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Singular Atmospheric Optics: From Wavefront Dislocations to Synthesis of Vortex Laser Beams
摘要： Studies on the singular optics of scalar wave fields carried out in the world and at V.E. Zuev Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences (IAO SB RAS) are reviewed. The study results of the processes of origination and annihilation of phase singularities are generalized. The methods for singular phase reconstruction and their applicability to the problems of adaptive focusing of radiation in randomly inhomogeneous media are examined. The energy, statistical, and topological properties of vortex optical beams propagating through a turbulent atmosphere are analyzed. The results of the synthesis of vortex beams with quickly controllable orbital angular momentum by the matrix approach developed at IAO SB RAS are described.
关键词： vortex beam,turbulent atmosphere,probability density function,intensity fluctuations
更新于2025-09-19 17:13:59
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Performance of photoelectron spin polarimeters with continuous and pulsed sources: from storage rings to free electron lasers
摘要： In this work the experimental uncertainties concerning electron spin polarization (SP) under various realistic measurement conditions are theoretically derived. The accuracy of the evaluation of the SP of the photoelectron current is analysed as a function of the detector parameters and speci?cations, as well as of the characteristics of the photoexcitation sources. In particular, the different behaviour of single counter or twin counter detectors when the intensity ?uctuations of the source are considered have been addressed, leading to a new de?nition of the SP detector performance. The widely used parameter called the ?gure of merit is shown to be inadequate for describing the ef?ciency of SP polarimeters, especially when they are operated with time-structured excitation sources such as free-electron lasers. Numerical simulations have been performed and yield strong implications in the choice of the detecting instruments in spin-polarization experiments, that are constrained in a limited measurement time. Our results are therefore applied to the characteristics of a wide set of state-of-the-art spectroscopy facilities all over the world, and an ef?ciency diagram for SP experiments is derived. These results also de?ne new mathematical instruments for handling the correct statistics of SP measurements in the presence of source intensity ?uctuations.
关键词： continuous source,intensity fluctuations,spin-polarimetry statistics,pulsed source,spin-resolved photoemission
更新于2025-09-11 14:15:04
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Finite-key analysis for high-dimensional quantum key distribution with intensity fluctuations
摘要： High-dimensional quantum key distribution (HD-QKD) can increase the photon information efficiency and be robust to noise. Several HD-QKD experiments have been demonstrated to verify above appealing features. However, device imperfections, which have great impacts on the security of HD-QKD system, have not been widely discussed. In this paper, we mainly investigate the finite-key analysis against coherent attacks for HD-QKD without and with intensity fluctuations. For the case without intensity fluctuations, we present the parameter estimation based on the Chernoff bound and the improved Chernoff bound. When considering the case with intensity fluctuations, we present the finite-key analysis based on Azuma’s inequality. By numerical simulations, we find that the performance of HD-QKD for the finite-key scenario based on the improved Chernoff bound is tighter than those based on the Chernoff bound or Hoeffding’s inequality in terms of the secret-key rate and the maximum transmission distance. Moreover, we find that intensity fluctuations affect the performance of HD-QKD greatly and the effect for short running time of transmission is more obvious.
关键词： Quantum key distribution,Finite-key,Intensity fluctuations
更新于2025-09-10 09:29:36