https://www.selleckchem.com/products/gdc-0068.html The ability of an eavesdropper to compromise the security of a quantum communication system by changing the angle of the incoming light is well-known. Randomizing the role of the detectors has been proposed to be an efficient countermeasure to this type of attack. Here we show that the proposed countermeasure can be bypassed if the attack is generalized by including more attack variables. Using the experimental data from existing literature, we show how randomization effectively prevents the initial attack but fails to do so when Eve generalizes her attack strategy. Our result and methodology could be used to scrutinize a free-space quantum communication receiver against detector-efficiency-mismatch type attacks.In a free space optical communication system based on vortex beams, the effects of spread and crosstalk caused by atmospheric turbulence should not be ignored. The orbital angular momentum (OAM) spectrum of the signal based on elliptic Gaussian beam (EGB) after propagation through non-Kolmogorov turbulent atmosphere are deduced, and a theoretical model of the spiral spectrum of EGB propagating through turbulent atmosphere is obtained. Numerically calculated OAM modes detection and crosstalk probability under different ellipticity parameters. The results show that the ellipticity parameter has a significant impact on the OAM spectral distribution of EGB and the transmission characteristics after turbulent atmosphere. The selection of appropriate ellipticity parameter can correspondingly reduce the degradation and crosstalk caused by turbulent atmosphere. We also compared a Laguerre-Gaussian beam (LGB) with EGB and pointed out the advantages and limitations of these two kinds of beams. The research results may be useful in the field of short distance optical communication and OAM-based multiplex communication.Exceptional points (EPs) have been shown to be useful in bringing about sensitive optical properties b