.Methods: CPA samples collected from different production areas in China were subjected to microwave digestion, and the contents of copper (Cu), nickel (Ni), chromium (Cr), lead (Pb), cadmium (Cd), arsenic (As), mercury (Hg), tin (Sn), and antimony (Sb) were determined by inductively coupled plasma-mass spectrometry (ICP-MS).Results: Heavy metal levels in the CPA samples followed the order: Cu (3.29-24.17 mg/kg) > Cr (0.04-7.33 mg/kg) > Ni (0.88-6.86 mg/kg) > Pb (0.00-3.84 mg/kg) > As (0.0011-1.08 mg/kg) > Cd (0.029-0.211 mg/kg) > Sb (0.03-0.21 mg/kg) > Sn (0.00-0.15 mg/kg) > Hg (0.000-0.032 mg/kg). Metal-to-metal correlation studies showed that there were significant correlations between Cu-Cr (p = -4.02), Cu-Ni (p = 0.561), Cu-As (p = 0.554) and Ni-As (p = 0.428) at the 0.01 level. Also, some metal-to-metal correlations were observed in Pb-Cr (p = 0.351), Pb-Cu (p = -0.310), Sb-Cd (p = 0.322), Sb-Hg (p = 0.311) and Cd-Sn (p = 0.309) at the 0.05 level. The highest concentrations of Pb and As in CPA exceeded the maximum permissible limits in China. Based on current safety standards, the concentrations of heavy metals in these CPA samples mean they are safe for human consumption.Conclusions: The status of heavy metal concentrations of CPA should be further investigated in Sichuan, Shaanxi, Shanxi and Jiangsu. In addition, ICP-MS is a reliable and rapid technique for the determination of the heavy metals in CPA.Keywords: Chinese prickly ash, Heavy metals, Inductively-coupled plasma-mass spectrometry, Food safet