Abstract
Continuous-variable quantum key distribution (CV-QKD) over air quantum channel enables to provide unconditional information security, which is the one of most promising techniques for information wireless transfer. Since the air channel is of fluctuation in nature due to the presence of air turbulence, the random variations have to be taken into account when the security of CV-QKD is analyzed. We study the secret key rate of CV-QKD over the air quantum channel in this paper. The fluctuation of air channel is characterized by beam wandering and phase distortion under weak air turbulence conditions. The impact of fluctuation on the CV quantum signals is reflected by transmittance perturbation and phase shift. Our numerical results show that the secret key rate may keep relatively high level as the air quantum link increases at the outset. However, when the air link distance further increases beyond certain range, the secret key rate decreases strikingly since the both transmittance perturbation and the phase shift simultaneously deteriorate the performance of CV-QKD. Nevertheless, operating the CV-QKD under weak air turbulence conditions is available.
Highlights
The machine possessing powerful-computational capacity, like the quantum computer [1], poses huge threat to the current classical cryptosystem which relies on computational complexity
The parameters associated with air quantum channel are adopted as follows
Note that the air turbulence must be limited within weak region so that the log-negative Weibull model of transmittance is appropriate. 2 < 1 means weak air turbulence conditions
Summary
The machine possessing powerful-computational capacity, like the quantum computer [1], poses huge threat to the current classical cryptosystem which relies on computational complexity. QKD combing with one-time pad strategy enables to provide unconditional information security, which is expected to address the security issue inherently in communications [3]. One is called discrete-variable QKD (DV-QKD), where the information is encoded to the discrete variables, like polarizations of single photon [4], [5]. The other is referred to as continuous-variable QKD (CV-QKD) since the information is encoded to the continuous variable of electromagnetic field, like conjugate quadratures [6], [7]. Compared to the DV-QKD that requires dedicated single photon source and counter, the CV-QKD employs the mature infrastructure of coherent optical communication.
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